Abstract:
An apparatus related to earmolds with venting configurations designed to relieve the occlusion effect. Various designs provide multiple vents allow residual ear canal air volume to vent to and from air outside the ear and the earmold. In various designs, the earmold includes one vent between the residual ear canal air volume and a volume of air internal to the earmold. A second vent provides passage of air internal to the earmold and air external to the ear and the inserted earmold when worn by a user.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/895,679 filed Mar. 19, 2007, which is incorporated herein by reference and made a part hereof. 
    
    
     FIELD 
     This application relates generally to hearing assistance systems and in particular to method and apparatus for venting hearing assistance systems. 
     BACKGROUND 
     For moderate and high-loss hearing aid users with vented earmolds, vent dimensions are typically chosen to provide an acceptable balance between acoustic feedback and the occlusion effect. Acoustic feedback occurs when amplified sound propagates from the ear canal, outward through the vent, and into the hearing aid microphone inlet thereby causing an audible and annoying whistle to the user. In general, this acoustic feedback whistling occurs at higher frequencies, typically above 1 kHz. The occlusion effect can be described as an unnatural perception of one&#39;s own voice, and occurs when a hearing aid user&#39;s earmold is insufficiently occluded thereby causing an accentuation of low-frequency speech energy in the ear canal that is typically perceived as a boominess. Although a wider, more open vent has been successful in prior art in providing the user with a more natural perception of their own voice, such a venting scheme makes the hearing aid more susceptible to acoustic feedback. 
     Thus, there is a need in the art for a venting scheme that allows the low-frequency speech energy to escape the ear canal more readily and attenuates acoustic feedback at higher frequencies. Compared to a single vent, dual vents configured as an acoustic filter address both these goals more robustly. 
     SUMMARY 
     The above-mentioned problems and others not expressly discussed herein are addressed by the present subject matter and will be understood by reading and studying this specification. 
     The present subject matter presents apparatus related to earmolds with venting configurations designed to relieve the occlusion effect. In various embodiments, multiple vents allow residual ear canal air volume to vent to and from air outside the ear and the earmold. In various embodiments, the earmold includes one vent between the residual ear canal air volume and a volume of air internal to the earmold. A second vent provides passage of air internal to the earmold and air external to the ear and the inserted earmold when properly worn by a user. According to various embodiments, an acoustical passage of the first vent and an acoustical passage of the second vent are elongate. The first and second vents are not in geometric alignment, or off-axis, in various embodiments. Various earmold embodiments include circular earmold openings for the vents. Various embodiments include noncircular earmold openings for the vents. Various embodiments include a wireless receiver in the earmold. Various embodiments include a sound tube between the earmold and a behind-the-ear hearing assistance device. Various embodiments include a receiver in the earmold wired to a behind-the-ear hearing assistance device. Various embodiments include hearing assistance electronics disposed within the earmold and vent openings in the earmold positioned to reduce acoustical feedback. 
     This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. The scope of the present invention is defined by the appended claims and their legal equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are illustrated by way of example in the figures of the accompanying drawings. Such embodiments are demonstrative and not intended to be exhaustive or exclusive embodiments of the present subject matter. 
         FIG. 1A  shows a side cross-sectional view of an in-the-ear hearing assistance device according to the prior art earmold venting. 
         FIG. 1B  shows an acoustical impedance lumped element equivalent circuit analog for the device shown in  FIG. 1A . 
         FIG. 1C  compares measured results to modeled results for the device shown in  FIG. 1A . 
         FIG. 2A  shows a side cross-sectional view of an in-the-ear hearing assistance device according to one embodiment of the present subject matter. 
         FIG. 2B  shows a view of the faceplate of the hearing assistance device of  FIG. 2A  according to one embodiment of the present subject matter. 
         FIG. 2C  shows the interior end of the hearing assistance device of  FIG. 2A  according to one embodiment of the present subject matter. 
         FIG. 2D  shows an acoustical impedance lumped element equivalent circuit analog for the device shown in  FIG. 2A . 
         FIG. 2E  compares measured results to modeled results for the device shown in  FIG. 2A . 
