Patent Description:
<CIT>, <CIT>, <CIT>, <CIT> and <CIT> are prior art references disclosing earphones.

The invention proposes an earphone as recited in claim <NUM>.

Other features, objects, and advantages will become apparent from the following detailed description, when read in connection with the following drawing, in which:.

<FIG> shows the human ear and a Cartesian coordinate system, for the purpose of identifying terminology used in this application. In the description that follows, "forward" or "front " will refer to the + direction along the X-axis, "backward" or "rear" will refer to the - direction along the X-axis; "above" or "up" will refer to the + direction along the Y-axis, "below" or "down" will refer to the - direction along the Y-axis; "on top of" and "outward" will refer to the + direction along the Z-axis (out of the page), and "behind" or "under" or "inward" will refer to the - direction along the Z-axis (into the page).

The description that follows will be for an earpiece that fits in the right ear. For an earpiece that fits in the left ear, some of the definitions, or the "+" and "=` directions may be reversed, and "clockwise" and "counterclockwise" may mean rotation in different directions relative to the ear or other elements than is meant in the description below. There are many different ear sizes and geometries. Some ears have additional features that are not shown in <FIG>. Some ears lack some of the features that are shown in <FIG>. Some features may be more or less prominent than are shown in <FIG>.

<FIG> shows several views of an in-ear earpiece <NUM>. The earpiece <NUM> includes a body <NUM>, an acoustic driver module <NUM>, which may be mechanically coupled to an optional electronics module <NUM>. The body <NUM> may have an outlet section <NUM> that fits into the ear canal. Other reference numbers will be identified below. The earpiece may be wireless, that is, there may be no wire or cable that mechanically or electronically couples the earpiece to any other device. Some elements of earpiece <NUM> may not be visible in some views.

The optional electronics module <NUM> may include a microphone at one end <NUM> of the electronics module <NUM>. The optional electronics module <NUM> may also include electronic circuitry to wirelessly receive radiated electronic signals; electronic circuitry to transmit audio signals to, and to control the operation of, the acoustic driver; a battery; and other circuitry. The electronics module may be enclosed in a substantially box-shaped housing with planar walls.

It is desirable to place the in-ear earpiece <NUM> in the ear so that it is oriented properly, so that it is stable (that is, it remains in the ear), and so that it is comfortable. Proper orientation may include positioning the body so that the electronics module, if present, is oriented so that the microphone is pointed toward the mouth of the user and so that a planar surface of the electronics module <NUM> is positioned near or against the side of the head of the user to prevent excessive motion of the earpiece. An electronics module <NUM>, if present, and the possible wireless characteristic of the earpiece makes the orientation and stability of the earpiece more complicated than in earpieces that have wires or cables and that do not have the electronics module. The wires tend to orient the earpiece so that the wire or cable hangs down, so the absence of the wire or cable makes proper orientation more difficult to achieve. If the electronics module is not present, proper orientation could include orienting the body so that the outlet section <NUM> is oriented properly relative to the ear canal. The electronics module <NUM> tends to be heavy relative to other components of the earpiece so that it tends to shift the center of mass outward, where there is no contact between the earpiece and the head of the user, so that the earpiece tends to move downward along the Y-axis and to rotate about the Z-axis and the X-axis.

<FIG> shows a cutout view of the body <NUM>. The body <NUM> includes a passageway <NUM> to conduct sound waves radiated by the acoustic driver in the acoustic driver module to the ear canal. The body <NUM> has a substantially planar surface13 that substantially rests against, the concha at one end. Extending from the body <NUM> is a positioning and retaining structure <NUM> that, together with the body <NUM> holds the earpiece in position without the use of ear hooks, or so-called "click lock" tips, which may be unstable (tending to fall out of the ear), uncomfortable (because they press against the ear), or ill fitting (because they do not conform to the ear). The positioning and retaining structure <NUM> includes at least an outer leg <NUM> and an inner leg <NUM> that extend from the body. Other implementations may have additional legs such as leg <NUM>, shown in dotted lines. Each of the two legs is connected to the body at one end <NUM> and <NUM> respectively. The outer leg is curved to generally follow the curve of the anti-helix at the rear of the concha. The second ends of each of the legs are joined at point <NUM>. The joined inner and outer legs may extend past point <NUM> to a positioning and retaining structure extremity <NUM>. In one implementation, the positioning and retaining structure <NUM> is made of silicone, with a <NUM> Shore A durometer. The outer leg <NUM> lies in a plane.

