Abstract:
A hollow golf club head having face end and tail ends, a strike face at the face end, a crown, a sole of length &gt;3.5 inches, volume 0.300 cm 3 , and a structural response modifying constraining member having first and second ends, the second being forward of the first and spaced from the strike face, the constraining member extending vertically and in contact with the sole and the crown at its first and second ends, and extending horizontally a maximum distance that is &lt;40% of the sole length, when the club head is in address position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 12/923,595, filed Sep. 29, 2010, which is a continuation of application Ser. No. 11/705,499, filed Feb. 13, 2007, which is a continuation of application Ser. No. 11/705,499, filed Feb. 13, 2007, which is a continuation-in-part of application Ser. No. 11/247,148 filed Oct. 12, 2005 and entitled “Golf Club Head Having a Displaced Crown Portion,” which claims the benefits of Provisional Application No. 60/617,659 filed Oct. 13, 2004 and entitled “Golf Club Head Having a Displaced Crown Portion” and Provisional Application No. 60/665,653 filed Mar. 25, 2005 and entitled “Crown for Wood-type Golf Club Head, and Heads Having Such Crown” under 35 U.S.C. §119(e). This application also claims the benefits of Provisional Application No. 60/772,881 filed Feb. 14, 2006 and entitled “Recessed Crown Internal Structures” under 35 U.S.C. §119(e). The entire contents of each of these prior applications are expressly incorporated herein by reference thereto. 
    
    
     BACKGROUND 
     This invention pertains generally to improved metal wood type golf club heads. A recent trend in golf club head design has been to increase the size of such heads to generate increased performance and create more “forgiving” golf clubs. Although this can be said to be true for golf clubs in general, it may be observed that wood type club heads in particular have increased in size dramatically over the past few years. This has presented a number of challenges in particular to designers of modern golf clubs of the “metal wood” variety, a detailed discussion of which is contained in the above referenced applications. 
     SUMMARY 
     A metalwood head configuration that provides substantial advancements in performance, is proposed. The sound at impact of exemplary club heads in accordance with the teachings of the various embodiments of the present invention is deemed improved and more appealing in comparison to many performance wood-type clubs produced recently. In particular, a metallic ringing sound produced at impact, while different from that produced by conventional oversized metalwoods, is confidence inspiring to golfers and equates to an overall impression of quality and performance. The sound produced at impact by a golf club head is related to the structural response of the head. Hollow metal wood club heads having modified structural geometries that improve performance may exhibit structural responses that result in poor acoustical performance. 
     Therefore, structures are disclosed for improving the acoustical response of a hollow metalwood golf club heads having performance driven modifications to their head shape. These and other features, aspects, and advantages of the club head according to the invention in its various embodiments will become apparent after consideration of the ensuing description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings in which: 
         FIG. 1  is a perspective view of an embodiment of a club head in accordance with the present invention. 
         FIG. 2  is a view taken from the top and parallel to the face of the club head of  FIG. 1 . 
         FIG. 3  is a heel view of the club head of  FIG. 1 . 
         FIG. 4  is a toe view of the club head of  FIG. 1 . 
         FIG. 5  is a silhouette of an embodiment of the golf club head in accordance with the present invention, overlaid with a silhouette of a known golf club head shown with phantom lines. 
         FIG. 6  is a perspective view of another embodiment of a club head according to the invention. 
         FIG. 7  is a top plan view of the golf club head of  FIG. 6 . 
         FIG. 8  is a heel view of the golf club head of  FIG. 6 . 
         FIG. 9  is a toe view of the golf club head of  FIG. 6 . 
         FIG. 10  ( a ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII (b)-XII(b) showing a first embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( b ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a second embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( c ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a third embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( d ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a fourth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( e ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a fifth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( f ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a sixth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( g ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing a seventh embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 10  ( h ) is a cross-sectional view of the golf club head of  FIG. 7  taken along line XII(B)-XII(B) showing an eighth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 11  is a top plan view of the golf club head of  FIG. 6 , showing internal features of the golf club head with hidden lines. 
