Data Representation - Sound

Question 1

What piece of hardware would you use to input sound into a computer?

Answer 1

Microphone

Question 2

How is sound stored as binary?

Answer 2

• Audio file is inputted through a microphone and broken down into thousands of samples per second,
• The more samples recorded per second the higher the quality of the audio file,
• Each sound sample is stored as Binary Data

Question 3

What is the correct order of stages in converting sound into a digital form

A - binary representation of level stored

B - microphone picks up sound waves

C - value read at specific point and rounded to a level

D - sound wave is converted to an electrical analogue signal

Answer 3

B - microphone picks up sound waves

D - sound wave is converted to an electrical analogue signal

C - value read at specific point and rounded to a level

A - binary representation of level stored

Question 4

What is sample rate?

Answer 4

The number of samples taken…per second

Question 5

What unit is sample rate measured in?

Answer 5

Hertz (Hz)

Question 6

What is measured when the wave is sampled?

Answer 6

Amplitude

Question 7

What does a sample represent?

Answer 7

Each sample represents the amplitude of the digital signal at a specific point in time

Question 8

The amplitude of a sound wave is…

Answer 8

how high the wave is from the crest or trough

Question 9

Explain the process of sound sampling

Answer 9

• Sampling is a method of converting an analogue sound signal into a digital file.
• At specific intervals (frequency) a measurement of the amplitude (bit depth) of the signal is taken.

-The higher the sampling rate / bit depth the better the quality of the sound file

Question 10

Describe how sound samples are stored

Answer 10

• The amplitude of each sound sample is converted into the equivalent binary number.
• The whole collection of data (binary numbers) is then stored in a digital file.

Question 11

Why does sound need to be sampled to be stored in a computer?

Answer 11

Sound exists as waves – however as computers only understand binary values this needs to be converted into such

Question 12

Define sampling resolution

Answer 12

number of bits…used to represent a sample

Question 13

What 3 things happen if you increase the sample rate?

Answer 13

• Better quality of recording
• Needs greater storage space
• Larger file size

Question 14

Why does increasing the sample rate increase sound quality?

Answer 14

• More detail about where the waves are recorded

- the shape of the sound wave is captured more accurately

Question 15

What sample rate is used for CD quality sound?

Answer 15

44,100 Hz

Question 16

What is the sample rate of telephone networks and VOIP services?

Answer 16

8 kHz

Question 17

Why do CDs provide better quality audio than telephone networks?

Answer 17

CDs have a higher sample rate (44,100 Hz) than telephone networks (8hz)…this leads to higher quality audio because there is more information about the audio

Question 18

What is Bit Rate?

Answer 18

The number of bits used per second of audio

Question 19

What are Bit rates are usually measured in?

Answer 19

kilobits per second (kbps)

Question 20

What is meant by bit depth?

Answer 20

The number of bits used to store each sound sample

Question 21

What happens when you increase bit depth when recording sound digitally?

Answer 21

The higher the bit depth, the higher the quality of the audio

Question 22

What happens when you decrease bit depth when recording sound digitally?

Answer 22

The lower the bit depth, the lower the quality of the audio

Question 23

How do you calculate bit rate?

Answer 23

Frequency × bit depth × channels = bit rate

Question 24

Give three examples of metadata stored in sound files

Answer 24

Artist  Title 
Track Title  
Album Title
Track Number  
Date Created / Year  
Genre  
Comments  
Copyright  
Duration  
File size  
Bit rate  
Sampling rate

Question 25

How do you calculate the storage requirements for the sampled sound data.

Answer 25

Storage size = sampling rate x sampling resolution x number of seconds the (original/analogue) sound lasts

Question 26

Describe how a lossy algorithm would compress the sound file

Answer 26

• Sound files are compressed using a lossy algorithm by analysing the waveform and removing sound that cannot be heard by people.
• To increase the compression, lossy algorithms remove more data which reduces the quality of the sound file (lowers fidelity)

Question 27

How do you calculate the compression ratio.

Answer 27

Original file size divided by compressed file size

Question 28

The purpose of a Digital to Analogue converter is to…

Answer 28

convert binary data into analogue form so we can hear it via a speaker