physics anybody?

[guitar08man]

im doing a summer project for school that involves building a guitar. The idea is that i understand some of the physics behind the guitar; in this case, pickup placement.

A physics teacher who is helping me out with this sent me these questions:

[ QUOTE ]
A guitar pickup that is closer to the bridge will be more or less likely to register higher order modes of vibration than a pickup that is farther from the bridge? (explain)


What words (both your own words and common guitar circle words) are associated with the sound from each of the pickups mentioned in the last question?


Research item. Is it important that one guitar pickup position (near or far from bridge) be a hummbucker and less significant for the other? (explain).

[/ QUOTE ]

i understand what modes of vibration are (we did a lab on this) and i think the answer to the first question is that a guitar would be more likley to pickup up the higher modes of vibration if it was nearer to the bridge. I could be wrong though.

Can anybody help me out?

[micha]

Re: physics anybody?

you know about induction?
get yourself into that stuff.

I agree about the higher frequencies in bridge and more bass in the neck position, and it really is caused by the bridge.
when you pick the string the vibration will be smaller and faster on the bridge side of the string, compared to the neck side.
and the vibe is bigger on the neck. the string flows around quite freely there, and that's why your neck PU usually has less wire inside the coil, than your bridge PU. to even out the output.

to make it short, a PU is nothing but a coil, running around some magnetic objects. if you move another object with magnetic-potential (strings) around in the M-field, this will cause some juice inside your coils.
more material would give you more output for sure (thicker strings, thicker sound).
just think of these generators on bicycles, they work somehow the same way and you can use these to make the process more clear to you (if you're not one of these posers with LED-light on your bike [img]/images/graemlins/laugh.gif[/img] ).
it's all about a moving magnetic field and a coil.

my english is just alright, but I'm not that trained in physical discussions in english really... [img]/images/graemlins/laugh.gif[/img]
but I hope some of this was of help for you.

if you need some more details or some formulas, let me know. I do studies in technics (including all this physical stuff) and I could look some things up for you if you need me to.


but a cool project!! your school seems to have some interessting offers...

[pebber]

Re: physics anybody?

[ QUOTE ]
A physics teacher who is helping me out with this sent me these questions:[ QUOTE ]
A guitar pickup that is closer to the bridge will be more or less likely to register higher order modes of vibration than a pickup that is farther from the bridge? (explain)


What words (both your own words and common guitar circle words) are associated with the sound from each of the pickups mentioned in the last question?


Research item. Is it important that one guitar pickup position (near or far from bridge) be a hummbucker and less significant for the other? (explain).[/quote

[/ QUOTE ]


gotta love this stuff, no? ok, I'm an electronical engineer, I do, so here we go:

answer 1:

a neck pup will have an output signal which is predominantly associated with the low-order harmonics of the triangle-shaped (->because you pluck the string not mid-length) standing wave => more mellow sound;
a bridge pup will have an output signal which has higher harmonic content => brilliant sound

basic idea: a pup placed in a particular location at a point x along a plucked string has a harmonic content that is proportional to the individual transverse displacements Yn(x,t) at that particular location, associated with the harmonic present in the transverse standing wave

to be continued..

[pebber]

Re: physics anybody?

[ QUOTE ]
A physics teacher who is helping me out with this sent me these questions:[ QUOTE ]
A guitar pickup that is closer to the bridge will be more or less likely to register higher order modes of vibration than a pickup that is farther from the bridge? (explain)


What words (both your own words and common guitar circle words) are associated with the sound from each of the pickups mentioned in the last question?


Research item. Is it important that one guitar pickup position (near or far from bridge) be a hummbucker and less significant for the other? (explain).[/quote

[/ QUOTE ]




answer 2:

this has nothin' to do with physics but words like bright, pierce, mellow, warm, etc.. come to my mind.. n-ah, next one


answer 3: (good question btw)

Yes it is! Why? because the difference in sound between SC and HB do not only come from the different impedances, but even so from the way the strings are sensed:

- a SC doesn't register movements parallel to it => output= bright sounding
- a HB, the distance between the poles causes the deletion of one harmonic (who's maximum is above one pole and who's minimum is simultaneously above the other pole) in the audible tonal spectrum => output=less bright sounding

so, the anticipate a next question he may add:
when you connect 2 SC to form a HB, a totally different range of harmonics is deleted because the coils are now at great(er) distance

will this do?

[guitar08man]

Re: physics anybody?

You rule pebber. you rule alot. [img]/images/graemlins/headbang.gif[/img]