Both singers and mixing engineers try their best to minimize microphone feedback on stage, and funnily enough, they usually end up blaming each other the moment that ear-piercing sound appears.

Avoiding microphone feedback is crucial not only to ensure your performance will sound professional, but also to protect the ears of performers and audience alike.

With this guide, we’ll look into a few common techniques to avoid microphone feedback, and its main causes. Whether you’re a seasoned performer or sound engineer, these practices can help you avoid one of the most common issues in live shows.

What Causes Acoustic Feedback?

Let’s first analyze why microphone feedback happens.

In a nutshell, feedback happens when the microphone signal re-enters the microphone, gets amplified, and loops. The result of this amplified sound is most likely a constant and screeching sound, but it can also be like a howling sound.

As you probably know, both the microphone and speaker can enhance certain frequencies. When you speak, the sound fills the room and reflects off surfaces, which causes feedback delay.

This isn't a big issue, but the shape of the room can amplify certain frequencies, called room modes. Feedback becomes a problem when the room's resonant frequencies match the boosted frequencies, creating a feedback loop and that annoying screech.

The first step to avoid this problem is to understand whether you’re using the right microphone.

Understanding Your Microphone

First and foremost, prevention is always better than cure. While in the following section we’ll look into ways to mitigate microphone feedback when you’re already performing, for now we’ll analyze different mics and how they behave.

Not all microphones are created equally, and we can divide them based on their pickup pattern, which is the way they capture sounds, and technology.

The pickup or polar pattern of a mic is the direction from which it captures sound. Cardioid mics pick up sounds from the front and block them from the back, which is great when avoiding feedback. Omnidirectional mics capture sounds from all directions, which makes them more prone to feedback.

As for the technology, you’ll most likely use either a dynamic or condenser mic.

Dynamic mics are less sensitive, so they’re ideal in live settings and enhance the dynamic range of a PA system. Condenser microphones offer a higher level of detail but are more prone to feedback. In general, they require a carefully controlled environment, like a recording studio, to truly shine.

So, which one should you use? That very much depends on how and where you use it. For rehearsals and concerts? A cardioid microphone. For podcasting and conventions? Directional microphones, or condenser mics if the environment is acoustically treated. You can also consider an omnidirectional microphone during panel discussion in certain circumstances.

As you can see, there’s no golden rule here, but the good thing about it is that you can get the perfect microphone for your purpose, and avoid microphone feedback as much as possible.

5 Tips on How to Stop Feedback on Mic

If getting the appropriate microphone is not enough, here are five tips on how you can prevent microphone feedback.

Tip #1: Work on your Microphone

The first thing to do is ensure you’re handling the microphone correctly.

First of all, if you keep the microphone close to your mouth, it will sound louder and allow you to lower the volume on the mixer, mitigating the chances of feedback. That's because you're increasing your gain before feedback (the sound pressure level at the microphone) before reaching a volume that might cause feedback.

Next, if you partially hold the grill of the mic capsule, you’ll make it more susceptible to feedback, and also compromise its ability to capture sounds. So, hold it in a way that makes the grill completely free and facing the sound source. If feedback still happens, try cutting frequencies between 800 Hz and 2 kHz or lower the volume.

Both techniques will most likely remove feedback. If not, let’s take a look at tip #2.

Tip #2: Check your Position on Stage

Always remember where the loudspeakers are in relation to your microphone: when they're far away and not facing each other, the chances of feedback are already greatly reduced.

Aside from the aforementioned benefit of using unidirectional mics, another aspect to consider is the number of microphones involved: the more open microphones you have, the higher the chances of getting feedback. Therefore, make sure microphones that are not necessary are switched off.

Tip #3: Ringing Out the System

Ringing out a sound system is a technique used by sound engineers to get rid of live feedback. The way you do this is by gradually increasing the PA system levels until you hear feedback, then using a graphic equalizer to pull down the problematic frequencies by roughly 3 dB.

I'd recommend you focus on cutting frequencies around 250 to 500 Hz for low-frequency feedback, whereas issues with singing frequencies may be around 1 kHz, and "screeches" will be above 2 kHz. It'll take time to get it right, and you might be tempted to over-equalize for a while, but once you master it, ringing out is an effective way to avoid mic feedback.

Tip #4: Communicate with the Sound Engineer

Sound engineers might look grumpy, busy, and pre-emptively annoyed with your lead guitarist, but they also tend to be reasonable people, and they'll use a preamp gain to set your sound right on stage.

If you’re using a directional microphone, hold it right, and be positioned correctly on stage, then it’s their job to use an equalizer to cut off frequencies. If you’re working with an in-house mixing engineer, they’re probably quite familiar with the PA system, so all you need to do is trust them and provide valuable feedback so that the performance will run smoothly.

Tip #5: Automatic Feedback Reducers and In-Ear Monitors

For wireless microphones, automatic feedback reducers are a fantastic option to eliminate feedback as they can handle it in real-time so that the singer can move around without issues. No sound engineer can react as fast as an automatic reducer! Also called a feedback destroyer or eliminator, this piece of gear can automatically find and remove the frequencies that are feeding back.

Finally, in-ear monitors, or IEMs, are a great way to reduce stage volume levels, preventing mic feedback caused by floor monitors. They'll also protect your ears in the long run, which is a very good thing, isn't it?

Final Thoughts

I hope this guide helped you understand how to avoid microphone feedback on stage! Bringing to life a successful live performance is no trivial task, but understanding how to avoid feedback is a great starting point.

Remember to protect your ears at all costs, as they're your most valuable tool. Use IEMs if you can, and avoid feedback by following the tips discussed above. Use the right microphone for the task, and be aware of your position on stage. Finally, trust the sound engineer, but don't be afraid to raise your concerns if something doesn't feel right.

Good luck, and stay creative!