(click on thumbnails for enlarged view)
All of the students participated in constructing the acoustic chamber inside the laboratory. The chamber is tiled with sound absorbing material and has a 4'x6' optical table floating on air in the middle. The chamber allows us to perform acoustic experiments as well as optical experiments on musical instruments without the room acoustics interfering with the experiment.
Kristy (class of 2003) and Greg (class of 2001) designed the optical system used for the electronic speckle pattern interferometry (ESPI) experiments.
Chris (class of 2001) and Dai (class of 2001) were in charge of designing and making a set of artificial lips so that we can study how the trumpet works without using humans in the experiments. When placed in contact with the mouthpiece of a brass instrument the lips sound and act very similar to human lips.
Kristy, Greg, and Jody (class of 2002) set up the optics for the ESPI experiments on the optical table inside of the acoustic chamber.
In order to make very precise acoustic measurements we use several instrumentation microphones. Greg and Elliot (class of 2002) built the driver circuits.
All of the experiments are controlled from outside of the acoustic chamber via a computer interface. Jody and Kristy wrote the controlling software.
Experiments are ongoing, but the initial results are very interesting. Below is a picture of a trumpet in the chamber being prepared for ESPI. Beside it are some ESPI pictures of a vibrating trumpet bell. The trumpet in this case is driven by a small speaker attached to the mouthpiece and the pattern of the vibration is very dependent upon the driving frequency as well as the amplitude. We have developed a model that predicts these patterns as a function of both frequency and amplitude. An article describing our results has been published in the scientific journal The Journal of Sound and Vibration.
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