MICROPHONE FOR A HEARING AID

Abstract: A microphone for a hearing aid comprises a housing with entrance means for letting pass sound waves into the housing, transducer means for converting the sound waves into an electrical signal, amplifier means for amplifying this electrical signal and connecting means for connecting the amplifier means with the terminals of a battery and for coupling the output signal of the amplifier means to a receive. The microphone further comprises an electronic circuit which is provided at an output of which a signal is available that can be transmitted directly to the receiver.

Description: Title: Microphone for a hearing aid The invention relates to a microphone for a hearing aid, the microphone comprising a housing with entrance means for letting pass sound waves into the housing, transducer means for converting the sound waves into an electrical signal, amplifier means for amplifying this electrical signal and connecting means for connecting the amplifier means with the terminals of a battery and for coupling the output signal of the amplifier means to a receiver. Such a microphone for example is disclosed in EP-A-0802700. The invention also relates to a hearing aid including a body accommodating a microphone of the above type, a battery and a receiver. Although hearing aids nowadays are much smaller than some years ago, while also the reliability and the sound quality have been improved, there still are some disadvantages that have to be overcome. Such disadvantages are for example the number of wires necessary to connect the microphone, amplifier, receiver and battery. These wires can influence negatively the reliability of the hearing aid and make the production thereof expensive. The wires are also at least part of the cause of interference by cellular phones and other radio frequency sources. Thus expensive solutions to prevent such interference are required. Another disadvantage is the size of the state of the art hearing aids, which is still too large to fit all ears with a Completely In the Canal (CIC) hearing aid. In the state of the art hearing aids the microphone generally is an electret microphone with integrated CMOS- or J-FET buffer. The amplifier comprises one or more discrete components and integrated circuits mounted on a hybrid printed circuit board. The receiver generally is a balanced armature receiver. EP-A-0802700 describes a microphone, the housing of which includes a differential preamplifier. DE-A- 19545761 describes a proposal to integrate an A/D converter in a microphone for a hearing aid, while US-A- 4,592,087 and US-A-4 , 689, 819 propose to integrate the power amplifier in the microphone of a hearing aid. The invention aims to overcome at least part of the still existing disadvantages of the state of the art hearing aids and to this effect provides a microphone for a hearing aid of the above-mentioned type, characterized in that in the housing of the microphone an electronic circuit is provided at an output of which a signal is available that can be transmitted directly to the receiver. Preferably, all active components of the electronic circuit are formed in one single integrated circuit. If necessary, some passive components, like resistors or capacitors, can be provided at the outside of the housing of the microphone. In a further embodiment of a microphone according to the invention, at the outside of the housing means are provided for a solderless contact with the battery terminals. According to again another embodiment of the invention, the body of the hearing aid comprises a battery holder with a removable cap, entrance means for sound waves being provided from outside the body to the interior of the battery holder and from the battery holder to the interior of the microphone housing. Preferably, the entrance means for the battery holder are formed in the removable cap. Embodiments of the invention and their advantages shall be discussed below with reference to the figures of the drawing, which show: Figure 1 a cross-sectional view of a first embodiment of the invention; Figure 2 a cross-sectional view of a second embodiment of the invention; and Figure 3 a cross-sectional view of a third embodiment of the invention. Figure 1 shows a part of a body 1 of a hearing aid comprising a battery holder 2 with a removable cap 2a for a battery, a space for accommodating the housing of a microphone 4 and an inlet channel 5 through which sound waves from the exterior can pass to the inlet opening 6, that is provided in a wall of the housing of the microphone. The microphone is a conventional microphone of the electret type, for example as described in US-A-5 , 255 , 246 ; details of the microphone are not given here, because they are not really relevant for the present invention. A hybrid 7 is provided on which an integrated circuit 8 and, if necessary, passive components 9, 10 are mounted by means of a flip-chip technology or by means of wire bonding. The connection between the microphone and the substrate of the hybrid is made by means of a flexible connection 11 of the type disclosed in US-A-5 , 255 , 246. On the side of the substrate of the hybrid that is at the outside of the housing solder pads 12, 12a are provided for connecting the microphone to the battery terminals, through leads 13 and 14 and for connecting the output signal of an amplifier, that is included in the integrated circuit to the receiver. For the sake of clarity, only the solder pads 12, 12a are shown, the solder pads for connection to the receiver and the receiver itself are not shown, but their structure will be clear to those skilled in the art. Instead of solder pads also other connection means can be provided as, for example, a flexible band with connecting wires printed on it (a so-called flexprint) . Instead of a hybrid also the use of a printed circuit board or a flexprint is possible. By the construction of a microphone in accordance Figure 1, all sensitive electronics parts are shielded from the outside by the metal housing of the microphone and by that side of the hybrid that is provided with a ground plane. Possible external components, like the components 9 and 10, that for example are necessary to decouple the power supply do not need to be shielded, because these components either operate on a relatively high signal level and therefore are much less sensitive for spurious RF signals, or do not affect the signal at all. In the embodiment of Figure 1 the shape of the microphone can be round, rectangular, or can have any other desired shape. Figure 2 shows another embodiment of the invention, in which the number of connecting wires is further reduced. The same components in this figure are indicated with the same reference numerals as in Figure 1, but increase by 100. The hybrid now is placed in such a way in the body, that it faces one side of the battery. Spring biased connecting elements 114 and 115 are provided to connect one terminal, generally the minus terminal of the battery, to the housing of the microphone and to connect the other battery terminal, generally the plus terminal, to the hybrid, respectively. The connecting wires 116 and 117 for transferring the output signal of the amplifier to the receiver remains the same, but now come from the other side of the housing than in Figure 1. These wires by means of solder pads 115, 115a are connected to the hybrid 107. In this embodiment the microphone preferably is circular. The construction of this hearing aid, due to the spring biased, is very simple and inexpensive, while the short connections to the battery also lead to a smaller chance on interference by RF sources. In the embodiment of Figure 3 the connections to the battery and to the receiver are as in Figure 1, and the same reference numerals as in that figure are used, but now increased by 200. In this embodiment the sound inlet opening for the microphone as provided in the body is changed into an advantageous configuration. In this embodiment the sound can enter the microphone through openings 215, that are provided in a wall of the battery holder 202, preferably in the cover 202a thereof and through an opening 216 in the wall of the battery holder that faces the microphone housing. By this construction sound waves enter the microphone housing via the battery holder and the sound inlet of the microphone is very well protected against sweat, dust, etc., which in the conventional embodiment often are detrimental for the reliability. By this construction also the band width of the microphone increases, because the acoustic mass of the conventional plastic tubing as sound inlet, such a shown in Figures 1 and 2, has an adverse effect on the frequency characteristics of the microphone. The microphone of the above-described third embodiment requires less volume in a hearing aid than the conventional microphones. Therefore the flexibility in designing the hearing aid is larger, among others because the sound inlet does not require additional space on the front plate of the hearing aid, which also already is occupied by switches, potentiometers, etc. Further, nowadays different producers of hearing aids require microphones with different sound inlet channels. With the microphone according to the third embodiment also this problem belongs to the past .

