# Computing - Sound

> Source: https://ollybritton.com/notes/a-level/computing/topics/sound/ · Updated: 2020-10-15 · Tags: computing, school, safe-to-post-online

##### What is the main difference between an analogue and digital signal??
Analogue signals are continuous while digital signals are discrete.

##### In one sentence, how does a digital-to-analogue converter for sound work??
Sound is captured by a microphone which is sampled at regular intervals and these samples are converted to binary.

##### The frequency at which samples of a sound are taken is called??
The sampling rate.

##### When an analogue sound signal is being converted to digital, what value is sampled??
Amplitude/voltage.

##### What is sample resolution??
The amount of bits used to record each sample.

##### What is the benefit of a higher sample resolution??
More accurate representation of the analogue sound.

##### What is the drawback of a higher sample resolution??
A larger file size.

##### What is the formula for file size of a sound??
$$
\text{file size} = \text{sample rate} \times \text{resolution} \times \text{length in seconds}
$$

##### What is the symbol representation of Nyquist Theorem??
$$
f_s > 2f_{\text{max}}
$$

##### What does $f_s$ stand for in the Nyquist Theorem??
Sample rate.

##### What does $f_{\text{max}}$ stand for in the Nyquist Theorem??
The max frequency in the sound.

##### What does the Nyquist Theorem state??
That the sample rate should be __over__ two times the highest frequency in order to create an accurate sample.

##### The theorem that the sample rate should be __over__ two times the highest frequency is called??
The Nyquist Theorem

##### Why are CDs sampled at $44.1kHz$??
Because the max of human hearing is $22kHz$, so it's over double.

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