EP2658289B1 - Method for controlling an alignment characteristic and hearing aid - Google Patents

Description

The present invention relates to a method for controlling a directional characteristic of a microphone device of an optional (binaural) hearing system having a first hearing device and a second hearing device. Moreover, the present invention relates to a corresponding (binaural) hearing system. A hearing device here means any device which can be worn in or on the ear and causes a sound stimulus, in particular a hearing device, a headset, headphones and the like.

Hearing aids are portable hearing aids that are used to care for the hearing impaired. In order to meet the numerous individual needs, different types of hearing aids such as behind-the-ear hearing aids (BTE), hearing aid with external receiver (RIC: receiver in the canal) and in-the-ear hearing aids (ITE), e.g. Concha hearing aids or canal hearing aids (ITE, CIC). 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 shown using the example of a behind-the-ear hearing aid. In a hearing aid housing 1 for Carrying behind the ear, one or more microphones 2 are installed for recording the sound from the environment. 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 the signal processing unit 3 is effected by a likewise integrated into the hearing aid housing 1 battery. 5

Many hearing aids today have the ability to automatically control the directional microphone between a directional mode, an anti-directional mode, and an omni-directional mode. Accordingly, the sound is amplified from the front or the rear, or it is processed equally from all directions without directionality. Automatic control is usually based on the detection of speech features extracted from the microphone signals. In a critical situation, such as having multiple people in a room, this automatic control function can lead to unacceptable decisions. Specifically, when two speakers speak from different directions with respect to the hearing aid wearer, this can lead to frequent switching operations. This results in a constantly fluctuating sound impression that confuses the hearing aid wearer.

From the document US 2010/158290 A1 is a hearing aid and a method for operating a hearing aid is known, which has a microphone system that can be switched to a first and a second directional characteristics. A signal-to-noise ratio (SNR) is determined for the first and second directivity characteristics. A switching device Switches the directional microphone to the higher SNR mode.

The document US 2008/0086309 A1 relates to a hearing aid and a method for tracking and selecting a speech source in an ambient sound mixture (summary of D2). A preprocessor generates n audio signals from n microphone signals. Post-processing determines for the n audio signals a probability of whether they contain speech. The post-processing then selects the signal with the highest probability for an acoustic output.

document US 2006/0160254 A1 relates to a system and a method of communication in which a spectacle frame has at least one directional microphone for receiving voice signals of the wearer and a communication device. One or more directional microphones are provided whose directional characteristics can be controlled. The recorded speech signals are interpreted and evaluated by a controller and the directional characteristics and / or the position of the microphones are set to the voice of the wearer.

document DE 10114101 A1 Finally, it relates to a hearing aid and a method of operation. In this case, signal parameters which influence the directional characteristic are set as a function of the result of a signal analysis of the input signal. The signal analysis includes a modulation analysis. Upon recognition of speech by the modulation analysis is switched from an omnidirectional reception to the reception in the direction of the hearing aid wearer.

In a concrete example, when a directional microphone is used to amplify the sound from one side of the hearing aid wearer, switching between the "left" and "right" directions can lead to very unpleasant fluctuations in the sound impression. In particular, that would
Hearing aid constantly switches to a louder speaker for a person speaking on the left and a person speaking on the right side of the hearing aid wearer. If both speakers have a comparable level, there would be between them
have a comparable level would be switched back and forth between them, which would lead to a speaker to strong differences in the respective sound level.

This problem has been encountered by the fact that was very slowly back and forth between the two microphone directions. As a result, rapid changes in the direction decision for the wearer are not so noticeable.

The object of the present invention is therefore to be able to more stably control a hearing system with at least one hearing device with regard to the directional characteristic. In addition, a corresponding (optionally binaural) hearing system is to be provided.

• Ermitteln eines ersten Merkmalwerts bezüglich Sprache in einem einer ersten Richtung zugeordneten ersten Signal der Mikrofoneinrichtung,
• Ermitteln eines zweiten Merkmalwerts bezüglich Sprache in einem einer zweiten Richtung zugeordneten zweiten Signal der Mikrofoneinrichtung,
• Gewinnen eines Steuerwerts aus den beiden Merkmalswerten und
• Steuern der Richtcharakteristik der Mikrofoneinrichtung anhand des Steuerwerts.

According to the invention, this object is achieved by a method for controlling a directional characteristic of a microphone device of a hearing system with at least one hearing device

• Determining a first feature value with respect to speech in a first signal of the microphone device associated with a first direction,
• Determining a second feature value with respect to speech in a second signal of the microphone device associated with a second direction,
• Obtaining a control value from the two feature values and
• Controlling the directional characteristic of the microphone device based on the control value.

