Sampling rate is the number of samples taken in a second and is usually…

The idea

Sampling rate describes how frequently a sound wave is measured when it is digitised. It is the number of samples captured in one second and is measured in hertz, where 1 hertz corresponds to exactly one sample per second. So a rate of 8 000 Hz means 8 000 samples are taken every second, and 44 100 Hz means 44 100 samples per second. A higher rate records changes in the wave more often, giving a more faithful representation but producing more data and a larger file. Sampling rate is not the same as bit depth, which is the number of bits used to store each individual sample. When answering, check the unit: hertz counts samples per second, so the number of hertz equals the number of samples taken each second.

What earns the marks

• Identifies sampling rate as the number of samples taken per second.
• States that sampling rate is measured in hertz.
• Applies the equivalence that 1 hertz equals one sample per second.
• Distinguishes sampling rate from bit depth, which is the bits per sample.
• Recognises that a higher sampling rate increases accuracy and file size.

Common mistakes and how to put them right

• Confusing hertz with the number of bits per sample.

  Put it right: Hertz counts samples per second, not bits.

• Believing 1 hertz means many samples per second.

  Put it right: It means exactly one sample per second.

• Mixing up sampling rate with bit depth when explaining accuracy or file size.

Exam tips

• Read the unit carefully: a value in hertz is a count of samples per second.
• Convert between hertz and samples per second directly, since they are numerically equal.
• Eliminate options that describe bit depth when the question asks about sampling rate.