Sonic autopsy
Inspect a local audio clip, compare a selected region and export measurements with your listening notes.
WORKING TOOLStart here
Use this workbench to investigate an audio file rather than guess its instrument or quality from one graph. The file is decoded and analysed locally in your browser.
By the end: Read the measured level and spectrum, distinguish estimates from identification, and retain a useful comparison report.
What you need: A browser-decodable local clip no larger than 25 MB and no longer than 120 seconds. No upload, microphone or separate editor is required.
Before you begin: Choose a local clip, up to 25 MB and 120 seconds, in a format this browser can decode. The workbench requires no upload or separate editor.
How to use this tool
- Choose a file, then select a channel and a valid start/end region. Use the player to hear the same region you intend to inspect.
- Run the analysis. Read the waveform, level and spectrum together; pitch and pulse candidates can be ambiguous or unavailable.
- Keep report A, analyse another file or region as B and write what changed. Export the report and notes before leaving the page.
Open → select → measure → compare → export
Your file stays in this tab. Choose up to 25 MB / 120 seconds; decoding depends on browser codec support. No account, upload or paid service is required. All measurements refer to decoded samples, not an inferred mastering history.
Choose a local audio clip to begin.
Sample peak is not true peak; RMS is not LUFS or calibrated sound pressure. Near-full-scale samples do not prove clipping. Spectrum uses a finite window at the selected start, with zero-padding for short regions; pitch assumes a monophonic periodic source between about 60 and 1,000 Hz. Pulse candidates are a simple energy-onset model, not verified beat tracking. Refreshing closes the session; export to keep the evidence. See Web Audio and autocorrelation and tempo.
Ask what the display can actually prove
A waveform displays amplitude over time. A spectrum estimates how energy is distributed by frequency over a selected interval. They answer different questions. Neither identifies the performer, recording location or instrument with certainty.
Keep your original file and examine a copy. Record its duration, sample rate and channels before editing. Then select a steady region and compare its spectrum with a transient region. Selection length and analysis settings influence the picture.
Worked example
For a controlled file pair, use Timbre Cabinet at MIDI note 69 (A4, 440 Hz) to export a sine and a square tone. Open the sine here, choose one channel and a region away from the start, then analyse and keep report A. Open the square and analyse a comparable region. Compare their spectra: the sine concentrates energy near one frequency while the square has additional harmonic structure. A finite window can spread peaks, so the graph need not show perfect vertical lines.
Try it yourself
Write your answer before opening the explanation. Use the worked example if you get stuck.
Question 1
A large peak appears near 440 Hz. Does it prove the sound is a violin playing A4? What extra evidence would you need?
Show answer and reasoning
No. Many sources can produce energy there, and the peak need not be the fundamental. Inspect harmonics, timing and context, and listen to the recording. Even that may not uniquely establish an instrument; provenance is stronger evidence of who or what was recorded.
Watch for: Louder waveforms are not automatically higher-quality audio. A flat-topped waveform can suggest clipping, but display scale and processing must be considered.
Summary + next step
Read the measured level and spectrum, distinguish estimates from identification, and retain a useful comparison report.
Keep the result: Reports and notes can be exported; keep your original audio separately. This analysis does not identify instruments or measure calibrated loudness.
Sources and further reading
Read these references for the concepts used in the lesson.
Lesson updated 2026-10-22 · Guidance updated 2026-10-22
Coverage and further development
Inspect local audio: select a channel and region, measure waveform and dynamics, inspect spectrum and pitch/pulse candidates, compare reports and export.