• mindestens einer Hörvorrichtung, wobei
• die Hörvorrichtung eine Mikrofoneinrichtung mit einer Richtcharakteristik aufweist, wobei
• die Mikrofoneinrichtung ausgebildet ist zum Ermitteln eines ersten Merkmalwerts bezüglich Sprache in einem einer ersten Richtung zugeordneten ersten Signal der Mikrofoneinrichtung und zum Ermitteln eines zweiten Merkmalwerts bezüglich Sprache in einem einer zweiten Richtung zugeordneten zweiten Signal der Mikrofoneinrichtung,
• in der mindestens einen Hörvorrichtung eine Steuereinrichtung ausgebildet ist zum Gewinnen eines Steuerwerts aus den beiden Merkmalswerten und zum Steuern der Richtcharakteristik der Mikrofoneinrichtung anhand des Steuerwerts.

In addition, the invention provides a (binaural) hearing system

• at least one hearing device, wherein
• the hearing device has a microphone device with a directional characteristic, wherein
• the microphone device is designed to determine a first feature value with respect to speech in a first signal of the microphone device assigned to a first direction and to determine a second feature value with respect to speech in a second signal of the microphone device assigned to a second direction;
• in the at least one hearing device, a control device is designed to obtain a control value from the two feature values and to control the directional characteristic of the microphone device on the basis of the control value.

Advantageously, therefore, the signals from two different directions are analyzed with respect to speech features, i. H. one or more properties characteristic of speech, analyzed. This analysis leads to feature values whose difference or other combination can be used to control the directional characteristic of the hearing system. Thus, therefore, the difference between values characteristic of speech serves as a reliable decision criterion for the formation of the directional characteristic of a hearing system.

Preferably, the first direction is opposite to the second direction. Thus, with regard to the characteristics of speech characteristics, signals from opposite directions are analyzed. This has the advantage that thereby two half-spaces can be analyzed separately from each other, and the directional characteristic can be designed accordingly. In particular, it is favorable if the hearing device is intended to be carried in or on the two ears of a user, and the first direction points to the left or the front with respect to the user. Accordingly, the second direction then points to the right or rear with respect to the user.

The feature values can each represent a probability with which speech is present in the respective signal of the microphone device. In addition, they can too simply represent an amplitude or level of a signal qualified as speech.

To obtain the control value, the difference between the two feature values can be related to the minimum of the two feature values. In particular, the reference should be made by dividing the difference by the minimum of the two feature values. This results in a pure numerical value, in which signal-to-noise ratios are taken into account.

The control value can be obtained according to an embodiment by means of a freely selectable assignment rule from the minimum difference. Thus, the decision-making can be made even clearer. For example, a hysteresis can also be installed.

It is also advantageous if the directional characteristic is formed by superimposing a directional signal and an omnidirectional signal of the microphone device, and thereby weighting the directional signal and the omnidirectional signal by means of the control value. This makes it possible that the microphone device is blended from a directional operation in an omnidirectional operation or vice versa.

In particular, the method can be implemented such that the directionality of the directional characteristic increases with increasing control value on the basis of omnidirectionality. However, the system can also be designed such that, depending on the increasing control value, it is superimposed from one direction to another direction.

It is particularly advantageous if a data connection between the at least one and a further hearing device of the hearing system is activated and / or deactivated as a function of the directional characteristic. This makes it possible that, if the automatic control of the directional characteristic specifies an omnidirectional diet of the microphone device, a data exchange between the two hearing devices is prevented, which leads to significant energy savings.

FIG 1

den prinzipiellen Aufbau eines Hörgeräts gemäß dem Stand der Technik;

FIG 2

ein Blockschaltdiagramm eines erfindungsgemäßen Ausführungsbeispiels und

FIG 3

eine beispielhafte Lookup-Tabelle für die Gewinnung eines Steuersignals.

The present invention will be further explained 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 an embodiment of the invention and

FIG. 3

an exemplary lookup table for obtaining a control signal.

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

According to one embodiment, a hearing aid system with two hearing aids (first hearing device and second hearing device) is provided. There is a data connection between the two hearing aids so that the output signals of both hearing aids can be processed together. In particular, can be realized by the data technically interconnected hearing aids a microphone device, the directional characteristic in the entire room is almost arbitrarily variable, provided that the two hearing aids are intended to be worn in or on the ears of the hearing aid wearer. The directional characteristic can be directed more or less sharply to a source. One speaks of a directional "beamformer" (beam former) whose intensity or beam width can be varied. In omnidirectional operation, sound is received uniformly from all directions, while in directional mode the reception beam is directed in a certain direction. In this preferred direction, the microphone device (here the directional microphone) has a higher sensitivity, while it is more or less damped in other directions.

