How to Fix Conference Room Audio Problems

Symptoms

Participants in conference rooms struggle to understand speakers on the far side of the table. Remote participants on video calls complain they cannot hear clearly. Echo cancellation on conferencing systems performs poorly because the room reverb exceeds the canceler design limits. Side conversations bleed into ceiling microphones. HVAC noise competes with speech during quiet discussion. The intelligibility problem worsens as the room gets larger and when ceiling height increases.

Common Causes

Most conference rooms are built with hard, reflective surfaces: glass walls, hard tabletops, plaster ceilings, and hard flooring. These surfaces create RT60 values of 0.8-1.5 seconds, far exceeding the 0.4-0.6 second target for speech communication rooms. The large glass wall typical of modern conference rooms reflects sound energy back into the room and toward ceiling microphones. HVAC systems in commercial buildings often exceed NC-30 in conference rooms. Ceiling speakers placed too high or with too wide a coverage pattern excite the reverberant field more than necessary. Tabletop speakerphones placed at the center of a large table are too far from speakers at the edges.

Measurement Procedure

1. Measure RT60 using SonaVyx — target is 0.4 to 0.6 seconds across 250Hz to 4kHz.
2. Measure background noise with the SPL meter — target is NC-25 to NC-30 (below 35 dBA).
3. Measure STI through the conferencing system — target is 0.60 or above.
4. For hybrid meetings, also measure STI as heard by remote participants by recording the far-end audio.
5. Note the per-octave-band RT60 to identify which frequency ranges need treatment.

Interpretation

Conference rooms with RT60 above 0.8 seconds will have intelligibility problems. Background noise above NC-35 degrades clarity during quiet speech. The combination of both high RT60 and high background noise is particularly damaging because the reverberant energy masks the direct speech signal. For video conferencing, the room acoustics affect not only in-room listeners but also remote participants because the room microphones pick up both direct speech and room reflections.

Solutions

Install acoustic ceiling tiles or suspended absorption panels to reduce ceiling reflections — this is the single most effective treatment for conference rooms because the ceiling is the largest unobstructed reflective surface. Apply absorption to the rear wall behind the primary display. Add absorption panels to side walls at seated ear height. Use an acoustic felt or fabric finish on hard table surfaces. For glass walls, apply acoustic curtains or film-based absorbers that maintain transparency. Upgrade ceiling microphones to beamforming arrays that reject room reflections. Reduce HVAC noise with duct silencers or lower fan speeds during meetings. Position speakers closer to seated listeners rather than relying on distant ceiling speakers.

Verification

After treatment, remeasure RT60 (target under 0.6 seconds) and STI (target above 0.60). Conduct a test video call with remote participants and confirm improved clarity. The improvement in echo cancellation performance is often the most immediately noticeable benefit — remote participants will comment that the room sounds much cleaner.

Measure conference room STI