Patent Publication Number: US-8526651-B2

Title: Receiver module for inflating a membrane in an ear device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/297,976, filed Jan. 25, 2010, the contents of which is incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention pertains to receiver modules for hearing aids and listening devices, and more particularly, to receiver modules configured to both emanate sound waves and inflate an expansible membrane suitable for mounting the hearing or listening device within the bony area of the ear canal. 
     BACKGROUND OF THE INVENTION 
     Hearing aids are devices used to detect, process, and amplify sound, and then transmit the detected sound to a user. Hearing aids therefore include electrical components, including a processor for analyzing and amplifying detected signals, a power source, a microphone, and a receiver. The microphone detects sound waves and creates electrical signals indicative of the detected sound waves. The electrical signals are typically processed within a processor where desirable aspects of the detected signals may be amplified, and the processed signals are then passed to the receiver. The receiver generally includes a movable membrane for generating pressure waves (i.e. sound waves) that are directed toward the ear drum of the user of the hearing aid. 
     Hearing aids have been developed that can be worn in more than one configuration. Some hearing aids include electrical components to be worn behind the ear, and components interior to the ear canal, with fluid connections between the interior components and the components worn behind the ear. Receiver In Canal (RIC) hearing aids are hearing aids where the electrical components required to detect, analyze, amplify, and transmit sound waves to the user are fully contained within the ear canal. For example, U.S. Pat. No. 7,227,968 discloses a device adapted for fitting an acoustic receiver within a bony portion of the ear canal using an expansible balloon-like device to seat the acoustic receiver within the bony portion of the ear canal and thereby enhance the transmission of sound waves and enhance the comfort experienced by a user. 
     Hearing aids today are typically assembled in one piece such that all the components—are encapsulated in a common plastic shell. The hearing aid is positioned at a relatively large distance from the eardrum, usually in front of the bony area of the ear canal. The reason for this is that the plastic material forming the shell encapsulating the above-mentioned components is hard, which makes it difficult to position such a hearing aid in the bony area of the ear canal without introducing pain to the user of the hearing aid. Another disadvantages of one-piece hearing aids include the large distance between the receiver output and the eardrum to be excited, acoustic feedback from the receiver to the microphone, vibrations of the receiver (which is transmitted to the ear canal and can be unpleasant for the user), a somewhat complicated and painful mounting of the hearing aid. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a receiver for use in a hearing aid, or other receiver in canal (RIC) transducer, adapted to both generate acoustic waves and pressurize an inflatable membrane. The receiver presented is optimized for the pressurization of the inflatable membrane by a valve subassembly connected to the exterior of the receiver housing. The valve assembly (or valve system) provides for fluid communication between an interior volume of the inflatable membrane and a portion of the receiver. In particular, in an implementation where the receiver has both a back volume and a front volume, the valve subassembly may provide for fluid communication between the back volume and the interior volume of the inflatable membrane. 
     A method of constructing the receiver&#39;s valve subassembly is provided where the valve assembly is created from multiple thin layers having holes or channels. The multiple thin layers, when attached to one another and to the exterior housing of the receiver, create small channels defining both an ingress port and an egress port. The receiver&#39;s valve subassembly can be further optimized to prevent backflow of pressurized fluid within the inflatable membrane back to the receiver, or back to an ingress port from which ambient air is drawn into the valve system. 
     Aspects of the present disclosure provide a receiver module adapted for being positioned within an ear canal. The receiver module includes a housing having a sound port for transmitting acoustic waves within the ear canal and an inflation port. The receiver module also includes a diaphragm within the housing. The diaphragm can be driven to create: (i) the acoustic waves in response to a first electrical input signal to the receiver module and (ii) a membrane-inflation pressure adjacent to the inflation port in response to a second electrical input signal to the receiver module. The receiver module also includes a front volume within the housing and in direct communication with the sound port. The front volume allows the acoustic waves to be transmitted through the sound port. The receiver module also includes a back volume within the housing on an opposing side of the diaphragm relative to the front volume. The back volume can be in direct communication with the inflation port. The receiver module also includes a valve system coupled to the housing directly adjacent to the inflation port. The valve system can include a plurality of layers to provide a flat configuration to the valve system. At least one of the plurality of layers can define an egress port. In response to the membrane-inflation pressure created by the diaphragm, the valve system can cause the inflation of an external inflatable membrane located within the ear canal by expelling air through the egress port. 
     Aspects of the present disclosure also provide a method of operating a receiver module to inflate an inflatable membrane positioned within an ear canal of a user. The receiver module can include a valve system that includes a plurality of layers mechanically coupled to a housing of the receiver. The valve system can have a flat profile with an overall thickness that is less than the width dimension of the housing. The plurality of layers of the valve system can have an egress port coupled to the inflatable membrane. The method of operating the receiver module includes drawing air in through an ingress port. The ingress port can be defined by at least one of the plurality of layers of the valve system of the receiver module. The method also includes generating, by use of a diaphragm, pressure within the back volume of the receiver module. The method can also include forcing air displaced by the generated pressure into the valve system and expelling the displaced air through the egress port. The plurality of layers of the valve system can be configured to substantially maintain a static pressure differential between the back volume and the egress port so as to optimize the receiver module for inflating the inflatable membrane. 
     The foregoing and additional aspects and implementations of the present disclosure will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments and/or aspects, which is made with reference to the drawings, a brief description of which is provided next. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other advantages of the present disclosure will become apparent upon reading the following detailed description and upon reference to the drawings. 
         FIG. 1  is a line graph illustrating pump pressure developed by Sonion 44A030 transducer along a frequency range. 
         FIG. 2  is a line graph illustrating power required by the Sonion 44A030 transducer along the same frequency range as that of  FIG. 1 . 
         FIG. 3  is a line graph illustrating the efficiency of the Sonion 44A030 transducer along the same frequency range as that of  FIG. 1 . 
         FIG. 4  is a reproduction of the operating parameters of a Duracell Zinc Air Battery 10, including an operation voltage curve. 
         FIG. 5  is a schematic of an embodiment of a two transducer device in accordance with the present invention. 
         FIG. 6  is a photographic depiction of a Sonion 44A030 dual transducer wired so that the polarity of one of the transducers can be switched relative to the other. 
         FIG. 7  is a graph showing the difference in sound pressure level (SPL) measured in a Zwislocki Coupler, which approximates the signal at the user&#39;s ear drum, corresponding to two transducers running 180 degrees out of phase in accordance with an embodiment of the present invention. 
         FIG. 8  depicts a photograph of a disassembled diaphonic valve as well as labeled schematics of the component parts that are also shown in  FIGS. 23A-26C  (for scale purposes, a portion of a U.S. dime is also shown). 
         FIG. 9  is a side schematic of the assembled component parts of the diaphonic valve illustrated in  FIG. 8 , and also shown in  FIG. 27D . 
         FIG. 10  is a schematic of a disassembled six-layered diaphonic valve in accordance with an embodiment of the present invention, which is also shown in  FIG. 28 . 
         FIG. 11  is a side schematic of the assembled component parts of the diaphonic valve illustrated in  FIG. 10 , and which is also shown in  FIG. 29 . 
         FIG. 12   a  is a side schematic of assembled component parts of a diaphonic valve similar to the embodiment illustrated in  FIG. 11 . 
         FIG. 12   b  is a side schematic of assembled component parts of a diaphonic valve similar to the embodiment illustrated in  FIG. 11 . 
         FIG. 13   a  is a side schematic of a driven bubble system with a transducer partially enclosed by the bubble, in accordance with an embodiment of the present invention. 
         FIG. 13   b  is a side schematic of a driven bubble system with a sound tube fully enclosed and a transducer partially enclosed by the bubble, in accordance with an embodiment of the present invention. 
         FIG. 13   c  is a side schematic of a driven bubble system with a transducer fully enclosed by the bubble, in accordance with an embodiment of the present invention. 
         FIG. 13   d  is a side schematic of a driven bubble system with a sound tube and a transducer fully enclosed by the bubble, in accordance with an embodiment of the present invention. 
         FIG. 13   e  is a side schematic of a driven bubble system with a transducer outside of the bubble, in accordance with an embodiment of the present invention. 
