Abstract:
A hearing aid ( 10 ) having an active occlusion reduction system ( 50 ) that counteracts occluded sounds generated within the volume ( 24 ) of the ear canal ( 20 ) that is not blocked when the hearing aid ( 10 ), or an ear piece thereof, is inserted into the ear canal ( 20 ) and an AOR transducer ( 44, 52 ) that has a flattened frequency response for low frequency portions of the occlusion sounds to enable a wide range of frequency response by the active occlusion reduction system ( 50 ). The low frequency portions of the occlusion sounds may be in the range of 10-100 Hz.

Description:
RELATED APPLICATIONS 
       [0001]    The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 61/245,052, filed Sep. 23, 2009, which is hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to a hearing aid. More particularly, the present invention relates to a hearing aid that provides occlusion reduction. 
       BACKGROUND OF THE INVENTION 
       [0003]    A conventional hearing aid typically comprises a housing that defines a generally closed cavity therein in which are arranged a power source, an input transducer, for example, a microphone, and associated amplifier for transforming external sounds into electrical signals, a signal processor for processing the transformed signals and producing signals optimized for particular hearing losses, and an output transducer, called a receiver, for transforming the processor signals into hearing-loss compensated sounds that are emitted into the ear. A hearing aid typically also comprises respective sound tubes extending from the input port of the microphone or the output port of the receiver to the housing outside surface to establish acoustic pathways between the microphone and the outside surroundings and between the receiver and the ear canal, respectively. 
         [0004]    Hearing aids may be constructed to be wearable in the ear (for example, in-the-ear (ITE); in-the-canal (ITC), and completely-in-the-canal (CIC) hearing aids). For this type of hearing aid, the ear canal is either partially or completely closed off from the surroundings outside the ear. So-called “occlusion effects” are a consequence of this occlusion of the ear canal. Specifically, there occurs a pressure build-up in the residual volume of the unblocked portion of the ear canal, defined by the hearing aid and the ear drum, from the sound emitted by the vibration of the tissue in the ear canal that is normally caused by the voice of the hearing aid user. The voice of the hearing aid user becomes amplified and hollow and dominates the sounds reaching the ear drum. This results in poor sound quality of the user&#39;s own voice as well as the other sounds reaching the ear drum. 
         [0005]    There are several ways to diminish or reduce these occlusion effects. For example, a hearing aid can be inserted, with a seal, deeply in the ear canal (the bony tissue part) so that the residual volume is not only reduced but also isolated from the portion of the ear canal (the soft tissue part) that mainly conducts a user&#39;s voice. Unfortunately, this type of insertion usually causes physical discomfort for the user since the bony tissue part of the ear canal is very sensitive to the contact with the hearing aid. 
         [0006]    More commonly, a hearing aid will be configured to have at least one ventilation channel or passage (“vent”) that extends from the portion of the hearing aid housing facing the residual volume to the portion of the hearing aid housing facing outside the ear. The vent facilitates transmission of acoustic energy from one side of the hearing aid to the other so that the ear canal is not completely blocked. The vent thus reduces occlusion effects by, first, providing a passageway to permit the body-conducted portion of a user&#39;s own voice to dissipate and, second, equalizing the atmospheric pressure between the air in the outside surroundings and in the residual volume. Disadvantageously, the vent also provides an acoustic bypass to the normal signal path via the hearing aid components (for example, the microphone, the signal processor, and the receiver). This bypass can reduce the efficiency of the hearing aid, for example, directionality or noise reduction, particularly in loud acoustic situations. Further, this bypass often gives rise to acoustical positive feedback because part of the acoustic energy produced by the receiver in the ear canal reaches, via the vent, the microphone, particularly in quiet acoustic situations that require high amplification by the hearing aid. 
         [0007]    A hearing aid vent can be formed in various ways, for example, as a thin hose or a tube extending through the hearing aid housing, or as a channel formed along the housing outside surface, or as a passage formed in an outside wall of the housing. To address occlusion effects, the vent should be configured with a relatively large diameter or cross-sectional size, especially to permit appropriate venting of the body-conducted portion of a user&#39;s own voice, which is most evident at low frequencies. In contrast, to minimize the acoustic bypass effects which also arise mostly at low frequencies, the vent should be configured with a diameter or cross-sectional size as small as possible. Normally, the vent sizing is adjusted, via various known means, during the adaptation of the hearing aid to the user so that the hearing aid is relatively free of feedback. Vent sizing is usually a compromise between hearing aid performance and user comfort. 
