Patent Publication Number: US-2022240004-A1

Title: Earphone having a controlled acoustic leak port

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of co-pending U.S. patent application Ser. No. 16/868,372 filed May 6, 2020, which is a continuation of U.S. patent application Ser. No. 16/286,346 filed Feb. 26, 2019, now U.S. Pat. No. 10,694,282, which is a continuation of U.S. patent application Ser. No. 15/723,079 filed Oct. 2, 2017, now U.S. Pat. No. 10,356,510, which is a continuation of U.S. patent application Ser. No. 15/339,563 filed Oct. 31, 2016, now U.S. Pat. No. 9,781,506, which is a continuation of U.S. patent application Ser. No. 14/951,028 filed Nov. 24, 2015, now U.S. Pat. No. 9,510,077, which is a continuation of U.S. patent application Ser. No. 14/626,806, filed Feb. 19, 2015, now U.S. Pat. No. 9,210,496, which is a continuation of U.S. patent application Ser. No. 13/528,566, filed Jun. 20, 2012, now U.S. Pat. No. 8,971,561, all of which are incorporated herein by reference. 
    
    
     FIELD 
     An embodiment of the invention is directed to an earphone assembly having a controlled acoustic leak port. Other embodiments are also described and claimed. 
     BACKGROUND 
     Whether listening to an MP3 player while traveling, or to a high-fidelity stereo system at home, consumers are increasingly choosing intra-canal and intra-concha earphones for their listening pleasure. Both types of electro-acoustic transducer devices have a relatively low profile housing that contains a receiver or driver (an earpiece speaker). The low profile housing provides convenience for the wearer, while also providing very good sound quality. 
     Intra-canal earphones are typically designed to fit within and form a seal with the user&#39;s ear canal. Intra-canal earphones therefore have an acoustic output tube portion that extends from the housing. The open end of the acoustic output tube portion can be inserted into the wearer&#39;s ear canal. The acoustic output tube portion typically forms, or is fitted with, a flexible and resilient tip or cap made of a rubber or silicone material. The tip may be custom molded for the discerning audiophile, or it may be a high volume manufactured piece. When the tip portion is inserted into the user&#39;s ear, the tip compresses against the ear canal wall and creates a sealed (essentially airtight) cavity inside the canal. Although the sealed cavity allows for maximum sound output power into the ear canal, it can amplify external vibrations, thus diminishing overall sound quality. 
     Intra-concha earphones, on the other hand, typically fit in the outer ear and rest just above the inner ear canal. Intra-concha earphones do not typically seal within the ear canal and therefore do not suffer from the same issues as intra-canal earphones. Sound quality, however, may not be optimal to the user because sound can leak from the earphone and not reach the ear canal. In addition, due to the differences in ear shapes and sizes, different amounts of sound may leak thus resulting in inconsistent acoustic performance between users. 
     SUMMARY 
     An embodiment of the invention is an earphone including an earphone housing having a tip portion dimensioned to be inserted into an ear canal of a wearer, a body portion extending outward from the tip portion, and a tube portion extending from the body portion. A primary output opening for outputting sound generated by a driver within the body portion into the ear canal is formed in the tip portion. A secondary output opening for venting air to the external environment is formed in a face of the body portion. The face of the body portion faces a pinna region of the ear when the tip portion is inserted into the ear canal. The primary output opening and the secondary output opening can be horizontally aligned with one another and face different directions such that they form an acute angle with respect to one another. 
     The secondary output opening may serve as a controlled leak port to expose an acoustic pressure within the earphone to the external, surrounding environment. In this aspect, the secondary output opening may be calibrated to modify an acoustic response of the earphone. For example, secondary output opening may be calibrated to reduce a sound pressure level at a peak around 6 kHz and tune a frequency response of the earphone to improve overall earphone performance. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  is a perspective view of one embodiment of an earphone. 
         FIG. 2  illustrates a side view of one embodiment of an earphone worn within a right ear. 
         FIG. 3  illustrates a top perspective cut out view of one embodiment of an earphone. 
         FIG. 4  illustrates a top perspective cut out view of one embodiment of an earphone. 
         FIG. 5  illustrates an exploded perspective view of the internal acoustic components that can be contained within one embodiment of an earphone housing. 
         FIG. 6A  illustrates a front perspective view of one embodiment of an acoustic tuning member. 
         FIG. 6B  illustrates a back perspective view of one embodiment of an acoustic tuning member. 
         FIG. 6C  illustrates a cross-sectional top view of one embodiment of an acoustic tuning member. 
         FIG. 7  illustrates a cross-sectional side view of one embodiment of an earphone having an acoustic tuning member. 
         FIG. 8  illustrates a cross-sectional side view of one embodiment of an earphone having an acoustic tuning member. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  is a perspective view of one embodiment of an earphone. In one embodiment, earphone  100  may be dimensioned to rest within a concha of an ear (in this example, a right ear) and extend into the ear canal for improved acoustic performance. In this aspect, earphone  100  may be considered a hybrid of an intra-concha earphone and an intra-canal earphone. Representatively, earphone housing  102  may form a body portion  104  which rests within the concha like an intra-concha earphone and a tip portion  106  which extends into the ear canal similar to an intra-canal earphone. A receiver or driver (not shown) may be contained within housing  102 . Aspects of the driver will be discussed in more detail below. 