         FIG. 3A  shows a side cross-sectional view of a custom or standard earmold for a behind-the-ear hearing assistance device according to one embodiment of the present subject matter. 
         FIG. 3B  shows a view of the faceplate of the hearing assistance device of  FIG. 3A  according to one embodiment of the present subject matter. 
         FIG. 3C  shows the interior end of the hearing assistance device of  FIG. 3A  according to one embodiment of the present subject matter. 
         FIG. 4A  shows one embodiment of a faceplate of a hearing assistance device with a noncircular vent shape to demonstrate that vent shapes may vary without departing from the scope of the present subject matter. 
         FIG. 4B  shows one embodiment of an interior end of a hearing assistance device with a noncircular vent shape to demonstrate that vent shapes may vary without departing from the scope of the present subject matter. 
         FIG. 5  demonstrates one example of a behind-the-ear hearing assistance device in wired electrical communications with a dual vented earmold having a receiver according to one embodiment of the present subject matter. 
         FIG. 6  demonstrates one example of a behind-the-ear hearing assistance device in wireless electrical communications with a dual vented earmold having a receiver according to one embodiment of the present subject matter. 
         FIG. 7  shows an embodiment with curved dual vents. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description of the present invention refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is demonstrative and therefore not exhaustive, and the scope of the present subject matter is defined by the appended claims and their legal equivalents. 
       FIG. 1A  shows a side cross-sectional view of an in-the-ear (ITE) hearing assistance device  101  according to the prior art. Device  101  includes a faceplate  100  which includes a vent  120  functioning as an acoustical passage that connects the outside air medium to the interior ear canal  102  with residual air volume  103 . Faceplate  100  also includes acoustical inlet  112  for microphone  114 , which is connected to electronics  116  and receiver  118 , which functions as a loudspeaker or earphone that generates acoustic pressure waves within the residual ear canal air volume  103 . The pressure waves propagate through the vent  120  and radiate out into the air medium. Using an acoustical impedance equivalent circuit analog as shown in  FIG. 1B  in which pressure is the potential quantity and volume velocity is the flux quantity, the vent  120  behaves as an inertance and is modeled as an inductor M whose value is directly proportional to the product of the ambient air density and the length of the vent, and inversely proportional to the surface area of the vent. Using the same analog, the exterior air medium behaves primarily as a radiation resistance and is modeled as a resistor R whose value is directly proportional to the product of the ambient air density and the square of the radial frequency, and inversely proportional to the product of a constant and the speed of sound. The constant depends upon the exterior vent&#39;s boundary conditions and is typically set at 2π or 4π, depending on a half- or full-space steridian field. The acoustical feedback venting gain (AFVG) can be computed from the equivalent circuit analog using standard voltage division techniques. Assuming receiver  118  is driven to produce a frequency-independent constant pressure P g  of 1 Pascal at acoustical outlet  122 , the AFVG is simply the potential P r  across resistor R and is show in  FIG. 1C  together with the measured data for a cylindrical vent of 16 mm length and 1.5 mm diameter. The data show how the venting configuration of device  101  attenuates low and mid frequency acoustic energy effectively while allowing high frequency acoustic energy to radiate outward much more easily. It should be noted that the peak at approximately 10 kHz in the AFVG is due solely to longitudinal standing waves in vent  120 . It should also be noted that an acoustical transmission line equivalent analog could be used to model the AFVG. 
       FIG. 2A  shows a side cross-sectional view of an ITE hearing assistance device  201  according to one embodiment of the present subject matter. 
