Spectrum Analyzer
Watch the frequencies move in real time while a file plays, or while you speak into the microphone.
Source
MP3, WAV, M4A, FLAC, OGG, Opus, AIFF, WMA, AMR and the sound of most videos. Files stay on your device.
Larger: finer pitch, slower response.
Display
No sound yet. Play the file or speak into the microphone.
Level in dBFS against frequency (log scale). A full-scale sine reads 0 dBFS. The peak frequency is interpolated between FFT bins.
How it works
- Choose a file to play, or switch to the microphone and allow access.
- Press Play.
- Adjust the FFT size, range and peak hold.
Live analysis of a file or a microphone
Choose a file and press play to watch its spectrum move in real time, or switch to the microphone to see sound in the room. The picture is level in dB full scale against frequency on a logarithmic axis. A full-scale sine wave reads 0 dBFS, so a tone at half amplitude reads -6 dBFS.
The microphone is analysed on your device and is never recorded or sent anywhere. It is not played through the speakers, so there is no feedback. The browser asks for permission first; if it was refused, the page explains how to allow it.
Settings
A larger FFT size resolves close frequencies better but reacts more slowly. Smoothing averages frames so a noisy spectrum settles. The fine view draws every bin; the 1/3 octave view groups the energy into the bands used in acoustics, which is easier to read for rooms and speakers. Peak hold keeps the highest value of each frequency until you reset it, and Freeze stops the display so you can read it.
The numeric readout gives the strongest frequency and its level. The frequency is interpolated between FFT bins, so a steady tone reads close to its true pitch. A table of the 1/3-octave levels is available as a text alternative to the chart.
Limits
The microphone signal here is not calibrated, so levels are relative to digital full scale, not sound pressure in dB SPL. The browser may add its own processing to a microphone; the page asks for raw input without echo cancellation, noise suppression or automatic gain, but a device can still apply its own.
Questions
Why does the page ask for microphone access?
Only the microphone mode needs it. Choose Audio file and no permission is requested.
Is this a measurement microphone tool?
No. It shows relative levels and frequencies, which is enough to find a hum, a resonance or the pitch of a tone, but it cannot give calibrated sound pressure levels.
Why does the peak frequency jump around with speech?
Speech changes pitch many times a second. Raise the smoothing, use a larger FFT size, or freeze the display on the moment you want to read.
Does it work on a phone?
Yes in current browsers, as long as the page is opened over HTTPS and microphone access is allowed.