Audacity Chirp Generator for Room Calibration

Audacity’s built-in Chirp generator provides an accessible, free method to create frequency sweeps for acoustic testing and room calibration. By synthesizing a logarithmic sine sweep across the audible spectrum, you can evaluate speaker response, identify room modes, and map acoustic reflections. This guide explains how to generate these sweeps in Audacity, why specific settings matter, and how to use them effectively for room analysis.

Generating the Sweep in Audacity

To create an acoustic test sweep, open Audacity and follow these steps:

  1. Navigate to the top menu and select Generate > Chirp...
  2. Set the Waveform to Sine. Pure sine waves are standard for acoustic transfer function measurements.
  3. Configure the Frequency settings:
    • Start: Set to 20 Hz (the lower limit of human hearing and typical sub-bass).
    • End: Set to 20000 Hz (the upper limit of human hearing).
  4. Configure the Amplitude settings:
    • Start: Set to 0.8 (or -2 dBFS).
    • End: Set to 0.8 (or -2 dBFS). Keeping the amplitude slightly below 1.0 prevents digital clipping during playback and processing.
  5. Set the Interpolation to Logarithmic.
  6. Set the Duration between 5.000 and 10.000 seconds. A longer sweep provides a better signal-to-noise ratio in larger spaces.
  7. Click Generate.

Why Logarithmic Interpolation Is Critical

Audacity offers both Linear and Logarithmic interpolation. For room calibration, you must always choose Logarithmic.

Human hearing and musical pitch perceive frequency on an octave-based (logarithmic) scale, where the interval between 20 Hz and 40 Hz represents the same musical distance as 10,000 Hz to 20,000 Hz. A linear sweep spends an equal amount of time at every Hertz, meaning 90% of the sweep duration would be concentrated above 2,000 Hz, leaving the bass and lower-midrange severely under-sampled. A logarithmic sweep spends equal time per octave, delivering equal energy across all frequency bands and providing the precise data needed to detect room resonance and standing waves.

Using the Sweep for Calibration

Once generated, export the sweep as an uncompressed WAV file (typically 24-bit, 44.1 kHz or 48 kHz).

To test your space:

  1. Position an omnidirectional measurement microphone at your primary listening position.
  2. Play the sweep through your studio monitors or reference speakers at a calibrated, comfortable listening volume (typically 75 to 85 dB SPL C-Weighted).
  3. Record the microphone input directly into a separate audio track.
  4. Use Audacity’s Plot Spectrum tool (Analyze > Plot Spectrum) on the recorded audio to view the overall frequency curve, or switch the track display to Spectrogram view to observe low-frequency ringing and decay times.

Considerations and Limitations

While Audacity is fully capable of generating pristine acoustic sweeps, it does not feature automated impulse response deconvolution or room correction filter generation out of the box. Dedicated room measurement tools often embed high-frequency timing chirps before the main sweep to calculate latency and phase alignment. Audacity's Chirp generates a raw, continuous sweep, making it best suited for baseline frequency response checks, manual acoustic analysis, or external processing.