How to Measure Impulse Response with Sine Sweep

TL;DR

The logarithmic sine sweep (Farina method) is the gold standard for impulse response measurement. It offers superior signal-to-noise ratio compared to balloon pops or MLS, and separates harmonic distortion from the linear response. This guide covers sweep generation, capture, deconvolution, and interpreting the resulting impulse response.

What You Need

A speaker capable of reproducing 50 Hz to 16 kHz (full-range preferred)
A measurement microphone or phone with a known frequency response
SonaVyx Impulse Response tool at /tools/impulse-response

Step-by-Step Procedure

Configure sweep parameters. Open SonaVyx IR tool and set the sweep duration. Longer sweeps yield better SNR: 5 seconds is a good starting point, 10-20 seconds for noisy environments. Set frequency range to 20 Hz - 20 kHz (or limit to your speaker's usable range to avoid wasting energy on inaudible frequencies).
Position source and receiver. Place the speaker at the sound source position (e.g., where a presenter stands, or where the PA speaker is located). Position the microphone at the listener position. For ISO 3382-1 compliance, source height should be 1.5 m and receiver at 1.2 m (seated) or 1.5 m (standing).
Set playback level. The sweep should be at least 45 dB above the background noise level at all frequencies. Play a test sweep and verify on the SPL meter that the level is sufficient. Typical levels: 80-90 dBA at 1 m from the speaker.
Ensure silence during measurement. Any noise during the sweep contaminates the impulse response. Close doors, stop HVAC if possible, and keep people still. If you cannot stop HVAC, use a longer sweep (10-20 seconds) to average out the noise.
Play the sweep and capture. Tap "Measure" in SonaVyx. The tool generates the logarithmic sweep, plays it through the speaker, and simultaneously captures the microphone signal. Wait for the full sweep plus the room's decay time before stopping.
Deconvolution. SonaVyx automatically performs the inverse filter convolution (Farina method) to extract the impulse response from the recorded sweep. This happens in WASM — no server roundtrip required. The result appears as a time-domain waveform showing the direct sound arrival, early reflections, and late decay.
Verify quality. Check the Impulse-to-Noise Ratio (INR). SonaVyx calculates this automatically. For ISO 3382-1 compliance: INR ≥ 35 dB for T20, INR ≥ 45 dB for T30. If INR is too low, increase the sweep level or duration and remeasure.
Export the IR. Save as 48 kHz / 24-bit WAV for use in convolution reverb plugins, REW, ARTA, or other analysis software. SonaVyx also derives RT60, EDT, C50, C80, D50, and Ts from the captured impulse response.

Sweep vs MLS vs Balloon Pop

Method	SNR	Distortion Rejection	Ease of Use
Log sine sweep	Excellent (scalable with duration)	Yes (separated by deconvolution)	Requires speaker
MLS	Good	No (distortion contaminates IR)	Requires speaker
Balloon pop	Poor (fixed energy)	No	Very easy, no speaker needed

Common Mistakes

Sweep too short. A 1-second sweep in a reverberant space gives poor SNR at low frequencies. Use at least 5 seconds; 10 seconds for rooms with RT60 > 2 seconds.
Clipping the microphone. If the sweep is too loud and the mic clips, the deconvolved IR will contain artifacts. Watch the input meter — keep peaks below -3 dBFS.
Moving during the sweep. Any movement of the source, receiver, or reflective objects during the sweep invalidates the measurement. Stand still and keep the room quiet.
Ignoring the decay tail. Stop recording only after the room has fully decayed (at least 2× the expected RT60 after the sweep ends). Cutting off the tail truncates the impulse response.

Tool Bridge

Open the SonaVyx Impulse Response Tool to generate sweeps and capture impulse responses. Results feed directly into the RT60 calculator for reverberation analysis.