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Video & Audio Tools

Audio Frequency Analyzer

See what an audio file is made of. The analyser runs a fast Fourier transform over the whole file and shows the average spectrum on a logarithmic frequency axis, the strongest frequencies with their musical notes, the balance between bass, mids and treble, the spectral centroid as a measure of brightness, and a spectrogram that shows how the frequencies change over time.

  • Files stay on your device
  • No sign-up
  • Free to use

How to use Audio Frequency Analyzer

  1. Drop an audio file onto the page.
  2. Choose the analysis resolution.
  3. Click “Analyse frequencies”.
  4. Read the results and download the spectrogram or spectrum.

Audio Frequency Analyzer features

Average spectrum

20 Hz to 20 kHz, logarithmic.

Peak frequencies

With note names and cents.

Balance

Bass, mids and treble energy.

Spectrogram

Frequencies over time.

Export

PNG spectrogram, CSV spectrum.

Private

Processed in your browser; nothing is uploaded.

When to use Audio Frequency Analyzer

  • Finding the frequency of a hum or whistle.
  • Checking the pitch of tones and instruments.
  • Inspecting mixes for too much bass or harshness.
  • Spotting low-quality or upsampled files.

Audio Frequency Analyzer FAQ

How accurate are the frequencies?

Each FFT bin is about 11 Hz wide at 4096 points and 5 Hz at 8192; peaks are refined between bins, so pure tones are measured to within about 1 Hz.

What does the spectrogram show?

Time from left to right, frequency from bottom to top, and loudness as brightness.

How can it reveal low-quality files?

MP3s at low bitrates cut off high frequencies – visible as a sharp edge in the spectrum around 16 kHz or lower. Upsampled files show nothing above the original limit.

Is the audio uploaded?

No. It is decoded and analysed in your browser.

Which formats can I use?

MP3, WAV, M4A/AAC, OGG, Opus, FLAC, WMA and AIFF, and the audio of MP4, MOV, WebM and MKV videos. Save in the original format or as MP3, M4A, WAV or FLAC.

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Frequency analysis with the FFT

Every sound is a mixture of frequencies. A pure tone has one, a voice has a fundamental and many harmonics, a cymbal spreads energy across the high range. The Fourier transform breaks a stretch of audio into these components, and the fast Fourier transform (FFT) does so efficiently.

The analyser decodes the file with the Web Audio API, mixes the channels to mono and slices the audio into overlapping windows of 2048 to 8192 samples. Each window is shaped with a Hann function to reduce leakage between frequencies and transformed with an FFT written for this tool. Averaging the power of all windows gives the overall spectrum.

Peaks are found as local maxima that stand out from their surroundings, refined by fitting a parabola through neighbouring bins, and translated into musical notes with the deviation in cents. Energy is summed for bass (20–250 Hz), mids (250–2000 Hz) and treble (above 2 kHz), and the spectral centroid – the energy-weighted average frequency – indicates how bright the sound is.

The spectrogram keeps the individual windows instead of averaging them. Drawn as an image, it reveals melodies, rhythm, noise and the cut-off frequencies of compressed audio.

All analysis runs locally.

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