While routinely blamed on the microphone, the fact is that microphones are passive devices that cannot reach out and “grab” sound. Rather, acoustic feedback is system-based. It is caused by a combination of factors, including room acoustics and amplification levels, plus
positioning, directionality, and transmission paths of microphones and loudspeakers, all of which can contribute to poor gain-before-feedback.
Bad microphone technique often prevents the sound system from performing well. Educating presenters on mic technique is just as important as great room acoustics. Understanding how room acoustics impacts the systems ability to perform is crucial to minimizing the occurrence of feedback.
Creating good sound without feedback is a balancing act between the room’s Potential Acoustic Gain (how loud it can get without feedback) and Needed Acoustic Gain (the amount of gain required so everyone can hear). While the mathematics of PAG/NAG are important in room design, familiarity with best practices in the placement and use of sound system elements should be sufficient for the effective use of existing systems. For more details, see the sidebar on Feedback Fixes.
The more reverberant the room, the more likely it is for feedback to occur. Highly reverberant spaces generally have reduced intelligibility, which in turn makes users want to turn up the volume in an effort to hear more clearly. Like feedback itself, it’s a vicious cycle. Fortunately, a little knowledge is all it takes to keep it under control.
Understanding the causes and potential cures for feedback is a critical skill in sound reinforcement. Fortunately, the phenomenon and its cures are well known.
When feedback occurs, remain calm. Turn down the sound system’s master gain (volume) to stop the squealing. Once you’ve got the system back under control, it’s time to look for causes and fix them. While instinct suggests that something is too loud, it might also be that something is pointed in the wrong direction. Here’s a full list of all available fixes:
frequency with minimal effect on the rest of the mix.
reduce room reverberation.
3/F,Building#10, Jiu Xiang Ling Industrial Zone,Xili
Nanshan District, Shenzhen, 518055, China