     Tube portion  114  may extend from body portion  104 . Tube portion  114  may be dimensioned to contain cable  120 , which may contain wires extending from a powered sound source (not shown) to the driver. The wires may carry an audio signal that will be audibilized by the driver. In addition, tube portion  114  may be dimensioned to provide an acoustic pathway that enhances an acoustic performance of earphone  100 . This feature will be described in more detail in reference to  FIG. 7 . In some embodiments, tube portion  114  extends from body portion  104  in a substantially perpendicular direction such that when body portion  104  is in a substantially horizontal orientation, tube portion  114  extends vertically downward from body portion  104 . 
     Housing  102  may include a primary output opening  108  and a secondary output opening  110 . Primary output opening  108  may be formed within tip portion  106 . When tip portion  106  is positioned within the ear canal, primary output opening  108  outputs sound produced by the driver (in response to the audio signal) into the ear canal. Primary output opening  108  may have any size and dimensions suitable for achieving a desired acoustic performance of earphone  100 . 
     Secondary output opening  110  may be formed within body portion  104 . Secondary output opening  110  may be dimensioned to vent the ear canal and/or output sound from earphone  100  to the external environment outside of earphone  100 . The external or surrounding environment should be understood as referring to the ambient environment or atmosphere outside of earphone  100 . In this aspect, secondary output opening  110  may serve as a leak port that allows a relatively small and controlled amount of air to leak from the ear canal and earphone housing  102  to the external environment. Secondary output opening  110  is considered a controlled leak port, as opposed to an uncontrolled leak, because its size and shape are selected to achieve an amount of air leakage found acoustically desirable and that can be consistently maintained not only each time the same user wears the earphone but also between users. This is in contrast to typical intra-concha earphones which allow a substantial amount of air leakage between the earphone and the ear canal that can vary depending upon the positioning of the earphone within the ear and the size of the user&#39;s ear. Thus the amount of air leakage is uncontrolled in that case, resulting in an inconsistent acoustic performance. 
     Controlling the amount of air leaking out of secondary output opening  110  is important for many reasons. For example, as the driver within earphone  100  emits sound into the ear canal, a high pressure level at low frequencies may occur inside the ear canal. This high pressure may cause unpleasant acoustic effects to the user. As previously discussed, tip portion  106  extends into the ear canal and therefore prevents a substantial amount of air from leaking out of the ear canal around tip portion  106 . Instead, air is directed out of the secondary output opening  110 . Secondary output opening  110  provides a controlled and direct path from the ear canal out of the earphone housing  102  so that an acoustic pressure within the ear canal can be exposed or vented to the surrounding environment, outside of earphone  100 . Reducing the pressure within the ear canal improves the user&#39;s acoustic experience. Secondary output opening  110  has a controlled size and shape such that about the same amount of air leakage is expected to occur regardless of the size of the user&#39;s ear canal. This in turn, results in a substantially consistent acoustic performance of earphone  100  between users. In addition, in one embodiment, the amount of air leakage can be controlled so that increased, if not maximum, sound output reaches the ear canal. 
     Secondary output opening  110  may also be calibrated to tune a frequency response and/or provide a consistent bass response of earphone  100  amongst the same user and across users. Secondary output opening  110  is calibrated in the sense that it has been tested or evaluated (in at least one specimen of a manufactured lot) for compliance with a given specification or design parameter. In other words, it is not just a random opening, but it has been intentionally formed for a particular purpose, namely to change the frequency response of the earphone in a way that helps to tune the frequency response and/or provide a consistent bass response amongst the same user and across users. In this aspect, secondary output opening  110  can be calibrated to modify a sound pressure frequency response of the primary output opening  108 . 
     For example, in one embodiment, secondary output opening  110  may be used to increase a sound pressure level and tune frequency response at a peak around 6 kHz. In particular, it is recognized that overall sound quality improves for the listener as the secondary output opening  110  becomes larger. A large opening, however, may not be aesthetically appealing therefore it is desirable to maintain the smallest opening possible. A smaller opening, however, may not result in a desired acoustic performance around a peak of 6 kHz (e.g., acoustic inductance may increase). In this aspect, a size and/or shape of secondary output opening  110  has been tested and calibrated to have a relatively small size and desirable shape yet still achieve an optimal acoustic performance at a peak of 6 kHZ. For example, secondary output opening  110  may have a surface area of from about 3 mm 2  to about 15 mm 2 , for example, from about 7 mm 2  to about 12 mm 2 , for example 9 mm 2 . In one embodiment, secondary output opening  110  may have an aspect ratio of about 3:2. Secondary output opening  110  may therefore have, for example, an elongated shape such as a rectangular shape or an oval shape. It is contemplated, however, that secondary output opening  110  may have other sizes and shapes found suitable for achieving a desired acoustic performance. 
     The size and shape of secondary output opening  110  may also be calibrated to provide earphone  100  with a more consistent bass response, for the same user and between different users. In particular, as previously discussed, when air leakage from an earphone to the surrounding environment is uncontrolled (e.g., when it occurs through a gap between the ear canal and outer surface of the earphone housing), the acoustic performance, which can include the bass response of the earphone, will vary depending upon the size of the user&#39;s ear and the positioning within the ear. Since secondary output opening  110  is of a fixed size and shape and therefore capable of venting an acoustic pressure within the ear canal and/or earphone  100  in substantially the same manner, regardless of the size of a user&#39;s ear and positioning of earphone  100  within the ear, earphone  100  has a substantially consistent bass response each time the same user wears earphone  100  and between different users. 
