Abstract: An electromagnetic transducer including a diaphragm mechanically connected to an armature, a coil wound tranversely around the armature, a permanent magnet adjacent the armature, and one or more additional magnetic members completing a magnetic circuit having a plane of symmetry longitudinally bisecting the armature, has a magnetic shield formed by two high-permeability casing halves joined together along a joint plane substantially concident with the plane of symmetry.

Abstract: This invention is concerned with a hearing aid including a microphone, an adjustable amplifier, and an acoustic transducer positioned within a first, large acoustic chamber defined by an in-the-ear housing. The acoustic transducer is in communication with a sound outlet passage which leads into the user's ear canal. The acoustic transducer includes a sound generating diaphragm driven by an acoustic driver. The diaphragm and driver are mounted in the acoustic transducer, with the diaphragm dividing the transducer into second and third acoustic chambers. A vent passage is provided between the first and third acoustic chambers. An acoustic resistance is mounted in the vent passage to modify the operating characteristics of the hearing aid.

Abstract: A high frequency emphasis microphone particularly adapted to a hearing aid application provides a steeply rising frequency response characteristic relative to frequency, and has a low pass sonic attenuator for providing to the undriven side of the microphone diaphragm a sonic counterpressure which at low frequencies substantially cancels ambient sound pressure delivered to the driven side of the diaphragm, the attenuator reducing this counterpressure at elevated frequencies to provide accentuated high frequency response. The attenuator includes a pair of inertance-forming restricted passageways passing a portion of incoming sound to a bypass port leading to the undriven side of the diaphragm, the passageways being defined by a U-shaped plate disposed within a chamber confronting the driven side of the diaphragm.

Abstract: A stepped frequency microphone particularly adapted to a hearing aid application provides a stepped frequency response characteristic relative to frequency, and has a low-pass sonic attenuator for providing to the undriven side of the microphone diaphragm a sonic counterpressure which at low frequencies substantially cancels ambient sound pressure delivered to the drive side of the diaphragm, the attenuator reducing this counterpressure at elevated frequencies to provide accentuated high frequency response.

Abstract: A passive ear protector device for positioning in the ear of the user for protecting the ear from sounds of high intensity. The device attenuates sound in a manner which tends to preserve the natural quality of the incoming sound, in particular with respect to the natural resonance of the ear canal.

Abstract: A hearing aid including a microphone, an adjustable amplifier, and a transducer comprising an acoustic driver driving a diaphragm disposed within an acoustic chamber, all mounted in an in-the-ear housing having a sound outlet passage leading from the acoustic chamber into the user's ear canal, is provided with a cleaning passage that is accessible from the outside of the housing and that connects to the inner end of the sound outlet passage, through a portion of the acoustic chamber. Throughout internal cleaning is effected by pumping a solvent through the continuous conduit formed by the cleaning passage, the acoustic chamber, and the sound outlet passage, without disassembly of the hearing aid.

Abstract: An acoustic transducer with an improved electret assembly mounting for providing spacings between the fixed and movable electrodes, and having as one feature the lowering of the undesired capacitance therebetween.

Abstract: A sub-miniature power amplifier for hearing aids configured to be completely self-contained and to fit within the user's ear features a Class D amplifier stage providing a peak-to-peak output voltage greater than the power supply voltage. By configuring all signal elements as digital units, circuit balance is readily maintained. A substantial economy of battery drain is achieved while preserving a low value of distortion at low signal levels. Oscillator frequency is governed by a single resistance element. The amplifier and an optional efficiency-improving inductor can be accommodated entirely within the residual volume of the motor chamber of a state-of-the-art earphone housing. Pulse feedback networks are provided to achieve positive stable latching of each output pulse throughout its duration without producing significant pulse duration distortions.

Abstract: A subminiature power amplifier for hearing aids configured to be completely self-contained and fit within the user's ear features a Class D amplifier stage. By configuring all signal elements as digital units, circuit balance is readily maintained. A substantial economy of battery drain is achieved while preserving a low value of distortion at low signal levels. Oscillator frequency is governed by a single resistance element. The amplifier and an optional efficiency-improving inductor can be accommodated entirely within the residual volume of the motor chamber of a state-of-the-art earphone housing.

Abstract: A battery-powered miniature acoustical transducer system for a hearing aid, including a microphone and an amplifier, has a combination filter and voltage regulator incorporated in its power supply circuit; the filter/regulator includes a field-effect transistor having its drain and source electrodes interposed in series between one battery terminal and a first power terminal of the amplifier, a resistor connecting the source and gate electrodes of the FET, a transistor having its emitter and collector interposed in series between the other power terminal of the amplifier and the gate electrode of the FET, and a junction diode connected from the FET source electrode to the transistor base, the diode junction and the base-emitter junction of the transistor both having highly non-linear voltage/current characteristics.

