In-the-ear hearing aid with directional microphone system

Information

  • Patent Grant
  • 6389142
  • Patent Number
    6,389,142
  • Date Filed
    Tuesday, March 31, 1998
    26 years ago
  • Date Issued
    Tuesday, May 14, 2002
    22 years ago
Abstract
Apparatus for use as an in-the-ear hearing aid. The apparatus includes a housing having a shell and a face plate, wherein the shell is molded to custom fit a hearing aid wearer's ear. A first non-directional microphone system is included having a first output signal representative of the sound received. A second non-directional microphone system is included having a second output signal representative of the sound received. A switch mechanism is included having an operator extending through the housing for switching the in-the-ear hearing aid between a non-directional mode and a directional mode. In the directional mode, the microphone system is adjustable to account for component tolerances. The switched directional/non directional microphone feature is employed in a custom in-the-ear Contralateral Routing of Signals (CROS) or Bilateral Routing of Signals (BiCROS) two instrument hearing aid system.
Description




BACKGROUND OF THE INVENTION




The present invention relates to a microphone system which may be used with an in-the-ear hearing aid system. In particular, the present invention relates to an adjustable microphone system, which may be used with an in-the-ear hearing aid, which allows the wearer to switch between a non-directional (or omni-direction) mode or a directional mode.




Typical hearing aids either include a non-directional or directional hearing aid system. A non-directional hearing aid system allows the wearer to pickup sounds from any direction. When a hearing aid wearer is trying to carry on a conversation within a crowded room, a non-directional hearing aid system does not allow the wearer to easily differentiate between the voice of the person the wearer is talking to and background or crowd noise. A directional hearing aid helps the wearer to hear the voice of the person he or she is having a conversation with, while reducing the miscellaneous crowd noise present within the room.




Traditionally, directional hearing aids are implemented with a single microphone having inlets to cavities located in front and back of a diaphragm. Directionality with a single microphone is accomplished with an acoustic resistor placed across a hole in the back inlet of the microphone acting in combination with the compliance formed by the volume of air behind the diaphragm. This system is termed a first order pressure gradient directional microphone because the microphone output is a function of the pressure differential across the diaphragm.




One measure of the amount of directivity of a directional hearing aid system is a polar directivity pattern


10


as shown in FIG.


1


. The polar directivity pattern


10


shows the amount of pickup at a specific frequency (in terms of attenuation in dB) of a directional hearing aid system as a function of azimuth angle of sound incidence. Accurate measurement of a polar directivity pattern requires an anechoic chamber. An anechoic chamber is an enclosed room that has minimum reflection of sound from its inner wall surfaces and that attenuates ambient sounds entering from the outside. Thus, inside an anechoic chamber, the direction of arrival of sound can be controlled so that it comes from only one specific angle of incidence.




A cardioid or heart-shaped polar pattern produces a directivity index of about 3-4 dB. The directivity index is the ratio of energy arriving from in front of the hearing aid wearer to the random energy incident from all directions around and imaginary sphere with the hearing aid at its center. However, a super cardioid polar pattern


14


, as shown in

FIG. 2

, which can also be obtained with a first order pressure gradient directional hearing aid microphone, produces a 5-6 dB directivity index. It has been found that producing a super-cardioid polar pattern


14


requires 1.72 times greater front-to-rear microphone port spacing than a cardioid polar pattern


12


. Because of limited space, a super cardioid directivity pattern is more difficult to achieve using a single directional microphone in a full-concha custom in-the-ear hearing device.




Conventional behind-the-ear type hearing aids have included a main body and a hook extending from the main body and arrange to engage the upper end of the ear lobe of the wearer to hang the main body on the ear. Known versions of behind-the-hearing aids that had variable amounts of directionality use mechanical shutters or valves to adjust the amount of directionality. For example, see U.S. Pat. No. 3,798,390 to Gage et al.; U.S. Pat. No. 3,836,732 to Johanson et al.; and U.S. Pat. No. 4,051,330 to Cole. Other known behind-the-ear hearing aid systems, such as U.S. Pat. No. 5,214,709 to Ribic suggests a behind-the-ear hearing aid system which includes the use of more than one non-directional microphone to make a directional microphone behind-the-ear hearing aid system.




Persons with an unaidable unilateral hearing loss or persons having one ear that cannot be aided with a hearing aid (known as a dead ear) and one ear with some aidable hearing loss often have great difficulty communicating in high noise levels. In such hearing loss configurations, this difficulty occurs because of the loss of the auditory system's normal ability to suppress noise, which is the expected result of the cross-correlation capability of the brain using the balanced, fused, binaurally-processed inputs from the two normal cochleas of a normal hearing person.




Contralateral Routing Of Signals (CROS) and Bilateral Routing of Signals (BiCROS) hearing aids, respectively, are often employed for such persons since they often have great difficulty wearing only one hearing aid. In essence, two instrument CROS and BiCROS systems take sound from the bad ear, process it, then send the processed sound via hard wire, RF, or induction transmission to a receiver in the other ear.




CROS systems are utilized for individuals with one unaidable ear and one ear with normal hearing or a mild hearing loss. A microphone is worn on the unaidable ear, and the receiver is worn on the better ear. BiCROS systems are utilized for individuals having one unaidable ear and one ear needing amplification. In the BiCROS system, a microphone is worn on each ear, and the receiver is worn on the better ear. CROS and BiCROS hearing aids overcome the loss of about 6 dB caused by the head blocking and diffracting sounds incident to one ear (the dead side) as they cross over to the better ear.




