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303 Cards in this Set
- Front
- Back
Give the standard value for the SPEED OF SOUND in meters per second.
Give the formulae for calculating the speed of sound though air at a given temp
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344 METERS PER SECOND
C = 331 + 0.6 x T
*Where C is the constant and T is the temperature |
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When adding or subtracting positive and negative numbers which rules apply? |
A negative + a negative is always a negative
A positive + a positive is always a positive |
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When multiplying or dividing positive & negative numbers which following rules apply? |
A positive number */÷ positive is a positive A positive number */÷ negative is a negative A negative number */÷ negative is a positive A negative number */÷ positive is a negative |
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When dividing a fraction by a fraction on the calculator you can use the fraction division function then change the ratio to a decimal using which button? |
The S : D Button |
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Name the units of decimal measurement and their values in number of zeros ?
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tera T 1000000000000 (12 zeros) giga G 1000000000 (9 zeros) mega M 1000000 (6 zeros) kilo k 1000 3 (3 zeros) hecto h 100 (2 zeros) deca da 10 (1 zero) deci d 0.1 (1 zero) centi c 0.01 (2 zeros) milli m 0.001 (3 zeros) micro μ 0.000001 (6 zeros) nano n 0.000000001 (9 zeros) pico p 0.000000000001 (12 zeros)
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What is the common log base? |
10 |
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What happens to air pressure when there is a compression of air particles? |
It increases |
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What happens to air pressure when there is a rarefaction of air pressure |
It decreases |
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What is 1 Hz describing? |
1 cycle per second 1 Hz is the measurement of one complete cycle (or one oscillation) of the compression and rarefaction of the pressure. |
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How long in milliseconds does it take before the ear perceives the delay between two sounds arriving as an Echo? |
35 ms |
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What progression do Octaves follow? |
Each Octave is double the frequency of the preceding one C0 = 16.352 hz & C1 = 32.703 hz |
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What mathematical progression does frequency follow? |
Logarithmic |
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What mathematical progression do harmonics follow? |
Linear |
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The ear perceives the difference between the peaks and troughs of a sounds amplitude as what?
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Loudness |
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What is RMS and what is it used for? |
Root Mean Square Used to determine average level of a signal. |
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What does the period of a wave describe? |
The amount of time it takes for one full cycle to take place |
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What equation describes the relationship between the period and the frequency of a sound wave? |
T = 1/f T=1/1 or 1 second T=1/2 or 0.5 seconds T=1/4 or 0.25 seconds / 250ms T=1/8 or 0.125 seconds / 125 ms T= 1/1000 or 0.001 seconds / 1ms T= 1/ 20000 or 0.00005 seconds or 0.05ms |
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In what two ways can wavelength be described? |
The distance travelled by sound during one period
The distance between any two consecutive corresponding points along the waveform. |
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Which equation describes the relationship between wavelength and the frequency? |
C = F x λ
λ = Lambda (Wavelength)
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What does Phase describe? |
Phase is used to describe the amount of deviation from 0 degrees when two identical waveforms are occupying the same space
Or how far along its cycle a given waveform is. The measurement of phase is given in degrees, with 360 degrees being one complete cycle |
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At how many degrees would an identical waveform be described as 'Out of phase' ? |
180 degrees (Inverted) |
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What happens if you sum two identical waveforms together? What would be the resulting increase in decibels? |
Double the amplitude +6 dB |
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What is Pan? |
A change in amplitude between left and rightchannels. |
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Describe comb filtering |
Comb filtering is the effect of alternating reinforcements /cancellations at different frequencies.
In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced spikes, giving the appearance of a comb.
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What equation do you use to calculate Phase shift? |
Ø = △t x 360 x f
Where
△t = Time difference (delay) in seconds f = Frequency ø = phase shift in degrees
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Approx. how far does a sound wave travel through air at room temperature in 3ms? |
1 meter |
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What does the Sum and Difference rule describe?
