(a) The diagram shows an analogue sound wave being digitised. Explain what the black dots on the diagram represent. [2] (b) Explain why the digitised versio...

(a) Explain what the black dots on the diagram represent. [2]

The black dots are sample points where the amplitude (loudness) of the analogue sound wave has been measured and recorded as a digital value. [1] Each dot captures the height of the wave at one specific moment in time. The analogue-to-digital converter (ADC) takes these measurements at regular intervals determined by the sampling rate. [1]

(b) Explain why the digitised version is not a perfect copy. [2]

The digital recording only captures the wave's amplitude at the discrete sample points, so any changes in the sound between samples are missed entirely. The faster the wave changes, the more detail is lost between samples. [1] Additionally, the amplitude value at each sample is rounded to the nearest level allowed by the bit depth (this is called quantisation). If the true amplitude falls between two available levels, the recorded value is an approximation, introducing a small error called quantisation noise. [1]

(c) Describe two ways the accuracy of the digital recording could be improved. [2]

Way 1: Increase the sampling rate (take more samples per second). This captures the wave at more frequent intervals, so less detail is lost between sample points. The digitised waveform follows the original shape much more closely. [1]

Way 2: Increase the bit depth (use more bits per sample). This provides more amplitude levels to choose from, so each sample value is a closer approximation to the true amplitude. The gap between consecutive levels becomes smaller, reducing quantisation error. [1]