Auto Microphone Muter
Posted on Mar 25, 2013 11889
Under: Microphone Circuits
If you've crossed the line and play guitar or bass and also sing in a band, you're almost certain to have run into the situation that you step away from the mike to do a solo (or one of those neato, expressive dance steps, or a facial impression of the pain you're pouring out to make these dulcet tones...), and had the mike pick up some unfortunate noise to funnel into the PA. You may even have fumbled for the mike mute switch as you stepped away and back to it, but that's almost terminally clumsy, as you have your hands full of your instrument. Wouldn't it be nice if the microphone was only `listening` when you stepped up to it?
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Muting a microphone is simple. Knowing when is hard. The real trick is having the microphone be smart enough to figure out that you want to sing now. When my amp-tech friend first asked me to figure out a way to mute a mike when the singer stepped away, I went on these little flights of fancy with infrared motion detectors, ultrasonic range finders and other even less practical stuff, but what finally came out was a cross pollenization idea. Most singer/guitarists stand up to sing (except for you intimate acoustic types!) and that means they touch the floor. The home burglar alarm industry has come up with a simple and durable way to detect people standing on a floor. There is a burglar detection product that is a laminated plastic film affair with metal strips inside that normally don't touch each other, but anything over about 5 pounds of force causes them to touch. The strips are brought out to leads to sense the contact. These contact mats are normally placed under carpets in places that intruders are likely to step. The pressure sensitive mats are available in two foot by three foot sections for a reasonable price at most burglar alarm suppliers. (Ask to talk to the installation tech, not the sales person!) You can't just use the mat contacts to open and close the mike lines directly because they would almost certainly cause unendurable hum, buzz and noise pickup. To avoid the noise, you need to use some switch...