Vibrations in brass instrument bodies: A review.

Abstract

The bodies of brass instruments vibrate when played, as evident to any player. These vibrations are driven mechanically at the player’s lips and by coupling with the internal acoustic field throughout the instrument. The coupling can equally well allow energy flow in the opposite direction, from the body to the player’s lips and to the internal acoustic field. The vibrating shell can also radiate directly into the room. Studies involving human or machine players suggest that the effect of the wall vibrations on the acoustic spectral components is of the order of a few decibels. However, for the most part, the direct radiation of the wall vibrations is approximately 20 dB below the level of the radiated internal acoustic field. The wall vibrations have a slightly different time envelope, though, and also have a formant-like region around a few kilohertz. Some of the pieces of this complex puzzle that need further investigation include the interaction between player and instrument, the effect of sound level on the coupling, the perceptibility of the radiated vibrations by auditors, and the variations within the brass family.