In order to adjust the direction and / or the width of the reception lobe, two different output signals of the directional microphone are examined with regard to speech components or speech characteristics. These output signals of the directional microphone come from different operating modes of the directional microphone. For example, they come from the two concrete modes that the reception lobe is on the one hand to the left and the other to the right. Alternatively, the operating modes may also be defined by the directional lobes being directed forward or backward relative to the hearing aid wearer. Thus, in one case speech features are examined in the signals from the left and the right and in the other case in the signals from the front and the back.

wobei abs die Absolutwertfunktion, min die Minimumfunktion und m1 sowie m2 die Merkmalswerte der Sprachmerkmale darstellen.Subsequently, a value f is calculated which indicates how large the difference in the speech characteristics between the two signals is. Speech features are for example the 4 Hz modulation, the so-called voice onset (level increase at the beginning of speech) or a speech-related signal-to-noise ratio. The absolute value of the difference is then normalized with the minimum of the feature values of both speech features. The value f results in the following formula: $$\mathrm{f}=\mathrm{Section}\left(\mathrm{m}\mathrm{1}-\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="imgf0001.png"\; state="\{\{state\}\}">m</figure-callout>}\mathrm{2}\right)/\min \left(\mathrm{m}\mathrm{1}.\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="imgf0001.png"\; state="\{\{state\}\}">m</figure-callout>}\mathrm{2}\right).$$

where abs represents the absolute value function, min the minimum function and m1 and m2 represent the feature values of the speech features.

The value f is large for large differences between both feature values m1 and m2. For example, if m1 = 0.1 and m2 = 0.8, then f = 0.7 / 0.1 = 7. This is the case, for example, if noise comes from a side other than the desired signal and if the signal Noise ratio is low.

On the other hand, if the signal-to-noise ratio is good, the difference between the two feature values m1 and m2 will be small. The minimum of both values, on the other hand, will be relatively high. This leads to a low value f. For example, the characteristic values are m1 = 0.8 and m2 = 0.7. This results in f = 0.1 / 0.7 = 0.14.

If, on the other hand, the signal-to-noise ratio is poor, the minimum of both feature values will increase the value f. This is the case, for example, when m1 = 0.1 and m2 = 0.2. The result then is the value f = 0.1 / 0.1 = 1.

If the signal-to-noise ratio is too poor, the directional microphone will not be useful. Moreover, it is also advantageous to switch to omnidirectional operation when the signal-to-noise ratio is low and, for example, strong voice signals are registered from both sides. The omnidirectional operation then leads to improved speech perception. In both cases, the value f is small and it should be generated from a control signal for omnidirectional operation.

On the other hand, if, as described above, there is only one speaker on one side, the value f is high and the directional operation should be used.

With an assignment rule, the value f can be converted into a control value w. The assignment rule may be an analytic function that maps the value f to the control value w. In addition, the assignment rule can also be a value table or a lookup table with which the control value w is determined from a value f. Such a lookup table is in FIG. 3 indicated.

With the control signal w, the microphone device or its directional characteristic can now be controlled. In this case, for example, in the omnidirectional operation or the directional operation can be switched. Although the previous and Also, the following examples always refer to the fact that is switched back and forth between a directional operation and an omnidirectional operation, for example, using the control value and a certain direction of the directional characteristic can be set. Thus, at low values f and w, it may be advantageous to align the beam former frontally forward, so that in poor conditions, the front direction is always strengthened.

The control of the directivity can also be optimized to not switch back and forth between two states, but to make a gradual transition between both states according to a predetermined function. If, for example, a directional signal and an omnidirectional signal are generated by the microphone device, then both signals can be mixed with one another for an output signal S_out, the omnidirectional signal S_omni and the directional signal S_dir. The mixing takes place, for example, as a function of the control value w according to the following formula: $$\mathrm{S\_out}=\mathrm{w}\cdot \mathrm{w\_dir}+\left(\mathrm{1}-\mathrm{w}\right)\cdot \mathrm{S\_omni}\mathrm{,}$$

This algorithm ensures that the directional microphone is used only in unique situations, such as having only one speaker in the current listening situation. This facilitates rapid switching in unique situations over the known concepts of slow crossfading to mask switching fluctuations. In multi-speaker situations, the hearing aid remains in omnidirectional mode and does not constantly switch back and forth. This reduces corresponding irritations in the hearing aid wearer.

