Patent Publication Number: US-RE38351-E

Title: High fidelity insert earphones and methods of making same

Description:
This is a continuation of application Ser. No. 08/597,940, filed Feb. 7, 1996, now abandoned, which is a continuation of application Ser. 08/430,698, filed Apr. 27, 1995, now abandoned, which is a continuation of Ser. No. 07/880,244 filed May 8, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to earphones and methods of making the same to obtain earphones and earphone assemblies which reproduce sounds with very high fidelity and with minimum noise and which are suitable for use by the most discriminating listeners. The earphones and assemblies of the invention are very compact and light in weight, are highly reliable and are readily and economically manufacturable. 
     2. Background of the Prior Art 
     “Audiophile” earphones have been marketed for use by audiophiles or discriminating listeners interested in the highest possible sound reproduction. Such audiophile earphones have been ostensibly capable of effecting high fidelity sound reproduction although it has been recognized by many users as well as the makers of such earphones that they have left much to be desired with respect to fidelity of reproduction. It has apparently been assumed by such users and makers that deficiencies in quality of sound reproduction are an unavoidable result of the use of earphones. 
     In a separate audiometry art, earphones have also been developed and marketed in limited quantities for use in specialized audiometry applications to measure the responses of a patient&#39;s ear and having features for obtaining desired response characteristics, one disclosure being contained in the Killion U.S. Pat. No. 4,763,753, issued Aug. 16, 1988. Another separate art, the hearing aid art, also contains many disclosures related to the achievement of improved response characteristics, including a paper entitled “SMOOTHING THE ITE RESPONSE: THE BF-1743 DAMPED COUPLING ASSEMBLY” by Mead C. Killion and William J. Murphy, first published in April 1981 and revised June 1982, by Industrial Research Products, Inc. Elk Grove Village, Ill. Such disclosures in the audiometry and hearing aid art relate to devices of relatively expensive construction which are designed for specialized applications and marketed in limited quantities. The applicability of the audiometry and hearing aid arts to the making of earphones for use in high fidelity sound reproduction has apparently gone unrecognized. 
     SUMMARY OF THE INVENTION 
     This invention was evolved after learning of the deficiencies of earphones marketed for use by audiophiles and with the general object of providing earphones which have improved high fidelity response characteristics and which are readily and economically manufacturable. 
     Important aspects of the invention relate to the recognition and discovery of problems with prior art arrangements and their causes and to an analysis of what is necessary to overcome such problems and otherwise provide improved earphones. It was discovered that one serious problem with audiophile earphones has been related to the failure to recognize the need to compensate for loss of external-ear resonance when using an earphone and the failure to provide compensating acoustic characteristics between the ear canal of a user and the transducer or receiver used to develop an audio signal from an applied electrical signal. It was further discovered that features of a damped coupling assembly of the hearing aid disclosed in the aforementioned Killion and Murphy paper might be applied with advantage to the construction of an audiophile earphone. With a damped coupling assembly as disclosed in that paper, a damper is coupled through a tube to an output port of a receiver and is disposed within the tip of an earmold. The arrangement produces a frequency response which will compensate for the loss of external ear resonance and which is largely independent of the total length of the coupling between the receiver and the earmold tip. 
     In accordance with the invention, an audiophile insert earphone is provided which uses a damped coupling assembly similar to that disclosed in the above-mentioned Killion and Murphy paper and operative to provide compensation for the loss of external-ear resonance. In accordance with one important feature of the invention, a pair of such earphones are combined in a dual earphone assembly usable for stereophonic reproduction. 
     Additional important features of the invention relate to features of construction which facilitate manufacture of insert earphones and which at the same time achieve reproduction of sounds with very high fidelity and with a high degree of reliability. Certain of such features relate to the provision of a housing member which can be readily molded from plastic in one piece and which serves the functions of connecting to an outlet port of a receiver, supporting a damper and providing a sound passage. The housing member also serves to releasably connect to a coupling device such as an earmold or ear tip and it performs all of such functions with a high degree of accuracy and reliability. Others such features relate to the provision of a resilient support for the receiver to minimize the effects of vibrations and noise and to methods of making the earphone to facilitate manufacture at low cost. 
     Another feature relates to the combination of electrical filters with the earphone and its damped coupling assembly to achieve optimum overall results. 
     Still another feature relates to a construction to facilitate removal and replacement of a damper and to the provision of a tool for that purpose. 
