Practice Audio Representation in CS Thinking

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

Audio representation is the way a computer stores sound as numeric data. Digital audio is usually created by sampling a sound wave many times each second and storing each sample with a certain number of bits.

Digital sound is a long list of measurements of a wave taken again and again over time.

Showing a random 20 of 50 problems.

Example 1

easy
8-bit audio gives 256 amplitude levels. How many levels does 1 extra bit (9-bit) provide?

Example 2

hard
A recording at 80008000 Hz tries to capture a 60006000 Hz tone. Does it succeed? Why or why not?

Example 3

challenge
An audio engineer must fit 3 minutes of stereo audio into 5 MB (1 MB=8,000,0001\text{ MB}=8{,}000{,}000 bits). If bit depth is 16 and 2 channels, what maximum sample rate (Hz) is allowed?

Example 4

medium
A WAV file is 50 MB; the MP3 of the same song is 5 MB. State the compression ratio.

Example 5

easy
If you increase the sample rate, what audio property improves?

Example 6

easy
A digital audio file stores sound as what?

Example 7

easy
A mono recording samples at 1000 Hz with 8-bit samples. What is the bit rate in bits per second?

Example 8

easy
A stereo clip samples at 100 Hz, 16-bit. What is its bit rate?

Example 9

challenge
Explain why doubling sample rate alone improves time-resolution of transients but not the steady-state pitch of a 440440 Hz tone.

Example 10

medium
A 30-second stereo recording at 4410044100 Hz, 1616-bit. File size in megabytes (1 MB=8,000,0001\text{ MB}=8{,}000{,}000 bits)?

Example 11

easy
How many channels does stereo audio store?

Example 12

medium
A 1-minute CD-quality stereo recording (44100 Hz, 16-bit, 2 ch) takes how many megabytes (1 MB=8,000,0001\text{ MB}=8{,}000{,}000 bits)?

Example 13

hard
Compare storage for 1 minute of audio at (A) 4800048000 Hz/2424-bit/stereo vs (B) 1600016000 Hz/88-bit/mono. By what factor is A larger?

Example 14

easy
A stereo clip records at 100 Hz, 8-bit. What is the bit rate?

Example 15

hard
A podcast must fit 30 minutes of mono audio into 10 MB (1 MB=8,000,0001\text{ MB}=8{,}000{,}000 bits) at 1616-bit. What is the maximum sample rate (Hz)?

Example 16

medium
Clip A: 2205022050 Hz, 88-bit, mono. Clip B: same except 1616-bit. By what factor is B larger than A?

Example 17

medium
A 5-minute stereo song at 4410044100 Hz, 1616-bit. How many total samples (across both channels)?

Example 18

medium
CD-quality audio is 44100 Hz, 16-bit, stereo. Compute the bit rate in bits per second.

Example 19

medium
Telephone audio: 80008000 Hz, 88-bit, mono. How many bytes for a 10-second call?

Example 20

medium
To capture frequencies up to 1500015000 Hz, what is the minimum sample rate by Nyquist?
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