Optimizing low-frequency reverberation in a critical listening room

To evaluate subtle nuances in different audio reproduction systems or conduct auditory perceptual studies, international standards, such as the ITU-R BS.1116-3, indicate the need for a space with minimal residual noise and very low reverberation in all frequencies of interest. We constructed a Critical Listening Room (CLR) designed to meet these stringent requirements. The first construction phase employed a “box-in-a-box” design, featuring external walls made of cement blocks and internal walls built with a light steel frame and triple-layered gypsum boards, all resting on a floating floor. This design achieved outstanding sound isolation, surpassing the NR10 criterion, with residual noise levels of less than 6 dBA. The second construction phase focuses on installing internal wall treatments to address the room's reverberation time, which remains notably high at lower frequencies (e.g., 7 s at 50 Hz). To mitigate this, mineral wool and membrane absorbers are commonly used. In this study, we evaluate the effectiveness of various absorber configurations in controlling low-frequency reverberation, presenting results from detailed acoustic measurements conducted in the CLR.