The positioning and retaining structure is substantially stiffer (less compliant) when force is applied to the extremity <NUM> in the counterclockwise direction as indicated by arrow <NUM> (about the Z-axis) than when force is applied to the extremity <NUM> in the clockwise direction as indicated by arrow <NUM> about the Z-axis. The difference in compliance can be attained by the geometry of the two legs <NUM> and <NUM>, the material of two legs <NUM> and <NUM>, and by prestressing one or both of the legs <NUM> and <NUM>, or a combination of geometry, material, and prestressing. The compliance may further be controlled by adding more legs to the legs <NUM> and <NUM>. The positioning and retaining structure is substantially more compliant when force is applied to the extremity along the Z-axis, indicated by arrow <NUM> than when force is applied about the Z-axis, indicated by arrows <NUM> and <NUM>.

In one measurement, the stiffness when force is applied the counterclockwise direction (indicated by arrow <NUM>) was approximated by holding the body <NUM> stationary, applying a force to the extremity <NUM> along the X-axis in the -X direction, and measuring the displacement in the -X direction; the stiffness when force is applied in the clockwise direction (indicated by arrow <NUM>) was approximated by holding the body <NUM> stationary and pulling the extremity <NUM> along the Y-axis in the -Y direction. The stiffness in the counterclockwise direction ranged from <NUM> N/mm (Newtons per millimeter) to <NUM> N/mm, depending on the size of the body <NUM> and of the positioning and retaining structure <NUM>. The stiffness in the clockwise direction ranged from <NUM> N/mm to <NUM> N/mm, also dependent on the size of the body <NUM> and of the positioning and retaining structure <NUM>. For equivalent sized bodies and positioning and retaining structures, the stiffness in the counterclockwise direction ranged from <NUM>. 0x to <NUM>. 3x the stiffness in the clockwise direction. In one measurement, force was applied along the Z-axis. The stiffness ranged from <NUM> N/mm to <NUM> N/mm, dependent on the size of the body <NUM> and of the positioning and retaining structure <NUM>; a typical range of stiffnesses might be. <NUM> N/mm to. <NUM> N/mm. For equivalent sized bodies and positioning and retaining structures, the stiffness when force was applied along the Z-axis ranged from <NUM> to <NUM> of the stiffness when force was applied in the counterclockwise direction.

Referring now to <FIG>, to place the earpiece in the ear, the body is placed in the ear and pushed gently inward and preferably rotated counter-clockwise as indicated by arrow <NUM>. Pushing the body into the ear causes the body <NUM> and the outer leg <NUM> to seat in position underneath the anti-tragus, and causes the outlet section <NUM> of the body <NUM> to enter the ear canal. Rotating the body counter-clockwise properly orients in the Z-direction the outer leg <NUM> for the steps that follow.

The body is then rotated clockwise as indicated by arrow <NUM> until a condition occurs so that the body cannot be further rotated. The conditions could include: the extremity <NUM> may contact the base of the helix; leg <NUM> may contact the base of the helix; or the extremity <NUM> may become wedged behind the anti-helix in the cymba concha region. Though the positioning and retaining structure provides all three conditions (hereinafter referred to as "modes", not all three conditions will happen for all users, but at least one of the modes will occur for most users. Which condition(s) occur(s) is dependent on the size and geometry of the user's ears.

Providing more than one mode for positioning the earpiece is advantageous because no one positioning mode works well for all ears. Providing more than one mode of positioning makes it more likely that the positioning system will work well over a wide variety of ear sizes and geometries.

