RT60 Measurement per ISO 3382-1: Performance Spaces

ISO 3382-1 Overview

ISO 3382-1:2009 specifies methods for measuring reverberation time and other room acoustic parameters in performance spaces such as concert halls, theatres, and auditoriums. It defines:

• T20, T30, EDT (Early Decay Time)
• Clarity C50 (speech) and C80 (music)
• Definition D50
• Centre Time Ts
• Sound Strength G

Measurement Method

The standard recommends using a logarithmic sine sweep (Farina method) as the excitation signal. SonaVyx generates sweeps from 20 Hz to 20 kHz with configurable duration (2-20 seconds). The captured response is deconvolved using the inverse filter method in the frequency domain to extract the room impulse response.

Source and Receiver Positions (§5.2)

For comprehensive room characterization:

• Minimum 2 source positions (on stage area)
• Minimum 3 receiver positions per source (in audience area)
• Receivers at least 2m apart and 1m from any wall
• Source at least 1m from any wall

Evaluating T20 and T30 (Annex A.2)

Reverberation time is extracted from the energy decay curve (EDC) computed via Schroeder backward integration of the squared impulse response:

• T20: Evaluated from -5 dB to -25 dB, extrapolated to -60 dB. Requires ≥35 dB INR.
• T30: Evaluated from -5 dB to -35 dB, extrapolated to -60 dB. Requires ≥45 dB INR.
• EDT: Evaluated from 0 dB to -10 dB, extrapolated to -60 dB.

Linear regression r² must exceed 0.995 for the result to be considered valid. SonaVyx validates this automatically and flags measurements with poor regression quality.