Hearing aid comprising a directional microphone system

1. A hearing aid adapted to be located at or in an ear of a user and to compensate for a hearing loss of the user, the hearing aid comprising

a forward path comprising

at least two input transducers, each for picking up sound from an environment of the hearing aid and providing respective at least two electric input signals;

a beamformer filter for filtering said at least two electric input signals or signals originating therefrom and providing a spatially filtered signal;

a signal processor for processing one or more of said electric input signals or one or more signals originating therefrom, and providing one or more processed signals based thereon, and

an output transducer for generating stimuli perceivable by the user as sound based on said one or more processed signals;

a feedback estimation system for estimating a current feedback from the output transducer to each of the at least two input transducers and providing respective feedback measures indicative thereof; and

a controller configured to receive said feedback measures from said feedback estimation system and to switch between two modes of operation of the hearing aid, a one-input transducer mode of operation, and a multi-input transducer mode of operation, in dependence of the feedback measures,

wherein the hearing aid comprises an ITE-part adapted for being located at or in an ear canal of the user and the ITE-part comprises said at least two input transducers and said output transducer.

2. A hearing aid according to claim 1 wherein the controller is configured to switch to the one-input transducer mode of operation in case a current feedback path difference measure between two of said feedback measures is larger than a first threshold value, and to select the electric input signal from the input transducer among the at least two input transducers having the smallest feedback measure, or a signal originating therefrom, as the input signal to the signal processor.

3. A hearing aid according to claim 1 wherein the controller is configured to switch to the multi-input transducer mode of operation in case a feedback path difference measure between each of said feedback measures is smaller than a second threshold value, and to select the spatially filtered signal as the input signal to the signal processor.

4. A hearing aid according to claim 1 wherein said feedback measure for a given input transducer comprises an impulse response of the feedback path from the output transducer to the input transducer in question, or a frequency response of the feedback path from the output transducer to the input transducer in question, the latter being measured at a number of frequencies.

5. A hearing aid according to claim 1 wherein the at least two input transducers are asymmetrically located relative to the output transducer.

6. A hearing aid according to claim 1 further comprising:

a BTE-part adapted for being located at or behind an ear (pinna) of the user, wherein the BTE-part and the ITE-part are electrically or acoustically connected to each other.

7. A hearing aid according to claim 6 wherein said ITE-part comprises a ventilation channel or other open structure allowing exchange of air between a volume near the ear drum and the environment, when the ITE-part is mounted at or in the ear canal of the user.

8. A hearing aid according to claim 7 wherein the at least two input transducers are asymmetrically located relative to the ventilation channel or to the other open structure.

9. A hearing aid according to claim 1 wherein the beamformer filter is configured to provide said spatially filtered signal as respective frequency sub-band signals.

10. A hearing aid according to claim 9 wherein the beamformer filter is configured to be individually set in an omni-directional or directional mode in the respective frequency sub-bands.

11. A hearing aid according to claim 9 wherein the controller is configured to select the spatially filtered signal or one of the electric input signals, or a signal originating therefrom, as the input signal to the signal processor, individually for different frequency ranges based on said frequency sub-band signals, and a feedback criterion.

12. A hearing aid according to claim 1 wherein said feedback measures are indicative of acoustic feedback or mechanical feedback.

13. A hearing aid according to claim 1 wherein the output transducer comprises a loudspeaker for providing the stimulus as an acoustic signal to the user or a vibrator for providing the stimulus as mechanical vibration of a skull bone to the user.

14. A method of operating a hearing aid adapted to be located at or in an ear of a user and to compensate for a hearing loss of the user, the method comprising

providing at least two electric input signals representing sound in the environment of the hearing aid as picked up by respective at least two input transducers;

providing a spatially filtered signal based on said at least two electric input signals;

processing one or more of said electric input signals or one or more signals originating therefrom, and providing one or more processed signals based thereon;

generating stimuli for an output transducer perceivable by the user as sound based on said one or more processed signals;

estimating a current feedback from said output transducer to each of the at least two input transducers and providing respective feedback measures indicative thereof; and

switching between two modes of operation of the hearing aid, a one-input transducer mode of operation, and a multi-input transducer mode of operation, in dependence of the feedback measures,

wherein the hearing aid comprises an ITE-part adapted for being located at or in an ear canal of the user and the ITE-part comprises said at least two input transducers and said output transducer.