An Acoustic and Perceptual Evaluation of Saxophone Pad Resonators

On some woodwind instruments, the key pads are often covered with what musicians and artisans refer as resonators. These are flat or domed disks made of metal or plastic fixed in the middle of the pad with a rivet. This article provides several analyses of the measured and perceptual behaviour of these pad resonators. In terms of their acoustic influence, resonators tend to lower the absorption coefficient of pads and when the tonehole is open, resonators can have an impact on the radiated sound. Input impedance measurements on an entire saxophone confirm that, when the holes are closed, pads without a resonator increase the damping, while the effect on open holes seems negligible. A perceptual study as well as in-vivo measurements are performed on four new alto saxophones of the same model (Yamaha YAS-480), the input impedances of which were found to be identical within the precision of the measurement setup. Two were kept in their original condition (provided with plastic resonators), while the other two were re-padded, one with metal resonators and one without resonators. In a first part of the study, 13 experienced musicians were asked to compare the saxophones on three criteria: brightness, ease of play and evenness. In a second part, musicians were asked to play an arpeggio while the pressure was recorded inside their mouth and at the bell of the saxophones. Results showed that the pad resonators increased the perceived ease of play and brightness of the saxophones. This is in agreement with a higher efficiency measured on saxophones with resonators as well as a higher harmonic spectral centroid in the radiated sound.