Electrical audio signal processing systems and devices – Hearing aids – electrical – Directional
Reexamination Certificate
1999-03-04
2002-07-23
Mei, Xu (Department: 2747)
Electrical audio signal processing systems and devices
Hearing aids, electrical
Directional
C381S356000, C381S328000
Reexamination Certificate
active
06424721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a hearing aid of the type having a directional microphone system, an earphone and a number of microphones. The invention is also directed to a method for the operation of a hearing aid having a directional microphone system, the hearing aid containing a signal processing unit, an earphone and a number of microphones.
2. Description of the Prior Art
Hearing aids having a directional microphone system composed of a non-directional microphone and a directional microphone directed toward the front are known, and allow the user to switch between the individual microphones by pressing a button (European Application 0 499 699). When the directional microphone directed toward the front is activated, speech comprehension improves given unwanted sound coming mainly from the side and from the back and given useful sound (i.e., audio signals which the user desires to hear) directly incident from the front. Given activation of the non-directional microphone, a good and natural speech comprehension is achieved given useful signals incident from all sides.
U.S. Pat. No. 4,751,738 discloses a hearing aid with a directional microphone system having a signal processing unit, an earphone and a number of microphones. Spaced microphones are employed whose output signals can be interconnected with one another with different weightings on the basis of different filter curves, for producing an individual directional microphone characteristic, particularly by processing in the signal processing unit (amplifier stage, summing stage and filter stage).
In some auditory situations, for example given useful sound incident from the side and from behind, such hearing aids having a non-directional microphone and a directional microphone directed toward the front allow only limited speech comprehension.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a hearing aid as well as a method for the operation of a hearing aid of the type initially described wherein improved speech comprehension is achieved for an optimally large number of auditory situations, including even auditory situations that rarely occur.
The above object is achieved in an inventive hearing aid having a number of microphones—non-directional or directional microphones, the respective output signals of which being interconnectable with one another with different weightings and with different delays, resulting in a directional microphone characteristic adapted to the individual auditory situation. By appropriate weighting and delay of the microphone output signals, useful signals incident, for example, from the side and from behind can thereby be appropriately acquired, for example during a mountain hike next to a babbling brook.
The interconnection of the microphones can ensue in pairs (directional characteristic of the first order) or can incorporate three or more microphones (directional characteristic of a higher order).
Overall, the directional microphone system of the inventive hearing aid is composed of a number of individual microphones having different principal directions. Either individual directional microphones or a combination of two non-directional microphones can be employed as microphones in conjunction with an electronic signal processing circuit for weighting and different delay of the respective output signals of the non-directional microphones.
Due to a multiple utilization of non-directional microphones, the number of sound admission openings required in the hearing aid housing can be reduced, so that, for example, the front, back, left, right, top and bottom directions can be “covered” with four non-directional microphones and respective additional electronic circuits for weighting and delay of the output signals of the non-directional microphones.
When the hearing aid is fashioned as a behind-the-ear (BTE) hearing aid, the individual microphones forming the directional microphone system can be attached to the main body of the hearing aid with an appropriate alignment of the sound admission openings. For example, four microphones can be provided for picking up sound from the front, back, below and from the side.
By attaching auxiliary members to the main member of the BTE hearing aid, microphones having corresponding sound admission openings that also allow further sound incident directions, for example lateral directions, to be taken into consideration, can be attached in the auxiliary member.
Such an auxiliary member attached to the main member can be fashioned as a hinged, lever-like element. Dependent on the respective auditory situation, the user can swing the auxiliary member out on the hinge to an “active” position and thereby align the microphones contained in the auxiliary member, and given a change in the auditory situation, can again swing the auxiliary member back against the main member to a space-saving, “retracted” position.
The auxiliary member can be fashioned as a tear-shaped or arcuate lever-like element, so that it has an optical approximation of an earing. As a result, the overall optical impression of the BTE hearing aid is improved.
When the hearing aid is fashioned as an in-the-ear (ITE) hearing aid, at least three microphones can be integrated into the main member of the ITE hearing aid. Advantageous directional properties are achieved when the sound admission openings of the three microphones are arranged on connecting lines crossing one another substantially at a right angle.
An auxiliary member that is implemented as a hinged, lever-like element can also be attached to the main member of an ITE hearing aid. Further microphones can be integrated in this auxiliary member, allowing further, for example lateral, sound incidence directions to be acquired supplementing the microphones contained in the main member.
The inventive method of the operation of a hearing aid having a directional microphone system includes the step of selectively setting the principal direction of the directional microphone system in adaptation to the existing auditory situation. By employing a number of microphones, a multitude of different principal directions can be set, allowing useful sound incident from the side or from the back to be taken into consideration.
In a normal position, the principal direction “front” is preferably set in the directional microphone system, so that useful signals incident from the front, for example when two persons standing opposite one another are talking, can be acquired.
The inventive method allows the principal direction to be set over a wide range of variation, so that a complete auditory situation occurring, for example, on a mountain hike can be received and heard with the useful signals incident from the side and from behind.
In the inventive method, it is preferably first determined from which direction the strongest useful signals are incident in order to align the principal direction of the directional microphone system in accord therewith. The maximum of the sound energy or of the acoustic pressure can be employed as a criterion for determining the principal direction.
Switching from a previously set principal signal direction can ensue dependent on various criteria. The respective criteria can be stored as thresholds in the hearing aid, so that a change of the principal signal direction ensues when one or more such thresholds is/are exceeded. The principal direction of the directional microphone system can be set as a switching criterion dependent on the modulation frequency of the output signals of the individual microphones (dependent on brief-duration fluctuations of the frequencies of the reception signals).
The modulation boost (level difference between briefly loud and soft reception signals) or the absolute frequency spectrum of the output signals of the individual microphones can be employed as further switching criteria.
The difference of the frequency spectra of the signals picked up from various directions can be employed as a further switching criterion
Mei Xu
Schiff & Hardin & Waite
Siemens Audiologische Technik GmbH
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