lab6 - 1 Physics 198 PHYSICS OF MUSIC Laboratory 6 Strings...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Physics 198 PHYSICS OF MUSIC Laboratory 6 – Strings Revisited Name ________________________________ Partner(s) ___________________________________ Introduction. The electric guitar utilizes magnetic pickups that sense the vibrations of the steel strings. A pickup is sensitive to a particular wave harmonic if it is placed under an anti-node of the standing wave on the string and insensitive if it is placed under a node. Thus with several pickups and electronics to combine the signals from them, desired timbre can be constructed electronically. In this lab we use a standard pickup combined with the computer-based spectrum analyzer we used in the past to revisit vibrations on strings. Goals : I. To investigate quantitatively the effect of wire tension on resonant frequencies. II. To investigate quantitatively the effect of wire length on resonant frequencies. III. To investigate the connection between harmonic structure and timbre. Equipment. A wooden platform with steel wire mounted so that the wire tension can be set with weights suspended by the wire; an electric guitar pickup, wooden fret and various slotted weights to suspend. The pickup is connected to a USB audio interface box (M-Audio, FastTrack) that also provides an output for headphones (Sennheisser EH150 ) and for a Radio Shack amplifier driving a speaker. The USB interface is connect to a Dell Optiplex 620 Computer equipped with SpectraPlus sound analysis software and a printer. (See wiring diagram and computer settings in appendix.) There should also be a few calculators capable of doing square roots; the calculator available through the computer can also be used. (Picture follows on next page.) Settings: (In principle the SpectraPlus parameters should already be set.) (1) The M-Audio USB interface should have the mic input turned all the way down (CCW), the “mix” knob should set entirely to “input,” i.e., also CCW, the “mono” button should be pressed in and the output knob adjusted for comfort. (2) The SpectraPlus package should be in the “real time” mode and have the following set under “options”: a. “Settings” should all be default except the “Sampling Rate” which should be 16000 and the “FFT size” which should be 32768. This will cover a frequency range up to 8000 Hz with a resolution of about 0.5 Hz. Please do not bother to measure or set frequencies to an accuracy of better that about 0.5 Hz. If it is within 0.5 Hz, then all is ok.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 b. “Scaling” should have both amplitude and frequency axis set to Linear.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 02/11/2012.

Page1 / 7

lab6 - 1 Physics 198 PHYSICS OF MUSIC Laboratory 6 Strings...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online