Audio bitrate (kbps)

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Quick Questions

Shade in the A or B circle for each question.

1. What does a bitrate of 128 kbps tell you about an audio file?

A The file is 128 kilobytes in total

B 128 thousand bits are used for each second of audio

2. Which audio file will usually be smaller if the songs are the same length?

A The 128 kbps file

B The 320 kbps file

3. Which statement about a 320 kbps file compared with a 128 kbps file is correct?

A It usually has higher quality but a larger file size

B It usually has lower quality but a larger file size

4. Which formula estimates file size from bitrate?

A file size = bitrate + length in seconds

B file size = bitrate x length in seconds

5. A song is 100 seconds long at 128 kbps. How many kilobits is the file?

A 12,800 kilobits

B 228 kilobits

Match the Pairs

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

Left column		Right column
1bitrate = 128 kbps		AA higher bitrate: about 320,000 bits per second, giving better audio quality but a larger file
2bitrate = 320 kbps		BFile size is found by multiplying, not adding. The formula should be size = bitrate * seconds.
3File size in bits is the bitrate multiplied by the length of the audio in seconds		C128 * 10 = 1280
4A 10 second clip at 128 kbps uses 1,280 kilobits (128 x 10)		DThis is backwards. A higher bitrate uses more bits per second, so the 320 kbps file is larger, not smaller.
5A 320 kbps song is smaller than a 128 kbps song		Esize_bits = bitrate * seconds
6size = bitrate + seconds		FA lower bitrate: about 128,000 bits per second, giving a smaller file with lower audio quality

Definitions

bitrate

Fill in the Blanks

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

_______ = 128 print(bitrate, "kbps")

size = bitrate _ seconds

print(128 _ 320)

low = 128 ____ = 320 print(high > low)

bitrate = 128 seconds = 180 size = bitrate * _______

Spot the Error

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

Question 1

A seconds = 200

B size_kbits = 128 + seconds

C print(size_kbits)

Question 2

A low = 128

B high = 320

C if low > high:

D print('smaller file')

Question 3

A kbps = 320

B seconds = 60

C kbits = kbps * seconds

D kbytes = kbits * 8

E print(kbytes)

Question 4

A song_secs = 180

B kbits = 192 * song_sec

C print(kbits)

Question 5

A bitrate = 128

B seconds = 240

C kbits = bitrate * seconds

D mbytes = kbits / 1000

E print(mbytes)

Answer Key

Audio bitrate (kbps)

Section A: Quick Questions

B — 128 thousand bits are used for each second of audio

A — The 128 kbps file

A — It usually has higher quality but a larger file size

B — file size = bitrate x length in seconds

A — 12,800 kilobits

Section B: Match the Pairs

bitrate = 128 kbps → A lower bitrate: about 128,000 bits per second, giving a smaller file with lower audio quality

bitrate = 320 kbps → A higher bitrate: about 320,000 bits per second, giving better audio quality but a larger file

File size in bits is the bitrate multiplied by the length of the audio in seconds → size_bits = bitrate * seconds

A 10 second clip at 128 kbps uses 1,280 kilobits (128 x 10) → 128 * 10 = 1280

A 320 kbps song is smaller than a 128 kbps song → This is backwards. A higher bitrate uses more bits per second, so the 320 kbps file is larger, not smaller.

size = bitrate + seconds → File size is found by multiplying, not adding. The formula should be size = bitrate * seconds.

Section C: Definitions

bitrate — The number of bits used for each second of audio or video, measured in kbps. A lower bitrate gives a smaller file but lower quality, e.g. 128 kbps is smaller than 320 kbps.

Section D: Fill in the Blanks

bitrate = 128
print(bitrate, "kbps")

size = bitrate * seconds

print(128 < 320)

low = 128
high = 320
print(high > low)

bitrate = 128
seconds = 180
size = bitrate * seconds

Section E: Spot the Error

B — File size depends on bitrate multiplied by length, so the line should use * (128 * seconds), not +.

C — 128 kbps is less than 320 kbps, so the lower bitrate is the one that gives the smaller file. The test should be low < high.

D — There are 8 bits in a byte, so converting kilobits to kilobytes means dividing by 8, not multiplying: kbits / 8.

B — The variable is called song_secs. Writing song_sec uses a name that was never created, so the program fails.

D — Bitrate gives kilobits. They must be divided by 8 to get kilobytes before dividing by 1000 for megabytes: kbits / 8 / 1000.