Do you have a feedback problem? In other words, does your sound system let out a loud scream of protest when you try to turn up the volume on the podium microphone? Or does the sound system produce a hollow sound? Does the cassette recording sound hollow, or do you hear a lot of audience noise instead of the talker?

Are there any solutions to these problems? All of these symptoms could be caused by having too many microphones turned on. In sound systems, the fewer microphones that are on, the better the sound will be. In fact, no microphone should be on unless it is actually being used.

Any microphone that is turned on will be picking up whatever sound waves pass the microphone capsule. If it is only picking up unwanted noise and reflections, it will still be mixed with the desired signal (i.e. talkers). This mixed signal will then be reproduced by the loudspeaker system or recorded on the cassette tape. The unwanted noise can make the cassette recording sound hollow. It can also decrease the intelligibility of the sound system.

There is another large benefit for keeping unused microphones turned off. You will be able to get more volume before feedback occurs. If you are having a feedback problem, first make sure that all the unused microphones are turned down or switched off.

Figure 1
Individuals can use the microphone's on/off switch.

There are three methods to accomplish this:

You can do this by training everybody to use switches on the microphones (Figure 1). This works well if everybody remembers to do it. Unfortunately, someone will forget to turn on the microphone under the stress of public speaking, and then they won't be heard. If you are recording, the future audience will only hear silence. Another common problem will also likely occur. The talker will forget to turn the microphone off. Then the next user will really turn the microphone off when they try to turn it on.

Figure 2
The Sound Operator can use the channel on/off (mute) switch.

A sound operator can turn the microphones on and off as needed via channel faders or the mute or on/off switch on the mixer (Figure 2). The advantage of this style is that the volume can now be adjusted for each talker or singer. This is the best and really only way to adjust and balance for music. For example, in a situation where the keyboard seems too loud for the soloist, a sound operator can adjust the levels to an appropriate mix. The relative level between singers and instruments require a human touch with preferably a musician's ear.

Figure 3
An automatic mixer automatically turns on/off microphones as needed.

A third method is to use an automatic mixer (Figure 3). This type of mixer automatically senses when someone uses a microphone and turns it on. This system works excellent for speech. An automatic leveler can be added to adjust the volume to keep the speech volume consistent.

If you want to get the best sound out of your system, you must use one of the above three methods of operation or a combination. For instance, the automatic mixer could be used for speech, along with a sound operator for the music.