Sound: Computer Science OCR: GCSE (9:1)

Analogue

The nature of sound waves, it means it varies continuously, not digital

Digital

Made up of discrete samples of numeric data.

Sample

A digital sound is broken down into thousands of these per second. Each of these is stored as binary data.

CD

Bit depth of 16 bits can be found on this optical media

DVD

Bit depth of 24 bits can be found on this optical media

Sample rate

How many samples, or measurements, of the sound are taken each second

Bit depth

The number of bits in each sample, the higher this number the more accurate the sample. This improves quality

Amplitude

Each sample taken represents this value of the digital signal at a specific point in time. It means the volume of the sound

Bit rate

The number of bits stored in the file per second of audio, it is calculated by sample rate * bit depth

Hertz

Samples per second are measured in this unit

Quality

This improves if we increase the sample rate or bit depth

File size

This goes up if we increase the quality, so we need more storage or bandwidth

Duration

How long an audio file plays for, in seconds. The longer this is the bigger the file

320

Bit rate (the number of bits per second of compressed audio) of files downloaded from most online music stores, measured in Kilobits per second (Kbps)

200KB

File size of a mono digital audio file with sample rate of 10,000 Hz, bit depth of 16 and duration of 10 seconds

9.6MB

File size of a mono digital audio file with sample rate of 20,000 Hz, bit depth of 24 and duration of 20 seconds