It is desirable to have an in-the-ear hearing aid system which allows the wearer to switch between a non-directional (omni-directional) and a directional hearing aid mode. Further, it is desirable to have an in-the-ear hearing aid system having an adjustable directional microphone system, wherein the adjustable directional microphone system. Further, it is desirable to have an in-the-ear hearing aid microphone system having an adjustable directional microphone system to allow compensation for small ears where the microphone inlets cannot be spaced far apart. It is also desirable to have an in-the-ear hearing aid microphone system which allows the in-the-ear hearing aid microphone system to be adjusted for manufacturing tolerances between the individual microphones. Finally, it is desirable to have a CROS or BiCROS hearing aid which offers a switched directional/non-directional capability.




SUMMARY OF THE INVENTION




The present invention includes an apparatus for use as an in-the-ear hearing aid. The apparatus includes a housing having a shell and a face plate, wherein the shell is molded to custom fit a hearing aid wearer's ear. A first non-directional microphone system is included having a first inlet opening in the face plate for receiving sound, and having a first output signal representative of the sound received. A second non-directional microphone system is included having a second inlet opening in the face plate for receiving sound and having a second output signal representative of the sound received. A switch mechanism is provided having an operator extending through the housing for switching the in-the-ear hearing aid between a non-directional mode and a directional mode.




The switch has an open position and a closed position. When the switch is in the closed position, the in-the-ear hearing aid operates in a directional mode. When the switch is in an open position, the in-the-ear hearing aid operates in a non-directional mode.




The apparatus may further include means for summing, selectively coupled to the first non-directional microphone system and the second non-directional microphone system, having a summed output signal representative of the sum of the first output signal and the second output signal. When the hearing aid is in the directional mode, the output signal has a polar directivity pattern representative of the summed output signal, the means for summing may further comprise means for adjusting the polar directivity pattern of the summed output signal. The means for adjusting the polar directivity pattern may include an inverting amplifier coupled to the second microphone system, and an adjustable low pass filter coupled to the inverting amplifier. In one embodiment, the adjustable phase delay includes an adjustable phase delay having an adjustable capacitor. The means for adjusting the polar directivity may further include an adjustable amplifier coupled to the second microphone system.




In one embodiment, the first inlet opening and the second inlet opening are relatively close together. In one particular embodiment, the first inlet opening and second inlet opening are less than one/half inch apart, and the first inlet opening and the second inlet opening are located in approximately the same plane, which is generally horizontal to the ground when the in-the-ear hearing aid is located in a wearer's ear.




In another embodiment, the present invention includes a microphone system for use with an in-the-ear hearing aid. The system includes a first non-directional microphone system having a first inlet opening for receiving sound and having a first output signal representative of the sound received. A second non-directional microphone system is included having a second inlet opening for receiving sound having a second output signal representative of the sound received. Means are provided for coupling the first non-directional microphone system to the second non-directional microphone system for switching the in-the-ear hearing aid between a non-directional mode and a directional mode.




The means for coupling may be a switch having a closed position and an open position, and wherein when the switch is in the open position, the in-the-ear hearing aid is in the non-directional mode, and when the switch is in a closed position, the in-the-ear hearing aid is in a directional mode.




The second non-directional microphone system may further include means for inverting the second output signal. The second non-directional microphone system may further include means for adjusting the phase delay of the second output signal relative to the first output signal. The means for adjusting the phase delay may include a low pass filter having an adjustable capacitor. Further, the second non-directional microphone system may further include means for adjusting the amplitude of the second output signal relative to the first output signal.




The present invention may include means for summing the first output signal and the second output signal. The means for summing may have an output coupled to an amplifier. The amplifier may include a phase delay.




In yet another embodiment, the present invention may integrate two switched directional/non-directional microphone systems as described above into a two instrument, in-the-ear CROS or BiCROS hearing aid. The connection between the two instruments of the CROS or BiCROS hearing aid may be made via a hard wire connection, RF, or induction transmission.











BRIEF DESCRIPTION OF THE DRAWINGS




Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein:





FIG. 1

is a cardioid polar directivity pattern of an in-the-ear hearing aid;





FIG. 2

is a super cardioid polar directivity pattern of an in-the-ear hearing aid;





FIG. 3

is a perspective view of an in-the-ear hearing aid in accordance with the present invention;





FIG. 4

is a system block diagram of one embodiment of the hearing aid in accordance with the present invention;





FIG. 5

is a schematic circuit diagram of one embodiment of the in-the-ear hearing aid in accordance with the present invention;





FIG. 6

is a pictorial drawing of a two instrument BiCROS hearing aid with a wire connecting the two units;





FIG. 7

is a graphical embodiment of the polar directivity pattern of a two instrument BiCROS hearing aid with both instruments switched into directional mode;





FIG. 8

is a system block diagram of an embodiment of a BiCROS in-the ear hearing aid having a switched directional/non-directional capability; and





FIG. 9

is a schematic circuit diagram of an embodiment of a two instrument BiCROS hearing aid having switched directional/non-directional capabilities.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




In

FIG. 3

, an in-the-ear hearing aid is generally shown at


16


. The in-the-ear (ITE) hearing aid


16


includes a housing


18


having a face plate


22


and a molded shell


20


. The molded shell


20


is adhered to the face plate


22


, indicated along line


24


. The molded shell


20


is custom molded to fit each individual hearing aid wearer by known processes, such as making an impression of the individual hearing aid wearer's ear and forming the molded shell based on that impression. The face plate


22


is coupled to a circuit board (not shown) located inside the ITE hearing aid


16


, which contains the circuitry for the hearing aid device.




Extending through the in-the-ear hearing aid


16


and specifically face plate


22


, is a battery door


26


, a volume control


28


, a switch S


1


, a microphone mic F, and a microphone mic B. The battery door


26


allows the hearing aid wearer access to the in-the-ear hearing aid


16


for changing the battery (not shown). The volume control


28


allows the hearing aid wearer to adjust the volume or amplification level of the hearing aid


16


.




