AV 101: How to Prevent Microphone Feedback at Meetings & Events
To be fair, microphone feedback isn't always bad. Think, The Beatles, Jimmy Hendrix, The Who, and on and on. For some audiences, feedback is just fine. But, if you're speaking in the event or conference environment, chances are you have a different audience. One that expects zero microphone feedback and presentations that come across as crisp, clean and easy on the ears.
In addition to five quick microphone clarity tips, we're also happy to share a detailed explanation on how microphone feedback occurs and how it can be prevented.
- Feedback occurs when a microphone hears itself coming back through the speakers, creating a loop of certain frequencies that continue to amplify louder and louder.
- Certain microphone types are inherently more prone to feedback than others due to the distance the microphone is placed away from the mouth of the person speaking.
- Lavalier microphones are generally the most feedback prone microphones for meeting and conference environments.
- Your room layout should allow for microphones to be placed behind the speakers with the speakers facing away from the microphones for greater feedback prevention.
- Digital mixing consoles often have graphic equalizers built-in, which are the most common way for audio technicians to prevent and control microphone feedback.
What causes microphone feedback?
Even the most basic PA system has a microphone, an amplifier and speakers. Whenever these three components are connected there is a chance for feedback. Feedback happens when the sound from the speakers makes it back into the microphone, is reamplified and sent back through the speakers.
A feedback loop is then created, which comes complete with its own frequency and howling sound. Placing a microphone too far away from a sound source, too close to a speaker, tapping a microphone or turning the volume up too high are the most common ways to create microphone feedback.
Microphone selection and position can prevent or limit feedback.
In a perfect world, a microphone would only pick up the presenter's voice, but microphones vary, are setup differently and presenters may not be speaking close enough or into the microphones. Let's keep in mind, the further away the microphone is away from the presenter's mouth the more likely it is for feedback to occur.
The advantage of lavalier microphones is that they can blend into clothing and are hardly noticeable. And as we know, the disadvantage is that clip on microphones may be worn further away from the sound source, which exposes presenters to feedback. With that said, using handheld, podium or headset microphones decrease your chances of experiencing feedback during a presentation. If a presenter chooses to sit close to a table top microphone, then in almost every respect it offers the same level of safety as a podium microphone. On the other hand, if a single tabletop microphone is placed at the center of a large table, between lots of people, presenters may be too far away from the mic and exposure to feedback is then increased. Remember, no matter the mic, the closer the better.
Speaker and microphone placement:
Another way to limit microphone feedback is to make sure the speakers in the room are not positioned to bounce sound back at your microphone. Using speakers that are one directional will allow you to place any microphones you have behind the speakers. It's also important that your audiovisual partner limits your exposure to microphone feedback through deliberate speaker and microphone placement as well.
Sometimes you can do everything right and still have feedback issues. This is where a good technician and graphic equalizers come in.
Because feedback is just one frequency looping through the audio system, rather than the entire audio spectrum, by removing that one frequency from the audio system, technicians may be able to stop the feedback loop without significantly impacting the overall sound quality.
As graphic equalizer allows audio technicians to do exactly that. If you have ever been in a meeting room while the technicians are setting up, chances are they're purposefully causing feedback to occur to prevent or get rid of feedback.
Referred to as ringing out the room, technicians purposefully turn up the microphones to cause feedback, then use a graphic equalizer or similar device to reduce or remove any frequency that may cause feedback from the system.
If feedback prevention is an event concern, particularly when lavalier microphones are going to be used, then you should ask your audiovisual provider if they will have graphic equalizer.
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