A directional microphone assembly for a hearing aid is disclosed. The hearing aid has one or more microphone cartridge(s), and first and second sound passages. Inlets to the sound passages, or the sound passages themselves, are spaced apart such that the shortest distance between them is less than or approximately equal to the length of the microphone cartridge(s). A sound duct and at least one surface of a microphone cartridge may form each sound passage, where the sound duct is mounted with the microphone cartridge. Alternatively, each sound duct may be formed as an integral part of a microphone cartridge.

Directional microphone assembly

A miniature unidirectional condenser microphone includes a diaphragm dividing a housing into first and second chambers. Each chamber communicates through a sound inlet port to the atmosphere. One of the sound inlet ports is covered by a sheet of porous, non-absorbent, hydrophobic thermoplastic material forming an acoustical resistance.

Unidirectional condenser microphone

An electroacoustic assembly comprising a microphone having a diaphragm and supported on a face plate susceptible to vibratory effects. Vibration sensitivity is reduced by opposing the pressure effects on the diaphragm caused, on the one hand, by vibration of the assembly in the ambient air mass and by vibration of the air mass leading from the ambient air mass to the diaphragm, and on the other hand, by vibration of the effective mass of the diaphragm, generally augmented with additional mass, and including the effect of the internal air mass adjacent the diaphragm. Applications include hearing aids in which the microphone and its support are mechanically coupled to receiver components that may impart significant motion thereto.

Microphone systems of reduced in situ acceleration sensitivity

A hearing aid is depicted which has a highly directional microphone system comprising means defining a front-to-back acoustic conduit through the hearing aid and a microphone assembly supported in acoustic isolation within the conduit in such a way as to define a sound passageway around the microphone assembly. The microphone assembly includes an acoustically sensitive diaphragm and associated electro-mechanical transduction means. A housing for the microphone assembly has a front orifice communicating exclusively with one side of the diaphragm which presents a predetermined acoustic impedance to sound waves of predetermined audible frequencies propagating in the passageway. The housing for the microphone assembly also has a rear orifice which communicates exclusively with the opposite side of the diaphragm. The rear orifice is effectively spaced from the front orifice by a predetermined acoustic path length which is such that sound waves, at least those in low and middle ranges of audible frequencies reaching opposite sides of the diaphragm through the front and rear orifices in the microphone housing establish a pressure gradient across the diaphragm. The rear orifice has a predetermined acoustic impedance greater than the acoustic impedance of the front orifice and of such magnitude as to produce a substantially cardioid directional characteristic for the hearing aid.

Hearing aid with directional microphone system

Apparatus for compensating for pressure changes in an acoustic transducer system includes a skeleton member having a predetermined configuration and adsorbent material having a regular structure and being supported on the skeleton member. The apparatus may include a plurality of members, each of the plurality of members having a plurality of hollows formed therein, at least one main surface of each of the plurality of members substantially facing and spaced apart from a main surface of an adjacent one of the plurality of members, and the adsorbent material may be provided within each of the plurality of hollows.

Apparatus incorporating an adsorbent material, and methods of making same

The disclosure is directed to an improvement in a microphone used primarily in head-worn hearing aids in which the microphone achieves a directional characteristic. The chamber and aperture in front of the diaphragm or other speech-responsive member is constructed in the normal manner while the chamber to the rear of the diaphragm or other speech-responsive member has a plurality of hollow elongated members secured within the walls of the microphone housing. The elongated members may be formed from sintered porous material such as metal, glass, or plastic, and may be arranged side-by-side or in a honeycomb arrangement. The elongated members attenuate the propagation of the sound waves, the attenuation being approximately 20 decibels lower than that reaching the other side of the diaphragm or other speech-responsive member without materially changing the inherent response characteristic of the microphone.

Johannes Wittkowski

Papers

Directional microphone for hearing aid