What question did this study set out to answer?

This work aims to establish acoustic criteria for rooms designed specifically for speech and communication. It focuses on ensuring effective sound environments through recommended limits on reverberation time.

May 14, 2026

Japanese standard and design guidelines for sound absorption in architectural spaces, Part 3: Recommended criteria for rooms intended for speech and communication

Key Points

This work aims to establish acoustic criteria for rooms designed specifically for speech and communication. It focuses on ensuring effective sound environments through recommended limits on reverberation time.
The recommended criteria classify rooms by directionality (unidirectional or bidirectional) and duration (short or long) of communication.
Reverberation time limits were established based on a unified function using the equivalent floor absorption coefficient and room volume.
The criteria's validity is assessed through physical indices and comparisons to existing standards.
Recommended upper limits for reverberation time are defined for the mid-frequency band based on room type adjustments.
Limits on low- and high-frequency reverberation times are provided relative to the mid-frequency band.
Ongoing verification shows a correlation between room dimensions and speech transmission effectiveness.

Abstract

The Architectural Institute of Japan is currently establishing an acoustic standard and its design guidelines of sound absorption to ensure a basic sound environment for a variety of architectural spaces. Based on the framework in Part 1, this part presents the recommended criteria for rooms intended for speech and communication. Rooms are classified into three types according to the directionality (unidirectional or bidirectional) and duration (short or long) of expected speech communications in them. For each room type, the recommended criteria are given as upper limits on the reverberation time in the mid-frequency band. These limits are calculated using a unified function with two parameters: (1) the equivalent floor absorption coefficient for a reference ceiling height of 2.5 m, as defined in Part 2, and (2) the room volume. For both low- and high-frequency bands, upper limits are set on the ratio of their reverberation times relative to that of the mid-frequency band. The validity of the criteria is being examined based on the relationship between physical indices and speech transmission performance in various room dimensions, comparison with existing related standards, and surveys of reverberation time in actual rooms. This part also reports on the progress of this verification process.

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