Sound

Submitted by: Uttam Shrestha014A058

Contents1.1.3 Sound• show understanding of how sound is

represented and encoded• use the associated terminology: sampling,

sampling rate, sampling resolution• show understanding of how file sizes depend

on sampling rate and sampling resolution• show understanding of how typical features

found in sound-editing software are used in practice

How sound is represented and encoded?In order to digital record sound, a

microphone is used, a device that converts the analogue sound into a digital form by altering the output signal from the device.

In order to store this digitally, the voltage is sampled at frequent intervals (typically 48 000 times per second, or 48kHz) and stored as a binary code (typically 16 or 32 bits per sample).

SamplingIn signal processing, sampling is the

reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete-time signal).

Sampling resolutionSampling resolution is the number of bits assigned to

each sample.A more accurate representation of the analog signal can

be achieved if more bits are used to store each sample.Sampling resolution  determines how many gradations

of amplitude (corresponding to loudness) can be represented in the digital waveform.

The sampling resolution allows you to set the range of volumes storable for each sample. If you have a low sampling resolution then the range of volumes will be very limited, if you have a high sampling resolution then the file size may become unfeasible. The sampling resolution for a CD is 16 bits used per sample.

Sample rate (Sampling Rate)The sample rate is the number of samples of a

sound that are taken per second to represent the event digitally.

The more samples taken per second, the more accurate the digital representation of the sound can be. For example, the current sample rate for CD-quality audio is 44,100 samples per second. This sample rate can accurately reproduce the audio frequencies up to 20,500 hertz, covering the full range of human hearing.

File sizeTo work out the size of a sound sample

requires the following equation:File Size = Sample Rate * Sample

Resolution * Length of sound

So, file size increases with increase in sample resolution and sample rate.

Sound editingRepresenting sound in digital form allows for editing this might mean removing background noise or specific frequencies. It might mean cropping or merging with other sounds.