Achieving good sound in your general sessions and workshops is a never-ending challenge. The basic components of a sound system include microphones, microphone cable, mixer, sound processing equipment (compressor/limiter, noise reduction system, equalizer), amplifier(s), speaker cable, and loudspeakers. Here are a few practical tips to help you or your sound person get clean, crisp sound:
Your ears should be the final judge. No matter how many stacks of black equipment with glowing lights your sound person has--if it sounds bad, it needs to be fixed!
Controlling feedback. Feedback is when the sound comes out of your speakers and "feeds back" into your microphone. You might get a high-pitched squeal, or, less often, a lower frequency sound. This can be caused by several things--your microphones are in front of or too close to your speakers, the wrong microphone is being used, or your equalization is not set properly.
Placing loudspeakers. Typically, speakers are on the floor, or elevated on a skirted table or stand, and just in front of and to the sides of your stage. By getting them off the floor, you can get the sound to carry farther. If the audience is very big (500 or more) the speakers are often "flown" from rigging above the stage. These speakers can usually be louder than if they were on the floor.
The presenters on stage have their own smaller speakers, called monitors, that allow them to hear themselves. If your stage is very wide (30 feet or more), you should put one or two smaller speakers under the stage near the middle to provide sound to the middle of the first several rows of attendees. These are sometimes known as fill speakers, and they don't need to be as loud as the main speakers. Consequently, they have their own amplifier so they can be run at a different volume. If your general session room is very deep, or your audience quite large, you may need to have an additional one or two sets of speakers farther into the audience. When this is necessary, you need to "delay" the sound from these speakers so they project their sound just as the sound from the main speakers arrives.
Microphone selection is critical to sound quality. Your sound technician will select microphones based on how many people will be using the mike at any one time. If you have a quartet singing together and sharing a single microphone, the tech will use an omnidirectional microphone. This will pick up sound from almost all around it. The trade-off is that it is more prone to feedback. With a single presenter, a unidirectional microphone is often used. This microphone tends to reject sound from behind it, but will pick up sound from the front (where the speaker is). Feedback is less likely, but the sound isn't quite as nice.
Lavalier, or lapel, microphones are usually omnidirectional. A lapel mike should be clipped to the speaker's clothing four to six inches below the chin. If you get clothing noise, one trick is to put an overhand knot (half-hitch for you Scouts) just below the microphone, with the loop about the size of a 50-cent piece. This will cancel out clothing noise below the knot.
Wireless without worries. Wireless systems have become far more reliable. Even though they still cost more to rent, many presenters prefer the freedom of a wireless microphone (lapel or handheld). I recently purchased a handheld UHF system (receiver and microphone) for just over $500.
Mixers and equalizers. The mixer allows the sound operator to cue the different microphones at the time they are needed. There are usually faders that can be raised or lowered to adjust the volume. Most mixers also have a limited ability to equalize the sound. This ability is often divided into frequencies--for example 10,000 hertz, 100 hertz, and then a mid-range (in the range of human voice). One can "shape" the sound by boosting or attenuating these frequencies, with controls for each channel on the mixer. This allows the technician to tune each microphone so it sounds better and there is less chance for feedback. Higher-end sound systems are "rack mounted" and have a separate equalizer allowing for more fine-tuning.
You rarely get compliments on good sound; but you're sure to hear about it if the sound is bad! This is one of those cases where no news is good news.