     In addition, it is believed that secondary output opening  110  may reduce the amount of externally radiated sound (e.g. uncontrolled sound leakage), as compared to an earphone without secondary output opening  110 . In this aspect, for the same sound pressure level produced by the driver diaphragm, earphone  100  having secondary output opening  110  would produce less externally radiated sound resulting in more sound reaching the ear canal than an earphone without secondary output opening  110 . 
     To ensure consistent venting to the surrounding environment, secondary output opening  110  may be formed within a portion of housing  102  that is not obstructed by the ear when earphone  100  is positioned within the ear. In one embodiment, secondary output opening  110  is formed within face portion  112  of body portion  104 . Face portion  112  may face a pinna region of the ear when tip portion  106  is positioned within the ear canal. Secondary output opening  110  therefore faces the pinna region when earphone  100  is positioned within the ear. In addition, where secondary output opening  110  has an elongated shape, the longest dimension may be oriented in a substantially horizontal direction when earphone  100  is positioned in the ear such that it extends outward from the ear canal. In this aspect, a substantial, if not the entire, surface area of secondary output opening  110  remains unobstructed by the ear when tip portion  106  is positioned within the ear canal. In other embodiments, secondary output opening  110  may have any orientation within face portion  112  suitable for allowing sound from the ear canal and/or earphone housing  102  to vent to the outside environment, e.g., vertical or diagonal. 
     Earphone housing  102 , including tip portion  106  and body portion  104  may be formed of a substantially non-compliant and non-resilient material such as a rigid plastic or the like. In this aspect, unlike typical intra-canal earphones, although tip portion  106  can contact and form a seal with the ear canal, it is not designed to form an airtight seal as is typically formed by intra-canal earphones that have a compliant or resilient tip. Tip portion  106 , body portion  104  and tube portion  114  may be formed of the same or different materials. In one embodiment, tip portion  106  and body portion  104  may be molded into the desired shape and size as separate pieces or one integrally formed piece using any conventional molding process. In addition, tip portion  106  may have a tapered shape that tapers from body portion  104  so that the end of tip portion  106  facing the ear canal has a reduced size or diameter relative to body portion  104  and fits comfortably within the ear canal. Thus, earphone  100  does not require a separate flexible (resilient or compliant) tip such as a rubber or silicon tip to focus the sound output. In other embodiments, tip portion  106  may be formed of a compliant or flexible material or be fitted with a compliant cap that will create a sealed cavity within the ear canal. 
       FIG. 2  illustrates a side view of one embodiment of an earphone worn within a right ear. Ear  200  includes pinna portion  202 , which is the meaty portion of the external ear that projects from the side of the head. Concha  204  is the curved cavity portion of pinna portion  202  that leads into ear canal  206 . Earphone  100  may be positioned within ear  200  so that tip portion  106  extends into ear canal  206  and body portion  104  rests within concha  204 . The tapered shape of tip portion  106  may allow for contact region  208  of tip portion  106  to contact the walls of ear canal  206  and form a seal with ear canal  206 . As previously discussed, tip portion  106  can be made of a non-compliant or rigid material such as plastic therefore the seal may not be airtight. Alternatively, the seal formed around tip portion  106  at contact region  208  may be airtight. 
     Face portion  112  of body portion  104  faces pinna portion  202  when earphone  100  is positioned within ear  200 . Secondary output opening  110  also faces pinna portion  202  such that sound exits secondary output opening  110  toward pinna portion  202  and into the surrounding environment. Although secondary output opening  110  faces pinna portion  202 , due to its size, orientation and positioning about face portion  112 , it is not obstructed by pinna portion  202 . 
       FIG. 3  illustrates a top perspective cut out view of one embodiment of an earphone. In particular, from this view it can be seen that primary output opening  108  and secondary output opening  110  are positioned along different sides of housing  102  such that the openings face different directions and form an acute angle with respect to one another, as described below. For example, primary output opening  108  may be formed in end portion  308  that is opposite back side  310  and faces the ear canal while secondary output opening  110  may be formed in face portion  112  that faces the pinna portion and is opposite front side  312  of housing  102 . 
     When tube portion  114  is vertically orientated, primary output opening  108  and secondary output opening  110  intersect the same horizontal plane  300 , i.e. a plane that is essentially perpendicular to a length dimension or longitudinal axis  360  of tube portion  114 . An angle (a) formed between primary output opening  108  and secondary output opening  110  and within the horizontal plane  300  may be an acute angle. In one embodiment, angle (a) may be defined by line  304  and line  306  radiating from a longitudinal axis  360  of tube portion  114  and extending through a center of primary output opening  108  and a center of secondary output opening  110 , respectively. In one embodiment, angle (a) may be less than 90 degrees, for example, from about 80 degrees to about 20 degrees, from about 65 degrees to about 35 degrees, or from 40 to 50 degrees, for example, 45 degrees. 
     Alternatively, an orientation of primary output opening  108  and secondary output opening  110  may be defined by an angle (β) formed by a first axis  340  through a center of primary output opening  108  and a second axis  342  through a center of secondary output opening  110 . First axis  340  and second axis  342  may be formed within the same horizontal plane  300 . Angle (β) between first axis  340  and second axis  342  may be less than 90 degrees, for example, from about 85 degrees to 45 degrees, representatively from 60 degrees to 70 degrees. 
