ISO 3382-1: Acoustics — Measurement of room acoustic parameters — Part 1: Performance spaces

Specifies methods for the measurement of reverberation time and other room acoustic parameters in performance spaces.

ISO 3382-1: Measurement of Room Acoustic Parameters

ISO 3382-1:2009 is the international standard for measuring acoustic parameters in performance spaces. Published by the International Organization for Standardization, it defines the methods for obtaining reverberation time, early decay time, and a suite of room acoustic parameters that characterize how a space supports music and speech. This standard is essential for architects, acoustic consultants, and venue operators.

Reverberation Time Parameters

The standard defines three reverberation time metrics derived from the Energy Decay Curve (EDC). T20 evaluates the decay slope between -5 dB and -25 dB, then extrapolates to 60 dB. It requires a minimum impulse-to-noise ratio of 35 dB. T30 uses the range from -5 dB to -35 dB, requiring at least 45 dB INR but providing more accurate results. EDT (Early Decay Time) measures from 0 dB to -10 dB and correlates most strongly with perceived reverberance, making it valuable for subjective room quality assessment.

Additional Room Parameters

Beyond reverberation time, ISO 3382-1 defines several parameters that describe early and late energy balance. C50 (Clarity for speech) is the ratio of early energy (0-50 ms) to late energy. C80 (Clarity for music) uses an 80 ms boundary. D50 (Definition) expresses the early energy fraction as a percentage. Ts (Centre Time) is the time of the first moment of the squared impulse response, indicating the balance between early and reverberant sound. Sound Strength (G) measures the sound energy relative to a reference impulse response measured in a free field at 10 meters.

Measurement Requirements

ISO 3382-1 specifies that measurements should use either an omnidirectional sound source with a log sweep or impulsive excitation. Multiple source and receiver positions are required to characterize spatial variation. The standard defines minimum source-receiver distances, source directivity requirements, and the number of measurement positions based on measurement precision (survey, engineering, or precision grade).

SonaVyx Implementation

SonaVyx implements the full ISO 3382-1 parameter set including T20, T30, EDT, C50, C80, D50, Ts, and Sound Strength. The log sweep generator provides configurable excitation signals from 2 to 20 seconds. Schroeder backward integration produces the EDC, and linear regression with r-squared validation ensures measurement quality. The INR is checked against ISO thresholds, with clear warnings when signal-to-noise ratio is insufficient for reliable T30 measurement.