Switch S


1


extends through the housing


18


and specifically face plate


22


. Switch S


1


allows the hearing aid wearer to manually switch the in-the-ear hearing aid


16


between a non-directional or directional hearing aid mode. Switch S


1


is electronically coupled to the circuit contained within the in-the-ear hearing aid


16


, which will be described in further detail later in the specification. With the novel idea of switch S


1


, a hearing aid wearer can switch to a non-directional hearing aid mode to hear sounds from all directions, or a directional hearing aid mode, such as for reducing background noise when carrying on a conversation in a crowded room.




Microphone mic F and microphone mic B include inlet tubes


30


,


32


which protrude through the in-the-ear hearing aid face plate


22


. Microphone mic F and microphone mic B are spaced a relatively short distance apart, preferably less than ½ inch. In one preferred embodiment, microphone mic F and microphone mic B are preferably ⅓ of an inch apart.




The axis of directionality is defined by a line drawn through the inlet tube


30


and inlet tube


32


in face plate


22


, indicated at


34


. The in-the-ear hearing aid


16


in accordance with the present invention is of a molded design such that the axis of directionality


34


is relatively horizontal to the floor when the in-the-ear hearing aid


16


is positioned within the hearing aid


16


wearer's ear. With this design, optimum directional performance of the in-the- ear hearing aid


16


is achieved.




Referring to

FIG. 4

, a block diagram showing the directional microphone system in accordance with the present invention, for use with an in-the-ear hearing aid is generally shown at


36


. The directional microphone system


36


utilizes two non-directional microphone circuits to achieve a directional microphone signal. The directional microphone system


36


includes a first non-directional microphone system


38


and a second non-directional microphone system


40


. The output signals from the second non-directional microphone system


40


(indicated by signal


44


) may be electrically coupled through switch S


1


, and summed at node


46


with the first non-directional microphone system


38


(indicated by signal


42


). The resulting output signal is indicated at


48


. The output signal


48


is electrically coupled to a hearing aid circuit


50


. For example, the hearing aid circuit


50


may be a linear circuit, a compression circuit, an adaptive high-pass filter, and may include a high-power output stage.




The in-the-ear hearing aid


16


may be switched between a non-directional mode and a directional mode through the operation of switch S


1


. In the non-directional mode switch S


1


is open (as shown), and non-directional microphone mic F feeds directly into hearing aid circuit


50


. For operation in a directional mode, switch S


1


is closed, and the first non-directional microphone system


38


and second non-directional microphone system


40


output signals


42


and


44


are summed at summing node


46


, with the resulting output signal


48


being coupled to hearing aid circuit


50


.




In one embodiment, the second non-directional microphone system


40


includes non-directional microphone mic B, an inverter


52


, an adjustable pulse delay


54


, and an adjustable gain


56


. The output signal of microphone mic B is coupled to inverter


52


, indicated at


58


. The output signal of inverter


52


is coupled to the adjustable pulse delay


54


, indicated at


60


. The output of adjustable phase delay


54


is coupled to the adjustable gain


56


, indicated at


62


. The output of the adjustable gain


56


is coupled to switch S


1


, indicated at 64.




The output signal


58


of microphone mic B is inverted by inverter


52


. Further, when switch S


1


is closed, the phase delay


54


of the output of mic B may be adjusted relative to the output of microphone mic F. Similarly, adjustable gain


56


adjusts the amplitude of the output signal received from mic B relative to the output signal


42


from microphone mic F. By providing such adjustment, the hearing aid manufacturer and/or the hearing aid dispenser may vary the polar directivity pattern of the in-the-ear hearing aid. The adjustable non-directional microphone system


40


allows the polar pattern to be adjusted to compensate for small ears which do not allow larger inlet spacing. Further, the adjustable non-directional microphone system


40


allows for adjustments to compensate for the differences in manufacturing tolerances between non-directional microphone mic F and non-directional microphone mic B.




The output signal


48


from first non-directional microphone system


38


and second non-directional microphone system


40


may be amplified by passing it through an amplifier


66


. The resulting output signal of amplifier


66


, indicated at


68


, is coupled to the hearing aid circuit


50


.




Referring to

FIG. 5

, a schematic diagram of one preferred embodiment of the-in-ear hearing aid directional microphone system


36


is shown. Non-directional microphone mic F has a coupling capacitor C


1


coupled to its output. Resistor R


1


is electrically coupled between coupling capacitor C


1


and summing node


46


. Non-directional microphone mic B has a coupling capacitor C


2


coupled to its output. Coupled to the output of C


2


is inverter


52


with adjustable phase delay


54


. The adjustable phase delay is an adjustable low pass filter. The inverter


52


is an operational amplifier OPAMP


1


, shown in an inverting configuration. Coupled between capacitor C


2


and the input node


70


of OPAMP


1


is resistor R


2


. Coupled between OPAMP


1


input node


70


and an OPAMP


1


output node


72


is resistor R


3


. Similarly, coupled between OPAMP


1


input node


70


and OPAMP


1


output node


72


is a capacitor C


3


.




As previously described herein, OPAMP


1


inverts the output signal received from non-directional microphone mic B. As such, when the output signal


42


and output signal


44


are summed at summing node


46


, the signals are subtracted, resulting in output signal


48


.




The gain between the input of OPAMP


1


and the output of OPAMP


1


is indicated by the relationship R


3


/R


2


. In one preferred embodiment, R


3


equals R


2


, resulting in a unity gain output signal from OPAMP


1


.




The phase delay


54


low pass capacitor C


3


may be adjustable. By adjusting capacitor C


3


, and/or resistor R


3


, the phase delay of the non-directional microphone mic B output relative to the non-directional microphone mic F may be adjusted. Coupled to the output node


72


of OPAMP


1


is a resistor R


5


in series with an adjustable resistor or potentiometer R


6


. Further, coupled to output signal


48


is an inverting operational amplifier, OPAMP


2


having an input node


74


and an output node


76


. Coupled between the input node


74


and the output node


76


is resistor R


4


. Also coupled between the input node


74


and the output node


76


is a capacitor C


4


. It is recognized that capacitor C


4


and resistor R


3


and R


4


may also be adjustable.




