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Spectrum Analyser & Mic Test
See your microphone level and live frequency spectrum, and check a mic works.
Free tools that run in your browser. Nothing you type, open or create is uploaded to NerdBible or anyone else.
Is my microphone working? Press Start and allow the microphone, then speak or clap.
Frequency spectrum
Waveform
Your microphone is analysed live in this tab only. Nothing is recorded, stored or uploaded, and the microphone closes when you press Stop or leave the page. Levels are in dBFS, decibels below the loudest sample the microphone can deliver, so 0 is the maximum and everything else is negative. Your browser's echo cancelling, noise suppression and automatic gain are switched off so you see the raw signal; some devices apply their own processing anyway.
How to use it
- Press Start and allow the microphone when your browser asks.
- Speak, clap or play a note. The meters, spectrum and waveform move with the sound, and the box at the top says whether the microphone is working.
- If you have several microphones, choose one from the list. Press Freeze to hold the picture, and Stop to close the microphone.
Questions
What do the peak and RMS levels mean?
Peak is the single loudest sample, which tells you how close you are to clipping at 0 dBFS. RMS is the average power, closer to how loud the sound seems. Speech at a normal distance usually sits around minus 30 to minus 20 dBFS RMS.
Why does my microphone show a level when I am silent?
Every microphone picks up some background noise from the room, fans and its own electronics. A quiet room with a good microphone reads below minus 60 dBFS; a laptop microphone often reads around minus 50.
Why is the frequency axis not even?
It is logarithmic, like hearing: each octave gets the same width, so the bass and treble are both readable. The labels mark 50 Hz to 20 kHz.
Can I measure sound pressure level with this?
No. dBFS is relative to the microphone's own maximum, and phone and laptop microphones are not calibrated, so these numbers cannot be turned into dB SPL without a reference.