The Physics of electric guitars and music

Guitar Pictures

DP Parameters

Topic Breakdown (Individual or Team assignments)

In this project, you will be building an electric guitar. Most of the materials will have to be hand-made by you and your teammate. You will be fully informed on how to use every tool and Mr. Davis will ensure you learn all the “theory” needed to build an electric guitar. However, be prepared to work independently and overcome problems with your teammate or on your own. This project covers many topics in physics and after building your electric guitar, you must be prepared to explain the following topics.

Topics

1. How a pickup works, (magnetic induction). How to determine the number of coils in your pickup using resistance/meter.
2. How the electronics are designed and why they work (Ohm's law, resistance, etc.)
3. Why we use audio taper potentiometers (decibels, linear volume). Table here
4. The relationship between volume knob angle and resistance, and coils and volume. Include derivations for both.
5. How the tuners work (simple machines, gear and radius ratios)
6. How a 1⁄4 inches jack works (include a good diagram to show connection)
7. How forces and torques are distributed around the guitar
8. Exact methods for calculating tension in the strings, and shearing on the glue. Include how the birch plywood board can improve tonality.
9. How vibrating strings produce sound (tuning, tension, thickness, length, loudness)
10. How sound is amplified and heard (how a speaker works, propagation, the human ear)
11. How strings produce sounds: Definitions for open chord, beat frequencies, harmonics, overtones, wavelength, standing wave, nodes, interference
12. How to follow I-IV-V song sheets
13. Overall summary of how guitar works - the big picture

 

Roles

While you will be working with a partner to build a guitar, you will also work with another partnership. Each person in the group of four must assume one of the following roles.

Documentarian – Collects information for the group to use for their DP’s. This includes taking pictures, recording video, writing daily blog entries on group progress, and collecting reflection pieces.

Physicist – This is the physics expert in the group. They don’t do all of the physics work—they will assign some research to other group members. The Physicist assembles all of the physics knowledge and makes it intelligible. The Physicist must ensure the group has good answers to topics: 1, 2, 3, 5, 7, 8, 9, 10, 11, 13.

Mathematician - This is the math expert in the group. They don’t do all of the math work—they will assign some research to other group members. The Mathematician assembles all of the math knowledge and makes it intelligible. The Mathematician must ensure the group has good answers to topics: 2, 3, 4, 5, 8, 11, 13.

Engineer – This is the expert on how to progress with each stage of guitar building. The engineer does not do all of the building but he or she advises the group on how to proceed with each step. The engineer must ensure the group has good answers to topics: 1, 4, 6, 11, 12, 13.

 

Guitar Building

Phase I: Build your guitar frame

• Cut and shape the body
  • Guitar body shape ideas
  • Guitar sizing specs
• Attach the neck
• Attach tailpiece with screws and ¼” phone jack (Picture)
• Install tuning knobs (Picture)
• Paint

Phase II: Build and test electronics

• Construct pickup with magnet and wire
• Test pickup with tuning fork, speaker, and oscilloscope
• Construct circuitry
• Install potentiometer and volume knob

Phase III: Stringing and tuning

• Install and slot nut blanks
• Attach and tune strings
• Install frets
• Cut a slide

Phase IV: Make music

• Test purity of tones
• Play a simple I-IV-V song