Use base frequencies 100 Hz and 150 Hz as an example |
The sum of 100 Hz & 150 Hz=250 Hz
The difference from 100 Hz & 150Hz=50 Hz
So if you combine 100 Hz and 150 Hz you will also hear the sum and difference frequencies:
50 Hz and 250 Hz |
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Describe what a Beat Frequency is? |
2 oscillators set at the same frequency e.g. 1 Hz Moving one oscillator +/- 1 Hz will result in you hearing a one second cycle effect. |
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Describe the term 'Out of Phase' |
When two identical waveforms are summed with a degree ofphase shift equaling 180 degrees this is known as Phase cancellation or being
'Out of Phase'
This will mean two identical sine waves at 180 degrees would result in silence
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Describe the 5 higher harmonics of a fundamental frequency of 100 Hz |
100 Hz (f1)
f2 = 200 Hz / f3 = 300 Hz /f4 = 400 Hz / f5 = 500 Hz |
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How many harmonics does a sine wave contain? |
None |
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What type of harmonics does a sawtooth wave contain? |
even and odd harmonics at decreasing amplitudes |
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What type of harmonics does a square wave contain? |
All odd harmonics at decreasing amplitudes |
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What type of harmonics does a triangle wave contain |
All odd harmonics alternating in polarity with steeper decreasing amplitude than a square wave |
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What is refraction? |
Refraction may be described as a change in direction as sound travels through different media (as discussed before, the speed of sound is dependent upon the temperature and the density of a medium) |
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What is diffraction |
Can be described as the bending of sound around physical objects. The degree of diffraction depends upon the size of the object in relation to wavelength of a sound frequency. |
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What is reflection |
When sound encounters a hard surface it will reflect or bounce off in a different direction. Depending on the shape of the said surface this change in travel direction |
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How would a Concave surface affect the sound |
Tend to focus sound. A satellite dish orradio telescope is an example of a concave shape that reflects sound to a focalpoint. |
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How would a Convex surface affect the sound |
Tend to scatter sound also known as diffusion. The royal Albert Hall has convex reflection treatment on the ceilingto scatter sound back toward the audience. |
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How would a corner surface affect the sound |
Tend to send incident rays back to towardsthe general direction of origin. |
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What is direct sound |
The shortest distance that sound needs to travelfrom the source to the listener |
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Describe an Early Reflection? |
Sound that has reflected off one or two surfaces. |
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Describe a reverb tail or cluster |
Sound that has reflected off numerous surfaces |
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Is pitch psycho-acoustic or physical? |
Psycho-acoustic |
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Is Frequency psycho-acoustic or physical |
Physical |
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Is Loudness psycho-acoustic or physical |
Psycho-acoustic |
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Is Timbre psycho-acoustic or physical |
Psycho-acoustic |
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Is spectral content psycho-acoustic or physical |
Physical |
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Is Amplitude Psycho-acoustic or physical |
Physical |
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What happens to the perception of pitch when listening to very low frequencies? |
It becomes harder to identify / differentiate pitch at lower frequencies Frequency with longer periods (LowerFrequency sounds) require longer note to determine pitch. |
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Describe what a fundamental frequency is |
The frequency that determines the pitch reference.
Also known as the 1st harmonic
This is typically the lowest frequency present within the harmonic content. |
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What is the 1st harmonic? |
Same as the fundamental frequency |
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What is a 'Formant' |
An overtone that holds no simple mathematical relationship to the fundamental frequency but contributes non-pitch related spectral content to the sound. |
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What is the A D S R of an envelope |
A = Attack D = Decay S = Sustain R = Release |
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Describe the Equal Loudness Contour (Fletcher Munson curve) |
A scale (measured in units of Phons) describing the relationship between frequency and perceived loudness. Human hearing is much more sensitive in certain frequency ranges 1kHz for example is perceived much louder at far lower Sound Pressure Levels (e.g. 10 phons) than say 60 Hz |
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What type of electrical component could the human ear be described as? |
The Human Ear is a Transducer. It converts one type of energy into another. In this case acoustic energy (sound pressure) arriving at the tympanic membrane is converted into electrical energy in the form of neurological impulses. |
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What are the 3 energy states that are involved in the transduction of sound in the human ear?
Name the 3 bones situated within the middle ear that convert acoustic energy into mechanical energy? |
Acoustic Energy – Pressure fluctuationscollected by the Pinna and auditory canal (Outer Ear)
Mechanical Energy – Movement of earcomponents (Hammer Anvil Stirrup and tympanic membrane Oval Window) (MiddleEar)
Electrical Energy – Cochlear receives soundin the form of the vibrations from the middle ear components and then sends apressure wave to the stereocilia up to the Basilar Membrane which then directs the wave to the cell hairs and onto the brain in the form of neural impulses. |
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What part of the human ear is mainly responsible for sound localisation? |
Pinna helps to localise sound,neuro-plasticity can adapt to changes (for example losing the pinna or outerear) but this takes time. Pinna is sensitive to high frequencies,less so to low frequencies. |
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What is I T D ? |
Inter Aural Time Difference
This localisation mechanism relies on arrival time differences between two ears.
Does not well on very high or very lowfrequencies.
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What is I A D? |
Inter Aural Amplitude Difference
This localisation mechanism relies on amplitude differences between the two ears.
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Describe Spectral Differences? |
This mechanism relies on timbre differences between sounds arriving at two ears, this mechanism does not work well on very low or high frequencies. |
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Describe the HAAS effect? |
Law of first wavefront precedence: If two or more versions of a sound are produced the first version to arrive at the listeners position will in most cases determine localisation. This remains true for delay times up to approx.50ms and it is applicable even when the second arriving version of the sound is approx. 15db louder than the first within the specific delay times. |
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Describe the Doppler effect? |
Caused by a sound emitting object chasingits own sound wave producing pressure fluctuations and thereby shortening the wavelength. As the sound wavelength is shortened the pitchwill increase and visa versa |
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Perception of distance is affected when the early reflections arrive closer to or further away from the direct sound? |
Closer to the direct sound. |
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Which Decibel scale deals with measuring acoustic energy? |
dB (SPL) |
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Where does the word Decibel come from? |
Deci meaning 10 to the minus 1 (or 1/10) and Bel (The Decibel scale was invented by Bell Labs) |
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Is the DeciBel a defined quantity or a reference? |
Decibels are a reference against something!
They are not a set defined quantity so for example -6dB means nothing in isolation.
