That sudden high-pitched squeal can stop a presentation, distract an audience and make even a well-planned event feel unsettled. The good news is that it is usually avoidable. To prevent audio feedback, the key is to plan the position and level of microphones, loudspeakers and monitors before guests arrive, then make careful adjustments during soundcheck.
Feedback is not always a sign that equipment is faulty. It is normally the result of sound from a loudspeaker being picked up by a microphone, amplified, played back through the speaker and picked up again. This repeating loop quickly builds into the familiar whistle, hum or howl. A reliable PA system, set up correctly for the room and event format, gives you much more control.
Why audio feedback happens
Every event space has different acoustic challenges. A carpeted meeting room with a seated audience behaves very differently from a glass-fronted venue, a busy exhibition stand or a private party in a hard-floored hall. Reflective surfaces such as windows, bare walls and ceilings send sound back into microphones, while background noise encourages people to turn the system up too far.
The most common cause is simple speaker and microphone placement. If a microphone is facing a speaker, or is positioned behind the front edge of a speaker, it can hear amplified sound directly. The closer the microphone gets to a loudspeaker, the less level is available before feedback begins.
Volume is another factor, but it is not the only one. Excessive microphone gain, unsuitable equaliser settings, open unused microphones and the wrong microphone type can all reduce the system’s feedback resistance. The aim is not merely to make everything louder. It is to achieve clear speech or music at the required level without feeding sound back into the system.
How to prevent audio feedback before the event
The best time to deal with feedback is during planning and setup, not while a speaker is standing at the lectern. Start by considering the audience size, room shape, expected sound level and how people will use microphones. A conference presentation, panel discussion, wedding speech and live band need different setups.
Put loudspeakers in front of microphones
For most speech-based events, front-of-house speakers should be placed ahead of the presenter and their microphone position, facing the audience. A lectern microphone or handheld microphone should never sit directly in front of a loudspeaker.
This may sound obvious, but venue layouts can make it difficult. A screen, stage, pillars or a narrow room sometimes forces equipment into less than ideal positions. In these cases, use speaker stands to raise loudspeakers above head height and angle them towards the audience rather than across the stage. The speaker should cover listeners, not performers or presenters.
Avoid placing microphones close to side-fill speakers, TV speakers or any temporary sound source used for playback. At exhibitions, in particular, neighbouring stands can create unexpected noise and reflections. Directional speakers and sensible placement help keep your audio contained.
Choose the right microphone for the job
Microphone choice has a direct effect on how easily you can prevent audio feedback. A handheld dynamic microphone with a cardioid pickup pattern is a practical option for speeches, Q&A sessions and vocal performances because it primarily captures sound from the front and rejects more sound from the rear.
The user still needs to hold it correctly. Encourage speakers to keep the microphone fairly close to their mouth, usually around 5 to 10 centimetres away, and speak across or into the grille. Holding it at waist level and asking the PA to compensate with more gain is a common route to feedback and unclear speech.
For presenters who need both hands free, a headset microphone often provides more gain before feedback than a lapel microphone because the capsule sits close to the mouth. Lapel microphones are discreet and useful for corporate presentations, but they need careful positioning and may not be suitable for louder rooms or energetic presentations. The right choice depends on the venue, programme and presenter.
Keep unused microphones muted
Every live microphone adds to the chance of feedback. An open microphone can pick up loudspeakers, audience chatter, air conditioning and handling noise, even when no one is speaking. Mute channels that are not currently needed, especially during panel changes, breaks and music playback.
For a panel event, this may mean opening only the active speaker’s microphone where practical, rather than leaving every channel fully up throughout the session. For a band, it means checking that spare vocal microphones are switched off or muted until required.
Set sensible levels at soundcheck
Start with the master level at a sensible position, then bring up each microphone channel gradually while the presenter speaks at their normal volume. Do not test only with a quiet “one, two”. Ask people to use the same projection, movement and distance from the microphone they will use during the event.
If feedback starts to develop, reduce the relevant microphone gain slightly before reaching for the master volume. Lowering the whole system may make the audience struggle to hear while failing to solve the actual problem. A sound engineer can identify the troublesome frequency using an equaliser, but equalisation should support good placement rather than replace it.
Manage monitors, music and room acoustics
Stage monitors are useful for musicians and presenters who need to hear playback or remote contributors, but they need particular care. Position a monitor in the microphone’s least sensitive area. With many cardioid handheld microphones, this is directly behind the microphone. Check the manufacturer’s pickup pattern where possible, as not every microphone rejects sound in exactly the same way.
Keep monitor volume only as high as needed. If performers need more level than a wedge monitor can provide without causing feedback, in-ear monitoring may be the better option. It reduces stage volume and gives performers clearer monitoring, though it needs additional equipment and a setup that suits the act.
Music playback can also affect speech microphones. If walk-in music is loud and someone begins using a lectern mic, lower the playback channel first. The same applies to video sound during presentations. A controlled mix keeps spoken word intelligible and reduces the temptation to increase microphone levels unnecessarily.
Room acoustics matter most in large, empty or highly reflective spaces. Soft furnishings, audience members and temporary drape can all reduce reflections, although these are not always within the organiser’s control. The practical answer is often to use more appropriately placed speakers at a lower level rather than one powerful speaker trying to cover the entire room. Distributed sound can improve coverage and clarity, but it requires correct timing and professional setup.
What to do if feedback starts during an event
If feedback occurs, act calmly and make a small correction. First, lower the gain or volume on the microphone channel causing the problem. If you cannot immediately identify the channel, reduce the master level briefly, then bring it back up in a controlled way.
Move the microphone away from the loudspeaker and ask the speaker not to point it towards the PA. Handheld microphones should not be cupped around the grille, as this changes their pickup pattern and makes feedback more likely. For lectern microphones, check whether the presenter has moved it or turned towards a speaker while talking.
Do not keep raising volume to overcome a noisy room. Consider whether additional speakers, a different microphone position or a change to the room layout would solve the underlying issue. For a long event, it is worth making these adjustments in a break rather than accepting poor audio for the rest of the programme.
Plan the system around the event, not just the room
A small boardroom may only need a compact PA and one wireless handheld microphone. A conference with video playback, several presenters and 150 delegates may need multiple loudspeakers, a mixer, lectern mic, roaming Q&A microphone and an operator. A party with a DJ requires a different balance again, particularly if announcements need to cut through music without feedback.
Hiring equipment as a matched system avoids common problems caused by mixing unsuitable components. It also means the PA can be scaled for the audience rather than hired on the assumption that bigger is always better. Excessive power in a compact, reflective space can make setup harder, while an undersized system encourages levels that strain both equipment and listeners.
For London events where venue access, time slots and room layouts can be tight, arrange a discussion before delivery. Share a floor plan, audience numbers, stage position and running order. AV2Hire can advise on suitable microphones, speaker placement and setup so the system is ready for a confident soundcheck.
Clear, comfortable sound should feel almost invisible to the audience. Give the room enough coverage, keep microphones close to the people using them, and allow time to test the setup properly. Those practical details are what keep the focus on the presentation, performance or celebration rather than the PA system.