         FIG. 13   f  is a side schematic of a driven bubble system with a sound tube fully enclosed and a transducer outside of the bubble, in accordance with an embodiment of the present invention. 
         FIG. 14  is a side schematic of a driven bubble system with a sound tube and a transducer fully enclosed by the bubble similar to the embodiment of  FIG. 13   d , in accordance with an embodiment of the present invention. 
         FIG. 15  is a side schematic illustrating two flat diaphonic valves attached to a single transducer, in accordance with an embodiment of the present invention. 
         FIG. 16  is a side schematic illustrating a stack of flat diaphonic valves and two transducers, in accordance with an embodiment of the present invention. 
         FIG. 17  is a side schematic illustrating a plurality of diaphonic valves alternating with transducers, in accordance with an embodiment of the present invention. 
         FIG. 18   a  is a side and cross-sectional schematic of a multi-tube inflatable member, in accordance with an embodiment of the present invention. 
         FIG. 18   b  is another side and cross-sectional schematic of a multi-tube inflatable member, in accordance with an embodiment of the present invention. 
         FIG. 19  is a graphic illustration of pressure and volume changes along a range of altitudes. 
         FIG. 20   a  is an illustration of an embodiment of the present invention inserted within an ear. 
         FIG. 20   b  is an illustration similar to  FIG. 20   a.    
         FIG. 21A  provides a diagram of a hearing aid mounted within an ear canal. 
         FIG. 21B  is a functional block diagram of a cross-section of a balanced armature receiver. 
         FIG. 21C  provides a block diagram view of the receiver having a valve subassembly for use in inflating an inflatable membrane. 
         FIG. 22  provides a block diagram of a receiver module having a valve subassembly for use in inflating an inflatable membrane that surround the receiver module. 
         FIG. 23A  is a top view of a first layer of the multi-layer valve system. 
         FIG. 23B  is a side view of the first layer of the multi-layer valve system. 
         FIG. 23C  is an aspect view of the first layer of the multi-layer valve system. 
         FIG. 24A  is a top view of a second layer of the multi-layer valve system. 
         FIG. 24B  is a side view of the second layer of the multi-layer valve system. 
         FIG. 24C  is an aspect view of the second layer of the multi-layer valve system. 
         FIG. 25A  is a top view of a third layer of the multi-layer valve system. 
         FIG. 25B  is a side view of the third layer of the multi-layer valve system. 
         FIG. 25C  is an aspect view of the third layer of the multi-layer valve system. 
         FIG. 26A  is a top view of a fourth layer of the multi-layer valve system. 
         FIG. 26B  is a side view of the fourth layer of the multi-layer valve system. 
         FIG. 26C  is an aspect view of the fourth layer of the multi-layer valve system. 
         FIG. 27A  is a top view of an assembled multi-layer valve system. 
         FIG. 27B  is a side view of the assembled multi-layer valve system. 
         FIG. 27C  is an aspect view of the assembled multi-layer valve system. 
         FIG. 27D  is a cross-section view of the assembled multi-layer valve system. 
         FIG. 28  provides the disassembled layers of a multi-layer valve system for mounting to an audio transducer having six layers and having a check valve. 
         FIG. 29  is a functional block diagram showing the assembled, six layer structure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-20  illustrate some of the functional aspects of using one type of expansible balloon-like device (e.g., a membrane or “bubble”) to assist in seating the acoustic receiver in the bony portion of the ear.  FIGS. 21-29  will then describe the receiver&#39;s valve subassembly that is useful in assisting the receiver in inflating the expansible balloon-like device 
     Pumping Efficiency and Power Consumption:  FIGS. 1-3   
     U.S. Provisional Patent Application Ser. No. 61/253,843, filed Oct. 21, 2010, which is incorporated herein by reference in its entirety, describes numerous embodiments of a device, the Ambrose Diaphonic Ear Lens or ADEL, in which a diaphonic valve is used to harvest sound pressure from the operation of a balanced armature audio transducer, for the purpose of inflating a bubble in the ear. 
     Experimental study of working embodiments of the ADEL have allowed the evaluation of bubble inflation pressure versus transducer frequency and the power efficiency of bubble inflation versus transducer frequency. For example, these measurements were performed on an ADEL device pumped with the pressure generated by a diaphonic valve fitted to the back volume of one half of a Sonion dual transducer (44A030).  FIG. 1  shows the pressure developed by the ADEL pump as a function of frequency. This graph shows that, for this particular example of the ADEL device, the highest pressure can be generated at about 4000 Hz. 
     However, the condition of peak pressure generation, as shown in  FIG. 1 , is not necessarily the optimal frequency for ADEL operation because the transducer draws different amounts of power when it is operated at different frequencies. 
       FIG. 2  shows the power required to drive this particular ADEL device as a function of frequency. 
     While the ADEL can generate the highest pressure at about 4000 Hz ( FIG. 1 ),  FIG. 2  shows that this frequency corresponds to a local maximum in power requirement. It is desirable to operate the ADEL at a frequency where the pumping is most energy efficient so as to make the optimum use of the limited power available in a battery driven application such as a hearing aid or an MP3 player. This frequency is found at the maximum of the ratio of pressure generated ( FIG. 1 ) to power required ( FIG. 2 ). A plot of this ratio vs. frequency is shown in  FIG. 3 . 
       FIG. 3  shows that operating this particular ADEL device at about 3000 Hz gives best energy efficiency: Pascals of pressure generated per milliWatt of power consumed. This conclusion is only useful provided that, at its most energy efficient frequency, the ADEL can actually generate a high enough pressure to fulfill its intended application. When the application is sealing an ADEL bubble in a listener&#39;s ear, a pressure of 1 kPa is more than adequate, and thus 3000 Hz is found to be a good operational frequency for this ADEL device. 
     By comparison,  FIG. 3  shows that high energy efficiency is also achieved at the highest frequencies measured: 8000 Hz. The trend of the data also suggests that it may be possible to continue to increase pumping efficiency by going to even higher frequencies, or at least that a similarly high efficiency might be maintained at even higher frequencies. This observation raises the attractive possibility of an ADEL device that inflates a balloon in the listener&#39;s ear by operating at a very high frequency, which is beyond the audible range. However,  FIG. 1  indicates that this may not be practical, at least for the particular embodiment evaluated here. The pressure generated by the ADEL drops off at high frequencies, and the trend indicates that at frequencies above the audible range, that the device may generate insufficient pressure for the application. Thus, this particular ADEL should be operated at 3000 Hz to provide the combination of performance and efficiency. 
     Finally,  FIGS. 1 and 3  show that workable pressures and reasonable power efficiencies are achieved over a very broad range of frequencies, from less than 100 Hz to as high as 8000 Hz with this particular transducer. Other transducers may have even broader usable ranges. This suggests that one can produce effective ADEL pumping using a wide range of sound including the environmental sounds picked up by a hearing aid, conversation, music etc. Tests on a prototype ADEL hearing aid device showed that normal conversation or recorded music played at normal levels produced enough pressure to inflate an ADEL bubble and produce an effective ear seal. 
     Battery Life Considerations:  FIG. 4   
     For an ADEL device, which inflates a bubble in the ear using sound generated by the device itself, it is important that the power required to inflate the bubble and to keep it inflated is a small enough percentage of the available battery power so as not to adversely impact the device performance. For the hearing aid application, the ADEL bubble inflation and bubble pressure maintenance should not consume any more than 5% of the available battery energy. 
     One example is the use of a Zinc Air Battery Powering an ADEL on a Behind the Ear (BTE), Receiver In Canal (RIC) Hearing Aid. The data sheet, shown in  FIG. 4 , is for the size hearing aid battery typically used in small BTE style RIC type products (5.7 mm dia×3.5 mm thick). It is a No. 10 Zinc Air Battery as manufactured by Duracell. 
     The “Typical Discharge Curve” shown in  FIG. 4  assumes a load impedance of 3000 ohms applied for twelve hour periods, with 12 hour rest periods in between. This suggests a hearing aid user would use the device for 12 hours per day. The graph shows a battery voltage of about 1.3 volts as being maintained for about 180 hours. The end point voltage appears to be 0.9 volts after a little more than 200 hours. This would imply that the power being dissipated for 180 hours is 1.3×1.3/3000 equal to 0.00056 Watts or 0.56 milliwatts. This further implies that the energy being expended from the battery over a 180 hour time period is 0.00056 Watts×180 Hours or 0.101 Watt Hours. 