Claims: Claims 1. Microphone for a hearing aid, the microphone comprising a housing with entrance means for letting pass sound waves into the housing, transducer means for converting the sound waves into an electrical signal, amplifier means for amplifying this electrical signal and connecting means for connecting the amplifier means with the terminals of a battery and for coupling the output signal of the amplifier means to a receive, characterized in that in the housing of the microphone an electronic circuit is provided at an output of which a signal is available that can be transmitted directly to the receiver. 2. Microphone according to claim 1, characterized in that at least all active components of the electronic circuit are formed in a single integrated circuit. 3. Microphone according to claim 1 or 2 , characterized in that the connecting means for connecting the microphone to the battery are formed by fixed spring biased connections, providing a solderless contact between the amplifier means and the battery terminals. 4. Hearing aid comprising a microphone according to any one of the claims 1-3, a battery in a battery holder and a receiver. 5. Hearing aid according to claim 4, characterized in that the entrance means for letting pass sound waves into the housing of the microphone are provided in the battery holder. 6. Hearing aid according to claim 4, characterized in that entrance means are formed by openings that are provided in a removable cover and the bottom of the battery holder and also in the wall of the microphone housing facing said bottom.

Inventors: DOLLEMAN HENDRIK, VAN HAL PAUL CHRISTIAAN, VAN HALTEREN AART ZEGER, WILMINK ENGBERT, DOLLEMAN, HENDRIK, VAN HAL, PAUL, CHRISTIAAN, VAN HALTEREN, AART, ZEGER, WILMINK, ENGBERT
Applicants: DOLLEMAN HENDRIK, HAL PAUL CHRISTIAAN VAN, HALTEREN AART ZEGER VAN, MICROTRONIC NEDERLAND BV, WILMINK ENGBERT, DOLLEMAN, HENDRIK, MICROTRONIC NEDERLAND B.V., VAN HAL, PAUL, CHRISTIAAN, VAN HALTEREN, AART, ZEGER, WILMINK, ENGBERT
Application year: 2000
Main classification: H04R25
IPC codes: H04R11, H04R25