When using a beamformer with binaural data connection between the two hearing aids, the invention makes it possible that the audio transmission between the two hearing aids is not activated or deactivated when they are in the respective Situation is not necessary or not advantageous. In this way, energy can be saved significantly. For example, a binaural audio data transfer can be dispensed with if omnidirectional operation is desired or set in both hearing aids.

The above embodiments relate to binaural hearing systems. In principle, the directional characteristic of a microphone device can also be controlled in a monaural hearing system in the manner described.

Based on FIG. 2 and 3 Now a concrete example is explained how the control value w can be determined. First, the speech features m1 and m2 in the according to FIG. 2 Realized algorithm entered. Both feature values m1 and m2 are supplied to a subtraction unit 10 and a minimum unit 11. The minimum unit 11 is followed by a limiter unit 12 to prevent a later division by 0. A division device 13 divides the difference signal of the difference unit 10 by the minimum of the two feature values m1 and m2, which has possibly been limited by the limiter unit 12. In a downstream unit 14, it can be selected whether the amount is formed by the quotient of the division unit 13 or not. For this purpose, the quotient is supplied on the one hand via an amount unit 15 a changeover switch 16 and on the other hand directly to the changeover switch 16. About a control unit 17, the changeover switch 16 is driven accordingly. The changeover switch 16 is followed by a smoothing unit 18, with which the value f is smoothed in order to avoid frequent switching between different operating modes of the microphone device. Subsequently, an amount is formed in an absolute value unit 19. If necessary, therefore, the upstream unit 14 can be dispensed with. So far, the function for calculating the value f has now been realized.

With the aid of a lookup table 20, the control value w is finally generated. The lookup table 20 represents an assignment rule here An example of this is in FIG. 3 played. In the concrete example, it is a function, according to the values f to about 0.45, to be transformed to a very small control value w less than 0.1. For values below a predetermined threshold value, an audio data connection can be dispensed with. The microphone device is to be used here essentially in omnidirectional operation. Only from values of f> 0.75 the situation is safely classified as favorable for directional operation, and these values are assigned a high control value close to 1. For values f between 0.45 and 0.75, a transition region which proceeds relatively steeply passes over.

With the resulting control values w, two signals can now be weighted according to the formula given above. In particular, a directional signal S_dir and an omnidirectional signal S_omni or another signal from a defined direction can thus be mixed with one another.

Claims (9)

1. Method for controlling a directional characteristic of a microphone device in a hearing system having at least one hearing apparatus, which method has the steps of:

   - ascertaining a first feature value (m1) for speech in a first signal, associated with a first direction, from the microphone device,

   - ascertaining a second feature value (m2) for speech in a second signal, associated with a second direction, from the microphone device,

   - obtaining a control value (w) from the two feature values, and

   - controlling the directional characteristic of the microphone device on the basis of the control value,

   characterized in that
   the control value (w) is obtained by relating the difference (10) between the two feature values to the minimum (11) of the two feature values.
2. Method according to Claim 1, wherein the first direction is opposite the second direction.
3. Method according to Claim 2, wherein the at least one hearing apparatus is worn, as intended, in or on one ear of a user, and the first direction points to the left of or in front of the user.
4. Method according to one of the preceding claims, wherein the feature values (m1, m2) each represent a probability of speech being present in the respective signal from the microphone device.
5. Method according to one of the preceding claims, wherein the control value is obtained from the difference based on the minimum by means of a freely selectable association specification (20).
6. Method according to one of the preceding claims, wherein the directional characteristic is formed by overlaying a directional signal and an omnidirectional signal from the microphone device, and, in the process, the directional signal and the omidirectional signal are weighted using the control value (w).
7. Method according to one of the preceding claims, wherein a value for the directionality of the directional characteristic increases starting from omnidirectionality as the control value (w) rises.
8. Method according to one of the preceding claims, wherein a data link between the at least one and a further hearing apparatus of the hearing system is activated and/or deactivated in dependence on the control value (w).
9. Hearing system having

   - at least one hearing apparatus, wherein

   - the hearing apparatus has a microphone device having a directional characteristic,

   - the microphone device is designed to ascertain a first feature value (m1) for speech in a first signal, associated with a first direction, from the microphone device and to ascertain a second feature value (m2) for speech in a second signal, associated with a second direction, from the microphone device, and

   - in the at least one hearing apparatus, a control device is designed to obtain a control value (w) from the two feature values, (m1, m2) and to control the directional characteristic of the microphone device on the basis of the control value,

   characterized in that
   the control device obtains the control value (w) by relating the difference (10) between the two feature values to the minimum (11) of the two feature values.

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