Rotating the body <NUM> clockwise also causes the extremity and outer leg to engage the cymba concha region and seat beneath the anti-helix. When the body and positioning and retaining structure <NUM> are in place, positioning and retaining structure and/or body contact the ear of most people in at least two, and in many people more, of several ways: a length <NUM> of the outer leg <NUM> contacts the anti-helix at the rear of the concha; the extremity <NUM> of the positioning and retaining structure <NUM> is underneath the anti-helix <NUM>; portions of the outer leg <NUM> or body <NUM> or both are underneath the anti-tragus <NUM>; and the body <NUM> contacts at the entrance to the ear canal under the tragus. The two or more points of contact hold the earpiece in position, providing greater stability. The distributing of the force, and the compliance of the portions of the body and the outer leg that contact the ear lessens pressure on the ear, providing comfort.

Referring again to View E of <FIG> and Views B, C, and D of <FIG>, the body <NUM> may have a slightly curved surface <NUM> that rests against the concha. The periphery of the slightly curved surface may line is a plane, hereinafter referred to as the body plane. In one implementation, the projection of the outer leg <NUM> of the positioning and retaining structure <NUM> on the Y-Z plane may be angled relative to the intersection of the body plane <NUM> and the Y-Z plane, as indicated by line <NUM> (a centerline of leg <NUM>) and line <NUM> (parallel to the body plane). When in position, the body plane <NUM> is substantially parallel to the X-Y plane. Stated differently, the outer leg <NUM> is angled slightly outward.

The angling of the positioning and retaining structure <NUM> has several characteristics. The structure results in a greater likelihood that the extremity will seat underneath the anti-helix despite variations in ear size and geometry. The outward slant conforms better to the ear. The positioning and retaining structure is biased inward, which causes more force to resist movement in an outward direction more than resists movement in an inward direction. These characteristics provide a marked improvement in comfort, fit, and stability over earpieces which have a positioning and retaining structure that is not angled relative to the plane of a surface contacting the concha.

If the angling of the position and retention structure does not cause the extremity to seat behind the anti-helix, the compliance of the extremity in the Z-direction permits the user to press the extremity inward so that it does seat behind the anti-helix.

Providing features that prevent over-rotation of the body results in an orientation that is relatively uniform from user to user, despite differences in ear size and geometry. This is advantageous because proper and uniform orientation of the earpiece results in a proper and uniform orientation of the microphone to the user's mouth.

<FIG> shows a cross-section of the body <NUM> and positioning and retaining structure <NUM> taken along line A - A. The cross-section is oval or "racetrack" shaped, with the dimension in a direction Z' substantially parallel to the Z-axis <NUM> to <NUM> times the dimension in direction X', substantially parallel to the X-axis, preferably closer to <NUM> than to <NUM>, and in one example, <NUM> times the dimension in the X' direction. In some examples, the dimension in the Z' direction may be as low as <NUM> times the dimension in the X' direction. The cross-section permits more surface of the outer leg to contact the anti-helix at the rear of the concha, providing better stability and comfort. Additionally, there are no corners or sharp edges in the part of the leg that contacts the ear, which eliminates a cause of discomfort.

As best shown in Views B and E of <FIG>, the acoustic driver module is slanted inwardly and forwardly relative to the plane of the body <NUM>. The inward slant shifts the center of gravity relative to an acoustic driver module that is substantially parallel to the positioning and retaining structure <NUM> or the electronics module <NUM>, or both. The forward slant combined with the inward slant permits more of the acoustic driver module to fit inside the concha of the ear, increasing the stability of the earpiece.

<FIG> shows a diagrammatic cross-section of the acoustic driver module <NUM> and the body <NUM>. A first region <NUM> of the earpiece <NUM> includes a rear chamber <NUM> and a front chamber <NUM> defined by shells <NUM> and <NUM>, respectively, on either side of an acoustic driver <NUM>. In some examples, a <NUM> nominal diameter driver is used. A nozzle <NUM> extends from the front chamber <NUM> into the entrance to the ear canal, and in some embodiments into the ear canal, through the body <NUM> and may end at an optional acoustic resistance element <NUM>. In some examples, the optional resistance element <NUM> is located within nozzle <NUM>, rather than at the end, as illustrated. An acoustic resistance element, if present, dissipates a proportion of acoustic energy that impinges on or passes through it. In some examples, the front chamber <NUM> includes a pressure equalization (PEQ) hole <NUM>. The PEQ hole <NUM> serves to relieve air pressure that could be built up within the ear canal <NUM> and front chamber <NUM> when the earphone <NUM> is inserted into the ear. The rear chamber <NUM> is sealed around the back side of the acoustic driver <NUM> by the shell <NUM>. In some examples, the rear chamber <NUM> includes a reactive element, such as a port (also referred to as a mass port) <NUM>, and a resistive element, which may also be formed as a port <NUM>. <CIT> describes the use of parallel reactive and resistive ports in a headphone device.