It only has meaning when used in context to a referenced & measured quantity.
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What is the reference value of the dBV scale? |
1 V |
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What is the reference value of the dBu scale? |
0.775 V |
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What is the reference value of the dBm scale? |
1 mW |
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What is the reference value of the dBw scale? |
1 W |
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Which dB scale uses the common log for its measurement? |
dB w dB m 10 log or common log is used when measuring power |
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What dB scales use 20 log for its measurement |
dBV dB SPL dBu dBm |
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If we double the power of a dBw reading how many decibels of a difference will we increase by? |
+3 dBw |
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If we double the voltage of a dB V reading how many decibels of a difference will we increase by? |
+6 dBV |
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Sound pressure is described using which unit of measurement? |
The Pascal |
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If I increase from 1 to 8 Pascals how many dB SPL of a difference am i increasing by? |
+18 dB 1 to 2 Pascal equals an increase of6dB(SPL) 2 to 4 Pascal equals an increase of6dB(SPL) 4 to 8 Pascal equals an increase of6db(SPL) |
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What is the reference for the dB SPL scale? |
20 micropascals 0.000020 Pascal |
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What is the formulae for determining dB SPL? |
M / R x 20log The measured value divided by the reference value x log amount (the log amount is dependent in the type of dB you are calculating) |
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What is the formulae for determining dBw |
M / R x 10log
The measured value divided by the reference value x log amount (the log amount is dependent in the type of dB you are calculating)
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When calculating dB values the measured value is always what? |
Where you are going to |
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When calculating dB values the reference value is always what? |
Where you are starting from |
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The SOL for prosumer equipment is? |
1.23 volts +4 dBu |
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When calculating dB what in what order would you use the measured and referenced values? |
START (Where you are going from) =Referenced amount
ENDING (Where you are going to) = Measured amount |
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Name the different dB scales commonly used in audio and their referenced values. |
dB SPL (Sound Pressure Level) ‘measured’ number iscompared to 20 μPa dBV (voltage) ‘measured’ number is compared to1 V dBu (unloaded) ‘measured’ number is compared to 0.775 V dBm (milliwatts) ‘measured’ number is compared to 1 mW dBw (watts) ‘measured’ number is compared to 1 W |
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What is the S.O.L ? |
The Standard Operating Level |
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What is the 0VL value for Semi Pro equipment |
-10 dBV |
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What is the unity gain level for broadcast standard equipment |
Broadcast +8 dBu |
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What is the S.O.L for Hi-Fi equipment? |
-10 dBu |
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Describe Gain Staging? |
Gain staging is bringing all signals into the console at the same standard operating levels in order to keep the noise floor low and the signal to noise ratio (SNR) high. |
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What does dBFS mean? |
Decibel Full Scale
This is the decibel scale used in digital audio systems. |
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At 0 dBFS what is the dBu reading? |
+24 dBu |
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1.23 Volts is described as what? |
'Pretty Good Line Input Level' |
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What is the 0 dBV in dBu ? |
+2.2 dBu so for example -10 dBv = -7.8 dBu |
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The dBFS (Digital scale) is measured using what level metering type? |
The dBFS (Digital scale) is measured in PEAK. |
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The dB u (analogue unloaded voltage) is measured using what level metering type? |
RMS (Average Level) |
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The noise floor for analogue is approximately what dBu from 0VU |
-94dB |
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How high can the noise floor be when using tape? |
-20dB |
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What is the typical S.O.L levels for digital audio |
-18 dBFS |
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Name the two types of level meter that would be typically found in a studio? |
Peak meter VU (Volume Unit) |
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What type of decibels are used to describe loudspeaker output level? |
Power decibels They must always state amplifier power in watts and also distance e.g. 110 dbSPL @ 1 watt @ 1 meter (Calculated using the 10log formulae) |
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Which law is used to describe the energy loss ratio of a loudspeaker powered by an amplifier at distance? |
The inverse square law
Distance / Power / SPL |
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If two separate sound sources are used in Parallel their combined level is described using what formulae? |
Sum dB = 10 log(10 dB1/10 + 10 dB2/10 +10 dB3/10 +10 dBn/10) |
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Name the three different dB weightings and their relative Phon values. |
dB a which is based on the 40 Phon line dB b which is based on the 70 Phon line dB c which is based on the 90 Phon line |
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What is a PPM meter?
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PPM = Peak Program Meter
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Describe VU ballistics? |
Response time of the meter needle VU meters can take up to 300 ms to respond fully to level changes |
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How much headroom should you leave in a mix to allow mastering |
-3dB |
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Describe the purpose of a correlation meter |
This type of meter will display phase relationships between left and right channels so will involve time arrival differences as well as frequency analysis.
