Simple Advice for Operating Sound Equipment
The core advice in the following post was taken from a training manual for new sound engineers, written by Larry Veley. It has been edited and expanded on by Jeff Veley.
What is Feedback?
Feedback is the annoying ringing or squeals heard from audio speakers.
Those new to operating sound equipment often find themselves frustrated and even embarrassed by this unpleasant sound. It is a clear indicator that something has gone wrong.
What Causes Feedback?
Feedback results when the microphone feeds back into the speaker system and vice versa forming a continuous oscillating loop. Upon exiting the speaker, the sound enters the microphone again. Here it is amplified, exits the speaker and starts the entire again. After a few seconds the sound is amplified to a level in which the ringing or squeal can be heard.
Remember, feedback is not always high pitch. Feedback occurs at the loudest and most dominant frequency. This means that it could be a low note too. Often low feedback sounds like a low droning, hollow sound. Either way, feedback can damage both audio equipment and the ears of audience members. It’s important to stop the feedback loop as soon as possible.
How Do You Stop Feedback?
If you should encounter a feedback problem, simply turn down the channel. If you have more than one channel on at a time and system starts feedback, you will have to turn each channel down, one at a time, to find the problem channel.
One of the most common causes of feedback is speaker positioning. Speakers should always be positioned in front (or downstage) of where microphones will be used. People that are unexperienced with using a microphone will wander in front of the speakers. This action will produce loud feedback within seconds. Often this person looks at the sound engineer, unaware that they are causing the feedback.
A simple way to prevent feedback is to conduct a sound check, prior to your event. In addition, hold a brief meeting with those that will be using a microphone. Let them know that “the speakers will squeal loudly if you walk past them with the mic in your hand”. This saves you and your hosts from embarrassment while also protecting the ears of your audience members.