         FIG. 12  ( a ) is a cross-sectional view of the golf club head of  FIG. 11  taken along line XIII(a)-XIII(a). 
         FIG. 12  ( b ) is a cross-sectional view of the golf club head of  FIG. 11  taken along line XIII(b)-XIII(b). 
         FIG. 13  is a silhouette of an embodiment of a golf club head in accordance with the present invention overlaid with a silhouette of a known golf club head shown in phantom lines. 
         FIG. 14  ( a ) is cross-sectional view of the golf club head of  FIG. 13  showing a first embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( b ) is cross-sectional view of the golf club head of  FIG. 13  showing a second embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( c ) is cross-sectional view of the golf club head of  FIG. 13  showing a third embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( d ) is cross-sectional view of the golf club head of  FIG. 13  showing a fourth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( e ) is cross-sectional view of the golf club head of  FIG. 13  showing a fifth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( f ) is cross-sectional view of the golf club head of  FIG. 13  showing a sixth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( g ) is cross-sectional view of the golf club head of  FIG. 13  showing a seventh embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 14  ( h ) is cross-sectional view of the golf club head of  FIG. 13  showing an eighth embodiment of an internal feature of the golf club head according to the invention. 
         FIG. 15  is a heel view of a golf club head in accordance with the present invention. 
         FIG. 15  ( a ) is a cross-sectional view of the golf club head of  FIG. 15  showing an internal feature of the golf club head according to the invention. 
         FIG. 15  ( b ) is a cross-sectional view of the golf club head of  FIG. 15  showing a second embodiment of internal feature of the golf club head according to the invention. 
     
    
    
     For the purposes of illustration these figures are not necessarily drawn to scale. In all of the figures, like components may be designated by like reference numerals. 
     DETAILED DESCRIPTION 
     A club head  200  is shown in  FIG. 1  depicting an exemplary embodiment of the present invention. The head has five primary surfaces, each defining a portion of the club head  200 , namely, a front surface defining a striking face portion  202 , a bottom surface defining a sole portion  204  (visible in  FIGS. 3 and 4 ), a side surface defining a skirt portion  206 , a first top surface defining a major crown portion  208 , and a second top surface defining a minor crown portion  210 . Major crown portion  208  and minor crown portion  210  together form a crown  211 . A hosel  212  may be provided for receiving a shaft (not shown) to which head  200  may be attached. Alternatively, head  200  may have a “hoseless” configuration well known in the art. 
     Striking face portion  202  has a loft angle, which is the general angle striking face portion  202  forms relative to vertical when head  200  is resting in an address position. The extremities of crown  211  may be determined by viewing the club head from a top-down direction in a plane that is generally perpendicular to the loft angle, as illustrated in  FIG. 2 . The perimeter of the shape visible in this perspective, and represented by a crown perimeter edge  214 , generally demarcates crown  211  from striking face portion  202  and skirt portion  206 , both of which will not be visible from this perspective (see  FIG. 1  instead). Crown perimeter edge  214  may comprise a top-line edge  218  that delimits crown  211  from face portion  202  and a tail edge  220  that delimits crown  211  from skirt portion  206 . Minor crown portion  210  may have a surface contour generally consistent with contemporary metal wood crowns, and may be generally delimited from major crown portion  208  by a major crown portion perimeter edge  216 . Either or both of edges  214  and  216  may not necessarily be represented by linear edges, but rather may be embodied as radiused or contoured transitions between the respective portions. In such instances, the line that passes through the approximate apex(es) along the radiused surface that joins said portions may be substituted for either or both of edges  214  and  216 . 