     Applying the guideline that the ADEL inflation pump can at most consume 5% of the available battery energy, this would be about 0.005 Watt Hours or 5 millwatt hours. If the battery powers the hearing aid for 12 hours a day and provides such service for 180 hours, this would be approximately 15 days. Thus, the ADEL can consume about 0.3 milliwatt hours/day for bubble inflation and bubble pressure maintenance. Based on measurements made on one prototype ADEL pump (ADEL device pumped with the pressure generated by a diaphonic valve fitted to the back volume of one half of a Sonion dual transducer 44A030, as discussed above) operating at 3.15 kHz (the most energy efficient condition, as discussed in connection with  FIGS. 1-3 ), capable of generating a bit more than 1 kPa with a power consumption of 0.9 milliwatts, this would indicate a maximum inflating time is about ⅓ of an hour or 20 minutes/day. 
     Twenty minutes of pumping per 12 hour day (what is allowed by a limit of 5% of battery energy) is far in excess of the amount of pumping required to inflate and maintain inflation of an ADEL bubble provided that the bubble is a statically inflated (low permeability) bubble, and the diaphonic valve is prevented from leaking with the addition of a check valve. ADEL bubble air loss is discussed in below. 
     Air Loss of a Statically Inflated Bubbles and Bubble Material Options 
     The following calculations determine the rate of air loss from a statically inflated ADEL bubble. This particular example is for a bubble composed of Kraton® polymer (a block copolymer of polystyrene and a polydiene, or a hydrogenated version thereof). These calculations are also a good approximation for the behavior of expanded polytetrafluroethylene (ePTFE) bubbles that have been coated with Kraton®, as well as for bubbles composed of polyurethane. In the case of an ePTFE bubble coated with Kraton®, the Kraton® is much more air permeable than the PTFE scaffolding of the ePTFE. It is assumed that the gas is leaking out though a membrane of Kraton equal to the total bubble wall thickness (including Kraton and ePTFE). This provides an over estimate of the air loss, and thus is a worst case scenario. 
     Characteristics of the bubble used for the estimate assume 1 cm diameter, spherical shape, 0.1 mil=0.00025 cm wall thickness. Calculations where done for two internal pressures (relative to outside atmospheric pressure) 100 Pa and 1 kPa. 
     In general for transport of a gas through a polymer: J=P (dp/dx), where J is the flux of gas through the polymer membrane in (cm 3  of gas)/((cm 2  of membrane area)(second)), P is the gas permeably of the membrane and (dp/dx) is the driving pressure gradient across the membrane, the x coordinate being distance in the membrane thickness direction. 
     The permeability of Kraton® to air is: 1×10 −9  ((cm 3  of air)(cm of membrane thickness))/((cm2 membrane area)(second)(pressure in cm of Hg)) [Reference: K. S. Laverdure “Transport Phenomena within Block Copolymers: The Effect of Morphology and Grain Structure” Ph.D. Dissertation, Chemical Engineering, University of Massachusetts at Amherst, 2001.] 
     The driving pressure gradient (dp/dx)≈(Δp/Δx) is 295 (cm Hg)/(cm thickness) if the interior bubble pressurization is 100 Pa, and it is 2950 (cm Hg)/(cm thickness) if the interior bubble pressurization is 1 kPa. 
     The resulting flux of air through the membrane, J, is 3×10 −7  (cm 3  of air)/(cm 2  of membrane)s when the interior bubble pressurization is 100 Pa, and J is 3×10 −6  (cm 3  of air)/(cm 2  of membrane)s when the interior bubble pressurization is 1 kPa. Based on the volume and surface area of a 1 cm diameter bubble, these calculations indicate that with a 1 00Pa internal pressure, the bubble will loose 2% of its gas in 12 hours and that at 1 kPa it will loose 20% of its gas in 12 hours, this time period being the assumed normal length of daily wear (see discussion related to  FIG. 4 ). This calculation is an estimate that assumes the air pressure inside the bubble remains constant throughout the process. This is a good approximation for the 2% loss found for 100 Pa, and this calculation is quite accurate. The estimate is poorer for the 20% loss at 1 kPa since such a significant loss will obviously reduce the bubble pressure and thus the driving force for further air loss. Thus the 20% at 1 kPa is a worst case estimate. The calculation is sensitive to the thickness of the bubble wall. A doubling the wall thickness to 0.2 mil will cut the gas loss rate in half to 1% for 100 Pa, for instance. Increasing the wall thickness to 1 mil will cut all calculated loss percentages by a factor of 10. 
     The calculations are most accurate for a case in which the diaphonic valve is used to periodically top off the pressure in the bubble. In this case, to maintain a pressure of 1 kPa in the bubble over 12 hours by intermittent use of the diaphonic valve, the ADEL would need to make up 20% of the bubble volume in that 12 hour period. This is a very small amount of pumping and would fall far below the 20 minutes per day of pumping necessary to stay below 5% of hearing aid batter use. 
     Experimental investigation of ADEL bubbles has shown that they can be inflated and remain inflated, with no noticeable loss of pressure for at least a day and in some cases up to a week. 
     Active Noise Cancellation to Quiet the Inflation of the Bubble:  FIGS. 5-7   
     In the previous sections, it was shown that a particular ADEL embodiment built with a Sonion 44A030 dual transducer has its best energy efficiency, for pumping air to inflate bubbles in the ear, at a frequency of about 3 kHz. At this operation frequency, the device can inflate and maintain inflation of a bubble in the ear over 12 hour periods, using less than 5% of the available battery power in a typical hearing aid. However, doing this requires initial and perhaps intermittent use of an inflation tone of about 3 kHz at a considerable amplitude (loudness). This tone may be unpleasant to the listener. Other ADEL embodiments, based on other transducers and other diaphonic valve configurations, may have their most energy efficient pumping at somewhat different frequencies. However, all such devices will have a frequency or range of frequencies in which pumping is most efficient, and this tone will often have the potential to be unpleasant to the listener when played with sufficient amplitude (power) to affect bubble inflation. 
     To mitigate this problem of an unpleasant inflation tone, two transducers are used in an ADEL device. The acoustical output of these two transducers, during the inflation of the ADEL bubble, is partially or completely out of phase so as to produce a noise cancellation (reduction in amplitude) and/or a shift in the audible frequency, so as to make the inflation process less objectionable to the listener. 
     One example of this invention is an ADEL device built with a balanced armature transducer (e.g. the type disclosed previously in U.S. Provisional Patent Application Ser. No. 61/253,843, filed Oct. 21, 2009, to Ambrose et al., incorporated herein by reference) paired with a second transducer. The ADEL generates pressure from sound pressure oscillations in the back volume of one of the transducers, and this pressure is used to inflate the bubble (closed or donut shaped) in the listener&#39;s ear. The other transducer is used to produce a sound output which is matched (to the degree possible) in frequency and amplitude and is 180 degrees out of phase with the output of the transducer with the ADEL. This arrangement quiets the device during ADEL bubble inflation. 
     For this device, during normal hearing aid (or other audio) operation, one of the two transducers (either the one with the ADEL or the one without the ADEL) can be turned off and the other transducer can provide the audio material to the listener. This requires a switching scheme, which may be mechanical or electronic, in which one transducer is turned on and off. It is also possible to run both transducers in phase, and thus reinforcing each other&#39;s signal, during normal hearing aid operation. This requires a switching scheme, which may be mechanical or electronic, in which one transducer has its electrical input reversed (180 degrees out of phase for bubble inflation) and then switched back (in phase for normal listening). 
     Another example is a two transducer device, in which the audio output of the two transducers may be run out of phase during bubble inflation to quiet the device, but in which both transducers are incorporated into ADEL pumps working from their back volumes. With two ADELs working to inflate the bubble, this device will inflate the bubble more quickly. It is desirable to the application for the bubble inflation process to be quick (less than 20 seconds and preferably less than 10 seconds), as well as quiet. 