     In other embodiments, an orientation of primary output opening  108  and secondary output opening  110  may be defined with respect to driver  302 . In particular, as can be seen from this view, front face  314  of driver  302  faces both primary output opening  108  and secondary output opening  110  but is not parallel to either the side  308  or the face portion  112  in which the openings  108 ,  110  are formed. Rather, an end portion of driver  302  extends into tip portion  106  toward primary output opening  108  and the remaining portion of driver  302  extends along face portion  112 . In this aspect, while both the primary output opening  108  and secondary output opening  110  may be considered in front of driver front face  314 , the entire area of secondary output opening  110  may face driver front face  314  while only a portion of primary output opening  108  may face driver front face  314 , with the rest facing a side of driver  302 . 
     As illustrated in  FIG. 4 , which is a more detailed representation of the earphone illustrated in  FIG. 3 , an acoustic and/or protective material may be disposed over one or both of primary output opening  108  and secondary output opening  110 . Representatively, acoustic material  432  and protective material  430  may be disposed over primary output opening  108 . Acoustic material  432  may be a piece of acoustically engineered material that provides a defined and intentional acoustic resistance or filtering effect. For example, in one embodiment, acoustic material  432  is a mesh or foam material that is manufactured to filter certain sound pressure waves output from driver  302 . Protective material  430  may be an acoustically transparent material meaning that it does not significantly affect an acoustic performance of earphone  100 . Rather, protective material  430  protects the device by preventing dust, water or any other undesirable materials or articles from entering housing  102 . Protective material  430  may be, for example, a mesh, polymer or foam, or any other material that allows an essentially open passage for output of sound pressure waves from driver  302 . 
     Similar to primary output opening  108 , acoustic material  436  and protective material  434  may be disposed over secondary output opening  110 . Similar to acoustic material  432 , acoustic material  436  may be a mesh or foam material manufactured to filter a desired sound pressure wave output from driver  302 . Protective material  434  may be an acoustically transparent material, for example, a mesh, polymer or foam, or any other material that protects earphone  100  from debris or articles and allows an essentially open passage for output of sound pressure waves from driver  302 . 
     Acoustic materials  432 ,  436  and protective materials  430 ,  434  may each be single pieces that are combined over their respective openings to form a sandwich structure that can be snap fit over the openings. Alternatively, the materials may be glued or otherwise adhered over the openings. In some embodiments, acoustic materials  432 ,  436  and protective materials  430 ,  434  may also be composite materials or multilayered materials. Additionally, it is contemplated that acoustic materials  432 ,  436  and protective materials  430 ,  434  may be positioned over their respective openings in any order. 
     Body portion  104  is divided into a front chamber  420  and back chamber  422  formed around opposing faces of driver  302 . Front chamber  420  may be formed around front face  314  of driver  302 . In one embodiment, front chamber  420  is formed by body portion  104  and tip portion  106  of housing  102 . In this aspect, sound waves  428  generated by front face  314  of driver  302  pass through front chamber  420  to the ear canal through primary output opening  108 . In addition, front chamber  420  may provide an acoustic pathway for venting air waves  426  or an acoustic pressure within the ear canal out secondary output opening  110  to the external environment. As previously discussed, secondary output opening  110  is a calibrated opening therefore transmission of sound waves  428  and air waves  426  through secondary output opening  110  is controlled so that an acoustic performance of earphone  100  between users is consistent. 
     Back chamber  422  may be formed around the back face  424  of driver  302 . Back chamber  422  is formed by body portion  104  of housing  102 . The various internal acoustic components of earphone  100  may be contained within front chamber  420  and back chamber  422  as will be discussed in more detail in reference to  FIG. 5 . 
       FIG. 5  illustrates an exploded perspective view of the internal acoustic components that can be contained within the earphone housing. Tip portion  106  of housing  102  may be formed by cap portion  502  which, in this embodiment, is shown removed from the base portion  504  of housing  102  to reveal the internal acoustic components that can be contained within housing  102 . The internal acoustic components may include driver seat  506 . Driver seat  506  may be dimensioned to fit within cap portion  502  and in front of front face  314  of driver  302 . In one embodiment, driver seat  506  may seal to front face  314  of driver  302 . Alternatively, driver seat  506  may be positioned in front of driver  302  but not directly sealed to driver  302 . Driver seat  506  is therefore positioned within front chamber  420  previously discussed in reference to  FIG. 4 . Driver seat  506  may include output opening  508 , which is aligned with secondary output opening  110  and includes similar dimensions so that sound generated by driver  302  can be output through driver seat  506  to secondary output opening  110 . Driver seat  506  may include another output opening (not shown) that corresponds to and is aligned with primary output opening  108 . Driver seat  506  may be, for example, a molded structure formed of the same material as housing  102  (e.g., a substantially rigid material such as plastic) or a different material (e.g., a compliant polymeric material). 
     Acoustic material  436  and protective material  434  may be held in place over secondary output opening  110  by driver seat  506 . In one embodiment, acoustic material  436  and protective material  434  are positioned between driver seat  506  and secondary output opening  110 . Alternatively, they may be attached to an inner surface of driver seat  506  and over opening  508  such that they overlap secondary output opening  110  when driver seat  506  is within cap portion  502 . Although not illustrated, acoustic material  432  and protective material  430 , which cover primary output opening  108 , are also considered internal acoustic components. Acoustic material  432  and protective material  430  may be assembled over primary output opening  108  in a manner similar to that discussed with respect to materials  436 ,  434 . 
