Kevin Eisensmith, Reporter
Richard Smith was a teacher of physics who wrote his doctoral thesis on trumpet acoustics before joining the Boosey & Hawkes Corporation, where he worked for 12 years as chief designer. He is now head designer and owner of Smith-Watkins Trumpets.
Smith presented an interesting, humorous, and thought-provoking lecture on the acoustical properties of brass instruments. Smith himself is not a brass player; his instrument of choice is the contra-bassoon! His talk was designed to get rid of the “3 M’s” surrounding trumpet playing: the Mythology, the Magic, and the Mystery.
He began by noting that there are two ways to judge the quality of an instrument: musical factors, which are more or less subjective; and physical factors, which are theoretically measurable. Among the musical factors are timbre or tone quality; intonation (internal, as opposed to the actual lengthening of an instrument via the tuning slide); and response or ease of playing. The latter made up the majority of the lecture.
Regarding internal intonation, Smith stated that there is “no such thing as a perfect instrument.” Because of the structure of the overtone system, a “d” is not always a “d;” when measured in cycles, the frequency of a d’ (or any other note) in one overtone series is not precisely the same frequency when that “same” d’ is a member of a different overtone series. Therefore, manufacturers are forced to make compromises in the construction of the instrument. (Smith illustrated this point - and many others - with demonstrations and graphs, which unfortunately, cannot be reproduced here.) This is not a new concept. Smith showed notes from a workbook of one D.J. Blaikley, who discussed what is known today as the node/anti-node system in 1878!
When discussing how a brass instrument works, Smith proved that “air flow” does not move a note through a brass instrument. In a remarkable demonstration, he produced a trombone mouthpiece with a hole drilled into the side of the cup at right angles to the throat. The purpose of this hole was to “vent” the flow of air. He used a membrane (he noted that condoms work best!) to prevent air flow into the body of the trombone. When he played the instrument, the air flowed out the vent hole (via a length of tubing, which added the necessary resistance); yet, notes were produced! The vibration of the membrane set up the standing wave or vibration in the trombone itself. This concept is similar to the alternating current / direct current concept in electricity.
Smith showed that only some of the energy used to play a note flows out the end of a bell. Some is reflected back through the length of the instrument. The “output” of any instrument is the combined effect of the leadpipe and bell. Therefore, if you lose too much energy because the leadpipe or the bell of an instrument is too large, that instrument will be too large to fill. He also stated that less than 1% of a player’s energy output actually produces sound
Finally, addressing the question, “Does the choice of material make any difference?” Smith showed a series of images created holographically that prove that metal does vibrate when a brass instrument is played. However, sound is affected only minimally and in a blindfold test a group of performers were unable to tell a difference between heavy- medium-weight, and light bells.
Smith’s presentation was certainly surprising and created a great deal of discussion from those in attendance. Could this be the end of “Trumpet Voodoo” as we know it?!