Although ports are often referred to as reactive or resistive, in practice any port will have both reactive and resistive effects. The term used to describe a given port indicates which effect is dominant. In the example of <FIG>, the reactive port is defined by spaces in the shell <NUM>. A reactive port like the port <NUM> is, for example, a tube-shaped opening in what may otherwise be a sealed acoustic chamber, in this case rear chamber <NUM>. A resistive port like the port <NUM> is, for example, a small opening in the wall of an acoustic chamber covered by a material providing an acoustical resistance, for example, a wire or fabric screen, that allows some air and acoustic energy to pass through the wall of the chamber. The mass port <NUM> and the reactive port <NUM> acoustically couple the back cavity <NUM> with the ambient environment. The mass port <NUM> and the resistive port <NUM> are shown schematically. The actual location of the mass port <NUM> and the resistive port <NUM> will be shown in figures below and the size will be specified in the specification. Similarly, the actual location and size of the pressure equalization hole <NUM> will be shown below, and the size specified in the specification.

Each of the body <NUM>, cavities <NUM> and <NUM>. driver <NUM>, damper <NUM>, hole <NUM>, and ports <NUM> and <NUM> have acoustic properties that may affect the performance of the earpiece <NUM>. These properties may be adjusted to achieve a desired frequency response for the earphone. Additional elements. such as active or passive equalization circuitry. may also be used to adjust the frequency response.

To increase low frequency response and sensitivity, a nozzle <NUM>, may extend the front cavity <NUM> into the ear canal, facilitating the formation of a seal between the body <NUM> and the ear canal. Sealing the front cavity <NUM> to the ear canal decreases the low frequency cutoff, as does enclosing the rear of transducer <NUM> with small cavity <NUM> including the ports <NUM> and <NUM>. Together with a lower portion <NUM> of the cushion, the nozzle <NUM> provides better seal to the ear canal than earphones that merely rest in the concha, as well as a more consistent coupling to an individual user's ears. The tapered shape and pliability of the cushion allow it to form a seal in ears of a variety of shapes and sizes. In some examples, the rear chamber <NUM> has a volume of <NUM><NUM> , which includes the volume of the driver <NUM>. Excluding the driver, the rear chamber <NUM> has a volume of <NUM><NUM>.

The reactive port <NUM> resonates with the back chamber volume. In some examples, it has a diameter in the range of about <NUM> to <NUM>, for example <NUM> and a length in the range of about <NUM> to <NUM>, for example <NUM>. In some embodiments, the reactive port is tuned to resonate with the cavity volume around the low frequency cutoff of the earphone. In some embodiments, he low frequency cutoff is around <NUM>, which can vary by individual, depending on ear geometry. In some examples, the reactive port <NUM> and the resistive port <NUM> provide acoustical reactance and acoustical resistance in parallel meaning that they each independently couple the rear chamber <NUM> to free space. In contrast, reactance and resistance can be provided in series in a single pathway, for example, by placing a resistive element such as a wire mesh screen inside the tube of a reactive port. In some examples, a parallel resistive port is covered by 70x800 Dutch twill wire cloth, for example, that is available from Cleveland Wire of Cleveland, OH. Parallel reactive and resistive elements, embodied as a parallel reactive port and resistive port, provides increased low frequency response compared to an embodiment using a series reactive and resistive elements. The parallel resistance does not substantially attenuate the low frequency output while the series resistance does. Using a small rear cavity with parallel ports allows the earphone to have improved low frequency output and a desired balance between low frequency and high frequency output.

