Each sample of a sound is stored as a binary number.
Describe how bit depth affects the stored value of a sound sample.
Mark scheme
Award up to two marks for a linked description such as:
- The bit depth is the number of bits used to store each sample/measurement (1) so a higher bit depth gives more possible/discrete values for the amplitude (1)
- A higher bit depth records the amplitude more accurately (1) because the stored value can be closer to the actual height of the wave (1)
- A low bit depth gives fewer possible amplitude values (1) so the amplitude is rounded to the nearest value, making the recording less accurate (1)
Do not accept sample rate/sample interval (number of samples per second) in place of bit depth.
Do not accept 'more bits gives better quality' or 'more accurate' on its own, without a development linked to the number of values or the amplitude stored.
Do not accept file size on its own, and a file size point cannot earn the second mark, as it does not describe the stored value.
Example answers and how they were marked
The bit depth is the number of bits used to store each sample, so a higher bit depth gives more possible values for the amplitude that can be stored.
Why: First point, the number of bits per sample (1), then the linked development, more possible values for the amplitude (1).
The bit depth is the number of bits used to store one sample.
Why: Gives the first point, the number of bits per sample (1), but does not develop how this affects the value that is stored.
A higher bit depth makes the sound better quality and more accurate.
Why: Near-miss: 'better quality' and 'more accurate' on their own, with no development linked to the number of values or the amplitude, so no mark is awarded.