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Audio quality versus file size

Short answer

File size equals sampling rate times bits per sample times channels times time divided by 8. Higher rate, bit depth and channels improve quality but enlarge files proportionally. CD audio is about 10.09 MB per minute versus telephone 0.46 MB; lossy compression reduces size with little audible loss.

Make a comparison between quality versus file size.

In digital audio, quality improves when the sampling rate, bit depth and number of channels are increased, but each increase makes the file bigger in direct proportion. A designer must find a balance between sound quality and storage or bandwidth.

File size (bytes) = sampling rate x bits per sample x channels x time (s) / 8

Factors

  • Sampling rate: higher rate captures higher frequencies (a rate of f gives frequencies up to f/2).
  • Bit depth: more bits give more levels, less quantisation noise and wider dynamic range (about 6 dB per bit).
  • Channels: stereo gives spatial effect but doubles the size of mono.

Comparison for one minute of sound

QualityRateBitsChannelsSize per minute
Telephone8 kHz8Mono480,000 B (0.46 MB)
AM radio11.025 kHz8Mono661,500 B (0.63 MB)
FM radio22.05 kHz16Stereo5,292,000 B (5.05 MB)
CD44.1 kHz16Stereo10,584,000 B (10.09 MB)

(1 MB = 1,048,576 bytes.)

Trade-off

  • High quality: music, professional work, but needs large storage and high network bandwidth.
  • Low quality: speech and web audio, small files that load fast but sound dull or noisy.
  • Compression (MP3, AAC) lowers the size by about 10 times with little audible loss, giving a better balance. Choose the lowest settings that still give acceptable quality for the purpose.

✓ Answer checked by Claude Opus 5.5 (high effort)

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