EP1154673B1

EP1154673B1 - Combining two signals in a hearing aid

Info

Publication number: EP1154673B1
Application number: EP00610046.5A
Authority: EP
Inventors: Thomas E. Christensen
Original assignee: Oticon AS
Current assignee: Oticon AS
Priority date: 2000-05-12
Filing date: 2000-05-12
Publication date: 2017-02-22
Anticipated expiration: 2020-05-12
Also published as: EP1154673A1; DK1154673T3

Description

FIELD OF THE INVENTION

The invention relates to communication devices, more specifically to the problem of combining two electrical signals, e.g. in connection with the presence of an occlusion effect or acoustical feedback or noise cancellation in a hearing aid, a headset or a telephone.

BACKGROUND OF THE INVENTION

Communication devices of various kinds are known where two or more signals often could be combined in order to achieve a desired effect. The communication devices count hearing aids, headsets and telephones, especially mobile telephones.
Hearing aids are devices intended for providing remedy for a hearing impairment experienced by a person. The hearing aid typically comprises a microphone, an amplifier and an output receiver assembled in a housing to be placed behind the ear or in the ear of the user. Examples from the hearing aid area counts occlusion effect and acoustic and magnetic feedback, which can be very annoying and often will totally destroy the communication to and from the hearing aid user.
A headset typically comprises at least one output transducer and one input transducer, for output of e.g. a telephone signal and for input to a telephone, respectively. Connecting wires or a wireless connection to a telephone may be provided.
A mobile telephone typically comprises at least one output transducer and one input transducer and receiving and transmitting means.
Japanese Patent 5-244696 to Akihiko discloses a hearing aid, which receives an acoustic signal via a microphone and a vibratory signal via a transducer, processes the corresponding electrical signals digitally, adds the processed signals to form a combined signal and radiates the combined signal as an acoustic signal. The adding of the signals takes place in a digital adding circuit. The purpose of adding the signals is to provide the wearer of the hearing aid with a feedback of his voice, which propagates through the bone structure of his head and is received as vibrations by the transducer.
Japanese Patent 6-233389 to Akiyoshi discloses a hearing aid, which performs the same operations as the ones disclosed in Japanese Patent 05244696 and further applies adaptive digital signal processing to the electrical signals in order to obtain a desired level of the voice feedback.
European Patent Application 0 137 550 by op de Beek et al. discloses improving an electrodynamic output transducer with a magnet system and a membrane, the membrane being mechanically connected to a plurality of driving coils and the driving coils being arranged in a common air gap of the magnet system. For each driving coil, a dedicated switching circuit is provided to selectively energize or short-circuit the driving coil in dependence of the value of an associated bit within an n-bit digital signal. The conductance of each of the driving coils corresponds with the significance of the associated bit within the digital signal. When the output transducer is operated, the position of the membrane is proportional to the value of the n-bit digital signal, and the output transducer functions together with the switching circuits as a digital-electrical-to-analog-acoustic signal converter.
United States Patent 5,949,889 to Cooper discloses a hearing aid system with ultrasonic transmission of information and command signals between the two hearing aids comprised in the system. Each hearing aid has an auditory channel with a microphone and an output transducer, and an ultrasonic channel also comprising a microphone and an output transducer.
United States Patent 4,449,018 to Stanton discloses a hearing aid with an upper and a lower auditory channel, each comprising a microphone and an output transducer.
United States Patent Application US2001/0017922 A1 by Kim , discloses an electrodynamic out-put transducer with an integrated vibrator, the output transducer and the vibrator sharing a permanent magnet, but having separate driving coils.
It is apparently desirous in hearing aids and other communication devices, such as headsets and telephones to combine two or more signals in order to provide a compensation for an undesired signal influencing the use of the communication device. This is particularly relevant in noisy environments and when the communication device is used by a person who has a hearing impairment making speech understanding more difficult when an environmental distortion is present.
In the field of hearing aids the occlusion effect and feedback problems are well-known phenomenon, which gives rise to a significant irritation and discomfort when using a hearing aid.
From other areas, such as the headset and the telephone areas, the problems are most often noise related. Noise reduction algorithms are often implemented in order to achieve a more clear communication.
For all areas counts that the combination of signals sets significant demands to the signal processing equipment. The problems of combining two or more signals in fact often gives rise to several problems and the result of the combination often results in a significantly reduced quality of the desired signal. The problems of combining two signals are particularly significant when the one signal is a digital signal and the other signal is an analog signal. In this situation the negative influence of the signals on each other is often devastating.
An objective of the present invention is to provide a method by which two signals may be added to each other with reduced negative influence on the desired output signal.
Another objective of the present invention is to provide a communication device where two signals may be added to each other with reduced negative influence on the desired output signal.
A further objective of the present invention is to provide a hearing aid, where two signals may be added to each other with reduced negative influence on the desired output signal.
A still further objective of the present invention is to provide a receiver (speaker), which can be used in a hearing aid of the type mentioned above in connection with the adding of two signals to each other with reduced negative influence on the desired output signal.

