EP1931172B1 - Hearing aid with noise cancellation and corresponding method - Google Patents

Abstract

The device has a microphone (MI) recording an interference sound outside the ear, and a receiver (H) outputting a processed electrical or electromagnetic useful signal. A sound transmission function (H-vent) is vent from the microphone to the eardrum (TF). The transmission function (H-anc) of a filter (F) is formed as a function of the sound function such that the interference sound reaching the eardrum through the vent is reduced in the effect on the eardrum by a balancing sound which is generated on the basis of an interference sound signal of the microphone from the receiver. An independent claim is also included for a method for reducing an interference sound when wearing a hearing device.

Description

The present invention relates to a hearing aid having a useful signal interface for receiving an electrical or electromagnetic useful signal, a microphone for receiving a noise signal and a receiver for outputting a processed useful signal, wherein when wearing the hearing aid in or on the ear a Vent is formed, through which a sound transmission function from the microphone to the eardrum of the hearing aid wearer. Moreover, the present invention relates to a corresponding method for reducing noise when wearing a hearing aid.

Hearing aids are portable hearing aids that are used to care for the hearing impaired. To meet the numerous individual needs, different types of hearing aids such as behind-the-ear hearing aids (BTE), in-the-ear hearing aids (IDO) and Concha hearing aids are provided. The hearing aids listed by way of example are worn on the outer ear or in the ear canal. In addition, bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The stimulation of the damaged hearing takes place either mechanically or electrically.

Hearing aids have in principle as essential components an input transducer, an amplifier and an output transducer. The input transducer is usually a sound receiver, z. As a microphone, and / or an electromagnetic receiver, for. B. an induction coil. The output transducer is usually used as an electroacoustic transducer, z. As miniature speaker, or as an electromechanical transducer, z. B. bone conduction, realized. The amplifier is usually integrated in a signal processing unit. This basic structure is in FIG. 1 using the example of a behind-the-ear hearing aid shown. In a hearing aid housing 1 for carrying behind the ear, one or more microphones 2 for receiving the sound from the environment are installed. A signal processing unit 3, which is also integrated in the hearing aid housing 1, processes the microphone signals and amplifies them. The output signal of the signal processing unit 3 is transmitted to a loudspeaker or earpiece 4, which outputs an acoustic signal. The sound is optionally transmitted via a sound tube, which is fixed with an earmold in the ear canal, to the eardrum of the device carrier. The power supply of the hearing device and in particular of the signal processing unit 3 is carried out by a likewise integrated into the hearing aid housing 1 battery. 5

Frequently problematic in hearing aids is low-frequency sound, which reaches directly to the supplied ear. For example, in many sound situations (car, road, airplane, construction site ...) disturbing low-frequency sound occurs, which passes through the vent of the hearing aid to the eardrum. The term "vent" (ventilation channel) is intended here to denote on the one hand the ventilation bore in an in-the-ear hearing device or in the earmold for a behind-the-ear hearing device. On the other hand, it is intended to be used for an imaginary circular opening equivalent to one or more actual openings such as those found in open-circuited appliances.

Noise suppression techniques are well known for hearing aids. As a rule, the interference in the microphone signal is suppressed and reproduced in a reduced manner. Low-frequency direct sound, which passes the hearing aid over to the eardrum, can not be suppressed in this way. Rather, this is further intensified by the increased playback of the hearing aid.

From the patent DE 103 32 119 B3 is an active noise suppression in a hearing aid device that can be worn in the ear or a hearing aid device with earmold that can be worn in the ear known. The penetration of direct sound through a ventilation channel of the hearing aid or earmold is prevented by means of a second microphone in the ventilation channel. The second microphone picks up an acoustic signal from the ventilation duct and a filter device shifts it with respect to the phase in such a way that after the phase-shifted signal has been emitted into the ventilation duct the direct sound is largely extinguished.