     Acoustic tuning member  510  is positioned behind the back face  424  of driver  302  (i.e. within back chamber  422  illustrated in  FIG. 4 ) and fits within base portion  504  of body portion  104 . In one embodiment, acoustic tuning member  510  is positioned near back face  424  of driver  302  but is not directly attached to driver  302 . In another embodiment, acoustic tuning member  410  can be directly attached to driver  302 . When acoustic tuning member  510  is positioned near driver  302 , acoustic tuning member  510  and body portion  104  define the back volume chamber of driver  302 . The size and shape of a driver back volume chamber is important to the overall acoustic performance of the earphone. Since acoustic tuning member  510  defines at a least a portion of the back volume chamber, acoustic tuning member  510  can be used to modify the acoustic performance of earphone  100 . For example, acoustic tuning member  510  can be dimensioned to tune a frequency response of earphone  100  by changing its dimensions. 
     In particular, the size of the back volume chamber formed around driver  302  by acoustic tuning member  510  and earphone housing  102  can dictate the resonance of earphone  100  within, for example, a frequency range of about 2 kHz to about 3 kHz (i.e., open ear gain). The ear canal typically acts like a resonator and has a particular resonance frequency when open and a different resonance frequency when closed. The acoustic response at the ear drum when the ear canal is open is referred to as the open ear gain. A resonance frequency around 2 kHz to 3 kHz is typically preferred by users. Acoustic tuning member  510  can be dimensioned to tune the resonance of earphone  100  to a frequency within this range. Specifically, when acoustic tuning member  510  occupies a larger region behind driver  302  (i.e., the air volume of the back volume chamber decreases), the open ear gain increases in frequency. On the other hand, when acoustic tuning member  510  occupies a smaller region behind driver  302  (i.e., the air volume within back volume chamber increases), the open ear gain decreases in frequency. The dimensions of acoustic tuning member  510  can therefore be modified to tune the resonance of earphone  100  to achieve the desired acoustic performance. 
     In addition, acoustic tuning member  510  may form an acoustic channel between the back volume chamber and an acoustic duct and bass port  518  formed within tube portion  114 . The dimensions of the acoustic channel along with the acoustic duct and bass port  518 , may also be selected to modify an acoustic performance of earphone  100 . In particular, the dimensions may be selected to control a bass response (e.g., frequency less than 1 kHz) of the earphone as will be discussed in more detail below. 
     In typical earphone designs, the earphone housing itself defines the back volume chamber around the driver. Therefore the size and shape of the earphone housing affects the acoustic performance of the earphone. Acoustic tuning member  510 , however, can be a separate structure within earphone housing  102 . As such, the size and shape of acoustic tuning member  510  can be changed to achieve the desired acoustic performance without changing a size and shape of earphone housing  102 . In addition, it is contemplated that an overall form factor of acoustic tuning member  510  may remain substantially the same while a size of certain dimensions, for example a body portion, may be changed to modify a size of the back volume chamber formed by acoustic tuning member  510 , which in turn modifies the acoustic performance of the associated earphone. For example, acoustic tuning member  510  may be a substantially cone shaped structure. A thickness of the wall portion forming the end of the cone may be increased so that an air volume defined by acoustic tuning member  510  is smaller or the thickness may be decreased to increase the air volume. Regardless of the wall thickness, however, the outer cone shape is maintained. Thus, both an acoustic tuning member  510  defining a large air volume and another acoustic tuning member defining a relatively smaller air volume can fit within the same sized earphone housing. 
     The ability to modify the air volume defined by acoustic tuning member  510  without changing the form factor is important because acoustic performance varies from one driver to the next. Some aspects of the acoustic performance can be dictated by the size of the driver back volume chamber. Thus, one way to improve the acoustic consistency between drivers is by modifying the back volume chamber size. Since acoustic tuning member  510  defines the driver back volume, it may be manufactured to accommodate drivers of different performance levels. In addition, acoustic tuning member  510  can be separate from earphone housing  102 , thus modifying its dimensions to accommodate a particular driver does not require an alteration to the design of earphone housing  102 . 
     Acoustic tuning member  510  also includes acoustic output port  512  that acoustically connects the back volume chamber to an acoustic duct formed within tube portion  114  of housing  102 . The acoustic duct is acoustically connected to bass port  518  formed within tube portion  114 . Bass port  518  outputs sound from housing  102  to the external environment. Although a single bass port  518  is illustrated, it is contemplated that tube portion  114  may include more than one bass port, for example, two bass ports at opposing sides of tube portion  114 . 
     In addition, acoustic tuning member  510  may include tuning port  514  which outputs sound from acoustic tuning member  510 . Tuning port  514  may be aligned with tuning output port  532  formed in housing  102  so that the sound from acoustic tuning member  510  can be output to the external environment outside of housing  102 . Each of acoustic output port  512 , tuning port  514 , the acoustic duct and bass port  518  are acoustically calibrated openings or pathways that enhance an acoustic performance of earphone  100  as will be discussed in more detail below. 
