Feedback. That annoying screeching noise that is one of every sound guy’s worst nightmares.
How do you stop it from happening?
First let’s look at what audio feedback is, then we can see how to stop it from happening in the first place.
What is audio feedback?
Audio feedback or sometimes referred to as acoustic feedback is that ringing sound sometimes present in audio systems. Audio feedback occurs when a sound loop exists between an audio input and an audio output. The signal loops between the output and input, and feedback is heard when the signal loop reaches unity.
One of the most common types of feedback is shown in the diagram below.
Of course there are many other forms of feedback and different situations like the microphone could be replaced by the pick-ups of an electric guitar.
So, where does feedback typically happen in a church service?
- Vocal worship microphones
- Choir microphones
- Electric/Acoustic Guitars
- Lavalier or headset microphones
Basically, it could happen with any microphone but these are the typical places that feedback happens.
How do you stop feedback?
In order to stop feedback you must interrupt the loop. Here are a few suggestions to controlling the issue of feedback:
- Turn it down. If you know what the problem channel is turn it down. A small amount is all that you will need and probably won’t even be noticed by your audience. I can’t tell you how many times feedback was reduced by just turning down the volume a little.
- Change the position of the microphone or the speaker so the speaker isn’t feeding into the microphone. Keep the speakers closer to the audience and the microphone further back away from the audience.
- Change microphones. Sometimes using a microphone that is more directional will help in eliminating feedback. Omni-directional microphones pick up sound all around the microphone. Cardioid microphones would be a good choice.
- Find the frequencies that are causing the feedback and eliminate or lower them. I’ve used RTA software to find the frequency then I eliminated them in the EQ.
- Turn all microphones off or mute them when not in use.
- Use a noise gate, which is something that will shut off the signal when it goes below a certain pre-set threshold.
- Turn in your stage monitors for in-ear monitors. If you have stage monitors keep a handle on their volume.
- Use a digital feedback eliminator. I’ve heard some great results on some of these and could be beneficial if you have a lot of issues with feedback.
- Don’t aim speakers at reflective surfaces such as walls.
Practice. These are just a few tips that you can follow, but they aren’t the only answers. Practice and see what works the best for you. Experiment in the different ways shown in this article and maybe you will come up with some of your own.
Do you have any tips on how to eliminate feedback? Or perhaps you have some amusing or not-so-amusing experiences and situations with feedback. Share with us your stories in the comment section below.