     An ADEL device providing active sound cancellation using two transducers can inflate a bubble in the listener&#39;s ear and can pump air to maintain inflation while continuing to play audio program material (hearing aid function, communications, MP3 audio, etc.). This can be achieved by superimposing the audio material signal on the inflation tone in one of the two transducers. The other transducer plays only the inflation tone, but 180 degrees out of phase. The net effect is that the inflation tone is fully or partially cancelled and the audio signal remains intact. 
     Alternatively, in a two transducer ADEL device, both transducers can play audio material, which may be the same or different, but which is not out of phase and which does not cancel itself out. At the same time, superimposed on this audio material, in each transducer, is the inflation tone. However, the two transducers play the same inflation tone 180 degrees out of phase with one another, producing a cancellation or partial cancellation of the inflation tone, while the audio material from both transducers is heard by the listener. 
       FIG. 5  shows a schematic of a particular embodiment of the two transducer, two ADEL, device. This example was constructed using the Sonion 44A030 dual transducer, which provides the two transducers needed for the device in a single package. The particular example shown in  FIG. 5  uses the device to inflate a donut shaped bubble  32 , but the application of the same dual transducer, dual ADEL approach to a closed (driven) bubble is evident based on the designs disclosed in U.S. Provisional Patent Application Ser. No. 61/253,843, filed Oct. 21, 2009, to Ambrose et al., incorporated herein by reference and provided, in part, in Appendix A). 
     As shown in  FIG. 6 , a Sonion 44A030 dual transducer, was wired so that the polarity of one of the transducers could be switched relative to the other. To inflate the sealed bubble, the two component receivers of the Sonion 4400 are driven in series with opposite polarity. This action reduces the sound in the receiver tube as heard by the user. Once the desired inflation pressure is reached the inflation signal is switched off and the receiver sections are driven in series with additive polarities. 
     The prototype in  FIG. 6  was constructed and measured so as to determine and confirm the sound pressures that would be available for pumping relative to the sound pressures presented to a hearing aid user.  FIG. 7  shows that the difference in sound pressure level (SPL) measured in a Zwislocki Coupler (approximates the signal at the listener&#39;s ear drum) is 30 dB lower for the Series Subtraction arrangement, corresponding to the transducers running 180 degrees out of phase, as opposed to Series Addition, where the transducers run in phase. Additionally, the back volume SPL, in either of the two transducers, which is available to create pumping pressure using the ADEL, is 80 dB higher than the SPL experienced by the user with the active cancellation of the inflation tone. 
     Flat Diaphonic Valve Mounted on the Transducer:  FIGS. 8-14   
     In order to produce the most compact ADEL design for insertion into the ear canal, a flat diaphonic valve was constructed with mounts to the side of a transducer case and which adds 0.4 mm or less to the overall device width. The working principle and practical operation of this flat diaphonic valve is not different from that described in previous provisional patent filings (i.e., U.S. Provisional Patent Application Ser. Nos. 61/176,886, 61/233,465, 61,242,315, and 61/253,843). However, the device disclosed here, has the advantage of compact design fitting onto the side of a balanced armature transducer. The entire device, including the transducer and the diaphonic valve is small enough to fit into the listener&#39;s ear, and is small enough to be partially or fully contained within an ADEL bubble. 
       FIG. 8  shows a photograph of a disassembled working device as well as labeled schematics of the component parts. A United States dime in the image provides a scale reference.  FIG. 9  shows a cross sectional view of the assembled, multilayered device. The device is built on the side of a balanced armature transducer  45 , which has a hole  57  in the middle of its outer casing. This hole, is a byproduct of the manufacture of this particular transducer  45 , and it leads directly into the back volume of the transducer  45 . If no such hole is present on a particular transducer to be fit with a diaphonic valve of this type, then one would need to be drilled. The back volume of the transducer  45  is separated, at least in part, from a front volume of the transducer  45  by a diaphragm  28 . A compensation port  56  connects the front volume and the back volume of the transducer  45 . Layer  1  of the valve structure is a plate containing a groove  51  or slot which will become an air ingress channel in the final valve, when all the layers are stacked on top of one another. Layer  2  is a plate with a single small hole  53  in it. When assembled, this hole  53  is aligned with the hole  57  in the transducer case  20  as well as with the circular terminus  55  of the air ingress channel. The hole  53  in Layer  2  is the orifice of the synthetic jet, which is the heart of the diaphonic valve. This orifice is smaller than the hole  57  in the transducer case and it is smaller than the circular terminus  55  of the air ingress channel. 
     Layer  3  of the flat diaphonic valve is a rigid frame with an open center. This central region is spanned by a thin and flexible polymer membrane  58  or film. In this particular device, the membrane used is composed of polyethyleneterephalate (PET). The membrane  58  could be composed of any of the polymer materials disclosed in the U.S. patent application Ser. No. 12/178,236, filed Jul. 23, 2008, and incorporated herein by reference in its entirety, as suitable for use as membranes in diaphonic valves. This membrane  58  could also be a nonpolymer film or foil such as a thin metal foil. The flexible film  58  is mounted on the underside of the rigid frame of Layer  3  so that in the assembled device this flexible film  58  rests directly on the top of the plate of Layer  2 . Above this flexible film is a narrow gap, which allows the flexible film space, below the bottom of Layer  4 , to flex upward. A flap  54  is cut in the center of the flexible film of Layer  3 . In the assembled device, this flap  54  is directly over the synthetic jet port in Layer  2 . Layer  4  is a top plate or cover  50  for the diaphonic valve. This cover  50  contains an egress port  59  by which air pumped by the diaphonic valve exits the device. In the particular embodiment shown, this egress port  59  connects to an egress air tube  38 , which may be used to route the air into the ADEL bubble for inflation. 
     Experimentation with prototype ADEL devices has shown that it is often desirable to prevent escape of air from an inflated ADEL bubble by leakage back through the diaphonic valve, during time periods when the diaphonic valve is not pumping, but during which the bubble needs to remain statically inflated. To prevent air leakage back through the diaphonic valve, the diaphonic valve itself can be designed to minimize leakage or a check valve may be added to the diaphonic valve by addition of two more layers to the structure shown in  FIGS. 8 and 9 . 
     The disassembled layers of the diaphonic valve with the added check valve are shown schematically in  FIG. 10 .  FIG. 11  shows the assembled, six layer structure. Layers  1  through  3  are the same as the first three layers in the flat diaphonic valve discussed previously. Layer  4  is a plate with a single small hole  63  in it. This hole  63  is not in the center of the plate, but is closer to one of the ends of the plate, along its long axis. Layer  5  is a rigid frame with a flexible membrane  58  on its lower side, similar to Layer  3 . However, in Layer  5 , there is no flap, but rather another small hole  62  in the flexible film  58 , which is located at the opposite end of the structure from the hole  63  in the plate of Layer  4 . Layers  4  and  5  comprise the check valve. The region of contact of the top of the plate of Layer  4  and the bottom of the film  58  of Layer  5 , between the hole  63  in Layer  4  and the hole  62  in the flexible film  58  in Layer  5 , comprises the sealing function of the check valve. Placing the holes in Layers  4  and  5  at opposite ends of the structure creates the largest possible valve seat for the check valve and thus improves the seal. The final layer, Layer  6 , is the same cover plate with an air egress port  59 . 
     As shown in  FIG. 12 , raising the rims  67  around the ports in Layers  2  and  4  improve the seating of the flexible membrane across these ports. This increases the pumping efficiency of the diaphonic valve and produces a tighter seal for the check valve.  FIG. 12   a  shows that this can be accomplished by thickening the rims  67  around the ports  53 ,  63 .  FIG. 12   b  shows that this can also be accomplished by pushing up or embossing the plate underneath the port. This also raises the rim  67  or lip of the port and produces the desired improvement in performance. 
       FIGS. 13   a - 13   f  show various ways the flat diaphonic valve  50  mounted on the side of a transducer  20  can be incorporated with an ADEL bubble. These figures show the flat diaphonic valve  50  without the additional check valve. However, the same configurations are possible with a flat diaphonic valve  50  containing a check valve as described above. 
       FIG. 13   a  shows a driven bubble system with the transducer partially enclosed by the bubble  31 . 
