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12 November 2003

To stay in tune, don't freeze an instrument

If you play the trumpet and want to be cool, you don't have to freeze your instrument. The trend amongst trumpet players these days is to freeze their instrument, thinking they can improve the tone, but engineers at Tufts University said cryogenic treatment has minimal effect on the sound.

"Our research shows that freezing trumpets does not make a better sounding instrument," said professor Chris Rogers at Tufts University's School of Engineering. "One of the great things about studying musical instruments, though, is if the player believes it will make a difference, he or she will play better, so it acts as a sort of placebo."

For two years, Tufts researchers analyzed 10 trumpets—five of which were cryogenically treated—and found there is no statistically significant difference between treated and untreated instruments. In fact, differences from player to player, and instrument to instrument, overshadowed any changes that cryogenic treatment might have produced.

Rogers and Jones cooled the instruments to –195°C (–321°F) and then let them slowly return to room temperature. The process is a dry one; the trumpet goes in a chamber cooled by liquid nitrogen, but the nitrogen never contacts the trumpet.

"We set out to see if the growing practice actually has any impact on the sound of the instrument—and found that it didn't," said Rogers. "Even though elite players from around the world have adopted this practice, it is unclear how or why cooling one's trumpet would affect the sound of the instrument."

A faction in the trumpet-playing culture believes a cryogenically treated trumpet has a better tone—often referred to as timbre by musicians—and a more distinct presence, a common term that musicians use to describe the "special sparkle" of a sound that one instrument has over other instruments.

Proponents of this practice believe that cryogenically treated trumpets play in tune more easily, as their notes are more centered. They also believe that the treated instruments won't tire the trumpeters as much. (Trumpets are one of the most physically demanding instruments to play.)

"Some musicians will say this allows them to play their trumpet all night long," said research partner and former graduate student Jesse Jones IV.

Firms that offer cryogenic processing say the treatment results in artificially aging a trumpet. They also say the process relieves any internal stresses due to manufacturing.

"Heating softens metal and relieves stresses, so it is difficult to understand how freezing a trumpet would also relieve stress," said Jones.

In 1998, Selmer Musical Instruments, maker of many orchestra wind instruments including the Vincent Bach Stradivarius trumpet, became interested in offering the cryogenic treatment as a factory option to its customers. Before moving forward, the company asked the Tufts engineers to independently verify the beliefs about cryogenically treating trumpets.

The Tufts team approached the research from three perspectives: materials science, quantitative acoustic measurements, and qualitative player responses. The sample set was comprised of 10 Bach Stradivarius trumpets randomly picked from the Selmer production line, half of which were cryogenically treated. The engineers then enlisted six players with proficiencies ranging from beginner to professional to help test the trumpets.

The materials science phase of the study found no changes in the crystalline structure of the brass on the microscopic level. The researchers attempted to identify differences in timbre by measuring frequency content of a sound and graphically displaying what frequencies are present to get a quantitative description of the sound.

"As far as we can tell, the differences from trumpet to trumpet, player to player, and session to session far overshadow any difference brought on by cryogenic treatment," Jones said.

The trumpet research is part of Tufts' Musical Instrument Engineering program launched by Rogers and Jones in 1998. An interdisciplinary partnership of the University's music, mechanical engineering, and electrical engineering departments, the program is one of just a handful of its kind in the country.

For more information on this subject go to www.isa.org/measurement.