Sound is the first thing an audience notices when it goes wrong, and the last thing they think about when it goes right. The cause is rarely poor equipment; usually the equipment is excellent and the room was never accounted for. Here is what is actually happening when “nobody can hear the speaker”, and how a system should be tested before your guests discover the problem for you.
Reverberation: the enemy of intelligibility
Large rooms with hard surfaces — marble, glass, high ceilings — reflect sound repeatedly before it decays. The listener receives the direct sound from the loudspeaker, then copies of it arriving fractions of a second later off the walls. The result is not a quiet sound but an unintelligible one: you can hear that the speaker is talking, but you cannot make out the words.
This is why turning the system up makes it worse — it raises the direct and the reflected sound together. The fix lies in loudspeaker aim, distribution and frequency shaping, so energy reaches the audience rather than the walls, and in absorbing what can be absorbed. The audience themselves, with their clothes and bodies, are the largest absorber in the room.
Why row five hears and the back row does not
A loudspeaker is not a lamp that lights evenly. Every system has a coverage pattern, and anything outside it receives weaker, less intelligible sound. In long rooms, rooms with balconies, or rooms divided by columns, one system at the front is never enough however large it is. The answer is distributed fill loudspeakers, time-aligned so their sound arrives together with the sound from the front rather than behind it as an audible echo.
Feedback is not a fault in the microphone
That sharp squeal happens when a microphone picks up what the loudspeaker is producing and feeds it back in a closed loop. The usual causes: a microphone in front of the loudspeakers rather than behind them, a speaker holding the microphone away from their mouth so its level is raised to compensate, or too many open microphones at once. The cure is as much procedural as technical: one open microphone for whoever is speaking, the rest muted.
Wireless and a crowded spectrum
Wireless microphones share radio frequencies with other equipment. In a building hosting several events, or alongside other radio devices, interference appears as dropouts or crackle. This is why the spectrum is scanned on site before the event and channels are assigned from what is actually there, not from what worked in another hall last week. Batteries remain a dull and common cause: they are changed before each session, not when the sound starts to fade.
The source everyone forgets to test
Many audio failures have nothing to do with the room: a video inside a presentation whose sound was never checked, a speaker’s laptop connected a minute before their talk so the sound comes out of its internal speaker, or a video call with a remote participant never tried from the room itself. Everything that will be played from a device should pass through the sound system at least once before the event.
How to test a system properly
- Walk the room. A system is not judged from the mixing position alone; listen from the first row, the back row, the sides and under the balcony.
- Test with speech, not taps. Tapping a microphone measures nothing about intelligibility. Read a full passage at a natural level, and in the language that will actually be spoken.
- Test with the actual speakers. Voices differ: some whisper, some project. Levels are set to them, not to the engineer.
- Allow for the difference a full room makes. An empty room is far more reverberant than a full one. The final tuning is reviewed once the audience is in, not only before.
- Rehearse the transitions. Failure usually happens in the moments in between: video to speaker, platform to floor for questions.
- Have a plan for silence. What happens if the keynote’s microphone dies mid-sentence? A replacement must be seconds away, in the hands of someone who knows it is their job to deliver it.
In short
Good sound is not a product you buy; it is a system designed for a particular room and managed throughout the event. The engineer who stays behind the desk from the first word to the last is not an added cost — they are what stops the sound being the thing people remember about your event.
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