When switch S


1


is open, the resulting amplification or gain from the output from non-directional microphone mic F is the ratio of resistors R


4


/R


1


. When switch S


1


is closed, the output gain contribution from mic B is determined by the ratio of R


4


/(R


5


plus R


6


). By adjusting the adjustable potentiometer R


6


, the amplitude of non-directional microphone mic B of the output signal relative to the output signal amplitude of non-directional microphone mic F may be adjusted. As previously stated herein, by adjusting both capacitor C


3


and resistor R


6


, the hearing aid may be adjusted to vary the polar directivity pattern of the in-the-ear hearing aid from cardioid (

FIG. 1

) to super cardioid (FIG.


2


), as desired.




In one preferred embodiment, the values for the circuit components shown in

FIG. 5

are as follows:
















TABLE 1













C1




=




.01 uF







C2




=




.01 uF







C3




=




.0022 uF







C4




=




110 pF







R1




=




10K







R2




=




10K







R3




=




10K







R4




=




1M







R5




=




10K







R6




=




2.2K















Non-directional microphone mic F and non-directional microphone mic B can be non-directional microphones as produced by Knowles No. EM5346. Operational amplifiers OPAMP


1


and OPAMP


2


may be inverting Gennum Hearing Aid Amplifiers No. 1/4 LX509.




The hearing aid in accordance with the present invention allows a person wearing an in-the-ear hearing aid to switch between a non-directional mode and a directional mode by simple operation of switch S


1


located on the in-the-ear hearing aid


16


. The circuit components which makeup the directional microphone system


36


and the hearing aid circuit


50


are all located within the hearing aid housing


18


and coupled to the inside of face plate


22


. Further, by adjustment of the adjustable phase delay


54


and adjustable gain


56


, the directional microphone system


36


may be adjusted to vary the polar directivity pattern to account for manufacturing differences. It may be desirable to adjust the polar directivity pattern between cardioid and super cardioid for various reasons, such as to compensate for limited inlet spacing due to small ears or to compensate for the manufacturing tolerances between non-directional microphone mic F and non-directional microphone mic B. It is also recognized that capacitor C


4


and resistor R


4


may be adjustable to compensate for each individual's hearing loss situation.




With the novel design of the present invention, the associated circuitry of the present invention allows the two non-directional microphones mic B and mic F to be positioned very close together and still produce a directional microphone system having a super cardioid polar directivity pattern. Further, the directional microphone system in accordance with the present invention is able to space the two microphones less than one inch apart, and in a preferred embodiment, ⅓ of an inch apart in order for the directional microphone system in accordance with the present invention to be incorporated into an in-the-ear hearing aid device. The in-the-ear hearing aid


16


circuitry, including the directional microphone system


36


circuitry and the hearing aid circuit


50


circuitry, utilize microcomponents and may further utilize printed circuit board technology to allow the directional microphone system


36


and hearing aid circuit


50


to be located within a single in-the-ear hearing aid


16


.




In

FIG. 6

, a BiCROS, in-the-ear (ITE) hearing aid system is generally shown at


101


. CROS and BiCROS systems are designed for individuals with little or no hearing in one ear and some hearing capability in the other ear. CROS/BiCROS systems take sound from the bad ear and send it, via hard wire (illustrated), RF (not illustrated), or induction transmission (not illustrated, but as in the Telex Wireless CROS system) to a receiver in the other ear. The BiCROS, ITE hearing aid


101


of

FIG. 6

includes two separate instruments


16


A and


16


B (each to be placed in an ear of the individual) and a wire cord


102


interconnecting the two instruments


16


A and


16


B at wire cord junctions


124


A and


124


B. One of the instruments


16


A will function as a transmitter unit and will be placed in the unaidable ear of the individual. The other instrument


16


B will function as a receiver and will be placed in the better ear of the individual. However, since both instruments


16


A and


16


B have the dual microphone system, each instrument


16


A and


16


B can be designated as either a transmitter or a receiver in the device configuration.




An in-the-ear CROS system (not-illustrated) will operate in a manner similar to the illustrated BiCROS system shown in

FIG. 6

, except that CROS systems are generally utilized for individuals with one unaidable ear and one ear with a normal hearing or a mild hearing loss. Thus, in a CROS system, a microphone set is worn only in the unaidable ear, and the receiver is worn in/on the better ear, while in the illustrated BiCROS system


101


, a microphone set is worn in/on both ears, and the receiver is worn on the better ear.




Each instrument


16


A and


16


B has a molded shell


20


A,


20


B which is custom molded to fit each individual hearing aid wearer by known processes, such as making an impression of the individual hearing aid wearer's ear and forming the molded shell based on that impression. Each instrument


16


A and


16


B also has a face plate


22


A,


22


B coupled to a circuit board (not shown) located inside the instrument


16


A and


16


B.




Extending through each instrument


16


A and


16


B and specifically face plate


22


A,


22


B, is a battery door


26


A,


26


B, a volume control


28


A,


28


B, a switch S


1


A, S


1


B, a microphone mic FA, FB, and a microphone mic BA, BB. The battery door


26


A,


26


B allows the hearing aid wearer access to the instrument


16


A or


16


B for changing the battery (not shown). The volume control


28


A,


28


B allows the hearing aid wearer to adjust the volume or amplification of the instrument


16


A or


16


B.




Switch S


1


A, S


1


B extends through the face plate


22


A,


22


B, and allows the hearing aid wearer to manually switch the instrument


16


A and


16


B between a non-directional or directional hearing aid mode. Switch S


1


A, S


1


B is electronically coupled to the circuit contained within the instrument


16


A or


16


B. With the novel idea of switch S


1


A, S


1


B, a hearing aid wearer can switch to a non-directional hearing aid mode to hear sounds from all directions, or a directional hearing aid mode, such as for reducing background noise when carrying on a conversation in a crowded room.




