Full marks6/6
Each sample measures the amplitude of the speech wave and stores it as a binary number. The bit depth is the number of bits used for each sample, so with 4 bits there are only 16 possible amplitude values, but with 16 bits there are 65,536. A higher bit depth therefore lets the app record the loudness of the speech more accurately, because each sample can be closer to the real wave and quiet sounds are less likely to be rounded away. This makes the voice memo sound clearer. However, every sample uses more bits, so a higher bit depth creates a larger file, which takes up more storage on the phone and may take longer to send. The developer should choose a bit depth that keeps speech clear without making the files unnecessarily large.
Why: Level 3 (6 marks): explains amplitude stored in binary, how bit depth gives more values and accuracy, and the file-size trade-off, applied to the voice memo app.
Some marks3/6
The bit depth is the number of bits used for each sample. A higher bit depth means the amplitude can be stored more accurately because there are more values. But it makes the file larger. The app should use a high bit depth for clear speech.
Why: Level 2 (3 marks): covers bit depth, accuracy and file size briefly with some linkage, but lacks detailed reasoning.
Some marks1/6
The bit depth is the number of samples taken per second. A higher bit depth means more samples are taken, so the file is smaller and the speech is more accurate.
Why: Level 1 (1 mark): a basic idea that more accuracy is linked to higher bit depth, but bit depth is confused with sample rate and the file-size effect is wrong.