Is there any sound worse than the one created by feedback from a Portable PA System? You know the sound, a ringing noise or terrible squealing or screeching. It’s something that you very commonly hear over Portable Public Address Systems, but it’s one that can very much be avoided with just a little bit of preparation and placement of the PA System components.
Before we get to these steps, you should know that if you are the speaker and you hear that awful screech, placing your hand over the mic will not dampen the sound, and will in fact just make it worse. Audio feedback is the ringing caused by a "looped signal", that is, a signal which travels in a continuous loop. In technical terms, feedback occurs when the gain in the signal loop reaches "unity" (0dB gain). One of the most common feedback situations is shown in the diagram below - a microphone feeds a signal into a sound system, which then amplifies and outputs the signal from a speaker, which is picked up again by the microphone.
Audio Speaker Placement
There seems to be a desire to place speakers as far out of sight as possible, but doing so can actually create your portable public address feedback problems. Rather than tucking the speakers to the rear or sides of the microphone position, place them out in front. Always position the speakers in front of the microphone.
Microphone Placement
Basically, the closer you get your mouth to the microphone the better. If you are using a handheld microphone, hold it about 2cm from your mouth. If you are walking around whilst presenting – make sure you don’t wander in front of the speakers. Always keep behind the audio speakers – the closer you are to the speakers, the more likely you are to cause feedback. If you walk in front of the audio speakers for any reason with the microphone, turn off the microphone first.
Sound Check
Make sure you always set up your Portable PA System ahead of an event. Taking the time to position the speakers and place microphones correctly will go a long way to ensure good quality sound during your event. With enough time, a good sound engineer can effectively troubleshoot any potential feedback issues. Make it clear to everyone involved that the setting should not be changed once they have been tested and set. Running a quick sound check before the event begins will ensure that the portable public address system is still working as it should and remains feedback free.
If you have any questions on Audio Feedback or any questions related to Portable PS Systems and Wireless Microphones please don't hesitate to contact Talk Audio Visual on 1300 552290 or info@talkaudiovisual.com.au
