How to use Audio Spectrogram Analyzer

Choose a supported WAV and select the channel to inspect.
Choose an FFT window and narrow the time or frequency bounds if you need a closer view.
Run the analysis, compare bands across time and save the PNG or CSV.

Example: Audio Spectrogram Analyzer

Find a steady tone in a short recording.

You add

Source: one-second mono WAV, 48 kHz, 1,500 Hz sine at amplitude 0.5. FFT: 1024; channel: Left or mono; start: 0; end: 1; minimum: 1000 Hz; maximum: 2000 Hz.

You get

Bin 32 is centered at 1,500 Hz with about -6.02 dBFS amplitude. The report gives 46.875 Hz bin spacing; the PNG and CSV cover the chosen band.

Options

FFT window size: A larger window narrows the frequency-bin spacing while spanning more time. Choose a shorter window to inspect quicker changes.
Analyzed channel: Left or mono reads the first channel; Right requires stereo. Average both stereo channels can cancel an opposite-phase signal.

Supported inputs and limits

Selected files128 MiB total

Supported duration600 seconds

RIFF WAV only: mono/stereo PCM16, PCM24, PCM32 or float32 at 8–96 kHz; up to 128 MiB and 600 seconds. Compressed WAV, extended headers and other containers are refused. Work stays on your device. At most 256 sampled windows and 200,000 cells. A long view can skip brief events between windows.

Where your input is processed

This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

Choose time or frequency detail

A larger window separates nearby frequency bins but spans more time. The display uses a Hann window and normalized one-sided amplitudes, with a -120 dBFS floor. It measures spectral amplitude, rather than perceived loudness. Narrowing the view reruns the analysis; it does not recover events omitted by a wider sampling hop.

Check the channel before interpreting a gap

Averaging both channels can cancel opposite-phase stereo. Compare left and right separately if a band disappears. A band at a frequency bin is evidence about this recording, not a diagnosis of its source or a guarantee of audible quality.

Questions about Audio Spectrogram Analyzer

Is the PNG all of the measured data?

The PNG shows the selected bin centers. The CSV stores their time, frequency and amplitude values.

Why can a stereo band disappear?

Averaging opposite-phase channels can cancel that signal. Compare left and right separately before interpreting the averaged view.

Is my input uploaded?

Nothing is uploaded.

Project manager: Tony Hines · Content updated 4 October 2026 · Report a problem