Microphone mic FA, FB and microphone mic BA, BB in instrument


16


A and


16


B include inlet tubes


30


A,


30


B and


32


A,


32


B which protrude through the instrument face plate


22


A,


22


B. Microphone pairs mic FA and BA in instrument


16


A and microphone mic FB and BB in instrument


16


B are spaced a relatively short distance apart, preferably less than ½ inch. In one preferred embodiment, microphone pair mic FA and BA in instrument


16


A and microphone pair mic FB and BB in instrument


16


B are preferably ⅓ of an inch apart.




An axis of directionality is defined by a line drawn through the inlet tube


30


A,


30


B and inlet tube


32


A,


32


B in face plate


22


A,


22


B, indicated at


34


. The instrument


16


A and


16


B in accordance with the present invention is of a molded design such that the axis of directionality


34


is relatively horizontal to the floor when the instrument is positioned within the hearing aid wearer's ear. With this design, optimum performance of the hearing aid system is achieved.




The combination of a switched directional/non-directional microphone system in a custom in-the-ear CROS or BiCROS hearing aid system as illustrated in

FIG. 6

will result in a significant improvement in signal to noise ratio for individuals in noisy listening situations.




Referring now to

FIG. 7

, a polar directivity pattern


110


is shown for a BiCROS hearing aid system, with both instruments


16


A and


16


B switched into directional mode. The pattern was obtained on an HA-1 2 cc coupler in an anechoic chamber. The polar directivity pattern


110


shows the amount of pickup at a specific frequency (in this case, 1K) of a BiCROS directional hearing aid system as a function of azimuth angle of sound incidence. In the illustrated pattern, the Directivity Index (DI—the ratio of sounds incident straight ahead to those incident all around an imaginary sphere) was 10.1 dB and the Unidirectional Index (UDI—the ratio of sounds incident on an imaginary front hemisphere to those from an imaginary rear hemisphere) was 5.0 dB. This polar pattern


110


indicates that sounds incident from the sides and rear will be significantly attenuated. The DI predicts up to a 10 dB improvement in signal-to-noise ratio, depending upon the amount of reverberation in the listening environment.




Referring to

FIG. 8

, a block diagram showing the BICROS, in-the-ear directional hearing aid system in accordance with the present invention is illustrated. In this embodiment, each of the two instruments of the hearing aid has its own microphone system. The directional microphone system


36


A,


36


B within each of the two instruments utilizes two non-directional microphone circuits


38


A,


40


A and


38


B,


40


B to achieve a directional microphone signal. Each directional microphone system


36


A,


36


B includes a first non-directional microphone system


38


A,


38


B and a second non-directional microphone system


40


A,


40


B. The output signals from the second non-directional microphone system


40


A,


40


B (indicated by signal


42


A,


42


B) may be electrically coupled through switch S


1


A and S


1


B, and summed at node


46


A,


46


B with the first non-directional microphone system


38


A,


38


B (indicated by signal


44


A,


44


B). The resulting output signal from each of the instruments is indicated at


48


A,


48


B. The output signal


48


A,


48


B from each of the instruments is coupled to a hearing aid circuit


50


. For example, the hearing aid circuit may be a linear circuit, a compression circuit, an adaptive high-pass filter, and may include a high-power output stage.




Each of the two instruments


16


A and


16


B may be switched between a non-directional mode and a directional mode through the operation of switch S


1


A, S


1


B. In the non-directional mode, switch S


1


A, S


1


B is open (as shown), and non-directional microphone mic F


38


A,


38


B feeds directly into hearing aid circuit


50


. For operation in a directional mode, switch S


1


A, S


1


B is closed, and the first non-directional microphone system


38


A,


38


B and second non-directional microphone system


40


A,


40


B output signals are summed at summing node


46


A,


46


B, with the resulting output signal


48


A,


48


B being coupled to hearing aid circuit.




In one embodiment, the second non-directional microphone system


40


A,


40


B of each instrument


16


A and


16


B includes non-directional microphone mic B, an inverter


52


A,


52


B, an adjustable phase delay


54


A,


54


B, and an adjustable gain


56


A,


5


B. The output signal of microphone mic B is coupled to inverter


52


A,


52


B, indicated at


58


A,


58


B. The output signal of inverter


52


A,


52


B is coupled to the adjustable phase delay


54


A,


54


B, indicated at


60


A,


60


B. The output of the adjustable phase delay


54


A,


54


B is coupled to the adjustable gain


56


A,


56


B, indicated at


62


A,


62


B. The output of the adjustable gain


56


A,


56


B is coupled to switch S


1


A, S


1


B, indicated at


64


A,


64


B.




The output signal of microphone mic B in each of the instruments


58


A,


58


B is inverted by inverter


52


A,


52


B. Further, the adjustable phase delay


54


A,


54


B may adjust the phase delay of the output of mic B relative to the output of microphone mic F in each of the instruments. Similarly, adjustable gain


56


A,


56


B adjusts the amplitude of the output signal received from mic B relative to the output signal from microphone mic F. By providing such an adjustment, the hearing aid manufacturer may vary the polar directivity pattern of each instrument.




The output signal


48


A,


48


B from first non-directional microphone system


38


A,


38


B and second non-directional microphone system


40


A,


40


B in each of the instruments may be amplified by passing it through amplifier


66


A,


66


B. The resulting output signal of amplifier


68


A,


68


B in each of the instruments


16


A and


16


B, is coupled to the hearing aid circuit


50


.




As mentioned above, in a CROS system (not illustrated), the instrument in the better ear will not contain the microphone mic B or the microphone mic F, as shown in the illustrated BiCROS system.