         [0008]    More recently, hearing aids have been constructed with active occlusion reduction (AOR) circuitry. U.S. Patent Publication 200810063228 (“Mejia, et al.”) shows a hearing aid having AOR circuitry. Hearing aids with AOR circuitry generally comprise a second input transducer (referred to as an “AOR microphone”) that is located inside the hearing aid housing facing the residual volume of the ear canal and that picks up all sounds, including occlusion sounds in the residual volume. The picked-up sounds are processed and combined with the processed external sounds picked up by the external microphone. The hearing aid having AOR circuitry treats the occlusion sounds in the residual volume as an error in a closed-loop feedback system. In particular, the hearing aid having AOR circuitry uses the occlusion sound signals to generate compensating sound signals (“occlusion-negating sounds”) that are projected by the receiver into the residual volume (which also projects the hearing-loss compensated sounds). The occlusion sounds in the residual volume get compensated as they combine with occlusion-negating sounds that the hearing aid generates. A hearing aid having AOR circuitry is typically still configured to have a conventional vent as well, with comparatively small dimensions, not to address occlusion reduction but to provide frequency response stability and balance barometric pressure differentials. 
         [0009]    Due to the limited bandwidth of hearing aid AOR transducers (specifically, the receiver and the AOR microphone) as well as processing delays, one adverse effect of a hearing aid having AOR circuitry is that the negative feedback of the closed-loop AOR system at 100-1000 Hz turns into positive feedback below 100 Hz, creating a gain boost between 10 and 100 Hz. A well-tuned and optimized hearing aid having AOR circuitry typically has a resonance peak of 5-10 dB between 10 and 100 Hz. As a result, sound in the frequency range of the resonance peak which is entering the hearing aid is amplified. This low frequency amplification is perceived as a very annoying artifact to the user. Hearing aid signal processing offers no suitable counteraction for the amplification of the entering low frequency sound because frequencies up to 200 Hz are passing through a typical hearing aid vent having a 1 mm diameter. 
       SUMMARY OF THE INVENTION 
       [0010]    The above problems are obviated by the present invention which provides an active occlusion reduction system that counteracts occlusion sounds generated within the volume of the ear canal that is not blocked when the hearing aid, or an ear piece thereof, is inserted into the ear canal; and an AOR transducer that has a flattened frequency response for low frequency portions of the occlusion sounds to enable a wide range of frequency response by the active occlusion reduction system. The AOR transducer may diminish the artifacts resulting from low frequency amplification caused by the active occlusion reduction system. Further, the low frequency portions of the occlusion sounds may be in the range of 10-100 Hz. 
         [0011]    Alternatively, the present invention provides an external microphone that converts ambient sounds originating outside the ear into first representative electrical signals; an internal microphone that converts sounds originating inside the ear canal, including at least occlusion sounds, into second representative electrical signals; a signal processing system operatively coupled between the external microphone and the internal microphone that modifies and combines the first and second electrical signals to generate third representative electrical signals; and a receiver that converts the third representative electrical signals into hearing-loss compensating sounds and occlusion-negating sounds and projects the hearing-loss compensating sounds and occlusion-negating sounds into the ear canal, at least one of the receiver and the internal microphone configured with a vent into the volume of the hearing aid. Either the receiver and internal microphone, or both, may comprise a vent opening formed between the rear volume of the receiver and the closed cavity of the hearing aid. The vent opening of the receiver may be formed with a diameter within the range of 0.01 to 0.05 mm and a length of approximately 0.2 mm whereas the vent opening of the internal microphone may be formed with a diameter within the range of 0.01 to 0.03 mm and a length of approximately 0.015 mm. Alternatively, the vent opening of the receiver or the internal microphone, or both, may be formed with a diameter within the range of 0.5 to 1 mm with the transducer further comprising an acoustic resistor adapted to overlie the vent opening. Alternatively, for either the receiver or internal microphone, or both, the vent opening may be formed as an aperture in the portion of the hearing aid defining the rear volume and a thin tube extending from the aperture into the closed cavity of the hearing aid. 