     Major crown portion  208  may be generally characterized as being displaced vertically lower than the adjacent portions of minor crown portion  210 . Major crown portion  208  may be further characterized as having a surface contour that does not follow the surface contour of minor crown portion  210 , whereby the bulk of major crown portion  208  is displaced vertically downward relative to adjacent portions of minor crown portion  210 . In one embodiment of the invention, major crown portion  208  may be characterized further still as having a concave surface contour while minor crown portion may be characterized as having a generally convex curvature, whereby the bulk of major crown portion  208  is displaced vertically downward relative to adjacent portions of minor crown portion  210 . Alternatively, the contour of portion  208  may be generally planar. Thus, head  200  may maintain similar to identical sole and striking face proportions to modern metal wood heads with a reduction in volume of about 15 to about 40 percent, depending on the surface contour selected for major crown portion  208 . Further, an appreciable amount of club head  200 &#39;s minimum structural mass is relocated vertically lower, resulting in an improved center of gravity position at a decreased structural mass, thereby allowing for the possibility of improved launch conditions even before discretionary mass is added to attain a desired finished mass of between about 190 g and about 215 g for a driver type metalwood. Additionally, by lowering major crown portion  208  there is a significant reduction of skirt  206 &#39;s surface area, and hence a corresponding reduction in material required to form the skirt, and therefore a corresponding increase in head  200 &#39;s weight budget. The increased weight budget may be strategically distributed to further improve head  200 &#39;s mass properties, or to construct additional performance-enhancing structural features. 
       FIG. 5  shows profiles of two club heads, each taken at a plane located generally at the center of each head. One is of a conventional metalwood club head shown in phantom lines, and the other is of head  200 . As shown, in addition to features such as major crown portion  208  and minor crown portion  210 , sole  204  may be generally flattened out towards the rear of the club head, generally lowering the junction between skirt  206  and the sole as compared to a conventional metalwood head. This further lowers the mass of the rear portion of the club head, particularly when discretionary mass is positioned on sole  204  proximate or adjacent to skirt  206  towards the rear of head  200 . Sole  204  may further be enlarged, e.g. lengthened in the rearward direction, whereby discretionary mass placed on sole  204  towards the rear of head  200  may further improve the depth and height values of head  200 &#39;s center of gravity, accompanied by an increase in moment of inertia. 
     Implementation of a recessed crown configuration alone may affect the inherent structural properties of head  200 . For example, head  200  may achieve the USGA mandated maximum coefficient of restitution (COR) of 0.830 using a similar face thickness, or thickness profile for a variable thickness face, as would be used in a conventionally shaped metalwood head of similar proportions, yet may exhibit reduced overall structural stiffness when manufactured using a similar process, e.g. thin-wall cast body and welded-in-place face insert. While maintaining equivalent ball speeds as those generated by a conventionally shaped head having the same COR, this reduction in stiffness may, for example, present challenges to club head designers with respect to the acoustical response of the head during use since the sound radiated from head  200  at impact may be directly related to structural response. 
     Modal analyses were performed on a variety of finite element models representing exemplary configurations of head  200 , each within the parameters of the numerous variables presented in the applicant&#39;s aforementioned patent application. By way of example, it was found that with similar overall dimensions, proportions and wall thicknesses as those of a conventionally shaped metalwood club head, head  200  may exhibit a reduction of between about 25% to about 50% in the primary modal frequency. These reductions in primary modal frequencies may be significant since the primary modal frequency may, for example, be viewed as the fundamental frequency of the audible response generated by head  200  at impact with a golf ball, and may alter the perceived quality of the sound produced at impact. 
     Generally, the effect that a particular mode will have on the overall sound quality of head  200  depends in part on the radiation efficiency of the mode. Radiation efficiency may be affected by several factors, for example the geometry of the structural area the mode occupies, the size of the structural area occupied by the mode, and the amplitude of oscillation of the mode. For example, since it may be difficult to predict the effect geometry may have on sound radiation efficiency, it may be possible to reduce the radiation efficiency of a particular mode by limiting the surface area of the mode, reducing the amplitude of oscillation of the mode, increasing the frequency of the mode, or a combination of any or all of the above. 
     Further, the acoustic performance of head  200  may vary inversely with the volume of the head. For example, it was found that when head  200  was configured to approximate the proportions of a 420 cm 3  driver type metalwood head, acoustic performance was deemed superior to that of a configuration which approximated the proportions of a 460 cm 3  driver type head. This may be due to the additional reduction in structural stiffness as a result of the increased surface area of the individual portions of head  200  in combination with the inherently less rigid geometry of the recessed crown configuration. 
