What question did this study set out to answer?

This study aims to evaluate the impact of omitting the 8-dB rule on sound transmission characteristics in a large dataset of building assemblies.

May 14, 2026

The impact of omitting the 8-dB rule from a large-volume, high-dynamic-range sound transmission loss dataset

Key Points

This study aims to evaluate the impact of omitting the 8-dB rule on sound transmission characteristics in a large dataset of building assemblies.
Analyzed over 2000 vertical and horizontal assemblies with STC ratings from 29 to 86.
Calculated STC ratings with and without the 8-dB rule.
Compared results to Speech Privacy Class and Zwicker loudness metrics.
Data shows little correlation between STC ratings and Zwicker loudness or human response.
Omitting the 8-dB rule significantly alters STC ratings for many assemblies.
Study suggests current ASTM E413 standards may need revision based on findings.

Abstract

Recent research demonstrates the 8-dB rule inherent in the Sound Transmission Class (STC) metric does not correlate with Zwicker loudness nor with human subjective response to sound transmission in buildings, contrary to statements within the current ASTM E413 standard. These studies have typically relied on a small number of assemblies with limited variation in assembly construction and dynamic range. This study provides a much larger volume sample with a far more diverse range of assemblies. This includes well over 2000 vertical (wall) and horizontal (floor–ceiling) assemblies, with STC ratings from 29 to 86. The data are used to calculate the STC ratings with and without the 8-dB rule, which are then compared to the Speech Privacy Class (SPC) and Zwicker loudness.

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