     Cable  120 , which may include wires for transmitting power and/or an audio signal to driver  302 , may be connected to acoustic tuning member  510 . Cable  120  may be overmolded to acoustic tuning member  510  during a manufacturing process to provide added strain relief to cable  120 . Overmolding of cable  120  to acoustic tuning member  510  helps to prevent cable  120  from becoming disconnected from driver  302  when a force is applied to cable  120 . In addition to providing added strain relief, combining cable  120  and acoustic tuning member  510  into one mechanical part results in a single piece which takes up less space within earphone housing  102 . A near end of the cable  120  and the acoustic tuning member  510  may therefore be assembled into earphone housing  102  as a single piece. In particular, to insert acoustic tuning member  510  into body portion  104 , the far end of cable  120  is inserted into body portion  104  and pulled down through the end of tube portion  114  until acoustic tuning member  510  (with the near end of the cable  120  attached to it) is seated within base portion  504 . 
     The internal components may further include a protective material formed over tuning port  514  and/or bass port  518  to prevent entry of dust and other debris. Representatively, protective mesh  520  may be dimensioned to cover tuning port  514  and protective mesh  522  may be dimensioned to cover bass port  518 . Each of protective mesh  520  and protective mesh  522  may be made of an acoustically transparent material that does not substantially interfere with sound transmission. Alternatively, one or both of protective mesh  520 ,  522  may be made of an acoustic mesh material that provides a defined and intentional acoustic resistance or filtering effect. Protective mesh  520  and protective mesh  522  may be snap fit into place or held in place using an adhesive, glue or the like. Although not shown, it is further contemplated that in some embodiments, an additional acoustic material, such as those previously discussed in reference to  FIG. 3 , may also be disposed over tuning port  514  and/or bass port  518  to tune a frequency response of earphone  100 . 
     Tail plug  524  may be provided to help secure cable  120  within tube portion  114 . Tail plug  524  may be a substantially cylindrical structure having an outer diameter sized to be inserted within the open end of tube portion  114 . In one embodiment, tail plug  524  may be formed of a substantially resilient material that can conform to the inner diameter of tube portion  114 . In other embodiments, tail plug  524  may be formed of a substantially rigid material such as plastic. Tail plug  524  may be held within tube portion  114  by any suitable securing mechanism, for example, a snap fit configuration, adhesive, chemical bonding or the like. Tail plug  524  may include open ends and a central opening dimensioned to accommodate cable  120  so that cable  120  can run through tail plug  524  when it is inserted within tube portion  114 . Connecting bass port  530  may also be formed through a side wall of tail plug  524 . Connecting bass port  530  aligns with bass port  518  when tail plug  524  is inserted into tube portion  114  to facilitate sound travel out bass port  518 . 
     In one embodiment, the internal acoustic components may be assembled to form earphone  100  as follows. Acoustic material  436  and protective material  434  may be placed over secondary output opening  110  and driver seat  506  may be inserted within cap portion  502  to hold materials  434 ,  436  in place. Acoustic material  432  and protective material  430  of primary output opening  108  may be assembled in a similar manner. Front face  314  of driver  302  may be attached to driver seat  506  so that driver  302  is held in place within cap portion  502 . Cable  120 , attached to acoustic tuning member  510 , may be inserted into and through tube portion  114  though body portion  104  until acoustic tuning member  510  is positioned within body portion  504 . Protective mesh  520 , protective mesh  522  and tail plug  525  may be positioned within housing  102  prior to or after acoustic tuning member  510 . Finally, driver  302  may be inserted within body portion  104  of housing  102 . The foregoing is only one representative assembly operation. The internal acoustic components can be assembled in any manner and in any order sufficient to provide an earphone having optimal acoustic performance. 
       FIG. 6A  illustrates a front perspective view of one embodiment of an acoustic tuning member. Acoustic tuning member  510  is formed by tuning member housing or casing  644  having a substantially closed body portion  642  and open face portion  540  which opens toward driver  302  when positioned within earphone housing  102 . Casing  644  may have any size and shape capable of tuning an acoustic response of the associated driver. In particular, the dimensions of casing  644  can be such that they help tune the midband and bass response of the earphone within which it is used. Representatively, in one embodiment, casing  644  forms a substantially cone shaped body portion  642  having an acoustic output port  512  acoustically coupled to an acoustic groove  646  (see  FIG. 6B ) formed within a back side of casing  644 . Although a substantially cone shaped body portion  642  is described, other shapes are also contemplated, for example, a square, rectangular or a triangular shaped structure. 
     In one embodiment, acoustic output port  512  may be an opening formed through a wall of casing  644 . Alternatively, acoustic output port  512  may be a slot formed inwardly from an edge of casing  644 . Acoustic output port  512  outputs sound from acoustic tuning member  510  to acoustic groove  646 . Acoustic groove  646  provides an acoustic pathway to an acoustic duct formed in tube portion  114 . Acoustic output port  512  and acoustic groove  646  are dimensioned to tune an acoustic response of earphone  100 . In this aspect, acoustic output port  512  and acoustic groove  646  are calibrated in the sense that they have been tested or evaluated (in at least one specimen of a manufactured lot) for compliance with a given specification or design parameter. In other words, they are not just random openings or grooves, but intentionally formed for a particular purpose, namely to modify the frequency response of the earphone in a way that helps to tune the frequency response and improve a bass response. 