     In one embodiment, head  200  was configured to have a volume of 340 cm 3 , which corresponds to a conventional head displacing about 460 cm 3 . A finite element analysis was performed on the head to determine the modal response at impact with a golf ball. The first, second and third modes were found to have frequencies of about 1960 Hz, 2460 Hz and 2920 Hz, respectively. All three modes were situated on the major crown portion. The first sole mode was found to be at approximately 3800 Hz. An example of a conventional head displacing about 460 cm 3  has first, second, and third modal frequency values of about 3940 Hz, 4010 Hz, and 4330 Hz, respectively, where the first and third modes are located on the crown and the second is located on the sole. Although head  200  exhibits improved launch conditions, and therefore greater carrying distance, in comparison to the exemplary conventional head, there is a significant reduction in the modal frequencies produced by impact. For many golfers, the sound of contemporary metalwood driver heads may be accepted and associated with good performance, therefore the difference in tones produced by head  200  may be unpleasant to some golfers and/or associated with poor performance, making acceptance of the club difficult. 
       FIGS. 6-9  show a head  300 , which is similar in shape and geometry to head  200  and includes an internal structure that may be used to improve structural response. Head  300  may include a striking face portion  302 , a sole portion  304  (see  FIG. 8 ), a skirt portion  306 , and a crown  311  comprising a major crown portion  308 , and a minor crown portion  310 . Head  300  is shown in cross section in  FIG. 10  ( a ), taken along line XII(b)-XII(b) of  FIG. 7 . A structural response modifying (SRM) element  400  is generally shown which comprises a constraining member  402  and a cantilever member  404 . 
     Constraining member  402  may generally constrain at least a portion of head  300  whose structural properties result in radiation of unwanted sound energy that detracts from head  300 &#39;s acoustic performance, when used to impact a golf ball. For example, constraining member  402  may constrain major crown portion  308  to skirt portion  306  (not shown). Alternatively, constraining member  402  may constrain major crown portion  308  to sole portion  304  alone (not shown). In another example, constraining member  402  may constrain major crown portion  402  to both sole portion  304  and skirt portion  306 , as shown in  FIG. 10  ( a ). Cantilever member  404  generally extends from constraining member  402  a distance, l c , terminating at an end  406 . At any point along l c , the cantilever member may have a height, which may be measured substantially orthogonal to the inner surface of head  300 , and which may generally have a value that is less than l c . 
     In another embodiment, cantilever member  404  extends along sole  304 , as shown in  FIG. 10  ( b ), whereas in yet another embodiment a cantilever member  404  extends along both sole  304  and major crown portion  308 , as shown in  FIG. 10  ( c ). 
     Further, h c  may vary along the length of the cantilever member  404 , generally decreasing in value towards end  406 , as shown in  FIG. 10  ( d ). Alternatively, cantilever member  404  may have at least a portion that has a constant h c  value and at least a portion where h c  varies. An example is shown in  FIG. 10  ( e ), where h c  remains substantially constant from end  406  until reaching a transition region  408 , which may smoothly transition cantilever member  404  to constraining member  402 . 
     Generally, constraining member  402  may reduce the surface of major crown portion  308  that is effectively unconstrained, thereby reducing the area that may oscillate freely. Thus, constraining member  402  may decrease the area occupied by major crown portion  308 &#39;s low frequency modes, and it may increase their frequencies, and may further reduce the amplitude of their oscillation. Cantilever member  404  may allow further tuning of the modal characteristics of major crown portion  308 , for example by increasing the bending stiffness of the unconstrained area of the major crown portion, which may decrease the amplitude of oscillation and increase modal frequencies. 
     It may be particularly advantageous for cantilever member  404  to extend across the entire inner surface of major crown portion  308  as shown in  FIG. 10  ( f ). Additional benefit may be realized by allowing cantilever member  404  to extend some distance into minor crown portion  310  adjacent striking face  302 , as shown in  FIG. 10  ( g ). 
     Constraining member  402  may be provided with at least one cut-out  410 , an example of which is shown in  FIG. 10  ( h ). Cut-out  410  may provide weight-saving benefits without substantially reducing the structural integrity of the member. 