         [0012]    Alternatively, the present invention provides an active occlusion reduction system having at least one vented AOR transducer. The AOR transducer may comprise a housing; a generally closed volume defined by the housing in which are arranged transducer components; a sound inlet/outlet port that is adapted to receive or project acoustic signals, respectively; a portion of the housing that defines a rear volume of the transducer; and a vent opening formed in the housing between the rear volume and a closed cavity of the hearing aid. The AOR transducer may further comprise an acoustic resistor adapted to overlie the vent opening. Alternatively, the AOR transducer may further comprise a thin tube extending from the vent opening into the closed cavity of the hearing aid. 
         [0013]    The present invention may also provide an active occlusion reduction system, comprising a vented in-the-ear transducer. The present invention may also provide an active occlusion reduction system, comprising a receiver; an AOR microphone, at least one of the receiver and the AOR microphone being vented; and a closed-loop feedback system operatively coupled between the receiver and the AOR microphone that enables the receiver to output occlusion-negating sounds to compensate for occlusion sounds received by the AOR microphone. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, and to the accompanying drawings, wherein: 
           [0015]      FIG. 1  is a diagrammatic representation of a hearing aid having active occlusion reduction (AOR) circuitry constructed according to the present invention; 
           [0016]      FIG. 2  is a schematic representation of a transducer of a conventional hearing aid having AOR circuitry; 
           [0017]      FIG. 3   a, b, c  are alternative schematic representations of an AOR transducer of the hearing aid of  FIG. 1 ; 
           [0018]      FIG. 4  shows a simulated frequency response of a conventional AOR microphone and an AOR microphone of the hearing aid of  FIG. 1 ; 
           [0019]      FIG. 5  shows a simulated frequency response of a conventional receiver and a receiver of the hearing aid of  FIG. 1 ; 
           [0020]      FIG. 6  shows amplitude and phase responses of simulated transducer transfer functions of a conventional hearing aid having AOR circuitry and the hearing aid of  FIG. 1 ; and 
           [0021]      FIG. 7  shows simulated closed loop responses of a conventional hearing aid without AOR circuitry; a conventional hearing aid having AOR circuitry; and the hearing aid of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  is a diagrammatic representation of a hearing aid  10  constructed according to the present invention. The hearing aid  10  comprises a housing or shell  12  that defines a generally closed cavity  14  therein in which are arranged the hearing aid components. The hearing aid  10  is configured to be snugly fit in a user&#39;s ear  16  so that one end of the aid  10  faces the outside surroundings (faceplate  18 ); the middle portion of the aid  10  rests in and blocks the ear canal  20  along soft ear tissue  22 ; and the other end of the aid  10  faces the residual volume  26  of the unblocked portion of the ear canal  20  defined by the housing  12  of the hearing aid  10  and the ear drum  28 . The residual volume  24  typically encompasses soft ear tissue  22  as well as bony tissue  24  of the ear canal  20 . The hearing aid  10  is made of conventional materials and may be manufactured by various methods. The hearing aid  10  also may be configured in various forms. 
         [0023]    The hearing aid  10  components include but are not limited to a power source (not shown), typically a battery, and an input transducer  42 , for example, a microphone. These components are conventional and well known, and can be operatively connected in well-known manners. The input transducer  42  is also referred to as an external microphone and serves to receive acoustic signals, i.e., sounds, from the outside surroundings and convert the sounds into electrical signals for further processing by the other components of the aid  10 . The external microphone  42  is arranged within the aid cavity  14  so that its sound input port  42   a  is adjacent to and operatively connected with an opening in the faceplate  18 . The aid  10  may also include a microphone sound tube  42   b  that may be integrally formed in the housing  12  or the external microphone  42  and that extends from the input port  42   a  of the external microphone  42  to the outside surface of the faceplate  18  to establish an acoustic pathway between the external microphone  42  and the outside surroundings. 
         [0024]    The hearing aid  10  components further include an output transducer  44 , referred to as a receiver, and signal processing circuitry  46 . The signal processing circuitry  46  includes but is not limited to an amplifier  46   a  that amplifies the converted signals from the external microphone  42  and a signal processor  46   b  that modifies the converted signals, for example, dampens and/or filters interference signals. As described below in more detail, a summation circuit  56  of active occlusion reduction (AOR) circuitry  50  is connected to the signal path of the signal processing circuitry  46  so that the converted signals are first input into the summation circuit  56  and the summation circuit  56  output is modified by the signal processor  46   b . The receiver  44  serves to receive the processed signals from the signal processing circuitry  46 , convert the signals into acoustic signals, and project the acoustic signals into the residual volume  26  of the ear canal  20 . The receiver  44  is arranged within the aid cavity  14  so that its sound output port  44   a  is adjacent to and operatively connected with an opening in the housing  12  facing the residual volume  26 . The aid  10  may also include a receiver sound tube  44   b  that may be integrally formed in the housing  12  or the receiver  44  and that extends from the output port  44   a  of the receiver  44  to the outside surface of the housing  12  to establish an acoustic pathway between the receiver  44  and the residual volume  26 . 