Referring to

FIG. 9

, a schematic diagram of one preferred embodiment of a BiCROS, in-the-ear hearing aid system with switched directional/non-directional microphone is shown. This hearing aid system has two instruments


16


A and


16


B. The first instrument


16


A, is designed to be placed in the individual's unaidable ear. The second instrument


16


B, having hearing aid amplifier


120


, is designed to be placed in the individual's better ear. A connection


102


for transmitting a signal from the first instrument


16


A to the second instrument


16


B may be made in a variety of ways, including a hard wire (illustrated), a RF transmission from the first instrument to the second instrument (not illustrated), or an induction transmission as in the Telex Wireless CROS system (not illustrated).




In the first instrument


16


A, non-directional microphone mic F


1


has a coupling capacitor C


6


A coupled to its output. Resistor R


7


A is electrically coupled between coupling capacitor C


6


A and node


74


A. Non-directional microphone mic B


1


has a coupling capacitor C


7


A coupled to its output. Coupled to the output of C


7


A is inverter


52


A with adjustable phase delay


54


A. The inverter


52


A is an operational amplifier OPAMP


4


, shown in an inverting configuration. Coupled between capacitor C


7


A and the input node


70


A of OPAMP


4


is resistor R


11


A. Coupled between OPAMP


4


input node


70


A and an OPAMP


4


output node


72


A is resistor R


12


A. Similarly, coupled between OPAMP


4


input node


70


A and OPAMP


4


output node


72


A is capacitor C


8


A.




As previously described herein, OPAMP


4


inverts the output signal received from non-directional microphone mic B


1


. As such, when the output signal


42


A and output signal


44


A are summed at summing node


46


A, the signals are subtracted, resulting in output signal


48


A.




The gain between the input of OPAMP


4


and the output of OPAMP


4


is indicated by the relationship R


12


A/R


11


A. In one preferred embodiment, R


12


A equals R


11


A, resulting in a unity gain output signal from OPAMP


4


.




The adjustable phase delay capacitor C


8


A may be adjustable. By adjusting capacitor C


8


A, the phase delay of the non-directional microphone mic B


1


output relative to the non-directional microphone mic F


1


may be adjusted. Coupled to the output node


72


A of OPAMP


4


is a resistor R


9


A in series with an adjustable resistor or potentiometer R


10


A. Further, coupled to output signal


72


A is an inverting operational amplifier, OPAMP


3


having an input node


74


A and an output node


76


A. Coupled between the input node


74


A and the output node


76


A is a resistor R


8


A. Also coupled between the input node


74


A and the output node


76


A is a capacitor C


5


A. It is recognized that capacitor C


5


A and resistor R


8


A may also be adjustable.




When switch S


3


A is open, the resulting amplification or gain from the output from non-directional microphone mic F


1


is the ratio of resistors R


8


A/R


7


A. When switch S


3


A is closed, the output gain contribution from mic B


1


is determined by the ratio of R


8


A/(R


7


A plus R


10


A). By adjusting the adjustable potentiometer R


10


A, the amplitude of non-directional microphone mic B


1


of the output signal relative to the output signal amplitude of non-directional microphone mic F


1


may be adjusted. As previously stated herein, by adjusting both capacitor C


8


A and resistor R


10


A, the hearing aid may be adjusted to vary the polar directivity pattern of the in-the-ear hearing aid to account for component tolerances.




In one known embodiment, the values for the circuit components shown in

FIG. 9

are as follows:
















TABLE 2













C6A




=




.01 uF







C7A




=




.01 uF







C8A




=




.0022 uF







C5A




=




110 pF







R7A




=




10K







R11A




=




10K







R12A




=




10K







R8A




=




1M







R9A




=




10K







R10A




=




2.2K















Non-directional microphone mic F


1


and non-directional mic B


1


can be non-directional microphones as produced by Knowles No. EM5346. Operational amplifiers OPAMP


3


and OPAMP


4


may be inverting Gennum Hearing Aid Amplifiers No. 1/4 LX509.




In the second instrument


16


B, non-directional microphone mic F


2


has a coupling capacitor C


1


B coupled to its output. Resistor R


5


B is electrically coupled between coupling capacitor C


1


B and node


74


B. Non-directional microphone mic B


2


has a coupling capacitor C


2


B coupled to its output. Coupled to the output of C


2


B is inverter


52


B with adjustable phase delay


54


B. The inverter


52


B is an operational amplifier OPAMP


1


, shown in an inverting configuration. Coupled between capacitor C


2


B and the input node


70


B of OPAMP


1


is resistor R


1


B. Coupled between OPAMP


1


input node


70


B and an OPAMP


1


output node


72


B is resistor R


2


B. Similarly, coupled between OPAMP


1


input node


70


B and OPAMP


1


output node


72


B is capacitor C


3


B.




As previously described herein, OPAMP


1


inverts the output signal received from non-directional microphone mic B


2


. As such, when the output signal


42


B and output signal


44


B are summed at summing node


46


B, the signals are subtracted, resulting in output signal


48


B.




The gain between the input of OPAMP


1


and the output of OPAMP


1


is indicated by the relationship R


2


B/R


1


B. In one preferred embodiment, R


2


B equals R


1


B, resulting in a unity gain output signal from OPAMP


1


.




The adjustable phase delay capacitor C


3


B may be adjustable. By adjusting capacitor C


3


B, the phase delay of the non-directional microphone mic B


2


output relative to the non-directional microphone mic F


2


may be adjusted. Coupled to the output node


72


B of OPAMP


1


is a resistor R


3


B in series with an adjustable resistor or potentiometer R


4


B. Further, coupled to output signal


72


B is an inverting operational amplifier, OPAMP


2


having an input node


74


B and an output node


76


B. Coupled between the input node


74


B and the output node


76


B is a resistor R


6


B. Also coupled between the input node


74


B and the output node


76


B is a capacitor C


4


B. It is recognized that capacitor C


4


B and resistor R


6


B may also be adjustable.




