Audio Spectrum Analyzer
See the frequencies in a sound from your microphone or an audio file: a live spectrum on a log scale, the loudest frequency and its note, and the waveform.
Asks for microphone access
Turn on the microphone to start.
Checking what this browser allows…
The microphone is used only while listening, and the sound is analysed in this tab — nothing is recorded or sent.
How is this calculated?
The browser’s analyser takes a Fourier transform (FFT) of the latest block of samples. Each bin is sample rate ÷ FFT size wide; the loudest bin is refined by a parabola through it and its neighbours.Runs in your browser — nothing you enter leaves this device.
About this tool
What it does
Audio Spectrum Analyzer shows which frequencies are in a sound, live. Listen through the microphone or play an audio file, and the spectrum is drawn from 20 Hz (the lowest bass we hear) to 20 kHz (the highest treble), on a logarithmic scale like the ear hears — each octave the same width — with the level of each frequency in decibels. Under it, the loudest frequency is named, with the musical note nearest to it and how many cents off. Use it to find a hum (mains hum is 50 Hz and its multiples in India and Europe, 60 Hz in the Americas), check what a microphone or speaker picks up, see the harmonics of an instrument, find a feedback frequency, or simply watch music. Show the spectrum as bars or a line, or switch to the waveform, an oscilloscope view of the last 20 milliseconds. More detail (a larger FFT size) separates close frequencies better but responds more slowly; smoothing steadies the picture. Freeze holds a moment still so you can read it.
How to use it
- Choose the microphone or an audio file.
- Press Start listening (and allow the microphone), or open a file and press play.
- Read the loudest frequency below the picture; choose bars, line or waveform.
- Raise the detail to separate close frequencies; press Freeze to hold the picture.
Limits and your data
- Levels are relative to the loudest the microphone or file can carry (dBFS), not sound pressure (dB SPL): a phone is not a calibrated sound level meter.
- Microphones in laptops and phones roll off low bass and filter some frequencies; what you see includes the microphone’s own character.
- The highest frequency shown is half the sample rate, usually 22 or 24 kHz, and is cut to 20 kHz.
- Turn off noise suppression in your system settings if it hides steady sounds such as a hum.
- The sound is analysed in this browser tab. Nothing is recorded or uploaded, and an opened file stays on your device.
Questions
What is a spectrum analyzer used for?
To see the frequencies in a sound: finding hums and feedback, checking microphones and speakers, studying an instrument’s harmonics, or tuning a room.
Why is there a peak at 50 Hz?
That is usually mains hum from the electricity supply, 50 Hz in India, 60 Hz in the Americas, often with peaks at 100, 150 Hz and so on.
What does the FFT size change?
Larger sizes split the spectrum into finer steps (shown beside each size) but look further back in time, so they react more slowly.
Can it measure how loud a room is?
Not accurately. It shows levels relative to the microphone’s maximum; a decibel meter needs a calibrated microphone.