How to Measure RT60: Step-by-Step Guide

TL;DR

RT60 measures how long sound takes to decay by 60 dB. SonaVyx measures RT60 using a logarithmic sine sweep deconvolved to extract the room impulse response, then applies Schroeder backward integration to compute T20/T30/EDT per octave band.

How to Measure RT60 Reverberation Time

RT60 is the time it takes for sound to decay by 60 dB after the source stops. It is the most fundamental room acoustic parameter, defined by ISO 3382-1. Accurate RT60 measurement helps you understand how a room supports speech, music, or both.

Step 1: Set Up the Sweep Signal

Open SonaVyx and navigate to the RT60 tool or the Room Analysis workflow. Select a log sine sweep as the excitation signal. A sweep duration of 5-10 seconds provides a good signal-to-noise ratio for most rooms. Connect a loudspeaker capable of producing at least 80 dB SPL at the measurement position. Place the speaker at one end of the room, facing into the space.

Step 2: Capture the Impulse Response

Position your measurement microphone at the listening area, at least 1 meter from reflective surfaces. Click Start Measurement in SonaVyx. The system plays the sweep through the loudspeaker, captures the room response through the microphone, and performs deconvolution to extract the impulse response. The Farina log-sweep method separates harmonic distortion from the linear impulse response, giving clean results even with inexpensive speakers.

Step 3: Analyze with Schroeder Integration

SonaVyx automatically computes the Energy Decay Curve (EDC) using Schroeder backward integration of the squared impulse response. This produces a smooth monotonically decreasing curve that is far more reliable than observing individual decay events. The EDC is displayed on screen with the regression lines overlaid.

Step 4: Read T20, T30, and EDT Values

From the EDC, SonaVyx extracts three key decay metrics. T20 evaluates the slope between -5 dB and -25 dB and extrapolates to 60 dB. T30 uses -5 dB to -35 dB, requiring better signal-to-noise ratio but giving more accurate results. EDT (Early Decay Time) measures from 0 dB to -10 dB and correlates with perceived reverberance. SonaVyx validates each measurement by checking the linear regression correlation coefficient (r-squared should exceed 0.95) and verifying the impulse-to-noise ratio meets ISO 3382 thresholds (35 dB for T20, 45 dB for T30).

Step 5: Review Octave-Band Results

Compare your RT60 values against target ranges for your room type. SonaVyx displays per-octave-band RT60 bars alongside typical targets for classrooms (0.4-0.6s), offices (0.5-0.8s), concert halls (1.5-2.5s), and other venue types.