     Typical h c  values may range from between about 1 mm and about 10 mm. For heads having proportions similar to modern driver type club heads, e.g., about 300 to about 550 cm 3 , it may be advantageous to provide more than one structural modifying element.  FIG. 11  shows head  300  in plan view and provided with two SRM elements  400 , shown with hidden lines. In this embodiment, h c  may be between about 1.5 mm and about 4 mm. Most preferably, height h c  may be between about 2 mm and about 3.5 mm. Although elements  400  are shown as positioned generally perpendicular to face portion  302  and parallel to each other, it should be appreciated that they may be oriented at a variety of angles relative to both face portion  302  and each other, and still achieve the desired result. 
     In another example, for a head approximating the proportions of a typical fairway wood sized head, e.g. 100-190 cm 3 , it may be advantageous to use a single element  400 , where height may range from about 2 mm to about 10 mm, and more preferably from about 3 mm to about 6 mm. 
     A finite element simulation was performed on head  300  provided with two SRM elements  400  positioned as shown in  FIG. 11 . For the simulation, both elements  400  were a combination of the types of  FIGS. 10  ( g ) and ( e ), as shown in  FIGS. 12  ( a ) and ( b ). Cantilever member  404  extends into minor crown portion  310 , transitioning smoothly into constraining member  402  over transition region  408 . The simulation showed that the addition of elements  400  increased the frequency of the first three modes, located on major crown portion  308 , to about 2815 Hz, 3270 Hz, and about 3700 Hz, or about 44%, 33%, and 27%, respectively, in comparison with the first three modes of head  200 . This reduction in modal frequencies results in a more pleasing sound at impact, and is complemented by an overall reduction in radiation efficiency of the low frequency modes. This results in the first sole mode being more audible at impact, dominating the acoustic response and delivering a pleasing sound to the end user of the head. 
     Although the benefits of implementing an SRM element comprising a constraining member and a cantilever member have been demonstrated for a head having a displaced crown configuration, it should be appreciated that the application of the element may not be limited solely to this head configuration. Similar needs for increased structural stiffness may be necessary for a variety of other head configurations. For example, as shown in  FIG. 13 , a head  500  is shown having a face portion  502 , a sole portion  504 , a skirt portion  506 , and a crown portion  508 . Head  500  has increased face to tail dimensions relative to a conventionally shaped metalwood head  550 , shown in phantom lines. The volumetric displacement of head  500  may not necessarily be substantially greater than that of head  550 , however, the surface area of crown portion  508  and/or sole portion  504  may be increased. When the thicknesses of these portions are kept to a minimum, crown portion  508  and/or sole portion  504  may be inherently less rigid than corresponding portions of head  550 . This may result in decreased modal frequencies in either crown portion  508 , or sole portion  504 , or both. 
       FIGS. 14  ( a )-( c ) show three embodiments of a structural response modifying element  510  having a constraining member  512  and at least one cantilever member  514  that may be adapted to head  500 .  FIG. 14  ( a ) demonstrates cantilever member  514  providing stiffness to crown  508 .  FIG. 14  ( b ) shows cantilever member  514  providing added stiffness to sole portion  504 .  FIG. 14  ( c ) demonstrates two cantilever members  514  providing stiffness to both crown portion  508  and sole portion  504 . In all the examples, constraining member  512  may optionally include at least one cutout (not shown), for weight savings. Further, although constraining member  512  has been shown as being fixed to crown  508 , skirt  506  and sole  504 , sufficient improvements to the structural response of head  500  may be achieved by constraining the crown to the sole alone, as shown for example in  FIGS. 14  ( d )-( f ). Further possibilities include using constraining member  512  to constrain either of crown  508  or sole  504  to skirt  506  alone, as shown in  FIGS. 14  ( g ) and ( h ), while providing additional stiffness with cantilever member  514 . In all embodiments, a single structural response modifying element  510  may sufficiently improve the structural response of head  500 . However, it is possible that a plurality of elements  510  may be required, for example, two, three, or more, depending on the size and geometry of the head. 