         [0025]    The hearing aid  10  components further include active occlusion reduction (AOR) circuitry  50 . The AOR circuitry  50  includes a second input transducer  52 , for example, a microphone. The second input transducer  52  is also referred to as an AOR microphone and serves to receive acoustic signals, i.e., sounds, from the residual volume  26  and convert the sounds into electrical signals for further processing by an AOR microphone processor  54  of the AOR circuitry  50 . The AOR microphone processor  54  serves to modify the converted signals. The summation circuit  56  of the AOR circuitry  50  receives the processed signals from the AOR microphone processor  54  and the converted signals from the amplifier  46   a . The signal processor  46   b  receives and modifies the summation circuit  56  output. The receiver  44  receives the processed signals from the signal processor  46   b , converts the signals into acoustic signals, and projects the acoustic signals into the residual volume  26  of the ear canal  20 . Alternatively, the summation circuit  56  may be connected to the signal path of the signal processing circuitry  46  to receive the processed signals from the signal processor  46   b , rather than the converted signals from the amplifier  46   a , and the processed signals from the AOR microphone processor  54  and to output a combined signal to the receiver  44 . The receiver  44 , the signal processing circuitry  46 , and the AOR circuitry  50  are conventional components and can be operatively connected in various well-known manners. 
         [0026]    Similar to the other transducers  42 ,  44 , the AOR microphone  52  is arranged within the aid cavity  14  so that its sound input port  52   a  is adjacent to and operatively connected with an opening in the housing  12  facing the residual volume  26 . The aid  10  may also include an AOR microphone sound tube  52   b  that may be integrally formed in the housing  12  or the AOR microphone  52  and that extends from the input port  52   a  of the AOR microphone  52  to the outside surface of the housing  12  to establish an acoustic pathway between the AOR microphone  52  and the residual volume  26 . As described in detail with reference to  FIGS. 3-7 , either the receiver  44  or the AOR microphone  52 , or both, are configured to assist the AOR circuitry  50  in achieving occlusion reduction in accordance with the present invention. 
         [0027]    To achieve barometric pressure relief, the hearing aid  10  may include a very small-sized vent  55  in the housing  12  of the hearing aid  10 . The vent  55  can be formed in various ways, for example, as a thin hose or a tube extending through the housing  12 , or as a channel formed along the housing  12  outside surface, or as a passage formed in an outside wall of the housing  12 . The vent  55  facilitates transmission of acoustic energy from one side of the hearing aid  10  to the other so that the ear canal  20  is not completely blocked. 
         [0028]      FIG. 2  is a schematic representation of a transducer  70  of a conventional hearing aid having active occlusion reduction circuitry. The transducer  70  comprises a housing  71  that defines a generally closed volume  72  therein in which are arranged the transducer components (not shown). The housing  71  is configured to have a sound inlet port (for an external microphone or AOR microphone) or sound outlet port  74  (for a receiver) that is adapted to receive acoustic signals from outside of the transducer  70  or project acoustic signals to outside of the transducer  70 , respectively. The transducer volume  72  is separated into two volumes  72   a ,  72   b  by a membrane  76 , a front volume  72   a  containing the pathway to the sound inlet/outlet port  74  and to the transducer components and a rear volume  72   b  defined by a portion  78  of the housing  71  away from the sound inlet/outlet port  74 . The membrane  76  has an aperture  76   a  formed there through that provides a pathway between the two volumes  72   a ,  72   b  and provides pressure relief between the two volumes. The housing of the transducer  70  may be configured in various known forms. 
