Why does my meeting room sound echoey on calls?

A meeting room sounds echoey on calls because hard surfaces (glass, drywall, hard floors) reflect sound back into the microphones, the mic gain is set too high, or the acoustic echo cancellation (AEC) in the VC bar or DSP is misconfigured for the room. The fix is usually a combination of acoustic treatment, microphone placement and DSP tuning rather than any single change.

The five causes that account for most echo complaints, in roughly the order they appear:

• Reverberant surfaces. Glass partitions, gypsum walls, polished concrete or wood floors and bare ceilings all reflect sound. The room's reverb time (RT60) is the time it takes for a sound to decay by 60 decibels. Untreated meeting rooms often run 0.8 to 1.2 seconds; you want 0.4 to 0.6 seconds for clean VC audio.
• Microphone gain too high. When the mics are turned up to compensate for soft talkers, they pick up more reflected sound. Remote participants hear an "echoey, swimmy" room. Reducing gain by 3 to 6 dB and asking talkers to lean in is often the fastest free fix.
• Speaker-to-mic geometry. A speaker pointed directly at a microphone creates a feedback loop the AEC has to fight. Ceiling speakers should be offset from the ceiling mics, not directly above them.
• AEC misconfigured. Acoustic echo cancellation is the algorithm that subtracts the speaker output from the mic input so remote participants don't hear themselves. In integrated VC bars it works automatically, but in separate-component rooms (Q-SYS Core, Biamp Tesira, Shure IntelliMix Room) the AEC reference signal must be configured against the actual speaker feed. Wrong reference equals nasty echo.
• Room mode standing waves. Rooms with parallel hard walls produce low-frequency resonance that masks speech intelligibility. More common in rectangular boardrooms with no soft furnishings.

The fix order that usually works:

1. Acoustic treatment first. Even modest treatment (carpet tiles, acoustic ceiling tiles, fabric wall panels on one or two walls, a few baffles) can drop RT60 from 1.0 to 0.5 seconds. Most cost-effective single intervention.
2. Microphone placement and gain. Move ceiling mics off any speaker centre line. Reduce gain. Fewer mics with higher selectivity (Shure MXA920 lobes, Sennheiser TCC2 zones) often outperform many mics turned up loud.
3. DSP and AEC tuning. A site visit to retune AEC reference, gain structure, mix-minus and noise reduction. On a Q-SYS or Biamp room this is often a 2 to 3 hour fix.
4. Speaker repositioning. As a last resort, rework the ceiling speaker layout if the original geometry is fighting the mics.

A site survey of an existing problematic meeting room by an integrator that does proper consultation and design will diagnose which of the above is dominant before any equipment change is recommended.

Quick reference: target RT60 of 0.4-0.6 seconds, fix acoustic treatment first, then mic placement and gain, then DSP/AEC tuning.