A Simple Guide for Beginners — Monks Music Academy

Audio feedback occurs when a microphone picks up sound from a speaker and re-amplifies it in a continuous loop. It can be prevented by keeping microphones away from speakers, using directional microphones, controlling gain levels, cutting problematic frequencies with EQ, muting unused microphones, and improving room acoustics. These are fundamental live sound techniques taught at Monks Music Academy.

What is Audio Feedback?

Audio feedback is the loud screeching, ringing, or howling sound that occurs when a microphone picks up sound from a speaker, which is then amplified and sent back through the same speaker in a continuous loop. It is one of the most common challenges in live sound engineering.

The signal path typically works like this:

As the cycle repeats, the signal grows louder with each pass. Within milliseconds, the system reaches an unstable level and produces the familiar high-pitched squeal that audiences and performers dread.

At Monks Music Academy, feedback control is introduced early in the sound engineering curriculum because it forms the foundation for successful live sound operation.

Why Does Feedback Happen?

Feedback does not occur randomly. Every feedback incident has a specific cause. The most common triggers include:

• Microphone Too Close to a Speaker — When a microphone captures a strong direct signal from a nearby loudspeaker, a feedback loop can form almost instantly. This is the most common cause in live sound environments.
• Excessive Gain or Volume — Setting microphone gain too high reduces the system’s available headroom and increases the likelihood of feedback. Even a well-positioned microphone can feed back if gain staging is poor.
• Boosted EQ Frequencies — Certain frequencies naturally resonate within a sound system or room. Excessively boosting these frequencies makes feedback much more likely.
• Hard, Reflective Rooms — Rooms with concrete walls, tiled surfaces, glass panels, and minimal acoustic treatment create strong reflections that can re-enter microphones and trigger feedback.

How to Eliminate Feedback — 9 Practical Steps

These are the same fundamental techniques taught in Monks Music Academy’s live sound training programme and are widely used by professional sound engineers.

1. Place Microphones Correctly

Speakers should always face the audience, not the microphones. Maintain as much physical distance as possible between microphones and loudspeakers.

Proper microphone placement is the simplest and most effective method of preventing feedback.

2. Use Directional (Cardioid) Microphones

Cardioid microphones are designed to capture sound primarily from the front while rejecting sound from the rear.

Position stage monitors within the microphone’s rear rejection zone whenever possible. This significantly reduces monitor spill into the microphone.

3. Control Gain and Volume Carefully

Always begin with low gain settings and increase them gradually during soundcheck.

Leave adequate headroom for performers who may sing louder or move closer to the microphone during the show.

4. Use EQ to Reduce Problem Frequencies

“Ringing out” a sound system is a standard live sound technique. The process involves:

1. Increasing system level until ringing begins.
2. Identifying the problematic frequency.
3. Applying a narrow EQ cut (notch filter).
4. Repeating the process until the system becomes stable.

This technique improves gain before feedback and creates a more reliable live mix.

5. Position Stage Monitors Correctly

Stage monitors are one of the most common sources of feedback.

Angle monitor wedges so that the microphone’s rear null point faces directly toward the monitor. Even small adjustments in monitor position can dramatically improve feedback resistance.

6. Mute Unused Microphones

Every open microphone introduces another potential feedback path into the system.

If a microphone is not being used, mute it immediately. Developing this habit improves both system stability and overall mix clarity.

7. Hold the Microphone Correctly

One of the most common mistakes in live performance is cupping the microphone grille.

Covering the microphone head changes its polar pattern and greatly increases the risk of feedback. Always hold the microphone by the handle or body, keeping hands away from the grille.

8. Improve Room Acoustics

Acoustic treatment reduces reflections that can re-enter microphones and contribute to feedback. Helpful acoustic solutions include:

• Curtains
• Carpets
• Acoustic panels
• Soft furnishings
• Portable acoustic treatment

Even temporary acoustic improvements can make a noticeable difference in live sound environments.

9. Use a Feedback Suppressor (Advanced)

Modern feedback suppressors automatically detect ringing frequencies and apply dynamic notch filters to reduce feedback in real time.

These devices can be extremely useful in complex venues and high-risk environments. However, they should be viewed as a backup tool rather than the primary solution. Proper microphone placement, gain structure, and EQ remain the most important methods of feedback prevention.

Common Mistakes to Avoid

The following mistakes are frequently observed during live events and student productions:

• Placing speakers behind microphones
• Raising gain too quickly
• Skipping soundcheck
• Leaving multiple unused microphones open
• Excessively boosting EQ frequencies
• Cupping the microphone grille

Avoiding these errors can significantly reduce the likelihood of feedback during a performance.