Abstract: A wax guard for a hearing aid is mushroom-shaped, having a cross passage through its head which intersects an axial passage in its stem. The axial passage contains an acoustic filter terminating the axial passage in its characteristic impedance. The cross passage is semi-circular in section to reduce the projection of the guard into an ear canal and the total area of the two branches of the passage exiting from the axial passage is equal to that of the axial passage. The guard removably snap fits into a metal ring glued into the outlet port of the hearing aid.

Abstract: An acoustical damping element for acoustical tubing such as a hearing aid earpiece, in which a disc of wire screen is positioned over a disc of flexible fabric of a selected acoustic resistance, over the mouth of the tubing. An insertion tool of diameter slightly less than that of the interior passage of the tubing then pushes the composite layers of screen and fabric into the tubing, thereby forming the screen and fabric into closed end concentric cylinders in the passage. The cylindrical sidewall of the screen presses the cylindrical sidewall of the fabric against the interior wall of the tubing to retain the damping element within the passage.

Abstract: The resonant frequency of piezoelectric transducers is made more uniform from unit to unit by reducing the sensitivity of that frequency to manufacturing variations in the diameter of the ceramic sensing disk that forms a part of the vibratory diaphragm assembly. The diaphragm member proper is stiffened, as by integrally formed radial ribs, within the zone of variability of the disk perimeter, effectively establishing a uniform boundary edge for the diaphragm area that is stiffened by presence of the disk.