     This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a high fidelity insert earphone assembly of the invention; 
     FIG. 2 is a cross-sectional view of one earphone of the assembly of FIG. 1, taken substantially along line  2 — 2  of FIG. 1; 
     FIG. 3 shows a piece of resilient material used in construction of the earphone of FIG. 1; 
     FIG. 4 is a cross-sectional view taken substantially along line  4 — 4  of FIG. 2; 
     FIG. 5 is a circuit diagram of a electrical filter unit of the assembly of FIG. 1; and 
     FIG. 6 is a side elevational view, partly in section, illustrating a device usable for removal of dampers of the earphones of the invention. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     In FIG. 1, reference numeral  10  generally designates an earphone assembly which is constructed in accordance with the principles of this invention and which is suitable for use by an audiophile, for example. It will be understood, however, that a number of features of the invention are not limited to any particular use. Certain features may be used, for example, in the construction of hearing aids for use by persons having a hearing impairment. 
     The illustrated assembly  10  includes a pair of earphones  11  and  12  for insertion into the entrances of the ear canals of a user. A pair of cables  13  and  14  connect earphones  11  and  12  to a junction unit  15  and a common cable  16  connects the junction unit  15  to a plug connector  17  which may be connected to an output jack of a stereophonic amplifier, for example. 
     FIG. 2 is a cross-sectional view of the earphone  11 , the construction of the other earphone  12  being preferably identical to that of the earphone  11 . The earphone  11  comprises a receiver  18  which is mounted in a chamber portion  19  of a housing member  20 . The receiver  18  has an acoustic output port and has electrical input terminals  23  and  24  and is operative for generating an acoustic output signal at the output port  22  as a function of an electrical signal applied to the terminals  23  and  24 . The terminals  23  and  24  are connected through wires  25  and  26  to conductors of the cable  13  and an outer sheath  27  of the cable  13  is bonded to a strain relief member  28 . Member  28  is secured in an opening of an end cap  29  which is secured to one end of the housing member  20  to close one end of the chamber portion  19 . 
     The housing member  20  includes a wall  32  at an opposite end of the chamber portion  19  and an outer wall  34  of the chamber portion  19  which is in surrounding relation to the receiver  18  and which may preferably be of generally cylindrical form. 
     The housing member  20  further includes a tubular portion  35  which projects from the end wall  32  of the chamber portion of the housing member and which is inserted in an opening  37  of an acoustic coupling device  38  arranged to be inserted into the entrance of an ear canal of a user. As shown, the coupling device  38  is in the form of an eartip of a soft compliant material and has three outwardly projecting flange portions  39 ,  40  and  41  which are of generally conical form and of progressively increasing diameters, arranged to conform to the inner surface portions of the entrance of the ear canal of the user and to provide a seal limiting transmission of sound to the ear canal. 
     In accordance with a releasable lock feature of the invention, an end section  42  of the tubular portion  35  is of increased cross-sectional size to provide an external shoulder  43  in facing relation to the wall  32 . In assembly, a portion  44  of the compliant material of the device  38  is stretched over the end section  42  and then expands into the space between the shoulder  43  and the wall  32  as shown, so as to lock the device  38  and housing member  20  together while permitting disassembly when desired. 
     Custom earmolds or other types of coupling devices may be substituted for the illustrated device  38 , the subassembly of the housing member  20 , receiver  18  and other parts being thus usable with various types of coupling devices. 
     In accordance with further important features of the invention, the tubular portion  35  defines a passage  46  which has an outlet end portion  47  for propagation of acoustic energy into the earcanal of a user and an inlet end portion  48  in communication with the outlet port  20   22 of the receiver  18 . The outlet port  22  is preferably in the form of a tubular member which is fitted into the inlet end portion  47  of the passage  46  as shown. An acoustic damper  50  is fitted in the outlet end portion  47  of the passage  46  and, as illustrated, includes a cup-shaped screen member  51  secured in a cylindrical support member  52 . The outlet end portion  47  preferably has an enlarged diameter to provide a shoulder  53  operative to limit movement of the damper  50  toward the receiver  18  during assembly and to accurately fix its position. As shown, the portion of the screen member  51  which is transverse to the direction of sound transmission is in recessed relation to the end of the tubular housing portion  22   35 and the terminal end of the tubular housing portion is spaced a substantial distance from the terminal end of the coupling device, the result being that problems with wax accumulations on the screen are minimized. However, should such accumulations occur, a special removal tool as hereinafter described may be used to remove a clogged damper  50  which can then be replaced with a new damper. 
     With the construction as thus far described, the housing member  20  can be readily molded from plastic in one piece and it serves the functions of connecting to the outlet port of the receiver, supporting the damper, providing a sound passage and releasably connecting to a coupling device which may be of various possible types, such functions being performed with a high degree of accuracy and reliability. 