Generally if the meter stays in the blue or in phase position(+180) all is good. If in the red position or out of phase (-180) not good. |
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How many samples are taken during 1ms of a 44.1kHZ recording |
44 samples |
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Where is the tympanic membrane located? |
The Middle Ear |
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Name the tube that provides equalisation of air pressure between the outer and middle ear? |
The eustation tube |
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What are the latin words for the 3 bones of the middle ear? |
Malleaus (Hammer)
Incus (Anvil)
Stapes (Stirrup) |
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What are the three bones located in the middle ear collectively known as? |
The auditory osscicles |
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Which part of the inner ear is filled with liquid? |
The cochlea |
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Which part of the inner ear is responsible for sending electrical impulses to the brain? |
The organ of Corti |
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How many times per second do the nerve endings / hair cells fire and recharge? |
1000 |
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Describe the purpose of EQ |
EQ is Equalisation. It is used for frequency dependent level control. |
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What is Q? |
Q is the Quality factor or bandwidth of the frequency attenuation / amplification |
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Name the three simplest types of filter? |
High Pass Filter or HPF Low Pass Filter or LPF Band Pass Filter or BPF |
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Describe what is happening when 'ringing' a filter |
Ringing occurs when very steep curves are used This results in resonance of the filter that will create aboost at the cutoff frequency |
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What type of EQ would be used to cut or boost a narrow range of frequencies? |
A peak EQ also known as a bell EQ |
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When any type of EQ is used what type of interaction is inevitably being introduced to the sound? |
Phase Distortion |
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Name the frequency range of VLF or very low frequency. |
20 Hz to 40 Hz |
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Name the frequency range of LF or low frequency. |
40 Hz to 125 Hz |
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Name the frequency range of LMF or low mid frequency. |
125 Hz to 315 Hz |
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Name the frequency range of MF or Mid frequencies |
315 Hz to 2 kHz |
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Name the frequency range of HMF or high mid frequencies. |
2 kHz to 4 kHz |
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Name the frequency range of HF or high frequencies. |
4 kHz to 10 kHz |
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Name the frequency range of VHF or very high frequencies. |
10 kHz to 20 kHz |
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Describe 'Masking' |
When two sounds compete for space in the same part of the audio spectrum they can obscure each other causing the sound to be 'Masked' EQ can help to keep competing sound frequency ranges separated. |
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What is the attenuation rate of a 1st order filter |
-6dB per octave (1 Pole) |
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What is the attenuation rate of a 2nd order filter |
-12dB per octave (2 Pole) |
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What is the attenuation rate of a 3rd order filter |
-18 dB per octave (3 Pole) |
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What is the attenuation rate of a 4th order filter |
-24 dB per octave (4 Pole) |
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What is the 'slope' 'order' or 'pole' of a filter describing? |
The rate of attenuation in dB per octave below the cutoff frequency. |
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What is a Shelf EQ |
Provides even gain cut or boost from a specified turnover or shelving frequency |
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What will be the result of using a low Q factor value |
A broader range of frequencies will be affected. |
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What will be the result of using a high Q factor |
A narrower range of frequencies will be affected |
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What is a Semi Parametric EQ? |
Offers non continuous control over the Q factor There may be 1 or more pre defined selections for the Q factor value. |
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What is a Fully Parametric EQ |
Offers full variable over the centre frequency Q bandwidth and Gain. |
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What is a Graphic EQ |
Pre defined range Variable Q factor |
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How do you calculate the centre frequency? |
Multiply Octave 1 by Octave 2 then take the square root of the result. |
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What 3 values do you require to calculate the Q factor? |
To calculate the Q factor you need. The centre frequency (f0) The low frequency (fL) The high frequency (fH) |
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With a given bandwidth how would you calculate the Q factor? |
Q = (f0) / (B) |
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True or False.
A bandwidth of 1 octave will always be represented by the same Q factor? |
True
Octaves follow a non linear progression which means the shape will stay the same. This means a Q factor of 1.4142 will always represent an octave of bandwidth no matter what the Centre frequency.
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What formulae is used to calculate the Q factor? |
Q = Fc / B |
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True or False Q is inversely proportionate to the bandwidth and directly proportionate to the centre frequency? |
True |
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What formulae is used to calculate Octaves? |
fH / fL = 2n if fH = 554 Hz and fL = 440 Hz 554 / 440 = 1.26 log2 1.26 =3.33 (or one third of an octave) |
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What formulae is used to calculate a specific musical notes frequency |
fH / fL = 2(x/12)
Here we use x/12 to determine the number of semitones we wish to calculate the frequency for.
