Professional Spectrogram for Bioacoustics
A free tool for building spectrograms and sonograms from field recordings. Supports adjustable FFT (256–8192), window functions (Hann, Hamming, Blackman, Kaiser), overlap and six colormaps. Analysis and rendering run in the browser via the Web Audio API — the tool keeps working offline after the first page load.
How to analyze a field recording
Drop a WAV, FLAC, MP3, OGG, M4A or AIFF file (up to 500 MB). For bat ultrasound, use recordings sampled at 96 kHz or higher.
Presets auto-configure the frequency range, FFT size, window and colormap for songbirds, raptors, bats, whales, frogs or insects.
Adjust FFT size to balance time vs frequency resolution. Switch to a log frequency scale for whale songs and pigeon vocalizations.
Use the Measure tool to draw a box — duration, bandwidth and center frequency appear below. Use Annotate to label calls with species names.
Save a PNG image with colorbar, a CSV of annotations (ready for Raven, R, Python) or a WAV of the filtered audio or selection.
Build sonograms, measure frequency and bandwidth, annotate calls
- Cursor — click the spectrogram or waveform to jump to that point in the recording.
- Measure — drag a rectangle to see duration, center frequency and bandwidth.
- Annotate — drag a region and enter a label (e.g. species name) to mark calls.
- Presets — pick birds, bats, whales etc. to auto-tune FFT, frequency range and colormap.
- Mouse wheel — zoom time. With Ctrl — zoom frequency.
- Shift + drag or middle-click — pan along the time axis.
- On touch screens: one finger to select/pan, two fingers to pinch-zoom.
- + / − / ⤢ buttons — zoom in/out and fit to window.
- Space — play / pause
- ← → — pan time
- + − — zoom in/out
- 0 — fit to window
- Esc — clear selection
- Delete — remove last annotation
Features
FAQ
What file formats are supported?
WAV, FLAC, MP3, OGG, M4A, AIFF, AAC, OPUS, WebM. For bat recordings (96–384 kHz), WAV or FLAC are recommended — they store ultrasound without loss.
Can I analyze bat echolocation?
Yes. Pick the Bats preset (20–100 kHz, FFT 256, 90% overlap). Your file must be recorded at 96 kHz or higher — otherwise ultrasonic content is filtered out at capture.
What is the difference between linear and log frequency scale?
Linear spreads frequencies evenly — good for birds and insects. Logarithmic stretches low frequencies — useful for whale songs, frogs and pigeon signals.
What does the FFT parameter do?
FFT size is a trade-off: larger (4096–8192) gives fine frequency resolution but blurs time. Smaller (256–512) gives sharp time but coarse frequency. Use 256–512 for bird trills and bat clicks.
How long can my recordings be?
Up to 30 minutes at 44.1 kHz or 10 minutes at 96 kHz work smoothly. Longer files need more memory — process them in chunks.
Can I apply a band-pass filter?
Yes. Open the Filter panel, pick a type (band-pass, high-pass or low-pass), set the cutoff frequencies and click Apply. The filtered audio can be previewed and exported.
We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.
