MXPA01005624A - Directional ite hearing aid using dual-input microphone - Google Patents

Abstract

A microphone of the dual-inlet type is installed in an In-The-Ear ("ITE") hearing aid. First and second outwardly-diverging channels are located in the faceplate, to connect the inlets of the microphone to two spaced-apart ports in the faceplate.

Description

EQUIPMENT FOR DIRECTIONAL EEO TYPE AUDITIVE PROSTHESIS USING DOUBLE ENTRANCE MICROPHONE Background of the Invention The present invention relates to devices for hearing aids, and more particularly refers to directional hearing aids. In the strictest sense, the invention relates to hearing aid devices of the In-the-Ear (EEO) type.

(Included in the EEO type are the so-called "half-shell" equipment, which are smaller than the full-size equipment, but larger than the channel apparatus and the "CEC" fully-in-channel devices.) Conventional hearing devices have only one omnidirectional microphone, so the patient can hear sounds from all directions around his head. This omnidirectionality harms the patient's ability to differentiate between, say, the voice of a conversation partner and background noise (such as a crowd). For this reason, devices for directional hearing aids have been developed.

As conventionally implemented, in the EEO devices, a directional hearing device has two small (EM size) omnidirectional microphones, which are separated by at least 6 mm and by a maximum of 12 mm. An alternative implementation of an EEO directional hearing device uses a capsule (sold under the D-MIC brand by Etymotic Research Inc.) containing a double-input directional microphone and an EM-size omnidirectional microphone together with an appropriate electronic circuit. The eneradas of the directional microphone are separated by 4 mm. In both cases, the directionality of the equipment occurs because there is a phase shift in the sound pressure near the inputs of the two omnidirectional microphones (and likewise, near the two directional microphone inputs). The sound will reach one input before it reaches the other, and the resulting phase shift in combination with an internal microphone delay will determine the polar response of the microphone. These two known EEO directional implementations share a significant reduction in the signal to noise ratio relative to conventional non-directional EEO equipment. Two factors contribute significantly to this problem.

The first factor is that a directional microphone with a closed space between the inputs (of two omnidirectional microphones or the two inputs of a double-input microphone) has a progressive attenuation (of 6 dB / octaves) at low frequencies. (This progressive attenuation is due to the fact that low frequency sounds have longer wavelengths.) As a result, for a particular spacing, the phase of changing the sound pressure near the inputs decreases with the reduction of sound frequency. incident.) This progressive attenuation reduces the sensitivity (and therefore the signal to noise ratio) of the apparatus, and requires significant compensation or electrical equalization. Such compensation amplifies low frequency noise, and interferes with the patient's hearing in silent situations. The second factor is that everything else stays the same; smaller microphones usually have a smaller signal-to-noise ratio. This is because a smaller microphone must have a smaller membrane, which makes the microphone less sensitive, since the sensitivity increases with the size of the membrane. In silent situations, the smallest directional microphones (EM size) may be unacceptably noisy. To address the problem of excessive noise in silent situations, both types of hearing aid devices EEO are provided with a switch operable by the patient. This switch puts the device in an omnidirectional mode, when the internal sound in the directional mode becomes unacceptable to the patient. A switch like this increases the cost of the components required to manufacture the equipment, and also occupies a considerable space ("real state") in the front plate. Because of the actual state required by the switch and the two separate microphones that must be spaced apart by a space of at least ß mm, certain patients, for example, those with small ears, may not be suitable for fitting to hearing aids. Alternatively, such patients may be forced to accept larger EEO equipment instead of "half shell" equipment, which are less visible, and are therefore aesthetically preferred. Additionally, if a device for hearing aids EEO -is built using two omnidirectional microphones, the microphones must be well adjusted with respect to the frequency of response, etc., which increases the cost of components and assembly. It would be advantageous to provide equipment for directional hearing aids of the EEO type where the internal noise is not substantially higher than in the conventional EEO apparatus. Such a configuration team will not require a switch in the mode operable by the patient, it would be less expensive to manufacture, and would use less space in the faceplate. According to the invention, the two small (conventionally, size EM) individual microphones that are conventionally used in the EEO devices are replaced by a larger conventional double-entry microphone (advantageously, EL size), (similar, but not identical to the one currently manufactured by Kno les Electronics, Inc. As Model EL). And in further agreement with the invention, the microphone inputs are connected to two separate doors on the front plate of the apparatus through two outwardly diverging channels which are located on the front plate. As a result of this structure the doors are separated far enough, so the device can be directional with maximum possibility of signal-to-noise ratio without taking up valuable space in the front plate of the apparatus.

Although double-entry microphones are conventionally used to make devices for directional hearing aids of the back-of-the-ear ("DDO") type, the inventor ignores any use of such a microphone to replace the two individual microphones previously used in EEO applications. . Now that this use is being applied, it is evident that the invention produces new and unexpectedly advantageous results. One of those results is that the microphone is so quiet, that the adjustment switch operated by the patient is not necessary; The device can be maintained in directional mode without unacceptable noise. This is due to the inherent characteristics of the EL-type double-entry microphone. (These characteristics will be discussed below). Since the switch is not required, the cost of the components is reduced and a valuable space on the faceplate is available for other uses. Additionally, the invention substantially reduces the cost of the components and the work required to assemble the hearing aid apparatus. The cost of a single double-entry microphone is substantially less than the cost of individual microphones that have the same characteristics, and requires less work to connect a microphone to the electronic hearing aid device than connecting two microphones (and a selector switch) . In addition, since a double-entry microphone is smaller than two individual microphones, the savings in space of the faceplate make it possible to build a directional device with a smaller volume. As a result, more patients can be provided with a "half shell" device.

