The acoustic spectrum of a modern trumpet with the bell section heavily damped has been compared to the spectrum of the same instrument with the bell section left free to vibrate. Measurements of the amplitude of vibration indicate that the damping significantly reduces the movement of the metal, and a corresponding change in the acoustic spectrum between the two cases is found. It is shown that the relative power in the fundamental may change by more than 3 dB when the vibrations in the bell section are damped. Two possible causes for the effects are considered: a change in input impedance, and the transfer of mechanical vibrations through the instrument to the lips. Results of modelling and experiments are presented that indicate the latter is the more plausible explanation; however, the etiology of the effect is still unknown.
Moore, TR, ET Shirley, AE Daniels, and IEW Codrey. 2005. The effects of bell vibrations on the sound of the modern trumpet. ACTA ACUSTICA UNITED WITH ACUSTICA 91 (3): 578-89.
ACTA ACUSTICA UNITED WITH ACUSTICA