How to Measure Reverberation Time (T20/T30): Methods, Equipment, and Standards

Reverberation time is the most fundamental descriptor of room acoustics. ISO 3382-1 (performance spaces) and ISO 3382-2 (ordinary rooms) define two measurement methods: the interrupted noise method and the integrated impulse response method. Both require a calibrated omnidirectional microphone and appropriate source.

• T20: decay time from -5 to -25 dB — suitable for noisy environments
• T30: decay time from -5 to -35 dB — requires higher SNR
• EDT (Early Decay Time): decay from 0 to -10 dB — correlates with perceived reverberance
• Minimum 6 measurement positions required per ISO 3382-2