Furthermore, the describes Patent US 5 182 774 A a headphone with noise canceling. A directional microphone picks up the sound pressure inside the headphone housing. A generator generates an anti-noise signal from the microphone signal which is output via the loudspeaker of the headphone. However, such ANC (Active Noise Cancellation) headphones are based only on ANC algorithms that take into account the mechanical designs and styles of headphones. However, this is not readily transferable to hearing aids that are constructed mechanically differently and worn just as different.

From the patent WO 2005/052911 A1 a hearing device with ear-earmould is known, comprising a signal processing device with an input transducer or first microphone, a signal processor and an output transducer or listener, wherein the signal processor is adapted to produce a compensation signal which at least partially attenuates the acoustic signals enter the ear canal through ventilation holes of the hearing aid. In addition, a second microphone is provided in the ear canal from which emanates a signal which is fed back into the signal processing device.

From the Patent US-B1-6,445,799 B1 is a noise-suppressing hearing device known. In this case, a positionable in the ear ear canal tube is provided with a microphone for receiving the sound in the ear canal and a speaker, the microphone and the speaker either at the outer end and / or on the inner, the eardrum facing, end of the ear canal tube are to be arranged. The recorded sound signal from the microphone in the ear canal is fed to a data processing unit, wherein the noise contained in the sound is filtered out and fed to the speaker in opposite phase.

In addition, in particular, there are problems with direct sound when the hearing aid is equipped with a wireless receiving system, in which the useful signal is coupled by radio into the hearing aid.

The object of the present invention is therefore to propose a hearing aid which receives an electrical or electromagnetic useful signal and is better prevented in the disturbing direct sound. Furthermore, a corresponding Störschallunterdrückungsverfahren should be presented.

According to the invention, this object is achieved by a hearing device with a useful signal interface for receiving an electrical or electromagnetic useful signal, a microphone for receiving a noise outside the ear and a handset for outputting a processed useful signal, wherein when wearing the hearing aid in or on the ear a vent is formed , is given by a sound transmission function of the microphone to the eardrum of the hearing aid wearer, and a filter which is connected between the microphone and the listener and whose transfer function is formed depending on the sound transmission function of the vents such that a passing through the vent to the eardrum Noise by a compensating sound, which is generated on the basis of a single sound signal, namely a resulting from the noise signal of the microphone by the listener, is reduced in an effect on the eardrum.

In addition, the invention provides a method for reducing background noise when wearing a hearing aid by receiving an electrical or electromagnetic useful signal by the hearing aid, recording a noise outside the ear by a microphone of the hearing aid and outputting a processed useful signal from a handset of the hearing aid, wherein the Carrying the hearing aid in or on the ear a Vent is formed, through which a sound transmission function is given by the microphone to the eardrum of the hearing aid wearer, and by filtering the noise signal of the microphone depending on the sound transmission function of the vents such that a through the vent to the eardrum passing noise by a compensating sound, which is generated on the basis of a single sound signal, namely one of the noise resulting from the background noise of the microphone by the listener, in its effect on the eardrum red is made.

Advantageously, a significant reduction of low-frequency direct sound when wearing hearing aids can be achieved by the hearing aid according to the invention and the inventive method. The extent of the reduction depends on the parameters of the respective hearing aid, z. B. Vent diameter, hearing aid type, etc., from. Another advantage of the proposed solution is that no additional hardware components are needed on the hearing aid, since the already existing on a hearing aid external microphone is used to record the noise. In addition, the signal processing effort to run the hearing aid is very low, since the determination of the filter (digital filter) is made in advance based on the parameters of the hearing aid configuration.

The hearing aid improved according to the invention can be designed for open supply. This is especially the case with a high-frequency supply. Here the direct sound can reach the eardrum almost unhindered, but according to the invention it is effectively suppressed as far as necessary by the compensating sound.

In other cases, a hearing aid may have an earmold that has a vent for ventilation. Also, the direct sound penetrating through the vent can be effectively reduced according to the invention.