     In some instances, sufficient reductions in radiation efficiency of low frequency modes may be obtained by providing metalwood heads with constraining members alone. Typically, in such instances a metalwood head  600 , as shown in  FIG. 15 , may have a maximum sole length l s  greater than about 3.5 inches, measured with the club head in an address position. As l s  is increased beyond 3.5 inches, modes may be present on a sole  604  or a crown  608  which detract from the overall acoustic performance of head  600 . The introduction of a constraining member  610  (shown in  FIGS. 15  ( a ) and ( b )) having a sole contact length l sc  may effectively modify modes generating poor acoustic signals, for example by increasing their frequency, reducing their amplitude of oscillation, and by limiting the unconstrained surface area of sole  604  and/or crown  608 . Maintaining the forward portion of metalwood head  600  free of constraining members allows the front structure of the head to deform freely, which benefits the energy transfer from head  600  to a ball (not shown) during impact, and allows favorable modes to dominate the acoustic signal.  FIG. 15  ( a ) shows a cross section of head  600  revealing a constraining member  610  that constrains crown  608  and sole  604  to skirt  606 .  FIG. 15  ( b ) shows constraining member  610  configured to constrain crown  606  and sole  604  alone. It should be appreciated that, as in previous examples, constraining member  610  may be used to constrain either of sole  604  or crown  608  to skirt  606  alone (not shown). As with all other constraining members discussed herein, constraining member  610  may contain a cut-out (not shown). 
     Generally, an improved acoustic response may be achieved by limiting l sc  to no more than 40% of l s  and more preferably to between 10-40% of l s . In another aspect of the invention, it may be preferable to limit l sc  to no more than 35% of l s . Furthermore, constraining member  610  may provide improvements to the acoustic response of head  600  when the l s  value is greater than or equal to about 3.75 inches. 
     Further techniques which may be used to modify or enhance the structural response of a hollow metalwood head that has poor acoustic performance include localized thickening of a portion of the head in a region of high modal stress. The region of high modal stress to be thickened should be in the area occupied by the mode or modes which are affecting the acoustic performance of the head. Modal stress refers to the relative stress caused in a given portion of the head by modal oscillations. The greater the amplitude of oscillation, the higher the modal stress. Generally, the maximum stress induced by the low frequency modes may not be so high as to require thickening of the affected portion for structural reasons. In most cases, the actual stress values attributed to the displacement of the mode may be a small fraction of the failure strength of materials commonly used to produce hollow metalwood clubs, such as steel alloys, titanium alloys, composites, aluminum alloys, plastics, and the like. However, it was found that by thickening the head portion in the highest modal stress area of a particular mode, the modal frequency could be improved, or increased, about 100 to about 350 Hz in general, and in some cases even more. Additionally, the mode&#39;s amplitude was decreased and the overall radiation efficiency of the mode also reduced. Thus, thickening of high modal stress areas of portions containing low frequency modes which detract from the acoustic performance of any of the aforementioned heads may effectively be used to improve overall acoustic quality of said heads. Typical thickness increases that will prove effective may generally be about 20% to about 100% of the portion thickness, depending on the material being used and the modal stress values. 
     Similarly, when a low frequency mode which detracts from a given hollow metalwood head&#39;s acoustic performance is present proximate the junction of two or more portions of that head, a constraining member may be used to tie the portions together. This may be effective when the constraining member is allowed to pass through the region of highest modal stress, thereby effectively reducing the amplitude of oscillation of the mode, increasing the mode&#39;s frequency, and generally reducing the mode&#39;s radiation efficiency. 
     It should be appreciated that the structural response modifying elements disclosed herein may be formed integrally along with the various portions of a particular head, for example by casting, or may be manufactured separately and affixed within the head, for example by welding, adhesive bonding, mechanical fastening or any suitable joining technique. When manufactured separately from the head, it may be beneficial to use materials that provide weight and/or cost savings for their construction. As examples, plastics, fiber reinforced plastics, or low density metals such as aluminum and magnesium alloys may be used to form the elements. 
     The above-described embodiments of the club head are given only as examples. Therefore, the scope of the invention should be determined not by the illustrations given, but by the appended claims and their equivalents.