T2 - Sound + Compression

Question 1

Analogue sound signals are which type of data

Answer 1

continuous.

Question 1

Digital signals are which type of data

Answer 1

discrete.

Question 2

How Sound is digitized:

Answer 2

by repeatedly measuring + recording the sound wave

Question 3

A to D converters:

Answer 3

Sounds is converted to a digital form
= stored + processed by a computer

Question 4

An Analogue to Digital Convertor (ADC) is used for

Answer 4

to convert inputs to digital signals.

Question 5

A Digital to Audio Convertor (DAC) is used for

Answer 5

to convert digital signals to outputs.

Question 6

Sound sampling -

Answer 6

measurement of amplitude of a
sound wave at a given time

Question 7

How is sound sampled:

Answer 7

• Sound is sampled using a bit depth and sample rate

Question 8

what does bit depth determine in sound sampling

Answer 8

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

Question 9

Sampling rate -

Answer 9

number of samples taken per second
(Hz)

Question 10

Sample resolution:

Answer 10

The number of bits used to record
each measurement

Question 11

More bits used per sample =

Answer 11

• the height of the wave to be more accurately measured
• increases file size

Question 12

Hertz

Answer 12

• 1Hz = 1 sample per second

Question 13

sample resolution aka

Answer 13

audio bit depth

Question 14

Sampling rate frequency:

Answer 14

The greater the frequency, the greater the accuracy, and file size

Question 15

Calculating sound file sizes:

Answer 15

sample rate * bit depth * duration

Question 16

Recording quality improves: as a result of

Answer 16

the more frequent
the more accurately recorded the wave height

Question 17

Increasing the sampling rate (frequency) =

Answer 17

means recording more data points

Question 18

Increasing the bit-rate =

Answer 18

improves the accuracy of each data point

Question 19

Lossy compression:

Answer 19

removes sounds that
we can’t easily hear or that is unnecessary

Question 20

Lossy compression cons:

Answer 20

-leaves out some data
=affects quality

Question 21

Lossy compression pros:

Answer 21

useful for storing,
downloading or streaming
-as it is smaller

Question 22

Lossless compression:

Answer 22

-reduce the file size
when compressed but do not
lose any information
-can be decompressed

Question 23

Eg of lossless:

Answer 23

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

Question 24

Uses of compression:

Answer 24

often used for files and data that are sent via the internet
Download times are reduced
Data allowances go further
No lagging

Question 25

Benefits of compression: (6)

Answer 25

• Smaller files = fewer packets = faster transmission time
• Quicker to complete transmission
• Reduces traffic over the Internet
• Reduces download times
• Images inside web pages appear faster
• Reduces space on disk / servers

Question 26

no lagging means

Answer 26

= transmission of
video + music data streams as fast as they are playing