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Audio Sample Rateの包括的な教育ガイドを準備中です。ステップバイステップの解説、数式、実例、専門家のヒントをお届けしますので、もうしばらくお待ちください。
The Audio Sample Rate Converter computes Nyquist frequency (half of sample rate — the maximum frequency that can be accurately captured) and uncompressed PCM file size from sample rate, bit depth, channel count, and duration. Common rates: 44.1 kHz (CD, music streaming), 48 kHz (video standard, broadcast), 96 kHz (hi-res studio recording), 192 kHz (specialty mastering). Higher rates capture more frequency detail but produce dramatically larger files with diminishing perceptual returns. Nyquist theorem: any sample rate can faithfully reproduce frequencies up to half the sample rate. 44.1 kHz captures 22.05 kHz (above the ~20 kHz upper limit of human hearing). 48 kHz captures 24 kHz. 96 kHz captures 48 kHz. 192 kHz captures 96 kHz — well into ultrasonic range. The argument for higher-than-44.1: better behavior of low-pass anti-aliasing filters near the Nyquist frequency, more 'headroom' for digital processing (EQ, compression artifacts), and arguably some psychoacoustic perception of frequency response shape near top of hearing. Practical benefit beyond 96 kHz is negligible for listening; valuable for production. File size formula: bytes per second = (Sample Rate × Bit Depth × Channels) / 8. Then × duration in seconds. 44.1 kHz / 16-bit / stereo: 44,100 × 16 × 2 / 8 = 176,400 bytes/sec = 10.6 MB/minute. 48 kHz / 24-bit / stereo: 288,000 bytes/sec = 17.3 MB/min. 96 kHz / 24-bit / stereo: 576,000 bytes/sec = 34.6 MB/min. 192 kHz / 32-bit float / stereo: 1,536,000 bytes/sec = 92.2 MB/min — 8.7× larger than CD quality. Producer workflow context: Record at 48 kHz / 24-bit / project-relevant channels for video work (standard sync rate for cinema/TV/streaming). Record at 88.2 or 96 kHz / 24-bit for high-end music production where downsampling to 44.1 kHz (CD) needs cleaner mathematics. Mix and process at recording rate; export to delivery format (44.1 kHz / 16-bit for streaming, 48 kHz for video). Don't record above 96 kHz unless specific mastering/archival reason — file sizes explode without proportional sonic benefit. Bit depth more important than sample rate for headroom: 24-bit gives 16 million levels vs 16-bit's 65,536 — much more important for dynamic range.
Nyquist = Sample Rate / 2; Bytes/sec = (SR × BD × Channels) / 8; File MB = Bytes/sec × Sec / 1024 / 1024
- 1Step 1 — Select sample rate (44.1 kHz CD, 48 kHz video, 96 kHz hi-res studio)
- 2Step 2 — Select bit depth (16-bit CD, 24-bit production standard, 32-bit float editing)
- 3Step 3 — Select channels (1 mono, 2 stereo, 6 for 5.1 surround)
- 4Step 4 — Enter duration in seconds
- 5Step 5 — Calculator computes Nyquist frequency: Sample Rate / 2
- 6Step 6 — Computes bytes per second: SR × BD × Ch / 8
- 7Step 7 — Multiplies by duration; converts to MB; outputs Nyquist, bytes/sec, and total file size
Standard CD format and digital download quality. ~10 MB/minute classic.
Studio recording session — 5 minutes uses substantial disk space at hi-res
Multiplying up to 96/24 stereo: 576,000 bytes/sec × 300 sec = 173 MB. Multi-track sessions with 24+ channels can hit GB per song.
Feature film 5.1 mix at full quality. Why production hard drives are huge.
Podcast raw recording. After compression (AAC 128 kbps), final file is ~28 MB — much smaller than uncompressed source.
Studio recording session setup
Storage capacity planning for projects
Comparing CD vs hi-res release file sizes
Educational reference for audio production students
Video production audio setup (matching video frame rate)
Podcast workflow file size budgeting
Can humans hear the difference between 44.1 and 96 kHz?
Generally no for listening, with caveats. Human hearing tops out around 20 kHz (younger adults; declines with age). 44.1 kHz can faithfully reproduce all audible frequencies. The argument for higher sample rates focuses on: (1) less aggressive anti-aliasing filter near 22.05 kHz which might affect 18–20 kHz response, (2) headroom for digital effects processing, (3) psychoacoustic effects from frequencies just above hearing threshold (debated). Listen tests are inconsistent — most can't distinguish above 96 kHz; some can distinguish 44.1 vs 96 in specific test conditions.
Why is 48 kHz the video standard but 44.1 kHz the music standard?
Historical. CD format (1980 Sony/Philips) chose 44.1 kHz because it matched existing video tape recorders used for audio mastering. Digital video (later) chose 48 kHz because it's mathematically cleaner with video frame rates (30/29.97/24/25 fps). The two coexist; resampling between them is standard but introduces tiny artifacts. For new work synced to video, record at 48; pure audio, 44.1 (or 96 if planning hi-res release).
Bit depth matters more than sample rate for dynamic range?
Generally yes. Bit depth determines noise floor and dynamic range. 16-bit: ~96 dB dynamic range. 24-bit: ~144 dB. 32-bit float: effectively unlimited dynamic range. For recording (especially live with unpredictable levels), 24-bit prevents clipping while preserving quiet detail. For final delivery (streaming, CD), 16-bit dithered is fine because final mixes have controlled dynamic range. Bit depth headroom matters during production; less during listening.
Should I record at 32-bit float?
Yes if recording live performance with unpredictable levels. 32-bit float has so much headroom that clipping is essentially impossible — even badly-set levels can be brought back to usable in post-production. 24-bit is fine for controlled studio recording where you can set levels properly. Both 32-bit and 24-bit are professional-grade; 32-bit doubles file size with safety benefit.
What about MP3 / AAC / lossy formats?
Lossy formats encode audio at lower bitrates (kbps) to reduce file size. AAC 128 kbps stereo = ~1 MB/minute (10× smaller than 44.1/16/stereo uncompressed). Quality varies: 128 kbps AAC is fine for casual listening; 256 kbps is transparent for most listeners. Lossy formats are for delivery, not production — never edit lossy files (quality degrades each save). Master in lossless, export to lossy only for final distribution.
プロのヒント
Record at 48 kHz / 24-bit / 2 channels (stereo) for video work; 88.2 or 96 kHz / 24-bit for music intended for CD or hi-res release. Don't go beyond 96 kHz unless mastering for archival/specialty release — file sizes explode without proportional benefit. Mix at recording rate; export to delivery format last.