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Data Representation and Multimedia: Question 10

Syllabus 1.1, 1.2, 1.3

Multiple choice AS 1 mark

A stereo sound recording (i.e. two audio channels, left and right) is digitised using a sampling rate of 22,050 samples per second and a sampling resolution of 8 bits per sample, for a duration of 10 seconds.

What is the uncompressed file size of this stereo recording, in bytes?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Number of samples per channel

Sampling rate multiplied by duration gives the number of samples taken by one channel:

22,050 samples/second x 10 seconds = 220,500 samples

Converting to bytes for one channel

Each sample uses 8 bits of sampling resolution. Total bits for one channel:

220,500 x 8 = 1,764,000 bits

Converting bits to bytes (divide by 8):

1,764,000 / 8 = 220,500 bytes

(This division undoes the earlier multiplication by 8, so for 8-bit sampling resolution specifically, the number of bytes per channel is always equal to the number of samples.)

Accounting for both stereo channels

A stereo recording stores two independent channels of samples (left and right), each needing its own 220,500 bytes:

220,500 x 2 = 441,000 bytes

Final answer

  • 441,000 bytes (option A)