Lesson 4.5.6.7

4.5.6.7 Digital representation of sound Quiz: AQA Computer Science, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.5.6.7, Digital representation of sound: 20 multiple choice questions for the AQA Computer Science (7517), Unit 5: Fundamentals of data representation, written with Revision Ninja.

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The 20 questions

  1. What is sample resolution in digital sound?

    • The length of the recording in seconds, which determines how much audio the file can hold
    • The number of samples taken per second, which sets how often the sound is measured in time
    • The number of channels in the recording, such as mono or stereo, used for playback
    • The number of bits used to store each sound sample, which sets how finely its level is recorded

  2. What is the sampling rate of a digital recording?

    • The number of bits in each sample
    • The total number of bytes in a file
    • The highest frequency a microphone can detect, in decibels
    • The number of samples taken per second, measured in hertz

  3. What does the Nyquist theorem state?

    • The sampling rate must be half the highest frequency in the signal to avoid any distortion
    • Sampling must use at least sixteen bits per sample, whatever the frequency of the signal
    • A sampling rate of at least twice the highest frequency in the signal is needed to capture it accurately
    • The sampling rate must be exactly equal to the highest frequency in the signal being recorded

  4. What is the commonly quoted range of human hearing?

    • About 0 Hz to 44.1 kHz
    • About 200 Hz to 200 kHz
    • About 2 Hz to 2 kHz
    • About 20 Hz to 20 kHz

  5. Which sampling rate is standard for CD-quality audio?

    • 8 kHz
    • 22.05 kHz
    • 96 kHz
    • 44.1 kHz

  6. Which bit depth is standard for CD-quality audio?

    • 16 bits
    • 24 bits
    • 8 bits
    • 4 bits

  7. Why does a higher sample resolution improve a recorded sound?

    • It increases the sampling rate automatically, so more samples are taken each second of sound
    • It allows more amplitude levels, so the waveform is represented more accurately
    • It makes the file compressed, so the samples take less space without losing any detail
    • It removes the need for a DAC, because the stored samples can drive a speaker directly

  8. A 10 second mono recording is made at 44.1 kHz with 16-bit samples. How many bytes does it need?

    • 1,764,000 bytes
    • 441,000 bytes
    • 882,000 bytes
    • 8,820,000 bytes

  9. A 5 second mono recording is made at 8 kHz with 8-bit samples. How many bytes does it need?

    • 80,000 bytes
    • 400 bytes
    • 40,000 bytes
    • 5,000 bytes

  10. A 1 minute mono recording is made at 22.05 kHz with 8-bit samples. How many bytes does it need?

    • 132,300 bytes
    • 1,323,000 bytes
    • 13,230 bytes
    • 2,646,000 bytes

  11. A signal's highest frequency is 4 kHz. What is the lowest sampling rate that Nyquist allows?

    • 8 kHz
    • 4 kHz
    • 16 kHz
    • 2 kHz

  12. What is the minimum sampling rate for a sound containing 15 kHz?

    • 15 kHz
    • 45 kHz
    • 7.5 kHz
    • 30 kHz

  13. A sample resolution of 12 bits gives how many amplitude levels?

    • 12
    • 8192
    • 1024
    • 4096

  14. If the sampling rate doubles for the same duration and bit depth, what happens to the file size?

    • It stays the same, since file size depends only on the bit depth and not on the sampling rate
    • It doubles only when the file is compressed, because compression is the only factor that adds data
    • It doubles, since storage equals samples per second times duration times bytes per sample
    • It halves, since each sample becomes larger when the number of samples per second is increased

  15. A 2 second mono recording is made at 16 kHz with 8-bit samples. How many bits does it need?

    • 256,000 bits
    • 32,000 bits
    • 128,000 bits
    • 512,000 bits

  16. A 9 kHz tone is sampled at 12 kHz. Which frequency appears in the samples?

    • 12 kHz, because the sampling rate is always captured
    • 3 kHz, because the tone aliases below the 6 kHz Nyquist limit
    • 9 kHz, because sampling always captures tones exactly
    • 6 kHz, because the Nyquist limit is always captured

  17. Why does a higher bit depth reduce quantisation noise?

    • More levels mean each sample is rounded by a smaller amount, so the rounding error is smaller
    • More bits increase the sampling rate, which removes the noise because more samples are taken
    • Noise is caused only by the DAC, so bit depth in the recording has no effect on noise
    • Bits reduce the noise by removing part of the signal, so the quieter parts are cut out

  18. A 30 second stereo recording is made at 48 kHz with 24-bit samples. Which size is closest?

    • About 0.9 MB
    • About 2.9 MB
    • About 17.3 MB
    • About 8.6 MB

  19. Which is the most likely effect of sampling a signal below the Nyquist rate?

    • The file becomes longer in duration
    • The sound becomes louder without distortion
    • The recording gains frequency content above the original
    • Frequencies are misrepresented, appearing as lower false frequencies

  20. Why is 44.1 kHz chosen as the sampling rate for CD audio?

    • It equals exactly twice 20 Hz, the lower limit of human hearing, so the range is covered
    • It is above twice the 20 kHz upper limit of human hearing, so audible frequencies can be captured
    • It is the lowest rate that a DAC can output, so every recording is made at that rate
    • It is the rate at which 8-bit samples fit exactly onto a single standard disk in one pass

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