The PEQ hole <NUM> is located so that it will not be blocked when in use. For example, the PEQ hole <NUM> is not located in the portion of the body <NUM> that is in direct contact with the ear, but away from the ear in the front chamber <NUM>. The primary purpose of the hole is to avoid an over-pressure condition when the earpiece <NUM> is inserted into the user's ear. Additionally, the hole can used to provide a fixed amount of leakage that acts in parallel with other leakage that may be present. This helps to standardize response across individuals. In some examples, the PEQ hole <NUM> has a diameter of about <NUM>. Other sizes may be used, depending on such factors as the volume of the front chamber <NUM> and the desired frequency response of the earphones. Adding the PEQ hole makes a trade off between some loss in low frequency output and more repeatable overall performance.

The body <NUM> is designed to comfortably couple the acoustic elements of the earphone to the physical structure of the wearer's ear. As shown in <FIG>, the body <NUM> has an upper portion <NUM> shaped to make contact with the tragus and anti-tragus of the ear, and a lower portion <NUM> shaped to enter the ear canal <NUM>, as mentioned above. In some examples, the lower portion <NUM> is shaped to fit within but not apply significant pressure on the flesh of the ear canal <NUM>. The lower portion <NUM> is not relied upon to provide retention of the earphone in the ear, which allows it to seal to the ear canal with minimal pressure. A void <NUM> in the upper portion <NUM> receives the acoustic elements of the earphone (not shown), with the nozzle <NUM> (of <FIG>) extending into a void <NUM> in the lower portion <NUM>. In some examples, the body <NUM> is removable from the earpiece <NUM>, examples, the body <NUM> is formed of materials having different hardnesses, as indicated by regions <NUM> and <NUM>. The outer region <NUM> is formed of a soft material, for example, one having a durometer of <NUM> shore A, which provides good comfort because of its softness. Typical durometer ranges for this section are from <NUM> shore A to <NUM> shore A. The inner region <NUM> is formed from a harder material, for example, one having a durometer of <NUM> shore A. This section provides the stiffness needed to hold the cushion in place. Typical durometer ranges for this section are from <NUM> shore A to <NUM> shore A. In some examples, the inner section <NUM> includes an O-ring type retaining collar <NUM> to retain the cushion on the acoustic components. The stiffer inner portion <NUM> may also extend into the outer section to increase the stiffness of that section. In some examples. variable hardness could be arranged in a single material.

In some examples, both regions of the cushion are formed from silicone. Silicone can be fabricated in both soft and more rigid durometers in a single part. In a double-shot fabrication process, the two sections are created together with a strong bond between them. Silicone has the advantage of maintaining its properties over a wide temperature range, and is known for being successfully used in applications where it remains in contact with human skin. Silicone can also be fabricated in different colors, for example, for identification of different sized cushions, or to allow customization. In some examples, other materials may be used, such as thermoplastic elastomer (TPE). TPE is similar to silicone, and may be less expensive, but is less resistant to heat. A combination of materials may be used, with a soft silicone or TPE outer section <NUM> and a hard inner section <NUM> made from a material such as ABS, polycarbonate, or nylon. In some examples, the entire cushion may be fabricated from silicone or TPE having a single hardness, representing a compromise between the softness desired for the outer section <NUM> and the hardness needed for the inner section <NUM>.

<FIG> shows a blowup view of the electronics module <NUM>, the acoustic driver module <NUM>, and the body <NUM>. The electronics module comprises plastic enclosure <NUM> (which may be multi-piece) that encloses electronic circuitry (not shown) for wirelessly receiving audio signals. Acoustic driver module <NUM> includes shell <NUM>, acoustic driver <NUM>, and shell <NUM>. The position of the mass port <NUM> and the reactive port <NUM> in shell <NUM> are shown. The position of the PEQ hole <NUM> on shell <NUM> is also shown. When the earpiece <NUM> is assembled, nozzle <NUM> fits inside the outlet section <NUM> of the body <NUM>. Referring again to <FIG>, the outside diameter of the nozzle <NUM> may be approximately the same as the inside dimension of the outlet section <NUM>, as indicated by arrows <NUM> and <NUM>.

