Sample Rate + Bit Depth | 2.4 | OCR GCSE Computer Science | J277

13 flashcards

How do we sample sound?: The amplitude (height) of the sound wave is measured / recorded at specific intervals.
Sample rate: The number of samples taken per second (Hz)
Why must analogue signals recorded by a microphone be converted into digital data?: So that the computers can read and store the sound file. This is done by analogue-digital converters.
What effect does a higher sample rate have on audio quality?: It will increase the audio quality as more sample are taken per second - resulting in a more accurate representation of the original sound wave.
What effect does a higher sample rate have on file size?: It will increase the file size as a binary value is recorded for each sample and more samples will be stored.
Why is a disadvantage of digital data?: It is not continuous like analogue data - therefore data is lost. e.g. the last peak on an analogue wave is much flatter in the digital data.
What is the bit depth (of an audio file)?: The number of bits available to represent each sample.
How many possible sounds does a bit depth of 4 bits give?: 16 possible sounds. (2⁴).
How many possible sounds does a bit depth of 2 bits give?: 4 possible sounds. (2²).
How does a higher bit depth affect audio quality?: Higher bit depth means more bits are available to be used and therefore the audio is clearer and more accurate. The microphone also picks up on quieter sounds.
How does a higher bit depth affect file size?: As each sample stores additional bits.
How is bit depth calculated?: file size = sample rate x bit depth x length (s)
Example: A sound file has a sample rate of 40 hertz and a bit depth of 6 bits. It lasts for 12 seconds. Give the answer in KB.: 40 x 6 x 12 = 2,880 bits 2,880 / 8 = 360 bytes 360 / 1000 = 0.36 kB