Representing sound

Question 1

Define digital

Answer 1

Data that takes form of Discrete values

Question 2

Define analogue

Answer 2

Data that varies in a continuous manner

Question 3

Define sampling resolution

Answer 3

Number of bits assigned to each sample

Question 4

Define sampling rate

Answer 4

Number of samples per seconds, in hz

Question 5

Define quantisation

Answer 5

Rounding sample value as a binary number

Question 6

Define Nyguists’ theorem

Answer 6

Most sample frequency is at least 2* rate of highest frequency in the analogue signal. This ensures that the original signal can be reconstructed exactly by the DAC

Question 7

What is the process of sound conversion

Answer 7

1. Pick up sound waves with a microphone. This converts it to analogue electrical signals
2. Signals processed by analogue to digital converter (ADC), which converts it to digital values using sampling. This is done by taking measurements of amplitude of the analogue signal at regular time intervals. Measurements then quantised into binary pattern and stored in computer memory

To play digital audio file:

3. Convert sound from digital values into analogue electrical signals using digital to analogue converter
4. Analogue signals then passed to speaker, vibrates speaker cone to move air to create analogue sound waves
5. Analogue waves produced may differ from o.g sound waves

Question 8

What is MIDI file type

Answer 8

Music information digital interface
Used to record and synthesise musical instruments
Editable files - so are smaller in size

Question 9

What is WAV file type

Answer 9

Used on CDs and editing

Question 10

What is MPEG file type

Answer 10

Lossy compression
Remove frequency outside 20Hz-20KHz
MP4 used most widely for distribution

Question 11

What are advantages of MIDI

Answer 11

Compared to other file type MIDI files are smaller
They are editable
Wide range of instrument support
MIDI files produce high quality authentic reproduction of every instrument.