Mead C. Killion

Directional microphone assembly

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.

Insert earphones for audiometry

Insert earphones, which are especially useful for audiometry applications include a transducer which is coupled to a resonance cancellation tube as well as to a main tube which is coupled to the ear, with series acoustic dampers in the tubes, operating in a known manner to obtain a smoothly varying frequency response characteristic. An electrical equalization network is coupled to the transducer, cooperating with the acoustic components to obtain a frequency response characteristic which is either flat or which matches that of the human ear. The dampers in series with the main and cancellation tubes have acoustic resistances which are respectively about 20% lower and 20% higher than the characteristic impedances of such tubes, operating to obtain a broadband increase in output.

Reference thresholds for the ER‐3A insert earphone

Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501-1508 (1978)]. Either the manufacturers provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.

Microphone with stepped response

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.

Response-modifying acoustic couplers for hearing aids

Response-modifying acoustic couplers are provided for use between an output port of a hearing aid unit and an earmold at the entrance to the ear of a wearer, including a passage and a chamber which respectively provide a high acoustic inertance and a high acoustic compliance to cooperate with other acoustic elements and to form an acoustic network producing a predetermined frequency response characteristic.

Variable recovery time circuit for use with wide dynamic range automatic gain control for hearing aid

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.

Clinical Use of an Insert Earphone

There are several applications of and advantages to using an insert earphone. An insert earphone has three parts: a transducer to convert electrical energy to sound, a conduit to deliver the sound into the ear canal, and a coupler connecting the device to the canal. The data from this study indicate that there is a distinct advantage in using insert earphones over TDH-49 phones (standard headphones) in the attenuation of low frequency ambient noise. The use of insert earphones will permit one to test hearing in areas of higher ambient noise than was previously possible. Insert earphones are used to shorten the hearing aid selection process. A technique is described in which only one real ear measurement is required for an accurate hearing aid fitting. Most, but not all, of the masking dilemmas that are encountered with standard headphones are circumvented or eliminated by using insert earphones. In brain stem auditory evoked reponse testing, the insert earphone reduces the stimulus artifact without influencing the acoustic signal. Finally, the insert earphone solves the collapsing ear canal problem.

Occlusion meter and associated method for measuring the occlusion of an occluding object in the ear canal of a subject

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. The second logarithmic amplifier is connected to receive the electrical signals from the second microphone and has a DC output signal that is logarithmically related to the peak amplitude value of the electrical signals received from the second microphone. The DC output signals are supplied to a DC meter. The DC meter may be analog, digital, or may be a video display that provides a visual indication of the difference between the DC outputs of the first and second logarithmic amplifiers. A method of measuring the degree of occlusion of an occluding object in an ear canal is also set forth.

AGC circuit particularly for a hearing aid

A high fidelity hearing aid is disclosed for providing high quality sound and is primarily directed to those users whose hearing loss is such that they need some amplification for low level signals, but do not need amplification for high level signals.

Earplug with improved audibility

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.