<FIG> shows a variation of the assembly of <FIG>. The implementation of <FIG> is the mirror image of the implementation of <FIG>, to indicate that the earpiece can be configured for either ear. In the implementation of <FIG>, an outside dimension of the nozzle is smaller than the corresponding inside dimension of the outlet section <NUM>, as indicated by arrows <NUM>' and <NUM>'. The difference in dimensions provides a space <NUM> between the nozzle and the outlet section <NUM> of the body <NUM>. The space permits the lower portion of the body <NUM> to better conform to the ear canal, providing additional comfort and stability. The rigidity of the nozzle results in the ability of the outlet section to conform to the ear canal, without substantially changing the shape or volume of the passage to the ear canal, so the acoustic performance of the earpiece is not appreciably affected by changes in ear size or geometry. The smaller dimension of the nozzle may adversely affect high frequency (e.g. above <NUM>. However, the circuitry for wirelessly receiving audio signals enclosed in electronics module <NUM> may be limited to receiving audio signals up to only about <NUM>, so the adversely affected high frequency performance is not detrimental to the overall performance of the earpiece. One way of allowing an earpiece to play louder is to overdrive the acoustic driver. Overdriving an acoustic driver tends to introduce distortion and adversely affects the bandwidth.

<FIG> shows a body <NUM> with a portion of the outlet section <NUM> and the nozzle <NUM> removed. The inside of the outlet section <NUM> and the outside of the nozzle <NUM> are both ovals. The minor axis of the outside of the nozzle, represented by line <NUM>' is <NUM>. The minor axis of the inside of the outlet section <NUM>, represented line <NUM>' is <NUM>. The width of the space <NUM> at its widest point is <NUM>.

One way of achieving good acoustic performance is to use a larger driver. A larger acoustic driver, for example a <NUM> nominal diameter acoustic driver can play louder with less distortion and with better bandwidth and intelligibility than conventional smaller acoustic drivers. However the use of larger acoustic drivers has some disadvantages. Acoustic drivers that have a diameter (nominal diameter plus housing) of greater than <NUM> do not fit in the conchas of many people. If the acoustic driver is positioned outside the concha, the center of mass may be well outside the ear so that the earpiece is unstable and tends to fall out of the ear. This problem is made worse by the presence of the electronics module <NUM>, which may be heavy relative to other components of the earpiece, and which moves the center of mass even further away from the side of the head.

As best shown in Views B and E of <FIG>, the acoustic driver module is slanted inwardly and forwardly relative to the plane of the positioning and retention structure <NUM> and the plane of the electronics module <NUM>. The inward slant shifts the center of gravity relative to an acoustic driver module that is substantially parallel to the positioning and retention structure <NUM> or the electronics module <NUM>, or both. The forward slant combined with the inward slant permits more of the acoustic driver module to fit inside the concha of the ear, increasing the stability of the earpiece.

While human ears show a great variability in size and shape, we have found that a majority of the population can be accommodated by providing sets of ear pieces offering a small number of pre-defined sizes, as long as those sizes maintain particular relationships between the dimensions of the retaining structure <NUM>. <FIG> shows dimensions characterizing the shape and size of the positioning and retaining structure <NUM>. Of particular interest are the radii and lengths of the outer edges <NUM> and <NUM>, respectively, of the legs <NUM> and <NUM>, i.e., the shape of the outer perimeter of the portion that contacts the ear.

According to the invention, the outer edge <NUM> of the outer leg <NUM> has a variable radius of curvature, more-sharply curved near the body <NUM> and flattening out at positions farther from the body <NUM>, to fit to the antihelix. In some examples, as shown in <FIG>, the leg is defined by two segments 22a and 22b, each having a different radius Roa and Rob, that is constant within that segment. In some examples, three different radii are used, with an intermediate radius smoothing the transition between the outer, flatter portion, and the inner, more-curved portion. In other examples, there may be many segments with different radii, or the entire leg may have a continuously variable radius of curvature. The center points from which the radii are measured are not necessarily the same for the different segments; the radius values are merely characterizations of the curvature at different points, not references to curves around a common center. The outer edge <NUM> has a total length Lo as measured from a point <NUM> where the leg joins the body <NUM> and an end point <NUM> where it meets the flat tip at extremity <NUM>.

