Small 2-stringed instruments:
The purpose of these instruments is to provide a hands-on experiment where students can examine the effects of various string tensions and of differing string diameters. A worksheet is provided to ensure that the students take the time to examine each variable property. Ideally, there will be one of these instruments for every three students in the class.
materials:
- One 1/2 inch by 1 1/2 inches by 16 inches hardwood board.
- Two screw-down wire connectors.
- Nuts (2) and Washers (2) for the wire connectors.
- Two adjustable guitar pegs.
- Attachment screws for the guitar pegs (generally 4 required).
- Short lengths of guitar strings. Local music stores may be an ideal source for free broken guitar strings.
- Small plastic jewellery beads and epoxy (optional).
Construction:
- Drill two staggered holes for the adjustable guitar pegs. Ensure that there is enough separation between the two holes such that the bulkier underside of the pegs will not interfere with each other.
- Drill two staggered holes for the wire connectors. Stagger these holes in the same way that you did the last two such that the string lengths are the same.
- Fasten all hardware using the appropriate screws/nuts/washers.
- Attach one end of a string to one of the wire connectors.
- Attach the other end of this string to the adjustable peg.
- Clip the excess wire.
- Optional: Epoxy the beads onto the ends of the wires and file smooth. This ensures that nobody will prick themselves with the music wire.
Slinky and String Demonstration:
Although simple, this demonstration can elucidate many of the properties of the music wires from stringed instruments. Have one student hold one end of the rope. Move the other end up and down with your hand to induce vibrations in the rope. This forms a larger, slower model for the music wires. Repeat using the slinky. The slinky simulates a music string with a larger diameter. Its oscillations will be slower. Furthermore, the slinky can then be used to show compression and rarefaction waves that are similar to sound waves. To do this, lay the slinky along the length of a table. Push/pull the end of the slinky to induce such waves.
materials:
- One 1/4 inch diameter rope.
- One slinky.
Build-up Guitar:
Few people ponder the relevance of each component of a guitar, or of any other stringed instrument, as it is being played. This simple apparatus will demonstrate the reasoning behind the eight-shaped box that is at the base of just about every guitar. It will allow the comparison of sounds between the (i) the string attached to the board (ii) the string attached to the board and one flat plywood piece and (iii) the string attached to the board and one box resembling that of an actual guitar. Lastly, the setup (ii) from above demonstrates nodes and antinodes on the plywood board if it is to be repeatedly plucked after table salt has spread evenly over the plywood.
materials:
- One 1/2 inch by 1 1/2 inches by 32 inches hardwood board.
- One screw-down wire connector.
- A nut and a washer for the wire connector.
- One adjustable guitar peg.
- Attachment screws for the guitar peg (generally 2 required).
- One full length guitar string.
- Three 12 inches by 15 inches segments of 1/8 inch plywood.
- Two 12 inches by 3 inches segments of 1/8 inch plywood.
- Two 15 inches by 3 inches segments of 1/8 inch plywood.
- Twenty 1/2 inch by 1/2 inch by 3 inches wood blocks.
- Salt.
- Carpenter's glue.
Construction:
- Drill a hole for the adjustable guitar peg near one end of the 32 inch long board.
- Drill a hole for the wire connector on the other end of the board.
- Using a router, cut two gauges in the 1/2 inch thick sides of the hardwood board. Ensure that these cuts are 1/8 inch wide and 1/4 inch deep. These gauges should begin at the wire connector end of the board and should run 7 inches in length.
- Fasten all hardware using the appropriate screws/nuts/washers.
- Attach one end of a string to one of the wire connectors.
- Attach the other end of this string to the adjustable peg.
- Clip the excess wire.
- Cut a 7 inch by 1 inch strip out of two of the three large plywood boards. This strip should be centered along the 12 inch long side.
- Paint one of the these two boards black.
- With the remaining plywood boards, the wood blocks, and the carpenter's glue assemble a rectangular box.
- Using a Dremel tool or a utility knife, cut away a small gauge in the side of the box to accommodate the long board's attachment.