Spectrum Analyzer
See your sound: live bars, waveform, or spectrogram from your microphone, computed entirely on this device.
Ready
ReadyView
FFT
Runs locally in your browser — nothing is uploaded.
This tool runs locally in your browser — no audio is uploaded.
How to use
- 1
Start and allow the mic
Press Start, allow microphone access, then play a tone (the tone generator page works well in another tab) or just speak.
- 2
Pick a view
Bars show energy across frequency bands — the default view. Wave shows the pressure signal over time. Spectrogram scrolls frequency over time so whistles and sweeps leave trails.
- 3
Tune resolution
FFT size 1024 reacts fastest, 4096 resolves closest tones; 2048 is the balanced default. Try the tone generator at 440 Hz and 455 Hz to see the difference.
How it works & limits
Your microphone stream feeds an AnalyserNode — a local Fast Fourier Transform — and the result is drawn on a canvas with requestAnimationFrame. Frequency data, waveform data, and the spectrogram history never leave this page; there is no upload path.
Read it with honest expectations: the vertical axis shows relative energy, not calibrated decibels; the top of the bar chart reaches about half the sample rate; and the microphone itself colors everything — most laptop mics roll off steeply below 100 Hz and above 12–15 kHz. Silence up there is usually the mic, not your sound.
FAQ
Why does nothing appear when I start?
Check the OS input level and that the right device is selected. Also confirm your browser tab has microphone permission — the page shows instructions for re-enabling it if you denied it.
Why are the lowest frequencies always empty?
Most microphones and rooms lose energy below about 100 Hz, and FFT bins down there are narrow. Play a 60 Hz tone from the tone generator to see whether your mic responds at all.
Which FFT size should I choose?
1024 for fast visual response (percussion, speech), 4096 to separate close tones (440 vs 455 Hz), 2048 as the everyday default.
Is my audio being uploaded anywhere?
No. The analyser runs in your browser; the canvas is drawn locally. Stopping the test releases the microphone completely.
Can it measure exact dB levels?
No — browser mics and gain controls are uncalibrated. The display is relative: useful for shape, peaks, and comparison, not absolute loudness.
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