The transfer function of the above-mentioned filter may have a vent diameter as a variable parameter. With an open supply, this vent diameter can be an equivalent diameter. This parameter makes it relatively easy to set an effective noise reduction for the individual case.

Preferably, a level limiting circuit is connected between the filter and the listener. This can be prevented that occurs at high signal levels overdriving.

• FIG 1 den prinzipiellen Aufbau eines Hörgeräts gemäß dem Stand der Technik;
• FIG 2 ein Blockschaltbild eines erfindungsgemäßen Hörgeräts gemäß einer ersten Ausführungsform;
• FIG 3 ein Blockschaltbild eines erfindungsgemäßen Hörgeräts gemäß einer zweiten Ausführungsform und
• FIG 4 ein Diagramm zur Vorab-Ermittlung eines Digitalfilters.

The present invention will be explained in more detail with reference to the accompanying drawings, in which:

• FIG. 1 the basic structure of a hearing aid according to the prior art;
• FIG. 2 a block diagram of a hearing aid according to the invention according to a first embodiment;
• FIG. 3 a block diagram of a hearing aid according to a second embodiment and
• FIG. 4 a diagram for the preliminary determination of a digital filter.

The embodiments described in more detail below represent preferred embodiments of the present invention.

The direct sound reaching a tympanic membrane of a hearing aid wearer is reduced by means of out-of-phase cancellation. As a useful signal, the hearing aid receives an electrical or electromagnetic signal wirelessly or by cable. A hearing aid signal processor SP processes the useful signal and supplies an output signal to a handset H. The handset H is arranged in the ear or in the auditory canal in the present example, while the remaining part of the hearing aid is outside the ear. The processed useful signal is converted in the receiver H into a useful sound and transmitted acoustically within the auditory canal to the eardrum TF of the hearing aid wearer.

The interference signal or ambient signal is recorded with the hearing aid microphone MI, and the resulting interference sound signal is amplified and digitized in an amplifier and A / D converter AD. The digital interference signal is subjected in a filter F for active interference suppression to filtering with the transfer function H_anc. After filtering, the signal is subtracted from the processed payload signal of the signal processor SP in a subtracter SU, i. H. added in antiphase, and in this form also reproduced on the listener H.

The hearing aid shell or the otoplastic of the hearing aid has a vent for ventilation, or there is directly open supply. Therefore, the noise can also go directly through the vent or the opening in the ear to the eardrum TF. For direct sound through the vent results in a transfer function H_vent, which leads to that in the first Low-frequency sound passes through this direct path to the tympanic membrane TF.

The transfer function H_anc is set in the filter F in such a way that the reproduced signal is canceled out of phase in phase with the signal which has been passed acoustically through the (equivalent) vent to the eardrum TF. For this purpose, the digital filter F is determined such that the following applies to the transfer functions: $$\mathrm{H\_vent}=\mathrm{H\_anc}\times \mathrm{H\_imohr}$$

In this case, in the transfer function H_anc an acoustoelectric conversion in the microphone MI, the processing in the amplifier and converter AD and a model of the vents are taken into account. The transfer function H_imohr represents the e-electro-acoustic transmission of the electrical signal from the speaker to the acoustic signal at the eardrum TF.

With particularly open hearing aid adaptation, there is the danger of overloading at high signal levels. The level above which override occurs is determined in addition to the equivalent vent diameter of the hearing aid speaker type. In order to prevent overdriving, according to a second embodiment of the present invention, a hearing aid according to FIG. 3 provided. This corresponds essentially to that of FIG. 2 , To protect against overdrive, however, a level limiter PB is inserted in the Störsignalpfad. Thus, after the ANC filtering by the filter F, the signal level is limited before the signal is supplied to the subtracter SU.

