When I sang, it was an agonizing experience to scream into the microphone. I was completely lost in the ocean of music, but then the microphone started to howl uncontrollably, and all the excitement vanished instantly.
In most cases, howling is a common issue that occurs in sound reinforcement systems. It's an abnormal phenomenon caused by the interaction between microphones and speakers. The problem arises because the microphone picks up sound from the speaker's output, creating a feedback loop. This happens when certain frequencies become too strong, causing the system to oscillate and produce that annoying howling sound. For howling to occur, three key conditions must be met: first, both the microphone and speaker are used simultaneously; second, the sound from the speaker can reach the microphone through the air; and third, the speaker's output is powerful enough, and the microphone is sensitive enough to pick it up.
Howling can be more than just an annoyance—it poses serious risks. If left unchecked, it can prevent the microphone volume from being adjusted properly. Even after adjusting, the howling may worsen, ruining the live performance. In extreme cases, the sound can ring and distort, degrading the audio quality. Worse yet, the speaker or power amplifier might get damaged due to excessive signal input. It's not uncommon for a tweeter to burn out during howling, as the high-frequency harmonics generated by the clipped signal can overwhelm the speaker’s components. Similarly, overloading the power amplifier could also lead to its failure.
To suppress howling, several strategies can be employed. First, reduce the chances of sound from the speaker reaching the microphone. Keep the microphone away from the speaker, lower the microphone volume if it's too high, and make sure the microphone isn't positioned in the direct path of the speaker's sound. Using directional microphones and speakers wisely can also help. By adjusting their angles, you can avoid overlapping sound radiation areas, which significantly reduces the risk of feedback.
Second, use electro-acoustic equipment like equalizers, feedback suppressors, and frequency shifters. These devices can help break the feedback loop by adjusting frequencies or reducing specific problematic ones. A compressor limiter can automatically manage the gain, preventing sudden volume spikes that might cause howling. However, this may affect the natural dynamics of the sound.
Third, ensure good acoustic design in the room. Poor acoustics, such as resonance or concave surfaces that focus sound, can amplify certain frequencies and increase the likelihood of howling. Using sound-absorbing materials and diffusive surfaces can help control these issues.
Fourth, choose appropriate speakers and microphones. Speakers with a narrow beam angle and flat frequency response are less likely to cause feedback. Similarly, microphones with lower sensitivity and a flat frequency response are better at minimizing howling.
By combining these techniques, you can effectively manage howling and improve the overall sound quality in any live setting.
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