When switch S


4


B is open, the resulting amplification or gain from the output from non-directional microphone mic F


2


is the ratio of resistors R


6


B/R


5


B. When switch S


4


B is closed, the output gain contribution from mic B


2


is determined by the ratio of R


6


B/(R


3


B plus R


4


B). By adjusting the adjustable potentiometer R


4


B, the amplitude of non directional microphone mic B


2


of the output signal relative to the output signal amplitude of non-directional microphone mic F


2


may be adjusted. As previously stated herein, by adjusting both capacitor C


3


B and resistor R


4


B, the hearing aid may be adjusted to vary the polar directivity pattern of the in-the-ear hearing aid to account for component tolerances.




In one known embodiment, the values for the circuit components shown in

FIG. 9

are as follows:
















TABLE 3













C1B




=




.01 uF







C2B




=




.01 uF







C3B




=




.0022 uF







C4B




=




110 pF







R5B




=




10K







R1B




=




10K







R2B




=




10K







R6B




=




1M







R3B




=




10K







R4B




=




2.2K















Non-directional microphone mic F


2


and non-directional mic B


2


can be non-directional microphones as produced by Knowles No. EM5346. Operational amplifiers OPAMP


1


and OPAMP


2


may be inverting Gennum Hearing Aid Amplifiers No. 1/4 LX509.




The hearing aid in accordance with the present invention allows a person wearing a BiCROS in-the-ear hearing aid to switch between a non-directional mode and a directional mode by simple operation of switch S


3


A in the first instrument


16


A and switch S


4


A in a second instrument


16


B. The circuit components which make up the directional microphone system are all located within the hearing aid housing and coupled to the inside of face plate. Further, by adjustment of the adjustable phase delay and adjustable gain, the directional microphone system may be adjusted to vary the polar directivity pattern to account for component tolerances. It is also recognized that capacitor C


5


A and resistor R


8


A in the first instrument


16


A and capacitor C


4


B and resistor R


6


B in the second instrument


16


B may be adjustable to compensate for each individual's hearing loss situation.




It will be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, material, and arrangement of parts, without exceeding the scope of the invention. Accordingly, the scope of the invention is as defined in the language of the appended claims.