     The ITE device  201  of  FIG. 2A  includes a faceplate  200  and an interior end  260 . The interior end  260  of device  201  includes a first vent  230  having an acoustical passage  231  of length  240  that connects the earmold&#39;s internal air volume  290  to ear canal  102  having its own residual air volume  103 . The acoustical passage  231  of the first vent  230  is elongate, in an embodiment. Ear canal  102  will differ in shape and size from person to person, so ITE  201  can be custom fitted to the user&#39;s ear to provide a comfortable fit and reduce air gaps between the device and the ear canal. The faceplate  200  of ITE device  201  includes an acoustical inlet  112  for microphone  114  and a second vent  270  having an acoustical passage  271  of length  220  which connects the exterior air medium to the earmold&#39;s internal air volume  290 . The acoustical passage  271  of the second vent  270  is elongate, in an embodiment. In various embodiments, the internal air volume  290  envelopes microphone  114 , electronics  116 , and receiver  118 . With this approach, sound waves are detected by microphone  114  via acoustical inlet  112 ; an analogous electrical signal is sent to electronics  116 , processed, amplified, and delivered to receiver  118 . Receiver  118  is adapted to transmit sound waves to the ear of a user through acoustical outlet  122 . It is understood that the electronics  116  may include known and novel signal processing electronics configurations and combinations for use in hearing assistance devices. Different electronics  116  may be employed without departing from the scope of the present subject matter. Such electronics may include, but are not limited to, combinations of components such as amplifiers, multi-band compressors, noise reduction, acoustic feedback reduction, telecoil, radio frequency communications, power, power conservation, memory, and various forms of digital and analog signal processing electronics. 
     The configurations, lengths, and air volumes of device  201  are selected to reduce the acoustical feedback gain (AFG) at high frequencies. The AFG differs from the AFVG in that the propagation path from the second vent  271  to the microphone inlet  112  is included in the AFG. The AFG is defined as the ratio of the sound pressure level detected by microphone  114  at acoustical inlet  112  to the sound pressure level produced by receiver  118  at acoustical outlet  122 . 
       FIG. 2B  shows the layout of a faceplate  200  demonstrating one example for placement of acoustical inlet  112  and the second vent  270  having surface area S 2 . It is understood that other shapes of acoustical inlet  112  and surface areas S 2  of the second vent  270  may be employed without departing from the scope of the present subject matter. Some such examples are shown in  FIG. 4A . It is also understood that the placement of acoustical inlet  112  relative to the second vent  270  may vary without departing from the scope of the present subject matter. To reduce the acoustical feedback gain, it may be advantageous to separate them as far as possible to reduce acoustic coupling between the microphone acoustical inlet  112  and the second vent  270 . 
       FIG. 2C  depicts a view of the interior (ear canal) end  260  of the hearing assistance device of  FIG. 2A  according to one embodiment of the present subject matter. A receiver can deliver sound via acoustical outlet  122  to the ear canal of a user. The first vent  230  having surface area S 1  connects the device&#39;s internal air volume with the residual air volume  103  of the user&#39;s ear canal. It is understood that other shapes of acoustical outlet  122  and surface area S 1  of the first vent  230  may be employed without departing from the scope of the present subject matter. Some such examples are shown in  FIG. 4B . It is also understood that the relative placement of acoustical outlet  122  to the first vent  230  may vary without departing from the scope of the present subject matter. It may be advantageous to reduce AFG by separating them as far as possible to reduce acoustic coupling between the receiver acoustical outlet  122  and the first vent  230 . 
     The dual vents are not in geometric alignment, or off-axis, in an embodiment. In some embodiments, the dual vents are realized as straight vents with a constant cross sectional area. In some embodiments, the dual vents are realized as twisted or curved as required by the internal geometry and position of transducers. In one embodiment, the first vent is adjacent to the second vent. In varying embodiments, the two vents are fashioned in a swirling pattern about each other.  FIG. 7  shows an embodiment in which the internal air volume  790  is connected to a first vent  730  via opening  731  and connected a second vent  770  via opening  771 . 
     It is understood that the first vent  230  and the second vent  270  shown in  FIG. 2A  are not necessarily drawn to scale. Furthermore, it is understood that the vent geometries may be varied to achieve desired effects and not depart from the scope of the present subject matter. Some examples include, but are not limited to, the vents being adapted to have varying widths, structure, curvature, and relative placement without departing from the scope of the present subject matter. Similarly, a variable vent could be inserted into either of the two vents to achieve the desired filtering effect. These plugs, typically used by dispensers and sometimes referred to as “vari-vents” could be chosen and inserted during a patient&#39;s fitting session so as to allow custom venting. It is also understood that the internal electronics  116 , microphone  114 , and receiver  118  are not intended to necessarily be drawn to scale. 
