2.5 Sound

Question 1

Analogue signals

Answer 1

Continous

Question 2

Digital signals

Answer 2

Discrete

Question 3

How is sound digitised?

Answer 3

By repeatedly measuring and recording the sound wave

Question 4

How can a computer store sound?

Answer 4

It must convert it into a digital form in order to be stored and processed

Question 5

ADC

Answer 5

Analogue to Digital Converter is used to convert inputs to digital signals

Question 6

DAC

Answer 6

Digital to Audio Converter is used to convert digital to outputs

Question 7

What is a sound sample?

Answer 7

A measurement of amplitude of a sound wave at a given time

Question 8

How is sound sampled?

Answer 8

Using a bit depth and sample rate

Question 9

Bit depth

Answer 9

Determines how closely the wave is sampled on the y-axis

Question 10

Sample rate

Answer 10

The number of samples taken per second (measured in Hz)

Question 11

Sample resolution

Answer 11

The number of bits (audio bit depth) used to record each measurement

Question 12

What is the effect of more bits per sample?

Answer 12

The accuracy of the recording is increased but so does the size

Question 13

1Hz = ?

Answer 13

1 sample per second

Question 14

What is the sample rate for a typical CD?

Answer 14

Sampled at 44,100Hz

Question 15

How to calculate sound file sizes?

Answer 15

File size (bits) = sample rate x bit depth x duration

Question 16

What does recording quality improve?

Answer 16

• The more frequently we sample the sound

- The more accurately we record the wave height

Question 17

What does increasing the sampling rate mean?

Answer 17

Recording more data points

Question 18

What does increasing the bit rate increase?

Answer 18

The accuracy of each data point

Question 19

What is the human hearing range?

Answer 19

20-20000Hz

Question 20

Lossy compression - MP3

Answer 20

Removes the sound that we can’t hear easily hear or that least affect the perceived playback quality

Question 21

How can lossy compression affect Sound quality?

Answer 21

It can reduce the sound quality which is negative

Question 22

What are the benefits of lossy compression?

Answer 22

Useful for storing, downloading or streaming

Question 23

Lossless compression

Answer 23

Reduce the file size when compressed but do not lose any information

Question 24

Give some lossless compression formats

Answer 24

• FLAC (Free Lossless Audio Codec)
• ALAC (Apple Lossless Audio Codec)
• WMA (Windows Media Audio)

Question 25

Give some uncompressed audio file formats

Answer 25

WAV and AIFF