     For example, it is recognized that acoustic inductance within earphone  100  controls a midband response and bass response of earphone  100 . In addition, the acoustic resistance within earphone  100  can affect the bass response. Thus, a size and shape of acoustic output port  512  and acoustic groove  646  may be selected to achieve a desired acoustic inductance and resistance level that allows for optimal midband and bass response within earphone  100 . In particular, increasing an acoustic mass within earphone  100  results in greater sound energy output from earphone  100  at lower frequencies. The air mass within earphone  100 , however, should be maximized without increasing the acoustic resistance to an undesirable level. Thus, acoustic output port  512  and acoustic groove  646  may be calibrated to balance the acoustic inductance and acoustic resistance within earphone  100  so that an acoustically desirable midband and bass response are achieved. Representatively, acoustic output port  512  may have a surface area of from about 0.5 mm 2  to about 4 mm 2 , or from about 1 mm 2  to about 2 mm 2 , for example, about 1.3 mm 2 . Acoustic output port  512  may have a height dimension that is different than its width dimension, for example, the height dimension may be slightly larger than the width dimension. Alternatively, a height and width dimension of acoustic output port  512  may be substantially the same. 
     Acoustic groove  646  may have cross sectional dimensions substantially matching that of acoustic output port  512 . As previously discussed, acoustic groove  646  may be a groove formed within a back side of casing  644 . Acoustic groove  646  extends from acoustic output port  512  toward the back end of casing  644 . When acoustic tuning member  510  is positioned within earphone housing  102 , acoustic groove  646  mates with housing groove  648  formed along an inner surface of housing  102  to form a closed acoustic channel  650  (see  FIG. 6C ) between acoustic output port  512  and tube portion  114 . Alternatively, housing groove  648  may be omitted and acoustic groove  646  may form acoustic channel  650  by mating with any inner surface of housing  102 , or acoustic groove  646  may be formed as a closed channel such that it does not need to mate with any other surface to form acoustic channel  650 . Sound waves within the back volume chamber formed by acoustic tuning member  510  travel from acoustic tuning member  510  to tube portion  114  through acoustic channel  650 . A length, width and depth of acoustic groove  646  (and the resulting acoustic channel  650 ) may be such that an acoustically desirable midband and bass response are achieved by earphone  100 . Representatively, the length, width and depth may be large enough to allow for optimal acoustic mass within earphone  100  without increasing the resistance to an undesirable level. 
     Referring back to  FIGS. 6A-6B , tuning port  514  may be formed along a top portion of acoustic tuning member  510 . In one embodiment, tuning port  514  is a slot extending from an outer edge of open face portion  540 . Alternatively, tuning port  514  may be an opening formed near the outer edge but does not extend through the outer edge. In addition to its tuning functions, tuning port  514  may also be dimensioned to accommodate wires  602  extending from cable  120  to the driver, as shown in  FIG. 6B . Representatively, cable  120  may be overmolded along a back side of body portion  642  such that an open end of cable  120  is positioned near tuning port  514 . Wires  602  extending from the open end of cable  120  may pass through tuning port  514  and attach to electrical terminals for example on the back side of the driver, to provide power and/or an audio signal to the driver. 
     Acoustic tuning member  510  may be formed by molding a substantially non-compliant material such as a plastic into the desired shape and size. Alternatively, acoustic tuning member  510  may be formed of any material, such as a compliant or resilient material, so long as it is capable of retaining a shape suitable for enhancing an acoustic performance of earphone  100 . Acoustic tuning member  510  may be formed separate from housing  102  such that it rests, or is mounted, inside of earphone housing  102 . Since acoustic tuning member  510  is a separate piece from earphone housing  102  it may have a different shape than earphone housing  102  and define a back volume chamber having a different shape than back chamber  422  formed without earphone housing  102 . Alternatively, housing  102  and acoustic tuning member  510  may be integrally formed as a single piece. 
       FIG. 6B  illustrates a back side perspective view of acoustic tuning member  510 . From this view it can be seen that acoustic groove  646  is formed by a back side of acoustic tuning member  510  and extends from acoustic output port  512  toward the back end of acoustic tuning member  510 . 
       FIG. 6C  illustrates a cross-sectional top view of acoustic tuning member  510  positioned within earphone housing  102 . As can be seen from this view, when acoustic tuning member  510  is positioned within housing  102 , acoustic groove  646  is aligned with housing groove  648  formed along an inner surface of housing  102  to form acoustic channel  650 . Acoustic channel  650  extends from acoustic output port  512  to tube portion  114  so that sound within the back chamber defined by acoustic tuning member  510  can travel from the back volume chamber to tube portion  114  as will be described in more detail in reference to  FIG. 7  and  FIG. 8 . 
     Still referring to  FIG. 6C , in addition to the acoustic characteristics achieved by acoustic output port  512  and acoustic groove  646 , body portion  642  may include a volume modifying portion  660  that can be increased or decreased in size during a manufacturing process to change the air volume within acoustic tuning member  510 . As previously discussed, acoustic tuning member  510  defines the back volume chamber around a driver within the earphone housing. Thus, increasing the air volume within acoustic tuning member  510  also increases the back volume chamber, which modifies the acoustic performance of earphone  100 . Decreasing the air volume within acoustic tuning member  510  decreases the back volume chamber. The volume modifying portion  660  can have any size and shape and be positioned along any portion of the inner surface of acoustic tuning member  510  sufficient to change the volume of the back volume chamber defined by acoustic tuning member  510 . For example, volume modifying portion  660  may be positioned along a center region of acoustic tuning member  510  such that the inner profile of acoustic tuning member  510  has a substantially curved shape. Volume modifying portion  660  can be formed by thickening portions of the wall of acoustic tuning member  510  or mounting a separate plug member within acoustic tuning member  510 . In addition, the size and shape of volume modifying portion  660  can be changed without modifying an overall form factor of acoustic tuning member  510 . Thus, during manufacturing, one acoustic tuning member  510  can be made to define a large air volume while another defines a smaller air volume, yet both can fit within the same type of earphone housing  102  because they have the same overall form factor. Cable  120  can be overmolded within volume modifying portion  660  of acoustic tuning member  510  as illustrated in  FIG. 6C . In other embodiments, cable  120  can be overmolded within any portion of acoustic tuning member  510 . 
