Re: AGA Physics lesson for today.


Rick N. Backer wrote:
> On 15 Nov 2005 12:04:18 -0800, "the librarian" <zootwoman@xxxxxxxxx>
> did courageously avow:
>
> >http://hyperphysics.phy-astr.gsu.edu/hbase/sound/sprop.html#c1
> >
> >Sound propagates through air as a longitudinal wave. The speed of sound
> >is determined by the properties of the air, and not by the frequency or
> >amplitude of the sound. Sound waves, as well as most other types of
> >waves, can be described in terms of the following basic wave phenomena.
> >
> >
> >http://hyperphysics.phy-astr.gsu.edu/hbase/sound/imgsou/souprocon.gif
> >
> >:)
> >
> >Since audible sound consists of pressure waves, one of the ways to
> >quantify the sound is to state the amount of pressure variation
> >relative to atmospheric pressure caused by the sound. Because of the
> >great sensitivity of human hearing, the threshold of hearing
> >corresponds to a pressure variation less than a billionth of
> >atmospheric pressure.
> >
> >The standard threshold of hearing can be stated in terms of pressure
> >and the sound intensity in decibels can be expressed in terms of the
> >sound pressure:
> >http://hyperphysics.phy-astr.gsu.edu/hbase/sound/imgsou/intens4.gif
> >
> >The pressure P here is to be understood as the amplitude of the
> >pressure wave. The power carried by a traveling wave is proportional to
> >the square of the amplitude. The factor of 20 comes from the fact that
> >the logarithm of the square of a quantity is equal to 2 x the logarithm
> >of the quantity. Since common microphones such as dynamic microphones
> >produce a voltage which is proportional to the sound pressure, then
> >changes in sound intensity incident on the microphone can be calculated
> >from
> >http://hyperphysics.phy-astr.gsu.edu/hbase/sound/imgsou/dv.gif
> >
> >where V1 and V2 are the measured voltage amplitudes .
> >
> >
> >http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
> >bodied electric guitar, the Fender Stratocaster has steel strings and
> >three magnetic pickups, the back, middle and front pickups. The back
> >pickup, situated closest to the bridge, has an offset angle of about
> >ten degrees towards the fingerboard underneath the lower strings to
> >give them more fundamental content. Its treble pole angles toward the
> >bridge to give those strings more high harmonic content. This gives a
> >gradual brightening of tone across the strings from bass to treble. The
> >Stratocaster has a switch that operates these pickups as individuals or
> >in combination. This guitar is noted for its high pitched screams
> >produced by the shape of the body and the single coil pickups.
> >
> >http://hyperphysics.phy-astr.gsu.edu/hbase/music/imgmus/spkup.gif
> >The three sets of pickups shown for an electric guitar such as the
> >Fender Stratocaster allow the player to adjust the quality of the sound
> >by choosing the amounts of signal used from each pickup. The knobs
> >shown are volume controls for the three sets.
> >
> >Of the string modes shown, the fundamental will actually be much larger
> >than the others, and the others diminish progressively. Using the
> >pickup set to the right gives much more fundamental and a mellower
> >sound.
> >http://hyperphysics.phy-astr.gsu.edu/hbase/waves/string.html#c3
>
> And Mulay was crowing he's chased you away. ;^)
>
> I thought not.
>
> Ken Wilson

If there were a bad AGA joke involving several people walking into a
bar, how would it begin? (Feel free to use a rowboat, if desired.)

--E

.

Relevant Pages

  • Re: AGA Physics lesson for today.
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  • Re: AGA Physics lesson for today.
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