If I want to know what is the frequency of A#4 I can first use A4 (concert pitch) toget fLA4= 440hz fH / fL = 2 (1/12) = 466.16
So A#4 = 466.16hz
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Reverb is the simulation of what? |
The reflectivequalities of an acoustic environment. |
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What are the various stages of reverberation? |
Direct sound Theshortest path sound travels from the source to the listener. Pre Delay (First Echo) Thetime between the direct sound and the first reflection Early Reflections Thefirst reflections arriving from all other angles The reverberant field Amountdepends on number of surfaces and obstacles |
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Describe the effect of diffusion on reverb? |
Diffusion is caused by sound reflecting off an uneven surface. The asymmetric reflections produced result in a less resonant reverberation tail. A good example of a diffuse surface is a cave. |
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Name four methods of producing reverb. |
Reverb Chamber Spring Reverb Plate Reverb Digital Reverb |
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What is a convolution reverb? |
These work by using an Impulse Response (IR) which is arecording of the reverberation of a space or a plate for example. |
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What does IPS mean on a tape machine? |
Tape speed measured in Inches per second |
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What is Multi Tap delay? |
Multiple playback heads Allows more delay repeating at differing intervals |
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Describe Slap Back Delay |
Used heavily in the 1950s by artists such as Johnny Cash, Elvis Presley etc. Characterised by very short delay time <100ms Short feedback and some tapeflutter. |
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How would you calculate the delay time for a song with a tempo of 120 BPM
The delay should be for crotchets (quarter notes) |
Δt = 60/BPM = 1 quarter note in 4/4
60/120 = 500ms |
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How would you calculate the delay time for a song with a tempo of 130 BPM The delay should be for quavers (eighth notes) |
Δt = 60/130 = 1 quarter note in 4/4 60/130 = 0.461 secs or 461ms 461 ÷ 2 (Halving the delay gives us eighth notes) = 230.5ms |
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What is an L.F.O? |
Low Frequency Oscillator An LFO is a very low frequency sine wave which cannot be heard but can be usedto affect (modulate) another signal or set of parameters in the digital domain. |
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What does ADT stand for |
ADT (Automatic Double Tracking) ADT uses a second tape machine with a very short delay (<10ms) added to theoriginal with oscillating varispeed (this was first done manually laterelectronically with a VCO acting as LFO) |
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Describe what a flanger does. |
Phase interactions / comb filtering with a varying delay time or a ‘sweepingfrequency’ |
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Describe the effect of a Phaser |
Very similar to a flanger except this effect is created using an all-pass filter whichdoes not effect amplitude of frequency but instead effects the phase of the signal. |
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Describe the Chorus effect |
Designed to emulate the sound of multiple people (sound sources) playing thesame instrument at the same time. E.g. a Choir Slight variations in time pitch and amplitude are used to mimic real chorus.
An LFO modulates delay time but with a longer delay than a flanger or phaser soas to avoid comb filtering.
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Describe how a Wah Wah effect is produced |
An LPF with a resonant peak (usually by ringing the cutoff frequency) moving up anddown the frequency spectrum. Usually modulated by a pedal or an LFO. |
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What is a Vocoder? |
The frequency response of a signal is super-imposed with the input of anothersignal. This is usually a vocal input. Chords / Notes on a separate input aremodulated by the vocal input as both these signals each pass through first an LPFand then a series of BPF’s which are each set to a different frequency range
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Describe the 'Leslie' effect |
Produced by Rotary Speakers (Level and Filter based effect) Produces a pan / tremolo / doppler type effect Commonly used on Hammond Organs. |
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What is a compressor? |
A compressor is a device that reduces the dynamic range of a signal Compression is a form of dynamic processing. |
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What are the typical controls found on a compressor |
Threshold Ratio Attack Release Gain |
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What is limiting? |
Limiting is a form of soft clipping A compressor with a ratio of 10:1 or higher is generally considered to be acting as a limiter. |
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Describe the purpose of a side chain in a compressor. |
A side chain allows a separate input to act as the control signal for the compressors voltage controlled amplifier. |
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What is the formulae for calculating compressed output? |
Compressed output = Input - Threshold + Ratio |
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What are the main reasons for using compression? |
Dynamic range control Add tone & colour (long release / reduce sustain) Transient control (peak enveloping) Add harmonic distortion / multi band (frequency based amplitude control) |
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What is the difference between a 'Hard Knee' and 'Soft Knee' compressor |
A hard knee compressor begins compression when the signal reaches thethreshold. A soft knee compressor begins compression slightly before the threshold isreached and increases compression as the signal rises above the thresholdcreating a smoother curve. |
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Describe Mid / Side (sum and difference) |
When combining two mono signals the same signal played in both speakers withno time difference but panned hard left and right will result in a centered or ‘Mid’ image
Conversely phase and time differences will result in the stereo imaging movingleft and right of the center or ‘Side’ imaging. |
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When we 'De-Ess' a signal what frequency range do we remove? |
2kHz - 9kHz |
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What does an 'Expander' do? |
An expander increases the dynamic range of a signal (opposite to compression) Attenuation is applied to low level signals and it occurs according to a given ratio.
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Describe what a Noise Gate does |
Gating mutes the signal below a certain threshold. |
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True or False Microphones use very large voltage levels to send the input signal? |
False Microphones use very small voltages Usually Microvolts & Millivolts |
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Describe the difference between an unbalanced and a balanced cable |
Unbalanced cables have a single common and return path. They are prone to noise and other electromagnetic interference. Balanced cables have a dual path design utilising CMR (Common Mode Rejection) (+/- and ground) This allows the signal to be split into positive and negative paths. Signal on one and Noise on the other. When the two are phase inverted and summed the noise cancels and the signal is doubled (+6dB) |
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Describe the three main properties of electricity as described in Ohms Law |
Current = Movement or flow Voltage = Potential difference between two points of a circuit Resistance = The opposition to current (this can be in the form of a wire likecopper or a light bulb) |
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What is a DI box? |
DI (Direct Injection) Takes an unbalanced (instrument level) input (1/4 inch jack) and outputs to a (line level) balanced cable |
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What electrical element is analogous to audio? |
Voltage (Potential Difference) It is analogous to the complete period of a sine wave (as compared against thepositive and negative terminals on a battery) |
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What is the benefit of impedance matching? |
A good match between the source and load components in terms of impedancewill give the best (SNR) |
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What is impedance? |
Frequency dependant resistance |
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What will happen if you attache an instrument level signal to a mic pre? |
If attaching high level impedance source like a guitar to a mic pre you will get avery low level and noisy signal as the voltage is being seen mainly by the instrument.
This is because the instrument has more impedance than the mic pre (frequency dependent resistance) A DI box should be used to lower the impedance of the instrument to match the mic pre. |
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What is 'Capacitance' |
The ability of a system to store an electric charge. The ratio of the change in an electric charge in a system to the corresponding change in its electric potential. A Capacitor is a device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator. Also known as a 'Condenser' |
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What does T R S stand for? |
Tip (Positive) Ring (Negative) Sleeve (Earth / Ground) The three connecting circuits in a 1/4 inch cable that allow signal to be transferred. |
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Name 4 different types of 'Jack' connector |
Mini jack / 1/8 (Headphones / 3.5mm)
1⁄4 Jack (Pro version of 1/8) Harder to unplug
Bantam / TT – Industry standard / Bigger than 3.5 and 1⁄4 Jacks
BPO (British Post Office) still in some studios for audio applications but rare |
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What is electro static noise? |
Hi frequency noise that may penetrate audio connectors and enter the audio signal path. A shield surrounding audio connectors can prevent noise from affecting audio signals. |
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What is electro magnetic noise? |
This type of noise has an extremely long wavelength which can penetrate shielding and so balanced cables are used to eliminate this type of noise. |
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Audio consoles have which two basic functions? |
Central routing system Consoles provide an easy way to route signals to and from different points without re-patching. Signal Processing Amplification, panning and EQ are examples of signal processing found in mixing consoles. |
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What is the function of a 'Bus'? |
An internal routing section enabling transport of a signal from one section (such as a channel path) of a desk to another (such as the main stereo outputs) |
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What is the function of an 'Aux' or 'Auxiliary' Bus |
Used to route signals to effect units, cue mixes etc. |
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What is the function of a 'Group' box |
Commonly used to collect signals from channel paths and route them to multi track inputs (recording) Group buses are also used to route signals to effects processors during mixdown. |
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What is the function of the main stereo bus? |
Used to mainly route signals from the channel or monitor paths to the main stereo mix outputs of a console. These outputs should be connected to a two track master machine such as a DAT or HD recording device. |
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On a 3 pin XLR cable what gender is the input and output? |
Input = Female Output = Male |
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What are the pin outs of an XLR cable? |
Abalanced XLR is wired as follows: Pin 1 = Return Pin 2 = Hot Pin 3 = Cold |
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What is Phantom Power? |
48v DC Used to power condenser microphones. |
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What type of microphone should you never use phantom power on? |
Ribbon Microphones. |
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What is the function of a PAD switch? |
To lower the level of incoming signals |
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What is the ø button used for on a console? |
To flip or invert the phase of a signal (180º) |
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What is the difference between 'Pre' and 'Post' Aux sends |
A Post Aux send is affected by the faderposition
A Pre Aux send is unaffected by the fader position
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What is the function of the 'Insert' section of a console? |
An‘Insert Send’ contains a copy of the signal in the path where the insert isplaced. This copy may be patched to another path / device (e.g. compressor).
An ‘Insert Return’ replaces the original signal in the path where the insert isplaced with a new signal (patched in). |
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Describe the function of the 'Talk Back' switch? |
Allows the communication between the engineer and themusicians. Talkback sections generally include a built in microphone, levelcontrol and on/off switch.
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Name the two main types of console design? |
Split Consoles Halfof the desk handles signals going to tape and the other half handles signalsreturning from tape.
In-Line Consoles Each I/O module contains two completely separate paths:
ChannelPath MonitorPath
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What is electricity? |
Electricity is the flow of moving electrons. |
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What path will electrons always take? |
The path of least resistance |
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True or False An electron is negatively charged? |
True |
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What is the polarity of a Neutron? |
It has no polarity as it is neutral (no charge) |
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Whats is the polarity of a Proton |
Positive charge |
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What is the equation for Ohms Law? |
V = I x R (Voltage = Current multiplied by Resistance) R = V / I (Resistance = Voltage divided by Current) I = V / R (Current = Voltage Divided by Resistance)
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Describe electrical resistance |
Resistance = The amount of opposition to current flow through the medium.
The lowerthe resistance the better a conductor the material.
The higherthe resistance the better an insulator the material. |
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What is electrical resistance measured in? |
Resistance is measured in Ohms Ω |
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What are the positive and negative terminals on a battery known as? |
The anode (positive) The cathode (negative) |
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True or False? Current is inversely proportional to Resistance and Directly proportional to Voltage? |
True |
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Describe AC electricity (Alternating current) |
Flow of electrons periodically flips between positiveand negative much like a sine wave. An alternating current is a phase basedsystem and is used in audio as its structure is analogous to the compression /rarefaction of air particles which causes sound. |
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Describe DC electricity (Direct Current) |
Implies electron flow in one direction.
