North American echolocation explorer

Bat Call Lab

Choose a bat. Listen to its call. Explore what changes.

37 species presetsSynthesized audioResearch notes inside
Species call studio

Big brown bat

Eptesicus fuscus
Reference preset
Starting frequency53.4 kHz
Ending frequency26.7 kHz
Call duration7.9 ms
These are simplified echolocation simulations. Playback brings the modeled frequencies into human hearing. The plots retain the original bat frequencies.
Frequency is divided by 10; call timing stays unchanged.
Approach and buzz timing are illustrative behavior models.
Ready. Start at a comfortable listening volume.
One call · frequency contourModeled track, not a recorded spectrogram
Big brown bat
A bat pass · call rhythm1.5 seconds at the bat’s timescale
Adjust the simulation

Change the model to explore variation. Sliders describe the original bat call, before audible conversion.

Harmonic strength and the call rate are modeling choices, not species measurements.

Downloads contain synthetic calls and are named accordingly. The settings file records all parameters and the source.

Species reference & interpretation
How to use Bat Call Lab

1. Start with a preset

Select a common or scientific name. Frequency and duration come from a published reference; rate and curve geometry are adjustable approximations.

2. Make ultrasound audible

Pitch ÷10 lowers the tone while keeping the sequence’s timing. This idealized synthesis does not recreate a detector’s zero-crossing circuitry.

Time expansion ×10 lowers frequency and stretches the complete sequence. A 1.5-second pass takes 15 seconds to play.

3. Watch the behavior

Search calls repeat steadily. Approach shortens the calls and gaps. The feeding model moves from search to approach to a rapid terminal buzz.

4. Compare like with like

The second species uses its reference settings with the same listening mode and behavior. A → B plays the selected model, a short pause, then the reference model.

Change a slider and press Play again to hear the update.

Call frequencies overlap, and bats change their calls with habitat, flight, and behavior. These simulations support teaching and exploration; they do not identify an unknown bat or represent social calls.
Research sources, coverage & model

Sources checked October 1, 2026. This library covers a broad selection from the United States and Canada, including southwestern species also occurring in Mexico. It is not a complete inventory of North America, Mexico, or the Caribbean.

What is measured, and what is modeled?

Presets use published mean high frequency, low frequency, and duration where available. These means often describe a selected, discriminating subset of calls rather than a whole species. “Characteristic frequency” (fc) is a separate reference measurement, not the endpoint or the frequency of maximum energy. The charts trace an analytic chirp through the start, a late-call anchor, and the end; they are not an FFT spectrogram.

Curve shape, onset envelope, call rate, deterministic ±3% variation, harmonic amplitude, and approach/buzz changes are explicit model choices. Every sample integrates the instantaneous frequency to preserve continuous phase within a call. Each call fades in and out; output amplitude is independent of natural source level. Comparisons do not simulate distance, echoes, habitat, detector response, or hearing sensitivity.

Listen to real NPS recordings ↗