Bit rate of digital audio

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Bit rate of digital audio

Name:
Date:
Class:
A

Quick Questions

Shade in the A or B circle for each question.

1. Which formula gives the bit rate of mono digital audio?
A Sample rate x sample resolution
B Sample rate + sample resolution
2. What does bit rate measure?
A The number of bits used to store each second of sound
B The number of seconds a sound lasts
3. A sound is sampled 100 times per second, and each sample uses 8 bits. What is the bit rate?
A 800 bits per second
B 108 bits per second
4. A sound has 1000 samples per second and 16 bits per sample. What is its bit rate?
A 1016 bits per second
B 16 000 bits per second
5. What happens to the bit rate if you increase the sample rate but keep the sample resolution the same?
A The bit rate stays the same
B The bit rate goes up
B

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left columnRight column
1bit rate = 8000 * 8 AbitRate = sampleRate * resolution
2bit rate = 44100 * 16 BThe sample rate and sample resolution are added instead of multiplied. Bit rate is sample rate x sample resolution.
3Bit rate is found by multiplying the sample rate by the sample resolution C705600 bits are stored for each second of sound
4Doubling the sample rate doubles the bit rate, so each second needs twice the storage D(2 * 8000) * 8 = 128000
5bitRate = sampleRate + resolution EA higher bit rate means MORE bits are stored for each second, so it needs more storage, not less.
6if bitRate goes up: storage per second goes down F64000 bits are stored for each second of sound
C

Definitions

bit rate
D

Fill in the Blanks

Complete each line of code by filling in the missing parts.

1.
bitRate ← sampleRate _ resolution
2.
sampleRate ← 8000 resolution ← 8 _______ ← sampleRate * resolution
3.
sampleRate ← 44100 resolution ← 16 bitRate ← sampleRate * __________
4.
IF bitRate1 _ bitRate2 THEN accuracy1 ← better ENDIF
5.
fileBits ← bitRate _ seconds
E

Spot the Error

Shade in the letter of the line that contains an error.

Question 1
A def bit_rate(rate, bits)
B return rate * bits
C print(bit_rate(8000, 16))
Question 2
A rate = 44100
B bits = 16
C bit_rate = rate + bits
D print(bit_rate)
Question 3
A rate = 1000
B bits = 8
C bit_rate = rate * bits
D print(bit_rate, 'bytes/s')
Question 4
A SET low TO 8000 * 8
B SET high TO 44100 - 16
C IF high > low THEN
D DISPLAY 'Better accuracy'
E END IF
Question 5
A bit_rate = 16000
B total_bits = bit_rate / 10
C print(total_bits)

Answer Key

Bit rate of digital audio
Section A: Quick Questions
Q1
A — Sample rate x sample resolution
Q2
A — The number of bits used to store each second of sound
Q3
A — 800 bits per second
Q4
B — 16 000 bits per second
Q5
B — The bit rate goes up
Section B: Match the Pairs
Q1
bit rate = 8000 * 8 → 64000 bits are stored for each second of sound
Q2
bit rate = 44100 * 16 → 705600 bits are stored for each second of sound
Q3
Bit rate is found by multiplying the sample rate by the sample resolution → bitRate = sampleRate * resolution
Q4
Doubling the sample rate doubles the bit rate, so each second needs twice the storage → (2 * 8000) * 8 = 128000
Q5
bitRate = sampleRate + resolution → The sample rate and sample resolution are added instead of multiplied. Bit rate is sample rate x sample resolution.
Q6
if bitRate goes up: storage per second goes down → A higher bit rate means MORE bits are stored for each second, so it needs more storage, not less.
Section C: Definitions
Q1
bit rate — The number of bits used to store each second of sound: sample rate x sample resolution. A higher bit rate means better accuracy but more storage per second.
Section D: Fill in the Blanks
Q1
bitRate ← sampleRate * resolution
Q2
sampleRate ← 8000 resolution ← 8 bitRate ← sampleRate * resolution
Q3
sampleRate ← 44100 resolution ← 16 bitRate ← sampleRate * resolution
Q4
IF bitRate1 > bitRate2 THEN accuracy1 ← better ENDIF
Q5
fileBits ← bitRate * seconds
Section E: Spot the Error
Q1
A — A Python function definition must end with a colon. The line should be def bit_rate(rate, bits): so the function body can follow.
Q2
C — Bit rate is sample rate times sample resolution, not plus. The line should be bit_rate = rate * bits.
Q3
D — Bit rate is measured in bits per second, not bytes. The unit label should be 'bits/s'.
Q4
B — The bit rate is found by multiplying sample rate by sample resolution. The line should be SET high TO 44100 * 16.
Q5
B — Bit rate is the bits stored for each second, so 10 seconds needs bit_rate multiplied by 10, not divided. It should be total_bits = bit_rate * 10.