Analogue sound is converted to binary by sampling at regular intervals.
Explain one reason why increasing the sample rate improves the quality of a digitised sound.
Mark scheme
Award up to two marks for a linked explanation such as:
- More samples are taken every second / the sample rate is higher (1) so the digital wave follows the shape of the analogue wave more closely (1)
- The amplitude is measured more often / at shorter intervals (1) so fewer changes in the sound are missed between measurements (1)
- The sample interval is shorter (1) so less of the sound wave is lost/goes unrecorded between samples (1)
- More data points are recorded for the same length of sound (1) so the digital representation is a closer copy of the original sound (1)
For both marks, the expansion must follow/associate with the statement.
Do not accept 'the quality is better/higher' or 'the sound is clearer' as a point on its own without a reason such as more samples or more detail.
Do not accept 'the samples are more accurate' or 'more data is collected' without saying what becomes more accurate or what the extra data records.
Do not accept 'the file size is larger' as a reason for improved quality.
Do not accept answers about using more bits per sample, as these describe bit depth, not the sample rate.
Example answers and how they were marked
More samples are taken every second, so the digital representation follows the shape of the analogue wave more closely.
Why: Point (more samples each second) (1) with linked reason (follows the analogue wave more closely) (1).
More samples are taken every second.
Why: Creditworthy point (1) but no linked reason about what the extra samples achieve, so stays on one mark.
Each sample is stored using more bits, so every measurement is more accurate.
Why: This describes bit depth, not the sample rate, so neither mark is awarded.