You can think of DC as AC at a frequency of 0 Hz |
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What is the power equation? |
P = I x V Power = Current x Voltage |
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How do you calculate the RMS level of a signal? |
1.) Square the values (S) 2.) Take the average (M) 3.) Take the square root of the average (R) |
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What are semi-conductors? |
Electrical component that allows current flow only under specific conditions. |
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What unit is electrical charge measured in? |
Coulombs
1 Coulomb = 6.23 x 10^18 Electrons
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What unit is electrical current measured in? |
Amperes |
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What is the equation for calculating electrical charge |
Q = I x T Charge = Current x Time |
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How many joules per second are consumed by 100 Watts of power? |
100 Joules 1W = 1 joule per second |
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Loudspeakers are analogous to what type of electrical component? |
A resistor |
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In order, what do the four colour bands on a resistor mean? |
Band 1 = 1st digit Band 2 = 2nd digit Band 3 = Multiplier Band 4 = Tolerance (+/-) |
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What does Kirchoff's law state? |
In circuits wired in series voltage is shared betweenresistors while current remains the same across the entire circuit.
In circuits wired in Parallel current is shared between the resistors while voltage remains the same across the entire circuit.
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What is the equation used to calculate the resistance in a parallel circuit |
1 / 1/R1 + 1/R2 + 1/R3 + 1/Rn + 1/ Rn etc.. |
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To calculate the resistance in a parallel circuit what should you put in the calculator? |
This would be for a resistance of 10 Ohms |
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What is the function of a capacitor? |
Temporarily Stores Charge If fed with AC they will block DC |
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Describe the structure of a capacitor |
Capacitors consist of two metal plates separated by a non conductive material called the 'Dieletric' |
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What is capacitance measured in? |
Farads |
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The time is takes to charge a capacitor is determined by what equation? |
1 x t capacitor is 63% charged 3 x t capacitor is 95% charged 5 x t capacitor s 99% charged |
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True or False A high frequency AC current fed into a capacitor will result in low capacitive reactance? |
True |
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True or False A low frequency AC current fed into a capacitor will result in high capacitive reactance? |
True |
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What is Impedance? |
Impedance is the overall resistance taking into account capacitive reactance and direct resistance. |
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Describe an inductor |
An indictor is created when passing a current through a wire which has been coiled around. |
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A current carrying conductor will induce what around itself? |
A magnetic field |
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Magnetic fields are represented with what? |
Flux lines |
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The number of flux lines describes what? |
Flux density |
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What is Bridged Impedance Matching? |
When the load impedance is equal to or greater than 10 times the output impedance |
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What will happen to the magnetic field if a conductor carries AC current? |
The magnetic field will move inwards / outwards of the conductor itself. |
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What happens when an accelerating magnetic field line crosses a second parallel inductor |
EMF (Electro Magnetic Force) is generated. |
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What is 'Back EMF' |
When a conductor is coiled magnetic fields will cut through the original conductor itself. The conductor will induce EMF upon itself that will oppose its own current flow. This is what is known as 'Back EMF' |
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What is inductance measured in? |
Inductance is measured in Henry's |
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What will be the 'Back EMF' produced by an inductor of 1 henry |
1Volt |
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Reactance and Resistance combine into what? |
impedance (Z) |
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What is the equation for calculating impedance? |
Where Z = Impedance R = Resistance X = Reactance |
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What kind of filter do you get if you pass output across the capacitor in a circuit that is wired containing both a capacitor and a resistor wired in series? |
Low Pass Filter |
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What kind of filter do you get if you pass output across the resistor in a circuit that is wired containing both a capacitor and a resistor wired in series? |
High Pass Filter |
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What is an LCR circuit? |
When a capacitor, inductor and resistor are wired in series low frequencies will 'drop across' the capacitor high frequencies will 'drop across' the inductor mid frequencies will 'drop across' the resister |
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Describe what the 'Cut Off' frequency of a filter is? |
The cutoff frequency of a filter is the frequency that is attenuated by -3dB The position of a filter is given by its 'Cut Off' frequency. |
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What formulae is used to calculate the cutoff frequency of a CR (capacitor resistor) filter? |
F -3dB = 1 ÷ (2π C R) Where F -3db = cut-off frequency C = capacitance R = Resistance |
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What is a transformer? |
Transformers consist of two wires wound around a magnetic core. The primary coil induces a magnetic field in the core and the core subsequently induces an (EMF) voltage in the second coil. This way it is possible to step up or down voltage and current. |
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What equation may be used to calculate voltage changes in step up / down circuits? |
V out / V in = NS / NP NS > NP (Step up transformer) NS < NP (Step down transformer) Where NS = Number of secondary coil windings NP = Number of primary coil windings |
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What is a Diode? |
A diode is semi conductor device that normally only allows current to travel in one direction |
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What are the three general guidance values used for Impedance matching? |
Low impedance = Less than 600 Ω Medium impedance = 600 Ω - 10 kΩ High impedance = More than 10 kΩ |
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What do DI (Direct Injection) boxes do to the impedance of a device? |
They lower it. |
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What is the main component of a DI box? |
The Transformer |
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What is an 'Active' DI box? |
This type of DI box is able to match impedance without the use of a transformer to step down voltage. |
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What electrical function is performed by a microphone? |
A microphone is an electroacoustic Transducer |
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What are the main characteristics of a dynamic microphone? |
Requires large SPL to begin transduction Slow transient response Less sensitive to smaller variations in SPL Limited High Frequency response Resilient (Can withstand high SPL) Less transparent (colour sound) Muddier in mid frequencies Effective when placed close to sound source |
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What is a 'Humbucking' coil? |
Eliminates Hum (Noise) by means of common mode rejection similar to the principles behind balanced cables. |
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What are the main characteristics of a Ribbon Microphone |
Fragile construction (Ribbon made of aluminium) Fast transient response Low impedance (requires transformer) Sensitive to wind Fast directional microphone (bi directional) Prone to proximity effect |
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Describe the principle of directionality |
Directionality is a measure of the microphones sensitivity to sound relative to the direction or angle from which it arrives |
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What is a 'Polar pattern' ? |
A polar pattern is a graph plotting the variation of sensitivity in 360 degrees of a given microphone.