Brief description of the Drawings The invention will be better understood with the following illustrative and non-limiting drawings, in which: Figure 1 Schematically illustrates a first preferred embodiment of the invention; Figure 2 schematically illustrates a second preferred embodiment of the invention; and Figure 3 Schematically illustrates a third preferred embodiment of the invention.

Detailed description of the preferred modalities Directional devices that use two omnidirectional microphones have a poorer signal-to-noise ratio than those that use a double-input type directional microphone. This is because in such dual-directional directional microphones, both sides of the diaphragm are open to the air. The sensitivity of such microphones is about 5 db higher than that of two separate omnidirectional microphones with the same distance. Another noise reduction of around 3 dB, is due to the design of two omnidirectional microphones requires two amplifiers, while the design that uses double input microphones requires only one preamplifier. As mentioned above, the signal to noise ratio of an apparatus for directional hearing augmentation increases with the increase in space between the doors of the apparatus. If, for example, this space is increased by 4 mm (as in the D-MIC invention referenced above) to 12 mm, the sensitivity of the microphone will increase by about 8 to 10 dB. The device will therefore be much quieter.

The signal-to-noise ratio is further enhanced by using a larger single microphone (EL size with a larger membrane area) instead of the EM-sized microphone with smaller membrane. Using an EL-size microphone instead of the EM-size microphone increases the signal-to-noise ratio by another 3 to 5 dB. The drawings are illustrative and are not necessarily to scale. The same element is always indicated with the same numerical reference in all the figures, and the corresponding elements (for example, 8, 8 'and 8") are indicated by apostrophes Referring first to Figure 1, the housing of an apparatus for The hearing aid generally indicated by the reference number 2 is of the type EEO The housing 2 can be of the "half shell" type A receiver 4 and a device circuit for hearing aids ß are contained within the housing 2. A face plate 8 seals the outer term of the construction 2. Attached to the faceplate 8 is a double-input microphone 10. The microphone 10, the receiver 4 and the circuit of the hearing aid apparatus 6 are all operatively connected together.

The microphone 10 can advantageously be a modified version of a microphone now manufactured by Knowles Electronics, Inc. (Itasca, IL) as the model number EL-3085. In the manufacturing EL-3085 microphone, the tubes are attached to the side walls of the cartridge, and an acoustic wire mesh resistor is mounted inside each tube. In the modified microphone, the tubes are removed and the wire is adhered directly to the walls of the microphone, covering the two holes that give access to the opposite sides of the membrane. As shown, each of the two inputs 12-1 and 12-2 of the microphone 10 contains an acoustic resistance 14-1, 14-2 made of, for example, wire mesh. The acoustic resistors 14-1, 14-2 provide a) a correct delay time to compensate the time required for a sound wave to travel between the doors of the hearing aid apparatus, and b) protection of the membrane from exterior particles. Two doors l-1 and 16-2 are located on the front plate 8. The doors 16-1 and 16-2 are separated by a distance that is at least 6 mm and that is a maximum of 12 mm. Each of the doors 16-1 and 16-2 is connected to a corresponding one of the inputs 12-1, 12-2 by a corresponding one of two divergent external channels 18-1, 18-2. In tests, devices for hearing aids built with directional microphone of double entry in size EL and having an inter-door space of 11 mm have an equivalent noise impulse (ANSI s3.22-1987) of less than 20 dB. This value is typical for non-directional EEO hearing aids. In the embodiment shown in FIG. 2, the inputs 12-1 'and 12-2' of the microphone 10 'are tubular, with 90 ° curves. In this example, channels 18-1 'and 18-2' are formed to accommodate the shapes of inputs 12-1 'and 12-2'. The microphone 10 'can conveniently be made by replacing angled tubes with the tubes existing in the model microphone EL-3085 described above, and moving the angled tubes towards the face plate 8'. In the embodiment shown in Figure 3, the channels 18 '' and 18-1 '' are formed by spaces between the cavity of the front plate 8 '', the microphone 10 and a rear cover 32. The microphone 10 '' is Adhered to the faceplate 8 '' with adhesive. The back cover 32 (which is of the same material as the faceplate) is sealed with adhesive to the microphone 10"and the faceplate 8". Although one or more preferred embodiments have been described above, the purpose of the invention is not limited to the following claims.

Claims (3)

1. A hearing aid device EEO (In The Ear), comprising: a double-entry microphone having first and second inputs; a receiver; an apparatus circuit for a hearing aid operatively connected to the microphone and the receiver; and an EEO shell in which the microphone, receiver, and circuit are placed; and a front plate secured to the shell and enclosing the microphone, receiver and circuit therein, the front plate having first and second doors that are open on the outside and which are separated by approximately 6 mm to 12 mm; and first and second diverging channels with outward direction, each extending between a corresponding one of the inputs, and wherein each of the input tubes is located in a corresponding one of the channels.

2. The hearing prosthesis apparatus according to claim 1, wherein the microphone has two input tubes, each connected to a corresponding one of the inputs, and wherein each of the input tubes is located in a corresponding one of the channels .

3. The hearing aid apparatus according to claim 1, wherein the front plate comprises a front cover and a rear cover, wherein the first and second doors are located in the front cover, wherein the rear cover is fitted within the front cover and sealed to the microphone, and wherein the first and second channels are separated between the front cover and the rear cover.