Methods

Research on the acoustical effect of cryogenic treatment on brass instruments performed at Tufts University's Department of Mechanical Engineering was split into 2 primary areas. Previous researchers designed and constructed a semi-anechoic chamber for the purpose of eliminating external lab noise from our trumpet recordings. Currently, we derived a procedure for testing all of the trumpets. This included the development of recording techniques and data analysis programs that will be discussed in more detail later.

The Semi-Anechoic chamber in the Tufts University Fluid Turbulence Lab (TUFTL) was designed and built by Chip Jones. The motivation behind its construction was excessive noise in the trumpet recordings from previous researchers at Tufts. The top view of our semi-anechoic chamber can be seen below.

The general dimensions can be seen on the diagram on the left. The outside height of the anechoic chamber is 7' 6". The inside height is 6' 4". All four vertical walls and the ceiling are completely covered with Sonex Foam. Questions regarding the materials used in wall construction can be forwarded to Chip Jones.

The cross in the upper left-hand corner of the diagram represents the location of the trumpet player for all trials. The arrow points in the direction the trumpet was pointed during all recordings. This direction is angled at approximately 45 degrees with either wall.

The circle in the lower right-hand corner represents the B&K Microphone Falcon Series 4190 used for all recordings. It is also angled at 45 degrees from either wall pointing directly at the trumpet player.

The B&K Microphone was run through a preamplifier and a conditioning amplifier with a gain of 3.16 Volts / Pascal and a Polarization Voltage of 200 Volts. All data was recorded using a SoundBlaster Live Sound Card on a Gateway Pentium Computer with 32 MB of RAM. All recordings were acquired with Sound Forge XP 4.0.

Four trials of data were taken on each of 10 trumpets, 5 of which had been cryogenically treated. Two trumpets were tested at a time in an alternating pattern. The 6 open notes (no valves depressed) were played in the following order on each trumpet: C4, G4, C5, E5, G5, C6. Two trials on each trumpet were recorded at a single time. The second set of trials were taken at a different time to assure repeatability from the trumpet player. All trumpets and trials were played with the same mouthpiece and by the same player, namely the Bach 5SV.

All data analysis was done on LabView and Microsoft Excel. Power Spectra were calculated for each note of each trial and then averaged. The average amplitude of fundamental and harmonic peaks of cryogenically treated and non-cryogenically treated trumpets was graphed and analyzed for statistically significant differences.

A screen shot of one of the LabView programs used in the data analysis can be seen below.

Selected Data and Results is available to users with access to the Data and Results Page.

This page was designed by Adam L. Cohen