Key terms

Sampling rate – how often we read the value of the signal

Resolution – the separation between “levels” for our samples (can we read the value to the nearest 1V, or 0.1V)

Bits per sample – the number of bits (binary digits) we need to record the value we measure.

Quantisation error – these are errors introduced when the signal resolution is insufficient.(e.g. signal value = 0.115V, we record

0.1V)

Key terms

Shannon-Nyquist theorem – states that the sampling rate must be at least twice the highest frequency component in order to accurately reproduce the signal.

Aliasing – spurious low frequencies not present in the original signal, which are introduced when the sampling rate is too low(think of the “wagon wheel effect”…!)

Starter questionA 30 second audio sample has a peak to peak voltage of 1.5V.

The signal is digitised, using 14 bits per sample and a sampling rate of 40kHz.

1. How many levels does this give?

2. What will the voltage resolution of the signal be?

3. What is the time separation between samples?

4. What is the maximum frequency component that can be accurately reproduced in the signal?

5. How much data is required to store one second of the signal?

6. How much data is required to store the entire signal?