The digital ANC filter F has to be designed considering hearing aid conditions, since these determine the (electro) acoustic transfer functions H_vent and H_imohr. Conveniently, this hearing aid specific design of the ANC filter F is pre-determined, e.g. As in the hearing aid fitting, designed parametrically. As input variables are accordingly FIG. 4 only known parameters such as (equivalent) vent diameter and vent length and hearing aid speaker type. By a dashed arrow is in FIG. 4 indicated that other specific parameters can be used as input variables. From these input variables, the analog transfer function H_vent can be determined. In turn, the digital filter F can be found by standard methods of signal processing. This is characterized by the corresponding filter coefficients.

The hearing aid system specific parameters are also used to determine a threshold from which the override of the loudspeaker H is expected. Accordingly, according to FIG. 4 in the filter design FD also obtained from the input variables, an overdrive threshold. This overdrive threshold is then stored in the level limiter PB (cf. FIG. 3 ) is used to limit the filter output signal.

Particular advantages of the described embodiments are obtained when the useful signal is coupled by radio into the hearing aid. In this application, the ambient sound is mainly disturbing. For example, any acoustic signal is annoying when a telephone signal is transmitted inductively to the hearing aid. Similarly, acoustically received noises are disturbing when a piece of music is transmitted via radio interface to the hearing aid. By out-of-phase cancellation taking into account the vent transfer function, however, such disturbances can be eliminated. In this sense, the hearing aid according to the invention or the method according to the invention can also advantageously be used for active ear plugs and, for example, during playback for wireline transmitted music (eg via an audio shoe).

Claims (9)

1. Hearing device having

   - a target signal interface for recording an electrical or electromagnetic target signal,

   - a microphone (MI) for recording an interference sound outside the ear and

   - a receiver (H) for outputting a processed target signal, with

   - a vent being formed when the hearing device is worn in or on the ear, through which vent a sound transmission function (H_vent) from the microphone (MI) to the eardrum (TF) of the hearing device wearer exists,

   characterised by

   - a filter (F), which is connected between the microphone (MI) and the receiver (H) and the transmission function (H_anc) of which is formed as a function of the sound transmission function (H_vent) of the vent such that an interference sound reaching the eardrum (TF) through the vent is reduced in its effect on the eardrum (TF) by a balancing sound, which is generated on the basis of a single interference signal, namely an interference sound signal of the microphone (MI) from the receiver (H) which results from the interference sound.
2. Hearing device according to claim 1, which is designed for open supply.
3. Hearing device according to claim 1, which comprises an otoplastic with a vent.
4. Hearing device according to one of the preceding claims, with the transmission function (H_anc) comprising a vent diameter as a variable parameter.
5. Hearing device according to claim 4, with the vent diameter being an equivalent diameter for an open supply.
6. Hearing device according to one of the preceding claims, with a level limiting circuit (PB) being connected between the filter (F) and the receiver (H).
7. Method for reducing an interference sound when wearing a hearing device by

   - recording an electrical or electromagnetic target signal by means of the hearing device,

   - recording an interference sound outside the ear by means of a microphone (MI) of the hearing device and

   - outputting a processed target signal from a receiver (H) of the hearing device, with

   - a vent being formed when the hearing device is being worn in or on the ear, through which vent a sound transmission function (H_vent) from the microphone (MI) to the eardrum (TF) of the hearing device wearer exists,

   characterised by

   - filtering the interference sound signal of the microphone (MI) as a function of the sound transmission function (H_vent) of the vent such that an interference sound reaching the eardrum (TF) through the vent is reduced in its effect on the eardrum (TF) by means of a balancing sound, which is generated on the basis of an single sound signal, namely an interference sound signal of the microphone (MI) from the receiver (H) resulting from the interference sound.
8. Method according to claim 7, with the filter transmission function (H_anc) of the filter (F) being adjusted beforehand by inputting a vent diameter accordingly as a parameter.
9. Method according to claim 7 or 8, with the signal being subjected to a level limitation after the filtering process.

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