Frequency Analyzer

See the frequency spectrum of microphone input or an audio file, with the dominant frequency and nearest musical note.

This browser does not provide the Web Audio API, so the analyzer cannot run.

How to use

In microphone mode, press Start microphone, allow access, and make a sound.
In file mode, choose an audio file and press Play.
The spectrum (logarithmic frequency axis), the dominant frequency and the nearest musical note are shown.

Notes

Analysis runs on your device with the Web Audio AnalyserNode (FFT size 8192). The microphone is released as soon as you stop, and files are decoded locally, never uploaded. The dominant frequency is the strongest FFT bin; for sounds rich in harmonics it may be a harmonic rather than the fundamental.

FAQ

What does the cents value mean?: It is the deviation from the nearest note; 100 cents equals one semitone. A plus means the sound is sharper than the note, a minus flatter. A4 = 440 Hz is the reference.
Why are very low notes hard to read?: FFT resolution and the microphone's own low-frequency sensitivity are the limits; below about 50 Hz the reading becomes unstable.