Load audio
Use Open Files for selected recordings or Open Folder to browse a directory as a playlist. File navigation appears above the plot when multiple recordings are available.
User guide
Using Spectra
Load recordings, tune the spectral view, and export clean images without sending audio anywhere.
Pick a view
Spectrogram shows time and frequency structure. Spectrum averages the visible window into a frequency profile for quick comparison.
Tune the STFT
Choose a window function, FFT size, window length, overlap, and channel. Larger FFTs improve frequency spacing but take longer to render.
Browse time
Set the visible time window, then scrub through the recording with the browse slider. Spectra remembers your requested window across file navigation.
Inspect points
Hold Command on Mac or Ctrl on Windows/Linux while moving over the plot to show a crosshair with the current time and frequency. In spectrum view, the crosshair reports frequency and level.
Zoom frequency
Set Min kHz and Max kHz to focus on the band you care about. WAV files keep their original sample rate, so ultrasonic recordings retain the correct Nyquist range.
Refine display
Change palette, invert colours, adjust dynamic range, and toggle the major/minor grid to make calls, harmonics, and noise bands easier to read.
Export figures
Save PNG exports the current plot as rendered. Wait for the busy overlay to clear before saving another heavy view.
Privacy
Spectra is a static browser app. Audio is decoded locally in your browser and is not uploaded by the site.