Abstract: A probe tube for use with an occluding object to test sound pressure levels within the ear canal is set forth. The probe tube has a flexible body portion having an elongated cross section. The elongated cross-section has a generally arcuate first side that contacts the wall of the ear canal and a generally arcuate second side that generally conforms to a surface of the occluding object. The flexible body portion also includes an aperture for conducting sound through the probe tube. The aperture extends along at least a portion of the length of the flexible body.

Abstract: An electronic device is set forth that allows external control of a controllable electronic function of the device. The device includes a function circuit for implementing an electronic function in response to a signal at a function control signal input. The function circuit receives DC power from a power supply that is connected between two battery terminals. The DC power from the power supply circuit is supplied at a predetermined DC voltage level. A control circuit is included in the device and is responsive to a signal superimposed on the predetermined DC voltage level of the power supply at the two battery terminals for generating a function control signal to the function control signal input of the function circuit. In accordance with one embodiment of the present invention, the invention is implemented in the context of a hearing aid.

Abstract: A power supply circuit is set forth which overcomes the problems associated with incorrect battery insertion. The power supply circuit includes first and second battery terminals for electrical connection to the battery. The first and second battery terminals are connected to a first transistor switching circuit. The first transistor switching circuit is responsive to power from the battery to through-connect a negative polarity power signal therethrough irrespective of the polarity orientation of the battery. The first and second battery terminals are also connected to a second transistor switching circuit. The second switching circuit is responsive to power from the battery to through-connect a positive polarity power signal therethrough irrespective of polarity orientation of the battery. The negative and positive polarity power signals are available for connection to a load device, such as a hearing aid amplifier.

Abstract: A power supply circuit is set forth which overcomes the problems associated with incorrect battery insertion. The power supply circuit includes first and second battery terminals for electrical connection to the battery. The first and second battery terminals are connected to a first transistor switching circuit. The first transistor switching circuit is responsive to power from the battery to through-connect a negative polarity power signal therethrough irrespective of the polarity orientation of the battery. The first and second battery terminals are also connected to a second transistor switching circuit. The second switching circuit is responsive to power from the battery to through-connect a positive polarity power signal therethrough irrespective of polarity orientation of the battery. The negative and positive polarity power signals are available for connection to a load device, such as a hearing aid amplifier.

Abstract: A hearing aid houses an integrated circuit having at least one programmable resistor for setting the audio response of the hearing aid. The programmable resistor has at least 14 discrete steps of programmed resistance. In a first embodiment of the programmed resistor, the difference in programmed resistance between successive steps changes logarithmically and a second embodiment has the difference in programmed resistance between successive steps changing logarithmically for the higher values of programmed resistance and changing linearly for the lower values of programmed resistance. The programmable resistor is connected between two terminals and comprises at least seven subcircuits. Each subcircuit comprises a resistor and a switch sharing a common node, the first of the subcircuits has one end connected to the first terminal.

Abstract: An instrument for measuring the degree of occlusion of an occluding object, such as an earmold, in the ear canal of a subject is set forth that overcomes the problems associated with prior art devices. The instrument includes a first microphone for transducing sound waves exterior to the ear canal into electrical signals and a first microphone for transducing sound waves within the ear canal into electrical signals. These electrical signals are respectively supplied to first and second logarithmic amplifiers. The first logarithmic amplifier is connected to receive the electrical signals from the first microphone and has a DC output signal that is logarithmically related to the peak amplitude value of the electrical signals received from the first microphone.

Abstract: A hearing aid apparatus is disclosed that employs both an omnidirectional microphone and at least one directional microphone of at least the first order. The electrical signals output from the directional microphone are supplied to an equalization amplifier which at least partially equalizes the amplitude of the low frequency electrical signal components of the electrical signal with the amplitude of the mid and high frequency electrical signal components of the electrical signals of the directional microphone. A switching circuit accepts the signals output from both the omnidirectional microphone and the directional microphone. The switching circuit connects the signal from the omnidirectional microphone to an input of a hearing aid amplifier when the switching circuit is in a first switching state, and connects the output of the equalization circuit to the hearing aid amplifier input when the switching circuit is in a second switching state.

Abstract: A gain control voltage is applied to a control terminal of a variable gain hearing aid amplifier which is logarithmically related to a signal voltage level which is sensed at either an input terminal or an output terminal of the amplifier and which is below a certain threshold value, and an impedance is connected to the control terminal which includes, in parallel a first capacitor, a series combination of a resistor and a second capacitor of larger value than the first, the impedance being operative at signal levels below the threshold value to provide a rapid recovery from short intense sounds and a much slower recovery from prolonged intense sounds.

Abstract: A high fidelity hearing aid amplifier is operable at a very low battery voltage and includes a single integrated circuit chip which provides a variable gain amplifier and gain control circuitry operative at low signal levels to enhance gain at higher frequencies relative to gain at lower frequencies, such circuitry including a logarithmic rectifier arrangement and a peak detector in a compression ratio control circuit. Operation at a low battery voltage is enhanced through a compression ratio control circuit which provides a level shift between an AC output of the logarithmic rectifier arrangement and the peak detector. Current mirrors are provided to obtained balanced and stable operation, and an arrangement is provided for manual control by a user to obtain an optimum response characteristic.

Abstract: A current controlled variable attenuator circuit using a current controlled resistor is disclosed. In paticular, the current controlled resistor and attenuator are particularly suited for use in hearing aids due to the resistor's and attenuator's easy implementation in bipolar integrated circuits. The current controlled resistor and attenuator also has wide application to other circuitry requiring controlled variable resistance elements having a broader linear response than previously available. The current controlled resistor consists of transistors having inherent non-linear characteristics which can be linearized by adding appropriate compensation circuitry.

Abstract: An earplug uses damping to render unimportant a Helmholtz resonance between the acoustic mass intrinsic to a sound channel thereof and the compliance of air in the earcanal, in combination with a readily manufacturable external structure coupled to the sound channel to increase response characteristics at higher frequencies in a predictable and well controlled manner in order to provide a highly desireable uniform frequency response.

Abstract: A system for detecting and transmitting body electrical signals in the presence of ambient electrical interference that uses a transmiter circuit including an amplifier coupled to and in close proximity to two or more body electrodes, a light pulse generator that receives its input from that amplifier and provides a pulse-duration-modulated series of light pulses, and a remote receiver including a transducer which demodulates the transmitted light pulses into electrical pulses of corresponding duration and frequency and a demodulator which accepts those electrical pulses and produces an amplified replica of the original signal developed between the body electrodes, thereby effectively providing complete electrical isolation of the electrode amplifier from the remaining bioelectrical signal analysis equipment.

Abstract: An earplug uses damping to render unimportant a Helmholtz resonance between the acoustic mass intrinsic to a sound channel thereof and the compliance of air in the earcanal unimportant, in combination with an external structure coupled to the sound channel to increase response characteristics at higher frequencies in a predictable and well controlled manner in order to provide a highly desireable uniform frequency response.

Abstract: An eartip electrode constructed of a plastic or vinyl tubular central channel having a soft foam material laterally surrounding the distal end of the channel. Electrical conductivity from the skin of the earcanal is provided by a very thin, soft conductive film coupled to and surrounding the foam material.

Abstract: Earphones especially adapted for use in audiometry have electroacoustical transducer elements located at a distance from the ear and incorporate coupling paths and chambers so arranged as to eliminate undesirable resonances and to obtain a smooth and accurate frequency response characteristic.