--- title: "Audio quality versus file size" subject: "Multimedia System" chapter: 2 key: "semester_8/multimedia_system:quality-vs-file-size" source: https://www.bctengineer.com/q/semester_8/multimedia_system/quality-vs-file-size site: BCT Engineering --- # Audio quality versus file size Multimedia System · Chapter 2: Sound / Audio System - Asked in: 2076 Bhadra, 5 marks - Video: [Audio Bit Depth and Sample Rate Explained](https://www.youtube.com/watch?v=xJKypZXc3B4) — iZotope, Inc. - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/multimedia_system/quality-vs-file-size - Whole chapter: https://www.bctengineer.com/md/semester_8/multimedia_system/chapter-2 ## Question Make a comparison between 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. ## Answer 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 | Quality | Rate | Bits | Channels | Size per minute | |---|---|---|---|---| | Telephone | 8 kHz | 8 | Mono | 480,000 B (0.46 MB) | | AM radio | 11.025 kHz | 8 | Mono | 661,500 B (0.63 MB) | | FM radio | 22.05 kHz | 16 | Stereo | 5,292,000 B (5.05 MB) | | CD | 44.1 kHz | 16 | Stereo | 10,584,000 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which changes increase both audio quality and file size? A. Lower sampling rate and fewer bits B. Mono instead of stereo C. Higher sampling rate, more bits per sample and more channels D. Using a smaller player Answer: C. Increasing sampling rate, bit depth or channels improves quality and raises size in proportion. (Key point: Factors raising size) 2. What is the formula for uncompressed audio file size in bytes? A. Rate x bits x channels x time / 8 B. Rate x bits x time / 8 only C. Rate x channels x time x 8 D. Rate x bits x channels / time Answer: A. Size = sampling rate x bits per sample x channels x time (s) / 8. (Key point: File size formula) 3. About how large is one minute of CD-quality stereo audio? A. 0.63 MB B. 5.05 MB C. 1.26 MB D. 10.09 MB Answer: D. 44,100 x 16 x 2 x 60 / 8 = 10,584,000 bytes, about 10.09 MB. (Key point: CD-quality size) 4. What does compression such as MP3 or AAC achieve? A. Doubles file size for quality B. Reduces size about 10 times with little audible loss C. Removes the need for sampling D. Converts stereo to mono always Answer: B. MP3/AAC lowers size about ten times with little audible loss, giving a better balance. (Key point: Compression trade-off) ## Related in Multimedia System - [MIDI versus digital audio](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Amidi-vs-digital-audio) — Multimedia System, chapter 2, asked 3× - [File size: 60 s, 44.1 KHz, 8-bit stereo](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aaudio-size-60s-44khz-8bit) — Multimedia System, chapter 2, asked 3× - [File size: 30 s, 44.1 KHz, 8-bit stereo](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aaudio-size-30s-44khz-8bit) — Multimedia System, chapter 2, asked 3× - [File size: 20 s, 44.1 KHz, 16-bit stereo](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aaudio-size-20s-44khz-16bit) — Multimedia System, chapter 2, asked 3× - [File size: 20 s, 44.1 KHz, 8-bit stereo](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aaudio-size-20s-44khz-8bit) — Multimedia System, chapter 2, asked 2× - [File size: 10 s, 44.1 KHz, 16-bit stereo](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Aaudio-size-10s-44khz-16bit) — Multimedia System, chapter 2, asked 2× ## Related in other subjects - [Linked list file system; block size impact](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Afs-linked-list-block-size) — Operating System, chapter 5 - [STL file: facet normals and file size](https://www.bctengineer.com/question.md?key=semester_4%2Fcomputer_aided_design%3Astl-format-numerical) — Computer Aided Design, chapter 6 - [Series versus parallel circuit comparison](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_engineering%3Aseries-parallel-comparison-table) — Basic Electrical Engineering, chapter 1 - [Text file versus binary file](https://www.bctengineer.com/question.md?key=semester_1%2Fcomputer_programming%3Atext-vs-binary-file) — Computer Programming, chapter 10