[CAUT] Semantics

[Fred Sturm]

On May 10, 2009, at 2:48 PM, Escapement wrote:

> My understanding of a transducer has always been that it is a device  
> that
> takes one form of information or energy and converts it into another  
> form.
> (Like the speaker example given where *electrical current* is  
> converted to
> physical vibrations through the electromagnetic voice coil).  The  
> speaker
> isn't a transducer because the voice coil vibrates the membrane - 
> it's a
> transducer because it takes the *electrical current* in the wire and
> converts it to vibrations *(sound)*.  In the same way that a  
> microphone is a
> transducer because it takes *sound* and converts it to an *electrical
> signal*.
>
> But with the soundboard I don't see this conversion.

	After thinking it over, I agree with you on this. A classic series of  
transducers would be a coal fire (heat energy) heating water to make  
steam that is directed at a turbine, causing it to spin (mechanical  
energy), which, by means of magnetic field and copper coils makes  
electric current (electrical energy), which, directed through the  
filament of a light bulb makes light energy (and heat energy). All are  
real conversions to obviously different forms of energy.
	With a piano, though, we have the mechanical energy of a finger  
moving a key, which causes a hammer to hit a string and sets it to  
vibrate. Mechanical energy converted to mechanical energy in a  
different form via the action of intermediary mechanical devices. The  
string is coupled to a soundboard, and energy is transferred causing  
the soundboard to vibrate, again a mechanical transfer to a mechanical  
form of energy. The soundboard, having a large surface area, and  
operating in atmosphere, transfers some of its vibrational energy to  
air particles, which oscillate creating waves. This still seems like  
mechanical energy to me. The air oscillations reach an ear drum,  
setting it vibrating. IOW, a whole series of transfers of mechanical  
movement from one device or medium to another. Not being versed in  
physics, I don't know whether there is a difference I am missing, but  
it seems much more like a continuum than any two steps in the example  
above.
	I wonder also about referring to sound as energy. It takes energy to  
make sound happen, so sound can be said to be a manifestation of  
energy. But is sound a "form of energy?"
	Maybe this is too abstruse to worry about, but some of the confusion  
in this discussion seems to come from assumptions like the notion that  
sound is equivalent to energy, and similar analogies that maybe aren't  
actually valid.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu