Audio Spectrum Analyzer — Free
Free audio spectrum analyzer with log-frequency display, peak hold, L/R colors and spectrogram. Verify with the built-in 1 kHz tone. Runs in your browser.
Protect your hearing. Start at a low volume. Never raise the volume to make a tone audible. Levels are shown in dBFS, relative to full scale — not SPL.
How it works
The spectrum is computed live in your browser from the master output tap. Nothing is uploaded or recorded. Levels are reported in dBFS, relative to full scale.
A spectrum analyzer turns sound into a picture of frequency content. Each bar is the level in one logarithmically spaced band, so octaves take equal space the way hearing works. Use it to confirm a test tone, spot hum, or compare left and right channels.
Log-frequency bars and spectrogram
Bars show the current instant. Enable the spectrogram to scroll history downward over time, which makes intermittent tones and dropouts visible. Peak hold keeps a thin marker at each band’s recent maximum until you toggle it off.
L/R colors and pause
Left renders in deep sky blue and right in warm amber. Pause freezes the display for inspection without stopping audio. All levels are dBFS, relative to full scale, and the peak value is always available as text for screen readers and keyboard users.
Frequently asked questions
What does the spectrum analyzer show?
It shows live energy per frequency on a logarithmic axis from 20 Hz to 20 kHz. The peak readout names the loudest band in hertz with its level in dBFS, relative to full scale.
How do I verify it works?
Press Play to start the built-in 1 kHz sine. The tallest bar and the text peak readout should sit at about 1000 Hz.
What are the blue and amber bars?
Blue is the left channel and amber is the right channel. Switch to L, R, or L+R to isolate what you see.
Does the display flash?
No. The display updates smoothly, respects reduced-motion settings, and can be paused at any time. Every visual has a text equivalent.