       FIG. 7  illustrates a cross-sectional side view of one embodiment of an earphone. Acoustic tuning member  510 , along with a portion of housing  102 , are shown forming back volume chamber  706  around driver  302 . As can be seen from this view, volume modifying portion  660  of acoustic tuning member  510  occupies a substantial area within back chamber  422  defined by earphone housing  102  therefore a size of back volume chamber  706  is smaller than housing back chamber  422 . As previously discussed, a size and shape of volume modifying portion  660  can be modified to achieve a back volume chamber  706  of a desired size. 
     Sound waves generated by the back face of driver  302  can be transmitted through acoustic channel  650  to acoustic duct  704  formed within tube portion  114  of earphone  100 . Acoustic channel  650  provides a defined acoustic path for transmitting sound from driver  302  to acoustic duct  704 . As previously discussed, acoustic channel  650  may be an enclosed channel formed by aligning or mating acoustic groove  646  along an outer surface of acoustic tuning member  510  and housing groove  648  along an inner surface of earphone housing  102 . Alternatively, acoustic channel  650  may be formed by one of acoustic groove  646  or housing groove  648 , or a separate structure mounted within housing  102 . 
     Acoustic duct  704  may be a conduit formed within tube portion  114  that allows air or sound to pass from one end of tube portion  114  to another end. Air or sound passing through acoustic duct  704  may exit acoustic duct  704  through bass port  518  so that sound within acoustic duct  704  can be output to the environment outside of housing  102 . 
     In addition to providing a sound pathway, acoustic duct  704  may also accommodate cable  120  and the various wires traveling through cable  120  to driver  302 . In particular, cable  120  may travel through acoustic duct  702  and the back side of acoustic tuning member  510 . As previously discussed, the wires within cable  120  may extend out the end of cable  120  and through tuning port  514  so that they can be attached to driver  302 . 
       FIG. 8  illustrates a cross-sectional side view of one embodiment of an earphone. The transmission of sound waves  802  generated by the back face of driver  302  through earphone  100  is illustrated in  FIG. 8 . In particular, from this view, it can be seen that acoustic tuning member  510  and housing  102  form back volume chamber  706  around the back side of driver  302 . Sound waves  802  generated by driver  302  travel into back volume chamber  706 . Sound waves  802  can exit back volume chamber  706  through acoustic output port  512 . From acoustic output port  512 , sound waves  802  travel through acoustic channel  650  to acoustic duct  704 . Sounds waves  802  traveling along acoustic duct  704  can exit acoustic duct  704  to the surrounding environment through bass port  518 . It is further noted that sound waves  802  may also exit back volume chamber  706  to the surrounding environment through the tuning port of acoustic tuning member  510 , which is aligned with tuning output port  532  formed in housing  102 . 
     Each of acoustic output port  512 , acoustic channel  650 , acoustic duct  704  and bass port  518  are calibrated to achieve a desired acoustic response. In particular, as the cross-sectional area of each of these structures decreases, the acoustic resistance within back volume chamber  706  increases. Increasing the acoustic resistance, decreases the bass response. Therefore, to increase the bass response of earphone  100 , a cross-sectional area of one or more of acoustic output port  512 , acoustic channel  650 , acoustic duct  704  and bass port  518  can be increased. To decrease the bass response, the cross-sectional area of one or more of acoustic output port  512 , acoustic channel  650 , acoustic duct  704  and bass port  518  is decreased. In one embodiment, the cross-sectional area of acoustic output port  512 , acoustic channel  650 , acoustic duct  704  and/or bass port  518  may range from about 1 mm 2  to about 8 mm 2 , for example, from 3 mm 2  to about 5 mm 2 , representatively about 4 mm 2 . 
     Additionally, or alternatively, where a smaller cross sectional area of one or more of acoustic output port  512 , acoustic channel  650 , acoustic duct  704  and bass port  518  is desired, a size and shape of volume modifying portion  660  within acoustic tuning member  510  may be decreased to balance any increases in resistance caused by the smaller pathways. In particular, decreasing the size and/or shape of volume modifying portion  660  will increase back volume chamber  706  formed by acoustic tuning member  510 . This larger air volume will help to reduce acoustic resistance and in turn improve the bass response. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, the secondary output opening, also referred to herein as the leak port, may have any size and shape and be formed within any portion of the earphone housing suitable for improving an acoustic response of the earphone. For example, the secondary output opening may be formed within a side portion of the housing that does not face the pinna portion of the ear when the earphone is positioned within the ear, such as a top side or a bottom side of the earphone housing, or a side of the housing opposite the pinna portion of the ear. Still further, acoustic tuning member may be used to improve an acoustic response of any type of earpiece with acoustic capabilities, for example, circumaural headphones, supra-aural headphones or a mobile phone headset. The description is thus to be regarded as illustrative instead of limiting.