       FIG. 13   b  shows a donut shaped bubble  32  with a sound tube and the transducer  20  partially enclosed in the bubble  32 . 
       FIG. 13   c  shows a driven bubble system with the transducer  20  fully enclosed by the bubble  31 . 
       FIG. 13   d  shows a donut shaped bubble  32  with the transducer  20  fully enclosed by the bubble and using an ingress tube  37  to connect to groove  51  in Layer  1 . A sound tube  40  is surrounded by the donut shaped bubble  32 . 
       FIG. 13   e  shows driven bubble  31  with the transducer  20  completely outside the bubble  31 . 
       FIG. 13   f  shows a donut shaped bubble  32  with the transducer  20  completely outside the bubble  32 . 
       FIG. 14  shows an embodiment of the ADEL with the flat diaphonic valve  50  in which the air ingress channel is absent. This is shown with the transducer  20  fully enclosed within the ADEL bubble  31 , but other embodiments lacking an air ingress port can also be partially enclosed by the bubble  31  or completely outside the bubble  31 . 
     In the device lacking an air ingress channel, air to inflate the bubble is drawn from the ear canal, down the sound tube  40 , into the front volume of the transducer  20 , through the pressure compensation port  56 , into the back volume of the transducer  20 , through the pumping diaphonic valve  50  and finally into the bubble  31 . This embodiment has the advantage of using air pressure to pull the bubble  31  into the listener&#39;s ear, producing a good acoustic seal. 
     More details of the flat valve subassembly of the receiver(s) and its use within various bubble-type hearing aids and listening devices will be described below in  FIGS. 21-29 . 
     Multiple Diaphonic Valves to Boost Pressure Output:  FIGS. 15-17   
       FIG. 15  shows an embodiment where two flat diaphonic valves  50   a ,  50   b  are attached to a single transducer  20 . The diaphonic valve  50   b  on the front volume is turned around to pump from outside into the front volume, thus pressurizing the front volume. This pressure leaks through the compensation port into the back volume, thus increasing the pressure of the back volume. The other diaphonic valve  50   a  on the back volume further increases pressure and pumps air out of the device via the egress port. This device can produce higher pressures than the single diaphonic valve on the back volume only. With two diaphonic valves, the first valve  50   b  increases pressure inside the transducer  20  and the second  50   a  boosts pressure even more before egress. The device in  FIG. 15  is illustrated using flat diaphonic valves. However, this same arrangement will also work with any of the previously disclosed diaphonic valve designs (i.e., U.S. patent application Ser. No. 12/178,236, filed Jul. 23, 2008, and U.S. Provisional Patent Application Ser. Nos. 61/176,886, 61/233,465, 61/242,315 and 61/253,843, filed May 9, 2009, Aug. 12, 2009, Sep. 14, 2009 and Oct. 21, 2009, respectively, and all of which are incorporated herein, by reference). 
       FIG. 16  shows that it is possible to stack two transducers  20   a ,  20   b  together with a diaphonic valve  50   a  between them and with additional diaphonic valves  50   b ,  50   c  on the front volume ( 50   b ) of the first transducer  20   a  and on the back volume ( 50   c ) of the second transducer  20   b.    
     This produces a cascade of pressure increases. Each transducer and diaphonic valve combination can only increase the pressure so much (about 1 kPa at most). However, by stacking the devices as shown, the second transducer/diaphonic valve combination begins with air which has already been pressurized. It can thus boost the pressure higher. When operating a device such as that shown in  FIG. 16  it is necessary to coordinate the phase of the inflation tones between the two transducers to ensure that the diaphonic valves all work in the same direction. Additionally, the diaphonic valve which sits between transducer  1  and transducer  2  necessitates that the two transducers have their inflation tones in phase with one another. 
       FIG. 17  carries the concept of a stack of transducers and diaphonic valves even further. One can build stacks of arbitrary numbers of alternating transducers and diaphonic valves to generate higher and higher pressure. The pressures achievable will eventually be limited by the mechanical strength of the components to resist increasing pressure. 
     The devices shown in  FIGS. 16 and 17  have open sound ports, and will thus tend to allow some pressure to escape from the stack of transducers and diaphonic valves. Other embodiments may have some or all of these sound ports blocked to create even greater pressures. Embodiments of the devices in  FIGS. 16 and 17  may have variations in the flow and sound impedance of the compensation ports (for instance by changing the size of the ports) as one progress up the stack of transducers. This may help to prevent back flow of pressure in the device. The transducers in a stack such as  FIGS. 16 and 17  may be run in phase or with other complex combinations of phase and amplitude differences to produce different pressure and sound outputs from the device. 
     The devices of  FIGS. 16 and 17  illustrate interleaved balanced armature transducers and diaphonic valves. Similar stacked devices for the purpose of pressure generation, pumping, and sound generation can be produced by interleaving diaphonic valves with other sound generating devices, such as piezoelectric diaphragms, or moving coil speakers. In these cases the piezoelectric diaphragms or speakers may have small compensation ports in them or in their surrounds in order to allow pressure to move from the front volume to the back volume or vice-versa. 
     Multi-Chambered Bubble from Joined Inflated Tubes:  FIG. 18   
     In the Sep. 14, 2009 U.S. Provisional Patent filing, Ambrose et al. (61/242,315) disclosed a design for a two walled, ADEL bubble, in which the required inflation volume is minimized by having the interior of the bubble un-pressurized.  FIG. 18  shows an example of a similar type of bubble design produced by bundling together inflatable polymer tubes.  FIG. 18   a  shows that using fewer, larger diameter tubes  106  gives a thicker bubble wall, while  FIG. 18   b  shows that using a larger number of smaller diameter tubes  106  produces a thinner bubble wall. 
     This design requires a circular pressure manifold, whereby pressure generated by the diaphonic valve is distributed to each of the tubular bubble wall sections. The example shown in  FIG. 18  is that of a bubble which encloses the transducer  20 . This same bubble design can also be incorporated into an ADEL device in which the transducer is outside the bubble or is partially enclosed by the bubble. 
     The inflatable, tubular sections of the device in  FIG. 18  may be adhered together laterally by an adhesive or melt or solvent bonding process. Alternatively the tubular sections may be left un-bonded laterally along their lengths. In this case the tubes  106  are only joined together at or near their two ends. The inflation of the un-joined tubes rigidifies the structure and give the bubble its shape. 
     Such an ADEL bubble can be formed from as few as 6 tubes and as many as twenty or more. The number of tubes is eventually limited by the need to distribute air flow and pressure to all of them via a pressure manifold. 
     Influence of Atmospheric Pressure on the Bubble:  FIGS. 19-20   
     An inflatable ear canal sealing device, such as the ADEL, must be able to tolerate changes in the outside atmospheric pressure without either loosing its seal or causing wearer discomfort. For instance, if a listener with an inflated bubble in his ear ascends rapidly to the top of a tall building or ascends in an airplane, the resulting drop in atmospheric pressure will allow the bubble in the ear to expand. Too much expansion of the bubble in the ear may cause discomfort. Conversely, if a listener with an inflated bubble in his ear descends rapidly from the top of a tall building or descends in an airplane, the resulting increase in atmospheric pressure will reduce the bubble volume. Too much contraction of the bubble may cause the loss of the acoustical ear seal. 
     As a first step, it is necessary to determine the maximum atmospheric pressure changes that the inflated ADEL bubble might experience in a listener&#39;s ear. Then, it is necessary to design the bubble and inflation system to tolerate these atmospheric pressure changes without undue adverse effects of the type discussed in the previous paragraph. 
     For the air in the ADEL bubble, pV=constant, where p is pressure and V is volume. This is a subpart of the ideal gas glass called Boyle&#39;s Law. It is valid for air over the range of pressures, temperatures and humidities found on Earth. 
     Δp=change in pressure from initial value P 
     ΔV=change in volume of bubble from initial value V 
     Then pV=constant=(p+Δp)(V+ΔV) 
     This can be rearranged to show that: 
     ΔV/V=Fractional Change in Volume=(1/(1+Δp/p))−1 
     In this equation ΔV/V and Δp/p necessarily have opposite signs. i.e. a positive increase in pressure Δp/p leads to a negative change in volume ΔV/V. Note that −(100%)*ΔV/V gives the percentage change in volume of an inflated ADEL bubble (as positive number) that must be dealt with due to a pressure change. 
