or  (Tap, tap...) Is this thing on? (Screeeeeeeeel!)

by Keith Snyder





We have reprinted what we believe to be a very helpful and informative article.


The notes add either additional information or clarification as to why we may have a different approach than the author.

Links to the original article, which contains illustrations and more material are at the bottom of this page.





Okay, I'm going to dispense with the attention-grabbing lead paragraph and just dive in.





Tapping on a microphone is NOT advised. More on the subject later.



This is a microphone:




I'm not going to try to tell you all the names of all the parts, or get into the details of how it all works. All we're trying to do here is get you familiar enough with these beasts to allow you to be comfortable while you're doing a speaking engagement or participating on a panel. (Or, at least, get you to where your discomfort has nothing to do with the microphone.)


Here's a very basic explanation of how a microphone works. You can skip it if you generally gloss over this kind of thing, but I've avoided technical jargon, so I think even those of you who glaze over when someone tries to tell you how to set your VCR clock will probably be able to follow it:




Inside the microphone is a little wafer that's hooked up to some little wires. When you talk, you cause the air in front of your head to ripple. These ripples are called "sound waves." When they hit the little wafer, it moves back and forth. The motion of the wafer is transformed into an electrical current which goes out the cable that's clipped onto the bottom of the microphone. The electrical current has plusses and minuses that correspond to the air ripples you made when you talked.


That current is tiny, so it goes into something called an "amplifier" which makes it bigger. Then the bigger current goes to a speaker. The plusses and minuses in the electrical current make the speaker cone (the round paper part) move back and forth. This makes the air in front of the speaker ripple in a way that's very close to the ripples you originally made when you talked. Only louder.




Sit or stand comfortably. Do not lean over and "eat the mic." If you're too close to the microphone, the little wafer inside it can get overwhelmed by how much sound you're putting out, and the result will be fuzzy, incomprehensible speech coming out of the speaker. (Ever notice that singers tend to pull their hand-held microphones back to arm's length when they get to the part of the song where they really belt it out? That's because they're aware of the possibility of overloading the microphone.)







Sound obey's one of Nature's principles known as the "Inverse Square Law."


This means that the sound level increases or decreases in relation to the distance between the  source and the receiver. (For example, the person speaking or singing and the listener or the microphone.)


Since sound generally travels in all directions from its source, the level varies not in direct relationship to distance, but, inversely according to the square of the distance.



As the  distance changes in a  1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 relationship, the sound level changes in a 1 - 1/4 - 1/9 -1/16 - 1/25 - 1/36 - 1/49 - 1/64 - 1/81 - 1/100 manner.



If you remember your school math and science lessons about the area of a circle you can see how the energy is distributed as the distance increases from the source.



Understanding this facilitates the proper placement and usage of microphones.




Do try to project when you talk, but don't get carried away and yell. The microphone is there to make you louder; you don't have to help it, except to enunciate and project, which you ought to be doing anyway.


If you're not sure if the microphone is ON, you can tap the screeny top part. If you hear a little "thump" in the speaker, the microphone is working.







Tapping on a microphone is NOT recommended with modern solid state equipment. Circuits and components (including loud speakers) can be overloaded and damaged. Older vacuum tube equipment prevalent in bygone days was more tolerant of brief overloads.






If the microphone is not on, see if it has an ON/OFF switch on the long cylindrical part. Turn it ON if it's not. (Not all microphones have ON/OFF switches.)




Sometimes, you may be faced with a wireless microphone when you're on a panel. It may look kind of like this:




The thing shaped like a bug is the actual microphone. Clip it to your lapel and then forget about it and speak normally. If there is a problem with this kind of microphone, you probably can't do anything about it (except for feedback, which I'll tell you about in a few paragraphs), so take it off, turn it off if it has an ON/OFF switch, and wing it.




Try out the microphone.


If it's a wireless microphone, clip it to your lapel and wander around the room, speaking normally. If you start to hear feedback, make a note of where you were standing when it happened, and DON'T STAND THERE ANY MORE! :)




Sometimes there's no audio engineer running things. When you're on your own and things go wrong, here's what you can do:




If the microphone cable has been run in such a way that the microphone position is making you uncomfortable, here's how to fix it:


* Turn the mic OFF (if it has an ON/OFF switch)

* Press the clippy button thing on the cylindrical cable end to release the cable.

* De-tangle the cable.

* Push the cylindrical cable end back into the mic and turn it ON.









Feedback can be both annoying and damaging to equipment (including pre-amplifiers, amplifiers and loudspeakers).





Feedback is that squealing sound that happens sometimes. The microphone is picking up too much of the sound that's being put out by the speaker. The sound goes into the microphone, out the speaker, back into the microphone, back into the speaker, and so on. Because it keeps getting amplified, it can build to an earsplitting shriek if left alone.


This is usually especially problematic with wireless microphones because the person using the microphone tends to wander around the room, and ends up standing in bad places.


If you're having feedback problems, here's what you can do. It's very complicated. Ready?


* Move the microphone somewhere else.


That's the whole secret. Try to make sure the screeny top part of the microphone is not pointing toward a speaker. If, for some reason, you can't move the microphone somewhere else, then try aiming the speakers differently. The whole idea here is to prevent the speakers from sending too much sound into the microphone.




In public speaking situations, microphones and speakers are part of what audio people call "sound reinforcement." That means that they are used to add volume to your voice, not to replace it completely. If you're talking normally with a decent amount of projection, a microphone that's set up correctly will handle things just fine. If there's a problem, don't worry that you're doing anything wrong.


If the audience can't hear you, and the microphone isn't bolted onto a lectern or something, try moving it closer to you. Bring it to you instead of the other way around.





Please remember how sound energy behaves (discussed in Note # 2) and make the necessary adjustments.







Thanks for stopping by! And feel free to poke around my web site,

Keith Snyder, Microphones -








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