         [0029]      FIGS. 3   a, b, c  are alternative schematic representations of the receiver  44  or the AOR microphone  52 , or both, of the hearing aid  10 . Like the transducer  70  of a conventional hearing aid, the receiver  44  or AOR microphone  52 , or both, comprises a housing  81  that defines a generally closed volume  82  therein in which are arranged the transducer components (not shown). The housing  81  is configured to have a sound inlet port (for the internal microphone  52 ) or outlet port  84  (for the receiver  44 ) that is adapted to receive or project acoustic signals, respectively. The transducer volume  82  is separated into two volumes  82   a ,  82   b  by a closed membrane  86 , a front volume  82   a  containing the pathway to the sound inlet/outlet port  84  and to the transducer components and a rear volume  82   b  defined by a portion  88  of the housing  81  of the receiver  44  or AOR microphone  52  away from the sound inlet/outlet port  84 . In a first embodiment shown in  FIG. 3   a , the housing  81  has a vent opening  89  formed in the rear volume  82   b . The vent opening  89  forms a pathway to the closed cavity  14  of the housing  12 . As a practical matter, the vent opening  89  for the receiver  44  can be formed in the range 0.01-0.05 mm diameter×0.2 mm length and for the AOR microphone  52  can be formed in the range 0.01-0.03 mm diameter×0.015 mm length. 
         [0030]    In a second embodiment shown in  FIG. 3   b , the housing  81  has a vent opening  89  formed in the rear volume  82   b  as well. In addition, the vent opening  89  can be covered by an acoustic resistor  92 . In such case, the vent opening  88  formed is similar to that of the first embodiment shown in  FIG. 3   a  but it can be formed with larger dimensions. As a practical matter, the vent opening  89  for the receiver  44  and for the AOR microphone  52  can both be formed in the range 0.5-1 mm diameter. The value of the acoustic resistor can be 1×10 10  mks acoustic ohms±50% for the receiver  44  and 1×10 10  mks acoustic ohms±50% for the AOR microphone  52 , optimized for the particular transducer. In a third embodiment shown in  FIG. 3   c , the housing  81  has a vent opening  89  formed in the rear volume  82   b  as an aperture  93   a  with an attached thin tube  93   b  extending from the aperture  93   a  into the closed cavity  14  of the aid housing  12 . The tube  93   b  may be formed integral with the rear portion  88  of the transducer housing  81  or as a separately attached element. 
         [0031]    In operation, the external microphone  42  picks up sounds from the outside surroundings of the ear  16  via its sound input port  42   a . The external microphone  42  converts the sounds into electrical signals that are passed to the signal processing circuitry  46  of the aid  10  and, in particular, the amplifier  46   a  which amplifies the electrical signals. The converted signals are then passed through a summation circuit  52  of the AOR circuitry  30  which passes its output to the signal processor  46   b . The signal processor  46   b  modifies the received signals, for example, by dampening and/or filtering interference, and passes processed signals to the receiver  44 . The receiver  44  converts the processed signals into acoustic signals and projects, via its sound outlet port  44   a , the acoustic signals into the residual volume  26  of the ear canal  20 . 
         [0032]    At the same time and separately, the AOR microphone  52  picks up acoustic signals from the residual volume  26  via its sound input port  52   a  and converts the acoustic signals into electrical signals that are passed to the AOR microphone processor  54 . The picked-up acoustic signals include both the acoustic signals projected by the receiver  44  and any occlusion sounds in the residual volume  24  from various sources, including body-conducted sounds. The AOR microphone processor  54  modifies the converted signals, for example, by amplifying and/or filtering. The summation circuit  52  combines the processed internal sounds with the converted signals outputted from the external microphone  42  and the associated amplifier  46   a . The signal processor  46   b  receives and modifies the summation circuit  56  output and the receiver  44  converts the processed signals from the signal processor  46   b  into acoustic signals and projects the acoustic signals into the residual volume  26 . Alternatively, the various components may be configured so that the summation circuit  56  is connected to the signal path of the signal processing circuitry  46  to receive the processed signals from the signal processor  46   b , rather than the converted signals from the amplifier  46   a , and the processed signals from the AOR microphone processor  54  and to output a combined signal to the receiver  44 . 
         [0033]    The AOR circuitry  50  treats an occlusion sound in the residual volume  24  as an error in a closed-loop feedback system and, in particular, uses the occlusion sounds to generate compensating sound signals (“occlusion-negating sounds”) that are projected by the receiver  44  into the residual volume  24  (which also projects the hearing-loss compensated sounds). As a result, the user hears only, or primarily, hearing-loss compensated sounds (representing sounds from the outside surroundings) since any occlusion sounds get compensated as they combine with occlusion-negating sounds that the aid  10  generates. 
