What causes feedback and how do you prevent it?

Feedback occurs when the sound from the speakers is picked up again by the microphone and keeps amplifying itself. You prevent it by placing the speakers in front of the microphones, muting inactive microphones and setting the volume in a controlled way. A technician monitoring the sound live is important here.

Why is a room with a lot of reverb difficult?

Hard surfaces such as glass, concrete and stone reflect sound back, which makes speech blur and become harder to follow. You solve this partly with the right loudspeaker positioning and microphone choice, and sometimes with extra sound damping in the space.

How many backup microphones do I need?

Always plan for at least one backup microphone and enough spare batteries. For important or recorded sessions a double set is common, so that if something fails you can switch within seconds without the audience noticing anything.

How do I make audience questions intelligible?

Use one or two wireless handheld microphones handed out by hosts, or a fixed question microphone in the aisle. Without a microphone, questions are lost on the recording and the people at the back cannot hear them.

Microphones and intelligibility: the complete guide

The short answer

Intelligibility at an event depends on three things: the right microphone for each speaker, a loudspeaker setup that fills the entire room evenly, and someone monitoring the sound live. Most sound problems are not caused by too little volume, but by the wrong microphone choice, a reverberant room or feedback. Solve those at the source and every word comes across clearly without having to crank up the volume.

You do not need to be a sound engineer for this. You tell us who is speaking, how they move and what kind of room it is, and the microphone choice and setup are determined around that. This guide explains the choices that make the difference between half understood and crystal clear.

Choose the microphone based on the speaker

There is no single best microphone. The right choice depends on how someone speaks and moves.

Headset and lavalier

A headset or lavalier keeps the hands free and delivers a constant volume, even when the speaker turns their head or walks through the room. Ideal for keynote speakers, trainers and presenters who move around. The headset sits closer to the mouth and therefore delivers a slightly fuller and more stable sound than a lavalier.

Handheld microphone

A wireless handheld microphone is flexible and reliable. Perfect for changing speakers, a moderator working the room and audience questions. The downside is that the speaker has one hand occupied.

Lectern and table microphone

For a speaker who stays fixed behind a lectern, a lectern microphone is enough. At a panel table, table or boundary microphones work well, provided they have a wide pickup range. You can read more about panel setups in the article on microphones for a panel discussion.

For meetings and discussions with many participants, this ties in with meetings and panel discussions. The broader setup falls under sound and intelligibility.

The room determines how you sound

A good microphone in a bad room still delivers bad sound. Hard surfaces such as glass, concrete and stone reflect sound back, which makes speech blur and drift away in reverb. A room with a lot of textile, carpet and audience absorbs sound and therefore sounds clearer.

You control the acoustics partly with the loudspeaker setup. Speakers that direct the sound into the room instead of against the walls reduce reverb and keep speech sharp. In large or difficult rooms, a distributed setup with several smaller loudspeakers helps more than one loud source. How to make a speaker come across clearly is covered in the article on intelligible speakers.

Preventing feedback

Feedback, that sharp squeal, occurs when the sound from the speakers is picked up again by the microphone and keeps amplifying itself. You prevent it with a few principles:

Place the loudspeakers in front of the microphones, facing the audience, not behind them
Mute microphones that are not in use
Keep the volume controlled rather than maximum
Use directional microphones that mainly pick up sound from close by

With four or more open microphones, a technician who mutes the inactive channels live is not a luxury but a necessity. That falls under technical support.

Wireless microphones: frequencies and batteries

Wireless microphones each have to work on their own free frequency, otherwise they interfere with one another. In a building with a lot of other wireless equipment, such as a conference centre or hotel, a frequency scan beforehand is wise. That way you know for certain your channels are clear.

Batteries are the most underestimated risk factor. A lavalier that fails halfway through a keynote is painful and avoidable. Start with fully charged batteries and keep spares at hand.

Audience questions: do not underestimate them

Questions from the room are often the least intelligible on recordings and are simply not heard at the back of the room. Two approaches work well: one or two wireless handheld microphones passed around by hosts, or a fixed question microphone on a stand in the aisle. When you expect a lot of interaction, choose two roaming microphones, so that the next questioner already has a microphone. More on this in the article on questions from the audience.

Intelligibility for recording and livestream

As soon as you record or stream, sound becomes even more critical, because viewers at home cannot look around them to grasp the context. The stream audio comes directly from the mixing desk, not through a camera microphone that also captures the reverb of the room. How that works is explained in the guide to corporate livestreams.

Intelligibility is one of the building blocks from the broader guide to AV technology for corporate events. In a large programme with many speakers, this plays out across multiple rooms, as in the guide to conference technology.

Common mistakes

Only paying attention to volume and ignoring the microphone choice
Placing speakers behind the microphones, which invites feedback
Leaving all wireless microphones open throughout the entire programme
Underestimating the room acoustics in a reverberant space
Not checking frequencies in a building full of wireless equipment
Letting audience questions be asked without a microphone
Not having backup microphones and spare batteries at hand

Intelligibility checklist

Microphone type chosen per speaker based on movement
Loudspeaker setup matched to the room and the acoustics
Speakers placed in front of the microphones against feedback
Wireless frequencies checked and distributed
Fully charged batteries and spares at hand
Microphones for audience questions planned in
A technician monitoring the sound live present
A short sound check with all speakers beforehand

If you want to rent equipment yourself, use the shop link above. If you want intelligibility fully taken care of, HuurAV provides advice, delivery, setup, installation, support and collection in Amsterdam and the surrounding area, including for a broad corporate event.

The next step

Describe your speakers, your programme and your room, and that is translated into a concrete sound plan with the right microphones and support. That way everyone understands every word, in the room and on the recording.

Guide to microphones and intelligibility at events