About this tool
The spectrum analyzer shows in real time which frequencies a sound contains. It splits the microphone signal into its frequency components with an FFT (fast Fourier transform) and draws them on a logarithmic axis from 20 Hz to 20 kHz – the way the ear perceives pitch. An optional waterfall diagram (spectrogram) shows the last ten seconds: each row is a moment in time, brightness is the level – so you can spot melodies, sweeps and recurring noise.
Typical uses: tracking down a hum from power supplies (50/60 Hz and multiples) or a whine from electronics, finding microphone feedback, reading the fundamental of an instrument or testing your hearing range with the Tone Generator. The loudest frequency is shown with its note name and cent deviation; for tuning, the Online Tuner is more precise. Loudness in dB(A) is measured by the Sound Level Meter.
How it works
- Tap “Start analyzer” and allow microphone access.
- Choose the frequency range: 2 kHz for low tones and hum, 20 kHz for the whole audible range.
- Read the loudest frequency. “Hold” freezes the spectrum, “Peak hold” shows the maxima of the last few seconds, “Waterfall” the history over time.
Frequently asked questions
How accurate is the frequency reading?
The tool uses a 16,384-point FFT; at a 48 kHz sample rate the bins are just under 3 Hz apart, and the peak is interpolated between them. For pure, steady tones the reading is usually accurate to 1 Hz. For tuning instruments, the tuner with pitch detection gives more precise values.
What does dBFS mean?
dBFS (decibels relative to full scale) gives the level relative to the microphone’s maximum: 0 dBFS is the maximum, everything below is negative. It is not a sound pressure level; how loud a sound is in dB(A) is shown by the sound level meter.
Why do I barely see very low or very high frequencies?
Phone and laptop microphones are optimized for speech and pick up frequencies below about 100 Hz and above about 15 kHz only weakly. A small bump there doesn’t mean the sound is quiet. Echo cancellation and automatic gain are switched off so they don’t distort the spectrum further.
Is the sound recorded?
No. The microphone signal is analysed only in the browser and discarded immediately; nothing is stored or uploaded.