ISO 3382-1: Scope and Field of Application
TL;DR
ISO 3382-1:2009 "Acoustics — Measurement of room acoustic parameters — Part 1: Performance spaces" defines measurement methods for reverberation time (T20, T30, EDT), clarity (C50, C80), definition (D50), centre time (Ts), sound strength (G), and lateral energy fraction. It applies to auditoria, concert halls, theatres, churches, and other performance spaces with volumes typically exceeding 100 m³. Part 2 covers ordinary rooms (offices, classrooms), and Part 3 covers open-plan offices. The standard specifies source and receiver requirements, minimum measurement positions, and uncertainty reporting.
Parameters Defined
ISO 3382-1 defines the following room acoustic parameters, each derived from the measured room impulse response:
| Parameter | Symbol | Description |
|---|---|---|
| Reverberation time | T20, T30 | Decay time from -5 to -25 dB or -5 to -35 dB |
| Early decay time | EDT | Decay time from 0 to -10 dB |
| Clarity | C80 | Early (0-80ms) to late energy ratio for music |
| Clarity of speech | C50 | Early (0-50ms) to late energy ratio for speech |
| Definition | D50 | Early (0-50ms) energy fraction |
| Centre time | Ts | First moment of the squared impulse response |
| Sound strength | G | Level relative to free-field at 10 m |
| Lateral energy fraction | JLF | Early lateral energy (requires figure-of-8 mic) |
Applicable Spaces
Part 1 is specifically for performance spaces — rooms designed for music, speech, or combined use before an audience. This includes concert halls, opera houses, theatres, lecture halls, churches, and multipurpose auditoria. For ordinary rooms like offices and classrooms, ISO 3382-2 provides simplified procedures with fewer measurement positions.
Measurement Requirements
The standard specifies requirements for excitation sources (omnidirectional loudspeaker or impulsive source), microphone positions (minimum distances, spatial averaging), and the impulse response quality needed for reliable parameter extraction. A minimum impulse-to-noise ratio (INR) of 35 dB is required for T20 and 45 dB for T30.
Relationship to Other Standards
ISO 3382-1 depends on accurate impulse response measurement, for which AES-2id provides detailed practical guidance. The reverberation time parameter T30 is used as input to STI calculations per IEC 60268-16. For building acoustics (sound insulation between rooms), ISO 16283 references ISO 3382-1 for background RT60 measurement.
SonaVyx Implementation
SonaVyx implements all primary ISO 3382-1 parameters in the RT60 measurement tool and impulse response analyzer. The Rust DSP engine computes T20, T30, EDT, C50, C80, D50, Ts, and G from the measured impulse response using Schroeder backward integration and linear regression.
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Last updated: March 19, 2026