0 degrees represents the front of the Mic. |
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What are the main characteristics of a condenser microphone? |
Low output (an internal amplifier is usually part of the microphone design) Very fast transient response times Highly sensitive with an extended HF response Should be placed further away from sound sources. Prone to feedback in live applications |
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What is compansion? |
A combination of compression / expansion used to return a compressed signal to its original dynamic range. Used in noise reduction. |
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What is ducking? |
Inverts the function of a gate so the gate stays open when signals drop below the threshold. Used with a key input (classically a mic input used in radio broadcasts) |
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Describe the function of a 'Transistor' |
Transistors are semi-conductors used commonly for current amplification and control, and as switches. |
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What material are most modern day microphone diaphragms made of? |
Mylar (a very elastic plastic) |
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What is the frequency range boost of a dynamic microphone that is caused by mechanical resonance? |
300 Hz |
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In order to avoid inherent phase cancellation issues which to microphone types should not be used at the same distance from the sound source? |
Dynamic & condenser mics |
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What type of waveform cannot be reproduced by a dynamic microphone |
A Square wave
A dynamic microphone cannot reproduce a square wave because it generates voltagebased on diaphragm movement (i.e. produces no output voltage when static).
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What is a SDC? List some of its characteristics |
Small Diaphragm Condenser Front load Better at high SPL (less sensitive) Greater dynamic range Greater frequency Higher self noise |
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What is a LDC
List some of its characteristics |
Large Diaphragm Condenser
Opposite of a SDC as well as:
More colour Less transparent Lower self noise |
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Name the 5 main 'Polar Patterns' |
Cardioid Figure of 8 (Bi directional) Hyper Cardioid Super Cardioid Omni Directional |
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Which microphone 'polar pattern' does not exhibit the proximity effect. |
Omni Directional microphones |
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How much time should you leave a valve microphone to both warm up and cool down.? |
1 hour to warm up. 10 minutes to cool down. |
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What should you always use with a ribbon microphone? |
A pop shield |
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What type of music are Small Condenser Microphones almost always used to record? |
Classical music. An SDC is very transparent which is ideal for classical music. |
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What unit is microphone sensitivity usually measured in |
Microphone sensitivity values may be expressed in miliVolts per Pascals or as a dB value referenced to 1 volt per Pascal. |
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What is 'self noise' ? |
This is the noise produced by amicrophone’s circuitry and design. Self-noise is usually described in decibels with a weighting curve applied. |
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What is the difference between a 'Pure pressure microphone' and a 'pressure gradient microphone' |
In a pure pressure microphone only pressure matters, sound only reaches one side of the mic. In a pressure gradient microphones it only matters that there is adifference between front and back of the diaphragm |
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What are the latin terms for the auditory ossicles? |
Malleus (Hammer) Incus (Anvil) Stapes (Stirrup) |
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What is the 0 dBu voltage for Broadcast equipment? |
+8 dBu 1.95 Volts |
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What is the standard dBu level and voltage for Broadcast equipment? |
+8 dBu 1.95 Volts |
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What is the standard dBu level and voltage for Professional equipment |
+4 dBu 1.228 Volts |
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What is the dBu level for Hi-Fi equipment |
-10dBu 0.245 Volts |
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What is the standard level for dBu and voltage on Semi-Pro Equipment? |
-10 dBV 0.225 Volts |
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What is the standard level for dBu and voltage on Semi-Pro Equipment? |
-10 dBV 0.316 Volts |
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What do the 4 bands on a resistor denote? |
Band 1 = 1st digit Band 2 = 2nd digit Band 3 = Multiplier Band 4 = Tolerance |
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What are the resistor band colour codes? |
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List the main components of a loudspeaker? |
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What is loudspeaker cone compliance? |
High compliance = easy to move the cone Low compliance = difficult to move the cone |
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What is the loudspeaker damping factor? |
he amplifier’s ability to control the loudspeaker (excursions) |
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What is the frequency of concert pitch? |
A4 = 440 hZ |
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What is the frequency of C5? Review frequency chart for the audio spectrum |
C5 = 523.5 Hz |
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What is the frequency of middle C? |
261.62 Hz |
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True or false If you add multiple logarithms with the same base you can multiply the arguments |
True |
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True or false If you are multiplying the same base you can add the exponents |
True |