SUMMARY OF THE INVENTION

According to the invention the first objective is achieved by means of a method as defined in claim 1.
Preferred embodiments of the method are disclosed in claims 2-4.
According to the invention the second objective is achieved by means of a device as defined in claim 5.
Preferred embodiments of the device are disclosed in claims 6-8.
According to the invention the third objective is achieved by means of a hearing aid as defined in claim 5.
Preferred embodiments are described in claims 10-13.
According to the invention the fourth objective is achieved by means of a speaker as defined in claim 14.
Preferred embodiments of the receiver are disclosed in claims 15.
The invention is explained in more detail with reference to the drawings in the following description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematical diagram showing the principles of the invention.
FIG. 2 is a schematical drawing of a hearing aid featuring the invention;
FIG. 3 is a schematical drawing showing a receiver according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

From FIG. 1 the principles of a hearing aid featuring the invention appear. A first microphone is provided for picking up acoustic input from the environment. The acoustic signals are transformed into an analog electric signal and converted into a digital signal in an AD converter. Afterwards the digital signal is processed and amplified in a processor. Following the processing the processed signal is converted into an analog signal in a DA converter and supplied to an output transducer, a so-called receiver. A second microphone is provided for picking up a boneconducted signal or an acoustic feedback signal. The boneconducted signal may result in the previously described occlusion effect and the acoustic feedback signal may result in a closed feedback loop giving rise to an uncontrolled oscillation in the hearing aid. Both situations are undesired for the hearing aid user. The signal picked up by the second microphone is processed and afterwards supplied to the same output transducer as the first signal. The output transducer features two separate driving coils and the first and the second signal are supplied one to each of these coils.
From FIG. 2 a hearing aid appears showing the location of the respective elements described in connection with FIG. 1. The necessary power supply, preferably a battery, is not shown. The skilled person will however immediately be able to implement this.
From FIG. 3 an output transducer appears in a cross sectional view. It appears that two electrically separated driving coils are located within a transducer housing. The driving coils are located in such a manner that each of these upon receiving an electrical signal through the terminals provided on the outside of the transducer housing will induce a field that drives the membrane likewise provided in the transducer housing. By providing the two driving coils electrically separated in the transducer housing a compact unit may be achieved and the two individual signals may be supplied to the transducer without interfering with each other. The two signals are hence supplied to the transducer in their desired undisturbed form and the resulting acoustic output signal will show a superpositioning of the two signals. In this manner it is possible to add a digital and an analog signal to each other, without disturbing one or both of the signals, and achieve a desired combined signal. It is of course also possible to combine two digital or two analog signals and still achieve an improvement in the combined signal.
Although the invention in the foregoing description of a preferred embodiment has been explained as implemented in a hearing aid, the invention is applicable to other types of personal communication equipment, such as headsets and mobile telephones.

Claims

A hearing aid (1) comprising: a first microphone (3) adapted to pick up acoustic signals from the environment and transform these into a first electrical signal, first signal processing means (4) for processing the first electrical signal, second signal generating means (6) for generating a second electrical signal and output means (8), where the output means (8) comprises an output transducer (8), characterised in that the output transducer (8) comprises a membrane (10) and a first and a second driving coil (7, 9), the first driving coil (7) being adapted to generate a first magnetic field in correspondence with the processed first electrical signal, the second driving coil (9) being adapted to generate a second magnetic field in correspondence with the second electrical signal, and the membrane (10) being adapted to be driven by the first and the second magnetic fields, thereby generating an acoustic output signal representing a sum of the processed first electrical signal and the second electrical signal.
A hearing aid (1) according to claim 1, where a further microphone (11) is provided for picking up a further acoustic signal.
A hearing aid (1) according to claim 1 or 2, where a processor (4, 12) is provided for establishing one or more characteristics of an incoming signal.
A hearing aid (1) according to any of the claims 1-3, where the first microphone (3) is adapted to pick up acoustic signals outside the ear of the hearing aid user.
A hearing aid (1) according to any of the claims 1-4, further comprising means (12) for processing the second electrical signal as an analog signal.
A hearing aid (1) according to any of the claims 1-5, further comprising means (4) for processing the first electrical signal as a digital signal.
A hearing aid (1) according to any of the claims 1-6, where the second signal generating means (6) comprises a second microphone (11) and a second signal processor (12).