     During normal operation of ITE device  201 , the pressure waves from receiver  118  within residual air volume  103  propagate through the first vent  230 , radiate into internal air volume  290 , propagate through the second vent  270 , and radiate out into the air medium. Using an acoustical impedance equivalent circuit analog as shown in  FIG. 2D  in which pressure is the potential quantity and volume velocity is the flux quantity, the first vent  230  and the second vent  270  behave as inertances that are modeled as inductors M 1  and M 2 , respectively, whose values are directly proportional to the product of the ambient air density and the length of the vent, and inversely proportional to the surface area of the vent. The internal air volume  290  behaves as an acoustical capacitance C whose approximate value is directly proportional to the air volume and inversely proportional to the product of the air medium&#39;s ambient density and its speed of sound squared. Using the same analog, the exterior air medium behaves primarily as a radiation resistance and is modeled as a resistor R whose value is directly proportional to the product of the ambient air density and the square of the radial frequency, and inversely proportional to the product of a constant and the speed of sound. The constant depends upon the boundary conditions of the second vent  270  and is typically set, for convenience, to 2π or 4π, depending on a half- or full-space approximated steridian freefield. The acoustical feedback venting gain (AFVG) can be computed from the equivalent circuit analog using standard voltage division techniques. Assuming receiver  118  is driven to produce a frequency-independent constant pressure P g  of 1 Pascal at acoustical outlet  122 , the AFVG is simply the potential across resistor R and is shown in  FIG. 2E  together with the measured data for a first cylindrical vent of 12 mm length, 1 mm diameter, an internal air volume  290  of 0.7 cc, and a second cylindrical vent of 6 mm length, 1 mm diameter. The data show how the venting configuration of device  201  allows acoustic energy in the 550 Hz region to pass more efficiently than a the single vent ITE device  101  while dramatically attenuating acoustic energy above 1 kHz. It should be noted that the peak at approximately 550 Hz in the AFVG is due to the judicious choice of internal air volume, vent lengths. It should also be noted that an acoustical transmission line equivalent analog could be used to model the AFVG of ITE device  201 . 
     It is understood that  FIG. 2A  is intended to demonstrate one application of the present subject matter and that other applications are provided.  FIG. 2A  relates to the use of the present dual vent design in an ITE (in-the-ear) hearing assistance device. However, it is understood that the dual vent design of the present subject matter may be used in other devices and applications. One example is the earmold of a BTE (behind-the-ear) hearing assistance device, as demonstrated by  FIG. 3A . Other hearing assistance devices may employ the present dual vent design without departing from the scope of the present subject matter. 
     The embodiment of  FIG. 3A  provides a way to transmit sound to the interior end  360  of an earmold device  301  using a BTE (behind-the-ear) hearing assistance device  314 . The BTE  314  delivers sound through sound tube  318  and hole  322  to the residual ear canal air volume  103  at the interior end of earmold device  301 . The remaining operation of the device is largely the same as set forth for  FIG. 2A , except that the BTE  314  includes the microphone and electronics and the earmold  301  contains the sound tube  318 . The faceplate  300  of device  301  includes a hole  312  for sound tube  318  and a second vent  370  having an acoustical passage  371  of length  320  which connects the exterior air medium to the earmold&#39;s internal air volume  390 . The interior end  360  of device  301  includes a first vent  330  having an acoustical passage  331  of length  340  that connects the earmold&#39;s internal air volume  390  to ear canal  302  the residual air volume  103 . According to various embodiments, the acoustical passage  331  of the first vent  330  and the acoustical passage  371  of the second vent  370  are elongate. The first and second vents are not in geometric alignment, or off-axis, in an embodiment. 
