Audio Spectrum Analyzer
See the frequencies in any sound in real time: start your microphone or open an audio file and watch a live FFT spectrum, octave bars or a scrolling spectrogram, with the dominant frequency and its musical note. Audio is analyzed in your browser and never recorded or uploaded.
Press Start analyzer and allow microphone access. Nothing is recorded or uploaded.
Resolution: – Hz per bin. Values are dBFS (0 dB = digital full scale), not calibrated sound pressure.
How to use the Audio Spectrum Analyzer
- Press Start analyzer and allow microphone access when the browser asks. Or choose Analyze an audio file.
- Make a sound: whistle, sing, play an instrument or a test tone. The dominant frequency and note appear at the top.
- Pick a view: Line for detail, 1/3-octave bars like a room analyzer (RTA), or Spectrogram to see how the sound changes over time.
- Freeze the display (or press F) and hover the graph to read any frequency and level.
- Tune the analysis: a larger FFT size gives finer frequency resolution, a smaller one reacts faster. Save PNG keeps a snapshot.
Frequency ranges at a glance
| Range | Frequencies | What you hear there |
|---|---|---|
| Sub-bass | 20–60 Hz | Rumble, kick drum body, pipe organ pedals, mains hum (50/60 Hz) |
| Bass | 60–250 Hz | Bass guitar, the fundamental of male voices (about 85–180 Hz) |
| Low mids | 250–500 Hz | Warmth or "muddiness", the fundamental of female voices (about 165–255 Hz) and its first harmonics |
| Mids | 500 Hz–2 kHz | Most instrument fundamentals and the body of speech |
| Upper mids | 2–4 kHz | Speech intelligibility, where the ear is most sensitive |
| Presence | 4–6 kHz | Clarity and attack, consonants |
| Brilliance | 6–20 kHz | Cymbals, "s" sounds, air; upper limit of hearing falls with age |
How the analyzer works
The browser's Web Audio AnalyserNode takes the latest block of samples (the FFT size), applies a Blackman window and runs a Fast Fourier Transform. Each output bin covers sample rate ÷ FFT size hertz: at 48,000 Hz and 8192 points that is 5.86 Hz. The dominant frequency is refined between bins with parabolic interpolation, so a steady tone usually reads within a fraction of a hertz.
The 1/3-octave bars add up the power of all bins in each standard band (centers at 1000 × 2n/3 Hz: …, 20, 25, 31.5, 40, 50, 63, 80, 100 Hz, …), which is how room analyzers (RTA) and graphic equalizers divide the spectrum. Smoothing averages each frame with the previous ones, which calms the display but makes it slower to react.
Practical uses
- Find a whine or hum: freeze the display and hover the peak to read its exact frequency and note.
- Check your speakers or room: play pink noise or a sweep from the Tone Generator or White Noise Generator on another device and look at the 1/3-octave bars for big dips and peaks.
- Tune or identify a pitch: the note readout shows the strongest frequency; for tuning instruments the Chromatic Tuner is more precise because it tracks the fundamental, not the loudest harmonic.
- Learn about sound: sing a vowel and watch the harmonics form an evenly spaced comb; whistle and see a single clean peak.
Frequently asked questions
What does a spectrum analyzer show?
It splits a sound into its frequencies and shows how loud each one is. The horizontal axis is frequency on a logarithmic scale (each octave takes the same width, like a piano keyboard), and the vertical axis is level in decibels relative to digital full scale (dBFS).
Which FFT size should I choose?
The frequency resolution is the sample rate divided by the FFT size. At 48 kHz, 8192 points gives about 5.9 Hz per bin and updates quickly; 32768 gives about 1.5 Hz per bin, which helps for bass notes, but reacts more slowly. Use 1024–2048 for fast-changing sounds like speech or drums.
Is this a calibrated sound level meter?
No. Phone and laptop microphones are not calibrated, and browsers may process the signal, so the levels are relative dBFS values. They are great for comparing frequencies, spotting hums and resonances, or checking a tone, but not for legal noise measurements. Use the Sound Level Meter for an approximate dB SPL reading.
Why do I see a peak at 50 or 60 Hz?
That is usually mains hum from the power grid (50 Hz in Europe and most of Asia and Africa, 60 Hz in North America), or its harmonics at 100/120 Hz and above. It often comes from ground loops, cheap power supplies or fluorescent lights.
Why does the microphone not work?
The browser needs your permission. If you clicked Block, click the lock or camera icon in the address bar, allow the microphone and press Start again. Also check that no other app is using the mic and that the right input is selected in your system settings.
What is the spectrogram view?
A spectrogram shows time from left to right and frequency from bottom to top, with color showing loudness. It reveals how a sound evolves: speech formants, bird song, a rising siren or a short click are easy to spot.