       FIG. 19  shows a plot of atmospheric pressure vs. altitude in meters constructed using a barometric pressure calculator on the web: http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/barfor.html. The calculations suggest that elevator rides in tall buildings should not pose much of a problem for the ADEL bubbles. The tallest building in the World is 800 m high and thus a bubble would decrease its volume by 8% upon ascending from the bottom (at sea level) to the top. The other very tall buildings in the world, in the US and Asia, are in the 500 m range and represent a volume decrease of 5%. The tallest building in Europe is 300 m (similar to the Eiffel tower) and this gives a bubble volume change of 3%. 
     Airplane rides and trips to the high mountains are more of a challenge. As  FIG. 19  shows, these can result in ADEL bubble volume changes in the 15% to 25% range.  FIG. 20  shows an ADEL bubble, in the ear, as it undergoes a significant change in outside atmospheric pressure. The bubble lays in the ear canal like a loosely inflated bag, and it makes contact with a significant length of ear canal wall. At lower atmospheric pressure ( FIG. 20   a ), the bubble is larger and this manifests itself as the bubble extending a little further along the ear canal. At higher atmospheric pressure ( FIG. 20   b ), the bubble is smaller and this manifests itself as the bubble extending a little less distance along the ear canal. The difference in bubble volume and position in the ear canal between  FIGS. 20   a  and  20   b  is not significant enough, even with a 25% change in bubble volume (the worst case scenario) to cause listener discomfort or to disrupt the acoustic seal in the ear. 
     Wrinkles in the ADEL bubble surface may result from the natural resting of the bubble along the ear canal surface which may be rough, for instance, by the presence of hairs. Also the bubble surface may be intentionally wrinkled by embossing or another mechanical or chemical processing technique. Wrinkles in the bubble wall aid the bubble in accommodating slight or moderate volume changes, in response to slight or moderate changes in the external atmospheric pressure. 
     Details of the Receiver&#39;s Flat Valve Subassembly and its Use in a Bubble-Type Hearing Aid or Listening Device System:  FIGS. 21-29 . 
       FIG. 21A  provides a diagram of a hearing aid mounted within an ear canal. The hearing aid includes a microphone  130 , a processor  140 , and a receiver  110 . The receiver  110  is securely lodged against the ear canal inner wall  104  and held in place by the force of the expanded balloon  120  against the ear canal inner wall  104 . The receiver  110  includes a sound port and is oriented within the ear canal with its sound port facing the tympanic membrane  105  (i.e. the ear drum). The processor  140  is coupled to the receiver  110  via an electrical conductors  150 . 
     In an exemplary operation of the hearing aid shown in  FIG. 21A , acoustic waves are detected by the microphone  130 . The microphone  130  generates electrical signals indicative of the detected acoustic waves and sends the electrical signals to the processor  140 . The processor  140  then analyzes the electrical signals and optionally amplifies desirable characteristics of the signals to create the electrical input signals transmitted to the receiver  110  via the electrical conductors. The receiver  110 , which is symbolically illustrated by the functional block diagram in  FIG. 21B , includes a diaphragm driven by a rod according to the electrical input signals. The driven diaphragm creates acoustic waves (i.e. sound waves) and the acoustic waves emanate outwardly from the sound port toward the tympanic membrane  105 . The acoustic waves generated in the receiver  110  excite the tympanic membrane  105  by causing it to vibrate, which causes the human auditory sensory system to be engaged and thereby generate electrical signals sent to the brain that create the perception of sound. 
       FIG. 21B  is a functional block diagram of a cross-section of a balanced armature receiver  110 . The receiver  110  includes a housing  119 , which houses a front volume  111  and a back volume  112 . The front volume  111  and the back volume  112  can be separated by an internal wall  117 . The front volume  111  and the back volume  112  are also separated, at least in part, by a diaphragm  116 . The diaphragm  116  is configured to be driven to create acoustic waves within the front volume  111  according to the electrical input signal  150  transmitted on the first and second input signal wires  151 ,  152 . The diaphragm  116  generates the acoustic waves when the driving rod  113  is oscillated through a coupling to a pivoting element  114  to push and pull the diaphragm and thereby generate pressure waves in the front volume  111 . The pivoting element  114  is oscillated according to electrodynamic forces generated by a time-changing magnetic field created by the input signal transmitted on the input contacts  151 ,  152  of the receiver  110 . 
     The front volume  111  also includes an associated sound port  118  that allows acoustic waves generated within the front volume  111  to escape the receiver  110 . The input signals cause movement of an armature  114 . The armature  114  is coupled to a driving rod  113  for driving the diaphragm  116  and is positioned between a permanent magnet  115 . The movement of the armature  114  can then cause the driving rod  113  to be driven up and down and thereby cause the diaphragm  116  to oscillate and thereby generate acoustic waves in the front volume  111 . The acoustic waves are then emitted from the sound port  118 , and can be directed toward a tympanic membrane of a user. 
     While the functional block diagram of the balanced armature receiver  110  provided in  FIG. 21B  provides a particular implementation of a pivoting element coupled to a driving rod to generate acoustic pressure waves by oscillating a diaphragm, the present disclosure is not so limited to the particular arrangement shown in  FIG. 21B . The present disclosure expressly contemplates the use of the valve subassembly with any audio transducer, including other forms of receivers and also with microphones. 
       FIG. 21C  provides a block diagram view of the receiver  110  with the valve subassembly  270 . The front volume  111  is continuous with, and in fluid communication with, the sound port  118 . In addition to the sound port  118 , the housing  119  of the receiver  110  includes an inflation port  161 , which penetrates the housing  119  into the back volume  112 . The receiver  110  also typically includes a compensation port  162 , which can be a hole in the internal wall separating the front volume  111  from the back volume  112 . The compensation port  162  can also allow for the equalization of static barometric pressure between the back volume  112  and the front volume  111 . An excess of pressure on one side of the diaphragm  116  over the other will bias its vibrations and modify (impede) its sound generating characteristics. The compensation port  162 , or pressure equalization port, provides a small physical pathway by which air can move between the front and back volumes  111 ,  112  thus equalizing pressure between them. The compensation port  162  can be placed anywhere in the inner housing, including in a flexible surround that seals the diaphragm  116  with the inner housing  117 . The compensation port  162  can also advantageously prevent undesirable pressure levels from being applied to the ear drum, which may be in fluid connection with the front volume  111 . In an implementation, more than one compensation port  162  may be provided between the front volume  111  and the back volume  112 . 
     The valve subassembly  270  of the receiver  110  is for use in inflating an inflatable membrane  220 . The valve system  270  has an ingress port  282  and an egress port  283 . The egress port  283  is coupled to the inflatable membrane  220  such that the egress port  283  is in fluid communication with an interior volume of the inflatable membrane  220 . The valve system can be configured to maintain a static pressure differential between the ingress port  282  and the egress port  283  by harvesting pressurized air generated in the back volume  112  by the driven diaphragm  116  during sound generation, and then preventing the pressurized air from flowing back out of the valve subassembly  270  through either the ingress port  282  or the fluid connection  281  with the back volume  122 . The valve subassembly  270  may incorporate flap valves or check valves constructed from various materials, for example, stretched polyethylene terephthalate (PET) or polyurethane (PU). The check valves or flap valves within the valve system  270  can be configured such that high pressure air can enter valve system  270  from the back volume  112  by overcoming the tension of the stretched PET materials. 
     The inflatable membrane  220  can be a balloon or membrane (a “bubble”), and can be used to produce a comfortable, adjustable and variable ear seal and works with the ear canal to produce a variable volume resonant chamber for safe, comfortable, rich sounding and high fidelity reproduction of audio. In an implementation, the inflatable membrane  220  can be configured to surround the receiver module, and provide a seal against the ear canal of a user, similarly to the inflatable membrane  120  shown in  FIG. 21A . Alternatively, the inflatable membrane  220  can be configured to partially surround the receiver module, or to not surround the receiver module at all. 
