3.5 - Representing Sound

Question 1

What is the difference between digital and analogue signals?

Answer 1

Analogue = continuous
Digital = discrete
Both can be converted to form one another

Question 2

How are analogue sound samples recorded?

Answer 2

Via an amplifier:
1) Each sample is quantised to measure the wave height and translate this into an integer value
2) The integer value is converted and stored digitally as a binary value
3) To output the sound the reverse is done

Question 3

What is the sample resolution?

Answer 3

Number of bits used to record each measurement
Amplitude
Higher sample resolution = more accurate measurement of amplitude but file size increases

Question 4

What is the sampling rate? What does it affect?

Answer 4

Number of samples taken in 1 second (Hz)
Level of detail in digital representation

Question 5

What is the formula for sample size?

Answer 5

Sample rate x sample resolution x length (s)

Question 6

What is Nyquist’s Theorem?

Answer 6

Samples must be twice the highest frequency in order to replicate the original kind wave as sound a made up of many components each at different frequencies
fs> 2f max

Question 7

What is the human hearing frequency?

Answer 7

20Hz - 20kHz

Question 8

What does MIDI (musical instrument digital interface) do?

Answer 8

Creates sounds as entered from an instrument or piece of software

Question 9

What are the benefits of MIDI?

Answer 9

Full sound signal doesn’t need to be transmitted only the instructions to play the puns need to be transmitted as event messages

Question 10

How to event messages work?

Answer 10

A sound processor can be lined to several instruments or computers
So timed sequences of event messages can be sent such as:
- synchronise tempo
- control tempo
- control pitch