Fourier Transform Audio Visualizer
Watch the discrete Fourier transform decompose sound into its component frequencies in real time. Use a built-in oscillator with four classic waveforms or grant microphone access to analyze your voice, an instrument, or any ambient sound.
Analysis
Click Run to play the tone (oscillator) or grant microphone access. The yellow line on the spectrum marks the loudest frequency. Try changing waveform shape to see how the harmonic content changes.
Controls
Use Run / Pause in the lab controls to start or stop the tone.
FFT settings
Display
Music presets
Reference Guide
The Fourier Transform
Any periodic signal can be decomposed into a sum of sines and cosines.
The browser uses the discrete fast Fourier transform (FFT) operating on short windowed buffers of the audio waveform.
Harmonic Series
Real instruments produce a fundamental plus integer-multiple harmonics:
A square wave contains only odd harmonics. A sawtooth contains all harmonics. A pure sine has only the fundamental.
FFT Size and Resolution
The frequency resolution is the sample rate divided by the FFT size:
A 2048-point FFT at 48 kHz gives ≈ 23 Hz resolution. Larger FFT = finer frequency detail but coarser time resolution. This is the time-frequency uncertainty principle.
Speech and Music
Human voices typically span 80-1000 Hz fundamentals plus harmonics out to 8 kHz. Vowels have characteristic formant patterns.
Concert A is 440 Hz. Doubling the frequency raises a note by one octave.
The spectrogram on the right scrolls left-to-right showing how the spectrum changes over time.
