Measuring the effect of the reflection of sound from the lips in brass musical instruments

Abstract

The lips of the player are often assumed to perfectly reflect sounds that strike them. Experimental and theoretical calculations of input impedance demonstrate the pressure that would build up if a flat, perfectly reflecting volume velocity source were used to excite the air into vibration. In reality the lips should project slightly into the instrument mouthpiece and absorb a small amount of the energy that strikes them and this study will quantify this effect using wave separation/impedance apparatus. For closed lips it is expected that the strength of resonances will be reduced, but that the correction will be small. The condition for reflection from lips that are not fully closed will differ more significantly from perfect reflection and it is anticipated that this data will be useful for integration into physical models of brass instruments.