       FIG. 3B  shows the layout of a faceplate  300  demonstrating one example for placement of acoustical inlet  312  and the second vent  370  having surface area S 2 . It is understood that other shapes of acoustical inlet  312  and surface areas S 2  of the second vent  370  may be employed without departing from the scope of the present subject matter. Some such examples are shown in  FIG. 4A . It is also understood that the placement of acoustical inlet  312  relative to the second vent  370  may vary without departing from the scope of the present subject matter. To reduce the acoustical feedback gain, it may be advantageous to separate them as far as possible to reduce acoustic coupling between the microphone acoustical inlet  312  and the second vent  370 . 
       FIG. 3C  depicts a view of the interior (ear canal) end  360  of the hearing assistance device of  FIG. 3A  according to one embodiment of the present subject matter. A receiver can deliver sound via acoustical outlet  322  to the ear canal of a user. The first vent  330  having surface area S 1  connects the device&#39;s internal air volume with the residual air volume of the user&#39;s ear canal. It is understood that other shapes of acoustical outlet  322  and surface area S 1  of the first vent  330  may be employed without departing from the scope of the present subject matter. 
       FIG. 4A  shows the layout of a faceplate  400  demonstrating one example for placement of an acoustical inlet  412  and a noncircular second vent  470 .  FIG. 4B  shows the layout of the interior (ear canal) end  460  demonstrating one example for placement of an acoustical outlet  422  and a noncircular first vent  480 . 
     Other embodiments are possible without departing from the scope of the present subject matter. For instance, in one embodiment, such as the one demonstrated by  FIG. 5 , a BTE  514  provides an electronic signal to an earmold having a receiver  118 . This variation includes a wired connection  518  for providing the acoustic signals to the earmold  501 . 
     In one embodiment, such as the one demonstrated in  FIG. 6 , a wireless approach is employed, such that the earmold  601  includes a wireless electronics for receiving sound from a BTE  614  or other signal source  616  having a wireless communications module. Such wireless communications are possible by fitting the earmold with wireless electronics  626 , receiver electronics  118  and a power supply. In bidirectional applications, it may be advantageous to fit the earmold with a microphone to receive sound using the earmold. In various applications, the BTE  614  includes a microphone. In various applications the signal source  616  includes a microphone. It is understood that many variations are possible without departing from the present subject matter. 
     It is understood that a custom earmold may be employed in various embodiments. It is understood that a standard earmold may be employed in various embodiments. 
     Several approaches to determining the dimensions of the earmold and vents are possible. Some typical limits on the values can be determined. The length L 2  of the second vent can vary from the thickness of the faceplate at its thinnest region to about 4 centimeters. The surface area of the second vent can vary from about 0.0003 cm squared to about 0.30 cm squared. It is noted that the surface area may vary along the length of the second vent. The length L 1  of the first vent can vary from the thinnest portion of the shell at the interior (ear canal) side to about 4 cm. The surface area of the first vent can vary from about 0.0003 cm squared to about 0.30 cm squared. It is noted that the surface area may vary along the length of the ear canal vent. The internal volume of the shell can vary from about 0.1 cubic centimeters to about 5 cubic centimeters. 
     The vents of the present subject matter can be formed using methods including, but not limited to, drilling, computer aided manufacturing, stereo lithography, and any other form of three dimensional manufacturing. In an embodiment, the device of the present subject matter (such as  201  in  FIG. 2A ) is formed using a stereo lithography apparatus (SLA). Forming the device using an SLA includes creating a three dimensional model of the device using a computer assisted drawing (CAD) program, in an embodiment. A software program is used to “slice” the CAD model into thin layers, such as five to ten layers per millimeter, in an embodiment. The SLA uses a specialized three-dimensional printer with a laser that forms one of the layers, exposing liquid plastic in the SLA&#39;s tank and hardening it. A moving platform within the tank drops down a fraction of a millimeter and the laser forms the next layer, in an embodiment. This process repeats, layer by layer, until the device is completely formed. 
     In various embodiments, the vents are constructed in a way which utilizes the internal air volume of the device. Examples include, but are not limited to those provided in  FIGS. 1A ,  2 A,  3 A,  5 , and  6 . It is understood that other embodiments employing vents outside of this internal volume are possible without departing from the scope of the present subject matter. 
     Although specific embodiments have been illustrated and described herein, other embodiments are possible without departing from the scope of the present subject matter.