For this project I constructed a Cristal Baschet of 1 octave range with a chromatic scale that is tuned to equal temperament. The instrument is made out of

· 12 6mm in diameter glass rods of 1 foot length

· 13 threaded zinc rods of ¼ inch diameter

· 13 threaded rods of 5/16 inch diameter

· 13 cable lugs,

· 52 nuts for the ¼ inch threaded rods

· 52 nuts for the 5/16 inch threaded rods

· 26 washers for the ¼ inch threaded rods

· 26 washers for the 5/16 inch threaded rods

· 13 aluminum bars of 2cm W x 2cm H x 5 inches L

· 1 aluminum plate of 3 inches W x 1/8 inch H x 36 inch L

· 1 workbench

· 1 3ft x 3ft aluminum sheet metal

· 1 angle bracket

· 4 ¼ inch screws

· 4 ¼ inch hand tightening nuts

First I drilled 13 ¼ inch holes 1.5 inches apart from each other down the length of the aluminum plate that were ½ inch away from one of the width edges. Next I drilled 13 5/16 inch holes down the center of the aluminum plate that are parallel to the previous holes. I then placed the ¼ in threaded rods in the ¼ in holes and the 5/16 inch rods in the 5/16 inch holes in the metal plate with the corresponding nuts and washers and cinched them down so that there was no part of either rods are sticking out from the bottom. I then placed the cable lugs with the glass rods about halfway down each ¼ inch rod and sealed it in place with 2 nuts and a washer on either side. I then added the aluminum bar which I had drilled 2 holes in (1/4 inch and 5/16 inch) to the top of each metal rod combination and cinched it down with 4 nuts and 2 washers.

Lastly I drilled 1 hole in the opposite side of the aluminum plate, screwed in the angle bracket, and then screwed in the other side of the angle bracket to the sheet metal cone I had created.

The generator of sound for this instrument is the friction of your fingers with water across the glass rods to create longitudinal waves.

The resonator of this instrument is the “fixed-mass loaded” ¼ inch threaded rod and the aluminum plate

The radiator of sound is the cone shaped aluminum sheet metal that directs the sound outwards

To tune the instrument first calculated the lengths of the metal rods using MATLAB and an equal temperament chart.

L = 91.7 %cm (length of f0)

L1 = 1/1.059463*L

L2 = 1/1.122462*L

L3 = 1/1.189207*L

L4 = 1/1.259921*L

L5 = 1/1.334840*L

L6 = 1/1.414214*L

L7 = 1/1.498307*L

L8 = 1/1.587401*L

L9 = 1/1.681793*L

L10 = 1/1.781797*L

L11 = 1/1.887749*L

L12 = 1/2*L

This proved to be futile as I quickly learned that this isn’t the pattern the notes were following. I then realized my mistake. It is mass loaded at one end and all of the masses were the same and not proportional to the length of each different length rod. I didn’t have accurate enough equipment to make different sized metal bars for each note (a project for later). I noticed others peoples builds online had metal bars that got smaller as the notes went higher. I then began tuning everything using my ear first and then honing in on the correct frequency using a tuner afterwards.

The actual measured lengths are

L0 = 53.2 cm

L1 = 51.2 cm

L2 = 49.3 cm

L3 = 49.1 cm

L4 = 46.0 cm

L5 = 44.9 cm

L6 = 44.1 cm

L7 = 43.2 cm

L8 = 42.6 cm

L9 = 41.7 cm

L10 = 40.8 cm

L11 = 40.0 cm

L12 = 38.9 cm

These seem to be flexural bending waves as the lengths change exponentially rather than linearly as would transverse waves. However I will say that each of the aluminum bars is attached to the resonating ¼ inch rod AND the 5/16 metal support rod so I assume that is why it might demonstrate different behavior (lengths)

A few notes (pun intended) and quirks about the instruments… and potential future upgrades

The glass rods have a particular position in which playing the instrument will sound louder. I had to change the position of each rod so a certain area of it was facing up. I wonder why this is? I wonder if the glass rods are created in a way such that it is not homogeneous… maybe the way they are created they are not perfect cylinders and some parts bulge slightly.

In the future I would like to make this 3 octaves, create a stand that isn’t a workbench (and that doesn’t absorb as much of the sound energy), and change the lengths of the aluminum bars to correspond to each note to find optimal resonance. I would also like to create a different radiator which is larger and rhombus shaped. This is supposed to create an effect that is similar to a gong where the sound energy builds up within it creating a much more interesting envelope and bringing out much different harmonics of each note especially in the lower end.