Audacity Chirp Generator: Set Start and End Frequencies

The Chirp generator in Audacity is a built-in audio synthesis tool used to produce tones that continuously change in pitch and volume over a designated timeframe. This article explains what the Chirp generator is, how it operates, and provides a clear, step-by-step guide on how to configure its start and end frequencies to create custom audio sweeps for calibration, testing, or sound design.

What is the Chirp Generator in Audacity?

The Chirp tool generates an audio signal that sweeps from one frequency and amplitude to another. Unlike Audacity’s basic Tone generator, which produces a static, unchanging pitch, a chirp dynamically modulates between two distinct states. It supports four different waveforms: Sine, Triangle, Square, and Sawtooth. Chirp signals are commonly used to create sound effects (such as laser or sci-fi sweeps), perform acoustic room testing, and calibrate audio hardware across a spectrum of frequencies.

How to Specify Start and End Frequencies

Specifying start and end frequencies in Audacity is done directly through the Chirp dialogue window. Follow these steps:

  1. Open the Chirp Dialogue: Navigate to the top menu bar, click Generate, and select Chirp... from the dropdown list.
  2. Set the Waveform: Choose your desired waveform (Sine is standard for pure frequency sweeps) from the Waveform dropdown menu.
  3. Specify the Starting Frequency: Locate the Frequency (Hz) section. In the Start field, type the numerical value in Hertz for your initial pitch (for example, 20 for low bass or 440 for musical pitch A4).
  4. Specify the Ending Frequency: In the End field directly beside or below the start field, type the target frequency where the sweep should finish (for example, 20000 to sweep up to the human hearing limit, or a lower value like 100 to create a downward pitch dive).
  5. Choose an Interpolation Method: Select either Linear or Logarithmic from the Interpolation setting.
    • Linear changes the frequency by an equal number of Hertz per second.
    • Logarithmic changes the pitch exponentially, which mirrors how human ears naturally perceive musical pitch intervals (such as octaves).
  6. Set Amplitude and Duration: Optionally adjust the Amplitude (from 0.0 to 1.0) for both start and end to control volume changes, then set the total time in the Duration box.
  7. Generate the Tone: Click Generate (or OK, depending on your Audacity version) to insert the generated chirp directly onto your timeline at the cursor position.