AQA · GCSE · Computer Science
Course version: 8525 · Version from Sept 2020
Representing sound: secs = number of seconds
In the sound file size formula, secs is the duration of the sound in seconds.
Checked against the AQA 8525 specification (opens in a new tab) on .
- Point 12 of 12
Study notes
From the checked teaching notes for this specification point.
The idea
In the sound file size formula, secs is the duration of the sound in seconds. It is the time term multiplied with sample rate and resolution to give total bits. For example, a 30-second recording uses secs = 30. If a duration is given in minutes, convert to seconds by multiplying by 60 before substituting. The formula is: size in bits = sample rate × resolution × secs; divide by 8 for bytes. Recognise that secs is a time in seconds, distinct from sample rate (samples per second in hertz) and resolution (bits per sample).
What earns the marks
- Secs represents the duration of the sound measured in seconds.
- Durations in minutes must be converted to seconds (multiply by 60) before use.
- The full bit size is sample rate × resolution × secs, divided by 8 for bytes.
Common mistakes and how to put them right
Using minutes directly in the formula.
Put it right: Convert to seconds by multiplying by 60.
Confusing secs with sample rate.
Put it right: Secs is duration; sample rate is samples per second in hertz.
Omitting secs from the calculation.
Put it right: All three terms (rate, resolution, seconds) are needed.
Exam tips
- Check the unit of any duration given and convert to seconds first.
- Write the formula with all three terms before substituting values.
- Convert the final bit total to bytes by dividing by 8.
Try the lesson
The start of the Representing sound: secs = number of seconds lesson, made from checked teaching notes for this specification point.
Have a go first
A sound is recorded for 4 seconds at a sample rate of 8000 samples per second. How many samples are taken in total?
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