Representing sound
Watch the whole lecture free
Make a free account to watch every lecture to the end: 6 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
That was the teaching part. The rest of this lecture is free with an account: 6 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
No password needed now: we email you a link to set one. Already have an account? Sign in, then come back to this page.
The teaching part (1 min) is free to watch. A free account opens the whole lecture: 6 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Sound is a wave
- Sampling
- Sample
- Sample rate
- Sample resolution
Read the transcript of the teaching part
Last time
Before we start: last time, in Representing text, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Sound is a wave
When you speak, the air vibrates in a wave. That wave is analogue: it changes smoothly, with no gaps. A computer can only store separate binary numbers. So how does your voice note get stored?
Sampling
The computer measures the height of the wave, called its amplitude, at regular moments. Each measurement is a sample. Each sample is turned into a binary number and stored, one after another.
Sample
A sample is a measurement of the amplitude of the sound wave at one moment in time. The amplitude is the height of the wave.
Sample rate
The sample rate is the number of samples taken each second. It is measured in hertz. Music on a CD uses forty-four thousand one hundred samples every second. A higher sample rate follows the wave more closely, so the recording is more accurate.
Sample resolution
The sample resolution is the number of bits used for each sample. With four bits, each sample can be one of sixteen levels. With sixteen bits, it can be one of sixty-five thousand five hundred and thirty-six. More bits means each height is measured more precisely.
Chapter 1.8: Representing sound
- Representing sound 6 min
Also for IGCSE Computer Science 0478
Which topics come up most in IGCSE Computer Science 0478 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.