Claims
  • 1. An in-the-ear hearing aid system, comprising:a first instrument and a second instrument, each of said instruments having a shell molded to custom fit a different one of a hearing aid wearer's ear, wherein said first instrument is placed in said wearer's worse hearing ear and said second instrument is placed in said wearer's better hearing ear, said first instrument further comprising: a first non-directional microphone system having a first inlet opening in a face plate for receiving sound and having a first output signal representative of the sound received; a second non-directional microphone system having a second inlet opening in said face plate for receiving sound and having a second output signal representative of the sound received; switch means having an operator extending through the first instrument for switching said first instrument between a non-directional mode and a directional mode; and connecting means for transmitting a signal from said first instrument to said second instrument.
  • 2. The hearing aid system of claim 1, wherein the switch has an open position and a closed position, and wherein when the switch is in the closed position, the first instrument operates in the directional mode.
  • 3. The hearing aid system of claim 2, wherein when the switch is in the open position, the first instrument operates in the non-directional mode.
  • 4. The hearing aid system of claim 2, further comprising means for summing, selectively coupled to the first non-directional microphone system and the second nondirectional microphone having a summed output signal representative of the sum of the first output signal and the second output signal.
  • 5. The hearing aid system of claim 4, wherein when the first instrument is in the directional mode, a directional output signal has a polar directivity pattern representative of the summed output signal; and wherein the means for summing further comprises means for adjusting the polar directivity pattern of the summed output signal between a cardioid polar directivity pattern and a super cardioid polar directivity pattern.
  • 6. The hearing aid system of claim 5, wherein the means for adjusting the polar directivity pattern includes:an inverting amplifier coupled to the second microphone system; and an adjustable phase delay coupled to the inverting amplifier.
  • 7. The hearing aid system of claim 6, wherein the adjustable phase delay includes an adjustable low pass filter having an adjustable capacitor.
  • 8. The hearing aid system of claim 6, wherein the means for adjusting the polar directivity further includes an adjustable amplifier coupled to the second microphone system.
  • 9. The hearing aid system of claim 8, wherein the adjustable amplifier includes an adjustable potentiometer.
  • 10. The hearing aid system of claim 1, wherein the first inlet opening and second inlet opening are relatively close together.
  • 11. The hearing aid system of claim 1, wherein the first inlet opening and second inlet opening are less than ½ inch apart.
  • 12. The hearing aid system of claim 11, wherein the first inlet opening and second inlet opening are located in approximately the same plane which is generally horizontal to the ground when the in-the-ear hearing aid is located in a wearer's ear.
  • 13. The hearing aid system of claim 1, wherein said connecting means further comprises a hard wired connection.
  • 14. The hearing aid system of claim 1, wherein said connecting means further comprises a radio frequency (RF) transmission.
  • 15. The hearing aid system of claim 1, wherein said connecting means further comprises an induction transmission.
  • 16. Apparatus for use as a Bilateral Routing Of Signals (BiCROS) type in-the-ear hearing aid, the apparatus comprising:a first instrument and a second instrument, each said instrument having a shell molded to custom fit a hearing aid wearer's ear, wherein said first instrument is placed in said wearer's worst hearing ear and said second instrument is placed in said wearer's better hearing ear, said first instrument and said second instrument each having: a first non-directional microphone system having a first inlet opening in a face plate for receiving sound and having a first output signal representative of the sound received; a second non-directional microphone system having a second inlet opening in said face plate for receiving sound and having a second output signal representative of the sound received; switch means having an operator extending through the first instrument for switching said first instrument and said second instrument between a non-directional mode and a directional mode; and connecting means for transmitting a signal from said first instrument to said second instrument.
  • 17. The apparatus of claim 16, wherein the switch has an open position and a closed position, and wherein when the switch is in the closed position, the in-the-ear hearing aid operates in a directional mode.
  • 18. The apparatus of claim 17, wherein when the switch is in an open position, the hearing aid operates in a non-directional mode.
  • 19. The apparatus of claim 17, further comprising means for summing, selectively coupled to the first non-directional microphone system and the second nondirectional microphone having a summed output signal representative of the sum of the first output signal and the second output signal.
  • 20. The apparatus of claim 19, wherein when the hearing aid is in the directional mode, the output signal has a polar directivity pattern representative of the summed output signal; and wherein the means for summing further comprises means for adjusting the polar directivity pattern of the summed output signal to account for component tolerances.
  • 21. The apparatus of claim 20, wherein the means for adjusting the polar directivity pattern includes:an inverting amplifier coupled to the second microphone system; and an adjustable phase delay coupled to the inverting amplifier.
  • 22. The apparatus of claim 21, wherein the adjustable phase delay includes an adjustable low pass filter having an adjustable capacitor.
  • 23. The apparatus of claim 21, wherein the means for adjusting the polar directivity further includes an adjustable amplifier coupled to the second microphone system.
  • 24. The apparatus of claim 23, wherein the adjustable amplifier includes an adjustable potentiometer.
  • 25. The apparatus of claim 16, wherein the first inlet opening and second inlet opening are relatively close together.
  • 26. The apparatus of claim 16, wherein the first inlet opening and second inlet opening are less than ½ inch apart.
  • 27. The apparatus of claim 26, wherein the first inlet opening and second inlet opening are located in approximately the same plane which is generally horizontal to the ground when the in-the-ear hearing aid is located in a wearer's ear.
  • 28. The apparatus of claim 16, wherein said connecting means further comprises a hard wired connection.
  • 29. The apparatus of claim 16, wherein said connecting means further comprises a radio frequency (RF) transmission.
  • 30. The apparatus of claim 16, wherein said connecting means further comprises an induction transmission.
  • 31. A hearing aid system, comprising:an in-the-ear, first instrument and a second instrument, the first instrument having a shell molded to custom fit a worse one of a hearing aid wearer's ears, the shell including a face plate, the second instrument is associated with a better one of the wearer's ears, the first instrument having a non-directional mode and a directional mode and including: a first non-directional microphone system having a first inlet opening in the face plate for receiving sound and having a first output signal representative of the sound received; a second non-directional microphone system having a second inlet opening in the face plate for receiving sound and having a second output signal representative of the sound received; a switch connected to the first instrument for switching the first instrument between the non-directional mode and the directional mode; and the system further including a signal connector between the first instrument and the second instrument for transmitting a signal from the first instrument to the second instrument.
  • 32. The system of claim 31, wherein the signal connector includes a transmitter in the first instrument, a receiver in the second instrument, and a signal path between the transmitter and the receiver.
  • 33. The system of claim 32, wherein the signal connector includes a transmitter in the second instrument and a receiver in the first instrument, whereby the system provides Bilateral Routing Of Signals (BiCROS).
  • 34. The system of claim 32, wherein the signal connector is a hard wire connection.
  • 35. The system of claim 32, wherein the second instrument includes a shell molded to custom fit the better one of the hearing aid wearer's ears.
  • 36. The system of claim 35, wherein the second instrument has a directional mode and a non-directional mode and includes:a second face plate; a third non-directional microphone system having a third inlet opening in the second face plate for receiving sound and having a third output signal representative of the sound received; a fourth non-directional microphone system having a fourth inlet opening in the second face plate for receiving sound and having a fourth output signal representative of the sound received; and a second switch connected to the second instrument for switching the second instrument between the non-directional mode and the directional mode.
  • 37. The system of claim 31, wherein the switch has an open position and a closed position, and wherein when the switch is in the closed position, the in-the-ear first instrument is in the directional mode using the first output signal and the second output signal.
  • 38. The system of claim 37, wherein the first instrument includes a summing circuit, in the directional mode the switch connects both the first output signal and the second output signal to the summing circuit, and the summing circuit produces a summed signal.
  • 39. The system of claim 37, wherein when the switch is in the open position, the hearing aid operates in the non-directional mode using one signal from one of the first microphone or the second microphone.
  • 40. The system of claim 31, wherein the switch includes an operator extending outside the shell such that the operator of the switch is manually accessible.
  • 41. The system of claim 31, wherein the first inlet opening and second inlet opening are located in approximately a same plane that is generally horizontal to the ground when the first instrument is located in a wearer's ear.
  • 42. The system of claim 31, wherein the signal connector includes one of a radio frequency transmission or an induction transmission.
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 08/763,520 filed on Dec. 11, 1996 now U.S. Pat. No. 5,757,933.

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Number Name Date Kind
3571514 Wruk Mar 1971 A
3770911 Knowles et al. Nov 1973 A
3798390 Gage et al. Mar 1974 A
3836732 Johanson et al. Sep 1974 A
3875349 Ruegg Apr 1975 A
3946168 Preves Mar 1976 A
3975599 Johanson Aug 1976 A
4051330 Cole Sep 1977 A
4142072 Berland Feb 1979 A
4449018 Stanton May 1984 A
4456795 Saito Jun 1984 A
4622440 Slavin Nov 1986 A
4712244 Zwicker et al. Dec 1987 A
4723293 Harless Feb 1988 A
4751738 Widrow et al. Jun 1988 A
5029215 Miller, II Jul 1991 A
5214709 Ribic May 1993 A
5226087 Ono et al. Jul 1993 A
5289544 Franklin Feb 1994 A
5483599 Zagorski Jan 1996 A
5524056 Killion et al. Jun 1996 A
Continuation in Parts (1)
Number Date Country
Parent 08/763520 Dec 1996 US
Child 09/052631 US