Similarly, the outer edge <NUM> of the inner leg <NUM> in <FIG> also has two segments 24a and 24b, with different radii Ria and Rib, and a total length Li measured between points <NUM> and <NUM>. In examples having more than two segments in the inner leg, unlike the outer leg, the radii may not have a monotonic progression. In particular, a middle segment may have the shortest radius, to make a relatively sharp bend between relatively straighter sections at either end. As with the outer leg, the inner leg may have two different radii, as shown, three radii, or it may have more, up to being continuously variable.

The radii and lengths of the inner and outer legs are interrelated. As the two legs are joined at one end, making the outer leg larger without a corresponding increase to the inner leg would cause the radii to decrease (making the curves more extreme), and vice-versa. Likewise, changing any of the radii would require one or the other of the legs to change length. As the retention feature is made smaller or larger, to fit different sized ears, the relationships between the different segments may be changed or kept the same. Using a particular set of relative lengths and curvatures allows a single retention feature design to fit a wide range of individuals with a small number of unique parts.

Table I shows a set of values for one embodiment of a retention feature design having three sizes with common relative dimensions (all given in mm). Table <NUM> shows the ratios of the various dimensions, including the mean and the percent variation from the mean of those ratios across the three sizes. One can see that the ratio of Roa to Rob, the two radii of the outer edge of the outer leg, and the ratio of Lo to Li, the lengths of the outer edges of the two legs, are very similar across all three sizes, with the ratio farthest from the mean still within <NUM>% of the mean ratio. Two of the ratios involving the inner leg's radii vary farther from their mean than that, though the ratio of the end radius of the outer leg to the end radius of the inner leg is very consistent across all three sizes, varying only <NUM>% from the mean. As the curvature of the inner leg is largely dictated by the curvature of the outer leg and the relative lengths of the two legs, it is the Roa/Rob and Lo/Li measures that will matter most. In general, three ear tips of the shape described, and having an outer edge <NUM> defined by two radii Roa and Rob having a ratio within <NUM>% of <NUM> and a total length Lo of the outer edge that is within <NUM>% of <NUM> times the length Li of the opposite edge <NUM>, and covering an appropriate range of absolute sizes between about <NUM> for the smallest outer leg length and <NUM> for the largest outer leg length, will fit a significant portion of the population.

Claim 1:
An earphone (<NUM>) comprising:
an acoustic driver (<NUM>);
an acoustic driver module including a rear chamber (<NUM>) and a front chamber (<NUM>) defined by a first shell (<NUM>) and a second shell (<NUM>), respectively, on either side of the acoustic driver (<NUM>), the rear chamber being sealed around a back side of the acoustic driver by the first shell (<NUM>), wherein a nozzle (<NUM>) extends from the front chamber into the entrance to an ear canal of a user; and
a body (<NUM>) having an upper portion (<NUM>) and a substantially planar surface (<NUM>) configured to rest against the concha of a user's ear when worn by the user, and a lower portion (<NUM>), the lower portion being not relied upon to provide retention of the earphone in the ear, which allows it to seal to the ear canal with minimal pressure,
wherein a first void (<NUM>) in the upper portion receives the acoustic driver module (<NUM>) and the nozzle extends into a second void (<NUM>) of the lower portion and the body providing a passageway for conducting acoustic energy from the acoustic driver to the user's ear canal, and
a positioning and retaining structure (<NUM>) including an inner leg (<NUM>) and an outer leg (<NUM>), the outer leg (<NUM>) and the inner leg (<NUM>) both attached to and extending from the body, being joint at a point (<NUM>), and the joined inner and outer legs terminating at an extremity (<NUM>),
wherein the outer leg (<NUM>) is curved when not worn by the user, wherein an outer edge (<NUM>) of the outer leg (<NUM>) has a variable radius of curvature, more-sharply curved near the body (<NUM>) and flattening out at positions farther from the body (<NUM>).