       FIG. 22  provides another block diagram of a receiver having its valve subassembly  270  for use in inflating an inflatable membrane  220  that surrounds the receiver module. The back volume  112  also includes an inflation port in fluid connection with an ingress port  282  for providing ambient air into the valve subassembly  270 . As egress port  283  provides a fluid communication between the valve system  270  and an interior volume of the inflatable membrane  220 . In an implementation of the receiver module shown in  FIG. 22 , the ingress port  282  can be on opposite side or same side as of the receiver module as the sound port  118 . In an implementation of the present disclosure, the valve system  270  is configured such that pressure waves generated by the oscillation of the diaphragm cause air to be displaced, or pumped, from the ingress port  282  to the egress port  283 . The pumping of the valve system  270  by driving the diaphragm causes the inflatable membrane  220  to inflate. 
       FIGS. 23-27  illustrate particular configurations of the valve subassembly  270  for use in the receiver module  110  for inflating the inflatable membrane  220 . The particular configuration shown is a multi-layer valve system, or valve subassembly, or valve structure, that is typically attached to the housing of a audio transducer having an inflation port  161 . The audio transducer utilizing the multi-layer valve system  270  may be, for example, a Sonion 44A030 receiver. 
     To produce the most compact design for insertion into the ear canal, a flat diaphonic valve may be constructed which mounts to the side of a transducer housing and which adds 0.4 mm or less to the overall device width. The multi-layer valve system disclosed here, has the advantage of compact design fitting onto the side of a balanced armature transducer. The entire device (i.e., the receiver module  110 ), including the transducer and the diaphonic valve is small enough to fit into the listener&#39;s ear, and is small enough to be partially or fully contained within the inflatable membrane  220 . 
       FIG. 23A  is a top view of a first layer  300  of the multi-layer valve subassembly  270 .  FIG. 23B  is a side view of the first layer  300 .  FIG. 23C  is a perspective view of the first layer  300 . The first layer  300  is a plate containing an air ingress channel  304  (i.e., a groove or slot) that provide a channel for air ingress in the assembled multi-layer valve system  270 , when all the layers are stacked on top of one another. The first layer  300  also includes a circular terminus  302 , which terminates the air ingress channel  304 , and which is aligned with the inflation port  161  on the audio transducer. 
       FIG. 24A  is a top view of a second layer  400  of the multi-layer valve subassembly  270 .  FIG. 24B  is a side view of the second layer  400 .  FIG. 24C  is a perspective view of the second layer  400 . The second layer  400  is a plate with a single small orifice  402  in it. When the multi-layer valve subassembly  270  is assembled, the orifice  402  is aligned with the inflation port (e.g., the inflation port  161 ) in the transducer case as well as with the circular terminus  302  of the air ingress channel  304  in the first layer  300 . The orifice  402  in the second layer  400  is the source of a synthetic jet, which moves air upwardly toward the membrane  220 . With reference to  FIGS. 21-22 , the orifice  402  is smaller than the inflation port  161  in the housing and it is smaller than the circular terminus  302  of the air ingress channel  304  of the first layer  300 . 
       FIG. 25A  is a top view of a third layer  500  of the valve subassembly  270 .  FIG. 25B  is a side view of the third layer  500 .  FIG. 25C  is a perspective view of the third layer  500 . The third layer  500  is a rigid frame  501  with an open central region. The rigid frame  501  has its central region spanned by a thin, flexible film  502 . The film  502  may be composed of polyethylene terephalate (PET). The flexible film  502  can be composed of any other polymer materials suitable for use as membranes in valves for sound generating, or sound activated, transducers. The flexible film  502  can also be a nonpolymer film or foil such as a thin metal foil. The flexible film  502  is mounted on the frame  501  so that, in the assembled multi-layer valve subassembly  270 , the flexible film  502  rests directly on the top of the plate of the second layer  400 . Above the flexible film  502  is a narrow gap, which allows the flexible film  502  space to flex upward. A flap  504  is cut in the center of the flexible film  502  of the third layer  500 . The flap  504  can be cut in the shape of a “U” as shown in  FIG. 25A . In the assembled multi-layer valve system, the flap  504  can be directly over the synthetic jet orifice  402  in the second layer  400 . While the third layer  500  is shown as being multiple components (i.e., the frame  501  and film  502 ), the third layer  500  can also be made as a unitary piece as well. 
       FIG. 26A  is a top view of a fourth layer  600  of the multi-layer valve subassembly  270 .  FIG. 26B  is a side view of the fourth layer  600 .  FIG. 26C  is an aspect view of the fourth layer  300 . The fourth layer  600  is a top plate or cover for the multi-layer valve system. The fourth layer  600  includes an egress channel  602  by which air pumped by the receiver module exits the device valve subassembly  270  and inflates the membrane  220 . In the particular implementation shown, the egress channel  602  can be connected to an egress air tube  702  as shown in  FIGS. 27A through 27D . 
       FIG. 27A  is a top view of the assembled multi-layer valve subassembly  270 .  FIG. 27B  is a side view and  FIG. 27C  is a perspective view of the assembled multi-layer valve subassembly  270 .  FIG. 27D  is a cross-section view of the assembled multi-layer valve subassembly  270 . The assembled multi-layer valve subassembly  270  includes the first layer  300 , the second layer  400 , the third layer  500  (including the film  502 ), and the fourth layer  600  as well as the egress air tube  702 . The air egress tube  702  terminates with the air egress port  283 . In an implementation, the air egress port  283  can be connected to the inflatable membrane  220  so as to fluidly couple the inner channel of the air egress tube  702  with an inner volume of the inflatable membrane  220 . 
     When assembled, the assembled multi-layer valve system  270  has a proximal face  706  (here, the surface of the first layer  300 ) for being attached to an audio transducer, such as the receiver  110 , and a distal face  708  (here, the surface of the fourth layer  600 ) opposite the proximal face  706 . The layers in the multi-layer valve system  700  are generally connected so as to provide an air-tight seal between each layer, and between the proximal face  706  and the audio transducer. When assembled, the air ingress channel  304  in the first layer  300  can create a pathway for ambient air to enter the valve system  700  through the tube defined by the surface of the housing of the audio transducer, the air ingress channel  304 , and the face of the second layer  400 . In such a configuration, the end of the air ingress channel  304  is the air ingress port  282 . Ambient air can be drawn through the air ingress port  282 , through the ingress air channel  304 , to the circular terminus  302 . The air is then forced, by, for example, pressure waves generated within an audio transducer (e.g., pressure from the back volume  112  of the receiver  110 ), to pass through the small orifice  402  in the second layer  400  and past the flap  504  in the flexible film  502  of the third layer  500 . The air is then directed into the air egress tube  702 , which can be sealed to the fourth layer  600 , and the air is directed outward to the air egress port  283 . The egress tube  702  can be sealed to the fourth layer  600  using a flexible sealant  720 , which can create an air tight seal between the inner volume of air egress tube  702  and the volume defined by the third layer  500 . Preferably, the flap  504  at least partially prevents air from passing back through the small orifice  402  so as to maintain a static pressure differential between ambient air in the ingress channel  304  and the air in the air egress tube  702  (and the membrane  220 ). 
     An operation of a receiver module  110  having an assembled multi-layer valve system  270  is described in connection with  FIG. 27D , which shows the multi-layer valve system  270 . In a receiver module  110  where the multi-layer valve system  270 , (i.e., the multi-layer valve sub-assembly) is mounted so as to seal the circular terminus  302  of the first layer  300  to the inflation port  161  of the receiver  110 . In an exemplary operation of the receiver module  110  thus assembled, ambient air may be drawn in, or introduced, through the air ingress port  282 , and through the  304 . The air is then forced through the small orifice  402  and past the flap  504 . The air can be forced past the flap  504  by pressure carried in acoustic waves emanating from oscillations of the diaphragm  116  within the receiver module  110 . As more air is forced into the cavity formed in the third layer  500  internal to the frame  501 , the air is then urged into the air egress tube  702  toward the air egress port  283 . The air can be prevented from escaping the multi-layer valve system  270  by using a flexible air tight sealant, such as, for example, the flexible sealant  720  applied to the junction between the air egress tube  702  and the fourth layer  600 . Alternatively, the air egress tube  702  can be integrally formed with fourth layer  600  or welded, soldered, or otherwise adhered to the fourth layer  600  so as to prevent air from escaping the cavity within the third layer  500  by a path other than through the air egress tube  702 , and out the air egress port  283 . 