Abstract: An audio loudness control system for processing a broad dynamic range of audio input signals (e.g. 70 to 100 dB) comprises a gain-controlled amplifier, a feed forward control signal generator having an audio signal input that develops a feed forward gain control signal having an amplitude representative of long-term input excursions of the audio signal above a predetermined loudness threshold, a feedback control signal generator having an input from the audio output of the amplifier that develops a feedback gain control signal having an amplitude representative of transient output signal excursions above the loudness threshold, and a selector gate that selects the gain control signal of instantaneously higher effective magnitude and applies the selected gain control signal to the gain control input of the amplifier.

Abstract: A microphone, particularly for hearing aid application, said microphone providing a stepped response characteristic relative to frequency wherein low frequency sounds will couple to the associated hearing aid with a restricted amount of amplification, while providing an emphasis or higher amplification for the higher frequencies in the bandwidth of interest.

Abstract: An improved transducer construction of the type having a U-shaped armature mounted to have a vibrating arm extending through the tunnel of a cooperating coil. The arms of the armature are joined by a smooth bend to provide improved shock-resistant characteristics. The coil is initially located and properly positioned relative to the arm extending through the tunnel by means of shims. The transducer includes a case comprising a cup, and a cover for the cup, both being of a magnetic material. The cup and cover are joined together by welding to insure low reluctance flux paths therebetween to retain the magnetic fields developed by the transducer within the casing.

Abstract: The present invention relates to an acoustic transducer including an improved electret assembly mounted in an improved case and having an electronic amplifier circuit comprising FET transistors. The electronic circuit further includes means for protecting the FET transistors against current surges.

Abstract: A priority mixer control for a multi-microphone audio system comprises a threshold signal generator that develops a scanning D.C. threshold signal starting at a maximum level for a time T1 and then decreasing in amplitude as a function of time. Each microphone channel is provided with a control channel including a comparator that compares the microphone signal, as an A.C. signal, with the threshold signal, and that switches the microphone channel to "on" condition when the microphone signal exceeds the threshold; all of the control channels are coupled to a threshold signal restoration means that drives the threshold signal back to its maximum level each time an audio channel is switched "on". An audio channel that has been switched "on" remains "on" for a time T2 substantially longer than the time T1. The number of channels currently in "on" condition is continuously monitored and the output gain is reduced whenever two or more channels are in "on" condition.

Abstract: An audio system comprising a record player, tape deck, microphones, or other signal source which generates stereo signals supplied to two main speakers for reproduction; the stereo signals are added together to afford an intermediate signal which is subjected to at least two successive equal delays to generate a plurality of delayed signals which are summed with the intermediate signal in predetermined amplitude and phase relation to generate a spatial effect signal that is essentially free of noticeable reverberations or echoes. This spatial effect signal is reproduced by a separate speaker in the same listening space as the main speakers to add ambience and diffuseness to the total sound field. In the preferred construction two delayed signals are employed, delay is effected with the signals in digital form, and the summing ratio for the intermediate, first delayed, and second delayed signals is approximately 1:2:1 with the intermediate signal and the second delayed signal in phase opposition.

Abstract: The present invention relates to an acoustic transducer including an improved electret assembly mounted in an improved case and having an electronic amplifier circuit comprising FET transistors. The electronic circuit further includes means for protecting the FET transistors against current surges.

Abstract: A transmission system is disclosed having an improved means for coupling sound to and from a transducer. The system includes a main sound channel and an associated cavity; damping elements are selectively positioned in or adjacent the cavity to provide a suitable acoustic impedance in the desired operating frequency range to effect a smooth acoustical operation.

Abstract: An electroacoustical transducer of the magnetic armature type having an efficient electromagnetic configuration with the armature being formed integrally with a support yoke. The yoke includes a base from which two arms extend generally parallel to the armature, the two arms engage pole pieces formed of laminations, and the vibrating end of the armature is positioned in the plane of the diaphragm and is connected thereto. The armature may include a boss or gusset adjacent to the contilever end of the armature to stiffen it and thereby raise the resonant frequency of the transducer. A casing is included which is spaced from the yoke and serves as a magnetic shield.

Abstract: A damping element comprising fiberous fuseable material shaped to form a cup-like member which may be inserted in the sound openings of an acoustic transducer to provide a selected acoustic resistance.