Representing sound: rate = sampling rate

The idea

In the sound file-size formula, 'rate' means the sampling rate: the number of samples taken from the sound wave each second, measured in hertz (Hz). A higher sampling rate captures the wave more closely and produces a more accurate recording, but it also increases file size because more samples are stored per second. For example, a rate of 44,100 Hz means 44,100 samples are taken every second. Distinguish sampling rate (samples per second) from resolution or bit depth (bits per sample): rate is how often you measure, resolution is how precisely each measurement is stored. Both multiply with duration to give file size in bits.

What earns the marks

• Define rate as the sampling rate, the number of samples taken per second.
• State the unit of sampling rate as hertz (Hz).
• Distinguish sampling rate (samples per second) from resolution or bit depth (bits per sample).
• Explain that a higher sampling rate improves accuracy but increases file size.

Common mistakes and how to put them right

• Confusing sampling rate with resolution.

  Put it right: Rate is samples per second (Hz), while resolution is bits per sample.

• Giving the unit of sampling rate as bits rather than hertz.

  Put it right: Bits describe resolution, not rate.

• Assuming a higher sampling rate reduces file size.

  Put it right: In fact more samples per second increase it.

Exam tips

• Quote the unit (Hz) whenever you state a sampling rate to show understanding.
• Contrast rate and resolution explicitly in one sentence to avoid mixing them.
• Link a change in rate to both accuracy and file size for full credit.