     Experimentation with prototype devices has shown that it is often desirable to prevent escape of air from an inflatable membrane  220  by leakage back through the valve system  270 , during time periods when the valve system  270  is not pumping, but during which the inflatable membrane  220  needs to remain statically inflated. To prevent air leakage back through the valve system  270 , the valve system  270  itself can be designed to minimize leakage or a check valve may be added to the valve system  270  by addition of two more layers to the multi-layer valve system sub-assembly as shown in  FIGS. 28 and 29 . The check valve can prevent back-flow of air by acting as a one-way valve that allows to pass when moving toward the egress port  283 , but not in the opposite direction, toward the ingress port  282 . 
       FIG. 28  provides the disassembled layers of a multi-layer valve system having six layers and having a check valve. The first layer  300 , second layer  400 , and valve layer  500  are the same as shown in connection with the multi-layer valve system  270  shown in  FIGS. 27A through 27D . In addition, a check valve is created from a first check valve layer  1110  and a second check valve layer  1120 . The first check valve layer  1110  is a plate with a single small hole  1112  in it. The hole  1112  may not be in the center of the plate, but can be closer to one of the ends of the plate, along its long axis. The second check valve layer  1120  is a rigid frame with a flexible film  1122 , or membrane, on its lower side, similar to the valve layer  500 . However, in the second check valve layer  1120 , there is no flap, but rather another small hole in the flexible film  1122 , which is located at the opposite end from the hole  1112  in the plate of the first check valve layer  1120 . The region of contact of the top of the plate of the first check valve layer  1120  and the bottom of the flexible film  1122 , between the hole  1112  and the hole  1124  in the flexible film  1122  provide a sealing function of the check valve. Placing the holes  1112 ,  1124  at opposite ends of the multi-layer valve system creates the largest possible valve seat for the check valve and thus improves the seal. The top and final layer  600  is the same cover plate shown in connection with  FIGS. 27A through 27D  and provides an air egress port  283  for air escaping from the valve system. 
       FIG. 29  is a functional block diagram showing the assembled, six layer structure of  FIG. 28 . Aspects of the multi-layer valve system are illustrated functionally, but are not necessarily illustrated to scale, or order to show additional details of the six layer structure. In an exemplary operation of the multi-layer valve system shown in  FIG. 29 , ambient air enters through the air ingress port  282  and is then forced, by acoustic waves generated within the back volume  112  of the audio transducer to push past the flap  504  in the flexible film  502 . As more air accumulates in the small cavity, or chamber, within the third layer  500 , pressure builds and the air pushes through the check valve by entering the hole  1112  and pushing past the seal created by the contact between the flexible film  1122  and the plate of the first check valve layer  1110 . When sufficient pressure is achieved, the air pushes through the hole  1124  in the flexible film  1122  and is urged through the air egress tube  702  where it emerges through the air egress port  283 . By preventing air from moving back through the seal, the check valve acts as a one-way valve allowing air to move in one direction, but not the other. The air emerging from the air egress port  283  can be directed into the interior volume of the inflatable membrane  220  and thereby inflate the inflatable membrane  220 . 
     Because the inflatable membrane  220  is not rigid, the inflatable membrane  220  and the receiver module  110  can be comfortably removed from the ear canal, even when inflated. Alternatively, or in addition, the receiver module  110  may be further configured with a deflation valve subassembly for deflating the inflatable membrane  220 . Deflating the inflatable membrane  220  may facilitate the removal of the receiver module  110  from the ear canal. In addition, the deflation valve subassembly can be remote-controlled such that, for example, a certain unique signal input to the receiver causes a movement of the deflation valve to release the pressure within the inflated membrane  220 . Or, the deflation valve can be manually actuated outside of the ear once the user has removed the membrane  220  from his or her ear while in the inflated state. 
     Implementations of the multi-layer valve system  270  illustrated in  FIGS. 27A through 29  can have an overall width, when assembled, less than the width of the housing  119  of the audio transducer the multi-layer valve system  270  is configured to be mounted to. In this way, the multi-layer valve system  270  is configured to be a flat valve system that maintains a low profile against the particular audio transducer selected and allows the entire receiver module  110 , thus assembled, to be inserted into a user&#39;s ear canal. Additionally, the overall thickness of the multi-layer valve system  270  can be less than the width dimension of the housing of a selected audio transducer. For example, in an implementation of the present disclosure where the receiver module  110  incorporates a Sonion 44A030 model transducer, the multi-layer valve system  270  can have a width and length less than the width and length of the 44A030. 
     Implementations of the multi-layer valve system  270  shown in  FIGS. 23A through 29  can include parts machined from stainless steel as well as layers of plastic film that are bonded to some of the stainless steel layers. For the purpose of producing diaphonic valves in large numbers at a reduced cost, it is desirable to have an manufacture the multi-layer valve system  270  from parts that are easily and rapidly fabricated and assembled. 
     The layers in the multi-layer valve system  270  can be made out of a wide range of materials such as steel, stainless steel, aluminum, other metals, polyethylene terephthalate (PET), polyether ketone (PEK), polyether etherketone (PEEK), polyamide (nylon), polyester, polyethylene, high density polyethylene, polytetrafluroethylene (PTFE), expanded polytetrafluorothylene (ePTFE), fluoropolymer, polycarbonate, acrylonitrile butadiene styrene (ABS), polybutylene terephthalate (PBT), polyphenylene oxide (PPO), polysulphone (PSU), polyimides, polyphenylene sulfide (PPS), polystyrene (PS), high impact polystyrene (HIPS), polyvinyl chloride (PVC), polypropylene (PP), polyolefins, plastics, engineering plastics, thermoplastics, thermoplastic elastomers, Kratons®, copolymers, or block copolymers. The layers can also be composed of blends or composites of these materials or versions of these materials to which have been added fillers, modifiers, colorants, and the like. Different layers of the structures may be composed of the same material or of different materials. 
     As an example, the multi-layer valve system  270  shown in  FIG. 28  may be made out of PET plastic. The characteristics of the multi-layer valve system shown in  FIG. 28  can be as follows. The first layer  300  may be made of PET, and the overall dimensions can be 0.04 mm high by 2.5 mm wide by 5.0 mm long, and the circular terminus  302  may have a diameter of 0.25 mm. The air ingress channel  304  may have a width of 0.06 mm or of 0.1 mm. The overall dimensions of the first layer  300  may also be 0.04 mm high by 2.25 mm wide by 3.27 mm long. The second layer  400  may be made of PET, and the overall dimensions can be 0.04 mm high by 2.5 mm wide by 5.0 mm long. The orifice  402  in the second layer  400  may have a diameter of 0.14 mm or of 0.15 mm. The frame  501  of the valve layer  500  may made of PET and can have overall dimensions of 0.04 mm high by 2.5 mm wide by 5.0 mm long. The overall dimensions of the valve layer  500 ′ may also be 0.15 mm high by 2.25 mm wide by 3.27 mm long. The flap  504  in the flexible film  502  may have a characteristic dimension of 0.2 mm. The first check valve layer  1110  may be made of PET and have overall dimensions of 0.04 mm high by 2.5 mm wide by 5.0 mm long or may also have overall dimensions of 0.04 mm high by 2.25 mm wide by 3.27 mm long. The second check valve layer  1120  can be made of PET and may have overall dimensions of 0.04 mm high by 2.5 mm wide by 5.0 mm long or may also have overall dimensions of 0.04 mm high by 2.25 mm wide by 3.27 mm long. The fourth layer  600  (or cover layer) can be made of PET and can have overall dimensions of 0.04 mm high by 2.5 mm wide by 5.0 mm long or may also have overall dimensions of 0.2 mm high by 2.25 mm wide by 3.27 mm long. The egress tube  702  can have an inner diameter of 0.3 mm and can be affixed to a 0.3 mm by 0.3 mm tubing port. In addition, the inflation port  161  in the receiver module  110  can have a diameter of 0.25 mm. 
     While particular implementations and applications of the present disclosure have been illustrated and described, it is to be understood that the present disclosure is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations can be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.