         [0034]    As mentioned above, using a conventional hearing aid with AOR circuitry has adverse effects and does not provide a wide range of low frequency response. The limited bandwidth of the AOR transducers (receiver and AOR microphone), for example, like the one shown if  FIG. 2 , is a particular problem. The configuration of the AOR transducers, especially the aperture  76   a  of the membrane  76 , creates a roll-off of the low frequency response of the transducer (i.e., the low frequency response is not flat and attenuates at frequencies lower than 100 Hz). The present invention, in contrast, provides for AOR transducers  44 ,  52  that generate a more flat response at those same low frequencies. As the membrane  86  vibrates, the sound pressure in the closed volume  82  of the transducer  44 ,  52 , either coming in as an input signal or going out as an output signal, is leaked to the closed cavity  14  of the housing  12  via the vent opening  89  and gets equalized. The vent opening  89  acts as an acoustic equivalent of a resistor and inductor combination and the closed cavity  14  of the housing  12  acts as a compliance. At low frequencies, the membrane  86  vibration (and thus the transducer  44 ,  52  response) would normally be diminished but the vent opening  89  and the closed cavity  14  permits the response to be flattened. 
         [0035]    The responses of the receiver  44  and/or the AOR microphone  52 , as well as the overall response of the AOR circuitry  50 , is flatter and smoother than without the vented AOR transducers  44 ,  52  and the Q-factor of the low-frequency resonance AOR system becomes low. The low frequency amplification effect (and resulting artifacts) is strongly decreased and shifted to the less-audible frequency range and may even be avoided. 
         [0036]    The AOR transducers  44 ,  52  provided by the present invention have greatly improved low-frequency responses and the hearing aid  10  having AOR circuitry  50  achieves better occlusion reduction in a wider frequency range. This is graphically seen in  FIGS. 4-7 .  FIG. 4  shows a simulated frequency response of a conventional AOR microphone and an AOR microphone  52  of the aid  10  constructed in accordance with the present invention. The simulation is done without a conventional vent in the housing  12  of the aid  10 .  FIG. 5  shows a simulated frequency response of a conventional receiver and a receiver  44  of the aid  10  constructed in accordance with the present invention. The simulation is done without a conventional vent in the housing  12  of the aid  10 . 
         [0037]      FIG. 6  shows amplitude and phase responses of simulated transducer transfer functions of a hearing aid having AOR circuitry with a) conventional transducers (receiver and AOR microphone); b) a receiver  44  of the aid  10  constructed in accordance with the present invention and a conventional AOR microphone; and c) both AOR transducers of the aid  10  constructed in accordance with the present invention (the receiver  44  and the AOR microphone  52 ). The simulations are done with a conventional vent, 1 mm in diameter and 1.5 mm in length, in the housing of the hearing aid.  FIG. 7  shows simulated closed loop responses of a hearing aid having a) no AOR circuitry; b) AOR circuitry with conventional AOR transducers (receiver and AOR microphone); and c) AOR circuitry with both AOR transducers of the aid  10  constructed in accordance with the present invention (the receiver  44  and the AOR microphone  52 ). Compared to the performance of the hearing aid having AOR circuitry with conventional AOR transducers, the stability of the hearing aid  10  having AOR circuitry in accordance with the present invention and its sensitivity to low-frequency disturbances is greatly improved using vented AOR transducers  44 ,  52 . 
         [0038]    Other modifications are possible within the scope of the invention. For example, the signal processing circuitry  46  and the AOR circuitry  50  are conventional and well known components, and can be configured and operatively connected in well-known ways other than those described above. Further, the hearing aid  10  components may be analog or digital components, or mixed, as preferred. 
         [0039]    Importantly, the hearing aid  10  may be a behind-the-ear (BTE) type with an earmold worn in the ear or any other acoustic-controlling device that either partially or completely closes off the ear canal from the surroundings outside the ear, for example, an in-the-ear headset or a sound protector. A BTE hearing aid is commonly used by a user with severe hearing loss who requires high-power amplification. A BTE hearing aid separates the receiver from the main body of the aid and may mount it directly in an earmold that is snugly fit into the user&#39;s ear canal. A BTE hearing aid having AOR circuitry also has an AOR microphone that may be mounted directly in the earmold. The present invention provides improved occlusion reduction in such cases.