Sample rate and bit depth

analogue waveform

amplitude which has a value between minimum and maximum

analogue to digital conversion

taking samples of the momentary amplitude of the waveform

a continuous analogue signal is converted into a series of binary numbers

Microphone conversion

Analogue to digital conversions

converting air pressure to voltage

Speaker Conversion

Digital to analogue conversions

voltage to air pressure

Sample rate

number of times amplitude of the signal is read during the conversion/sampling process

measured in hertz

determines the frequency response

CD and DVD quality levels

16 bit or 24 bit

DVD: 48kHz CD: 44.1kHz

Nyquist’s theoreom

Sample rate should be double human hearings frequency capture capabilities (20kHz)

Aliasing

when the sample rate is not high enough producing inaccuracies in frequency reproduction

creating unwanted artefacts

Bit Depth

level of detail of the amplitude measured on each sample

higher bit depth the greater the dynamic range

better the signal to noise ratio

dithering

randomly generated noise introduced in the conversion process

randomises the effect of quantisation error

can mask distorted noise or abrupt cutoffs in signals

Shure SM58 frequency response

Frequency boost between 4kHz-10kHz

helps the signal cut through the mix

giving clarity and brightness

Frequency boost reduced between 7-8kHz

controls shrill high frequencies and sibilance

Roll off above 10kHz means less detail

roll off below 100 Hz limits capture of rumble

when an analogue signal experiences interference

picks up noise

impacting the waveform

when a digital signal picks up noise

doesn’t degrade quality if noise is picked up