Re: Re:Re: Information on contact microphones

[Chris Muir <cbm@well.com>]

At 3:17 PM -0700 10/23/98, Jesse Kudler wrote:
>I knew that a speaker and a mic were basically the same thing reversed, 
>but
>isn't a contact mic different from a dynamic mic?  Contact mics don't pick
>up sounds, they pick up vibrations.  That's why they have to be touching 
>the
>mic'ed object and why they can't feed back.

Sure they can feedback, no problem. All you need is enough gain in the
circuit. For example, a contact mic placed on an acoustic guitar is quite
prone to feedback. The surface that it is on (the top of a guitar)
resonates pretty freely. If the gain through the system is enough to ensure
that the vibration induced in the top (from a speaker reproducing an
initial stimulus picked up through a contact mic) gets re-introduced into
the system (re-picked up by the contact mic) at a greater level than the
initial stimulus you get feedback.

Chris




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