     Additional important features relate to the provision of a resilient support for the receiver  18  to minimize problems with noise and vibrations while facilitating assembly of the earphone. A piece of foam material  54  is provided having a generally rectangular form and a central opening  55  as depicted in FIG.  3 . In assembly, strain relief member  28  at the end of the cable  13  is installed in an opening in the end cap  29  and the conductors of the cable are connected directly or through the separate wires  25  and  26  as illustrated to the terminals  23  and  24  of the receiver  18 , being optionally extended through a resilient foam element  56 , as shown. Then the output port  22  of the receiver is inserted in the opening  55  of the piece  54  and the receiver is inserted into the chamber portion  19  and moved toward the wall  32  to press fit the output port  22  into the inlet end portion  48  of the passage  46 . During this assembly step, a portion  58  of the piece  54  is compressed between the end of the receiver  18  and the wall  32  and portions  59  and  60  of the piece  54  are folded back and compressed between the receiver and the outer wall  34  of the chamber portion  19 . As shown in the cross-sectional view of FIG. 4, parts of the folded-back portions  59  and  60  extend along the sides of the receiver  18  as well as along the top and bottom of the receiver  18 . This assembly step is readily and quickly performed and results in a resilient support of the receiver  18  within the housing member  20  in a manner such as to minimize transmission of noise and vibrations thereto, functioning with a high degree of reliability. It also results in an acoustic seal between the output port  22  and the inlet end  48  of passage  46 . As a final assembly step, an epoxy or equivalent bonding means is used to secure the end cap  29  to the end of the housing member  20 . 
     FIG. 5 is a schematic diagram of the configuration of the junction unit  15  which connects the earphone cables  13  and  14  to the common cable  16  and which includes special electrical filters for enhancing the performance of the earphones  11  and  13 . One conductor  63  and one conductor  64  of the cables  13  and  14  are directly connected to a ground conductor  65  of the common cable  16 . A second conductor  67  of the cable  13 , a second conductor  68  of the cable  14 , and conductors  69  and  70  of cable  16  are respectively connected to pads  71 ,  72 ,  73  and  74  of a circuit board  76  which is formed with two circuits operative to increase the signal applied to the receivers of the earphones  11  and  12  as a function of increasing frequency. 
     As shown, a capacitor  77  and a resistor  78  are connected in series between pads  71  and  73  while a resistor  80  is connected directly between pads  71  and  73 , in parallel with the series combination of capacitor  77  and resistor  78 . Similarly, a capacitor  81  and a resistor  82  are connected in series between pads  72  and  74  while a resistor  84  is connected directly between pads  71  and  73 . It will be apparent that at very low frequencies, when the capacitive reactance is high, the series impedances are determined primarily by the value of the resistors  80  and  84 . As the frequency increases, the series impedances are reduced, increasing the amplitudes of higher frequency components of the applied signals. 
     This electrical filtering operation is found to be highly desirable, permitting the use of an amount of acoustic damping sufficient to smooth out peaks in the acoustic responses of the earphones  11  and  12  while obtaining optimum frequency response characteristics. By way of example, the value of each of the resistors  78 ,  80 ,  82  and  84  may be 100 ohms and the value of each of the capacitors  77  and  81  may be 0.22 microfarads. The circuit board  76  and the parts thereon preferably have quite small dimensions. Each of the resistor and capacitor parts preferably has maximum dimensions of 0.150″×0.300″×0.100″. These dimensions are desirable to obtain a compact junction unit and are such that if desired, as when a single earphone is to be used, the filter for each filter might be located within the earphone, e.g. between the receiver  18  and the end cap  29 . In a two earphone assembly such as the illustrated assembly  10 , however, it is generally preferable to locate the filters in the junction unit  15 . 
     FIG. 6 illustrates a tool usable for removal and replacement of a damper which has become clogged with wax or otherwise defective. A support rod  86  carries a threaded element  87  which has a pointed end  88  to be pushed into the screen of a defective damper while the rod  86  is rotated to engage the threads of the element  87  with a lip of the cylindrical support  52  of the damper  50 ; the rod  86  being then retracted to withdraw the defective damper. Replacement dampers  89  may be contained in a chamber  90  within the support rod  86  and may be accessed by removal of an extension  91  of the rod  86 , the extension  91  having a reduced diameter threaded end portion  92  which is screwed into an internally threaded end portion of the replacement damper chamber  90 . 
     Aspects of the present invention described above enable an insert earphone that provides high fidelity sound reproduction, without requiring a long flexible tube between a hollow elongated tubular portion of the insert earphone housing and a resilient sealing member that seals with the ear canal of a wearer. 
     It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.