Topic Sixteen - Digital Sound

Question 1

What is sampling?

Answer 1

Sampling is how we convert a continuous-time signal (analog signal) into a discrete-time signal (digital signal)

It involves measuring the analog signal at particular intervals to create a sequence of numbers which can be stored digitally

Question 2

What is the sampling rate?

Answer 2

The sampling rate is how frequently we look at the changes in the signal.

Signalling rate depends on what you want to capture (fast changing signal/high frequency needs a higher sampling rate)

Question 3

What is quantisation?

Answer 3

The process of approximating a voltage amplitude with its nearest available digital representation

Question 4

What is aliasing?

Answer 4

When we under sample there is the creation of frequency components not present in the original signal. This is referred to aliasing.

Question 5

What is analog-to-digital conversion?

Answer 5

Converts an analog signal into digital

Question 6

What is digital-to-analog conversion?

Answer 6

Converts a digital signal into analog

Question 7

What are some common sampling rates and why are they used?

Answer 7

In order for a signal to be perfectly reproduced, a signal must be sampled at a rate equal to at least twice it’s highest frequency components not present (Nyquist sampling theorem)

Other sampling rates include:
44.1kHz, 48KHz, 96kHz, or 192kHz

Higher rates beyond human hearing can be used to analyze animal sounds.

Question 8

What are some common bit depths and why are they used?

Answer 8

Commonly 16 or 24 bit

More bits reduces the quantization noise

Question 9

What are the advantages to representing sound digitally?

Answer 9

• Easy to generate
• Easy to make exact copies
• Easy to store
• Easy to process by a computer