Tennis racquet sounding device

A sounding device for attachment to the strings of a tennis racket which provides a unique audible sound which indicates where on the tennis racket the ball is struck by the racket. The device includes a frame for clamping a thin plastic diaphragm against the surface of the strings in the central region of the racket. The frame includes a sounding board which extends parallel to the diaphragm for amplifying the sound produced by the diaphragm when the adjacent strings are struck by the tennis ball.

FIELD OF THE INVENTION 
This invention relates to a sounding device attachable to a tennis racket 
for providing an audible indication that the ball is being struck by the 
racket within a defined area of the strings. In learning to stroke with a 
tennis racket, it is highly important that the player reinforce his 
practice effort by learning where on the racket he is making contact with 
the tennis ball. There is central area slightly closer to the handle end 
of the racket where contact with the tennis ball produces the maximum 
response. This area, known as the "sweet spot," produces negligible 
reaction at the grip end of the handle when impacting the tennis ball. It 
is difficult for a student or an instructor to know whether a player is 
consistently hitting or missing the sweet spot. 
SUMMARY OF THE INVENTION 
The present invention is directed to a sounding device which can be clamped 
to one side of the strings of the racket in the region corresponding to 
the sweet spot. A ball striking the racket in this area causes the device 
to produce a characteristic sound signaling the student and the instructor 
that the ball is making contact with the desirable area of the racket. As 
the point of impact moves further and further away from the sweet spot, 
the quality of the sound modifies in a characteristic manner, indicating 
to the trained ear the degree to which the player is failing to obtain the 
desired point of impact. 
In brief, the present invention provides a sounding device comprising a 
rectangular frame having a pair of spaced parallel side members connected 
at their ends by a pair of bridging members. A backing plate secured to 
the frame forms a sounding board. A diaphragm of plastic material 
supported between the bridging members extends parallel to but is spaced 
slightly away from the backing plate. The surface of the diaphragm is 
substantially flush with the side members of the frame. The device is 
clamped to one side of the strings with the outer surface of the diaphragm 
in contact with the strings.

DETAILED DESCRIPTION 
Referring to FIG. 1, the numeral 10 indicates generally a standard tennis 
racket having an oval shaped frame 12 and handle 14. The frame is strung 
with an interlaced grid 16 of stringing in a conventional fashion. The 
sounding device of the present invention, indicated generally at 18, is 
clamped against the strings in a central area corresponding generally to 
the so-called "sweet spot" which lies along an axis extending through the 
center of the handle and is located approximately a third of the way 
between the handle and the outer end of the frame. 
The sounding device 18 as shown in detail in FIGS. 2-5 includes a generally 
rectangular mounting frame 20, including a pair of spaced parallel side 
members 22 and 24 joined at their ends by a pair of spaced parallel 
bridging members 26 and 28. The frame members are preferably rectangular 
in cross-section and made from a single piece of material, such as molded 
plastic. A thin backing plate 30 extends across one side of the frame. The 
backing plate may be integral with the frame or be a separate sheet of 
thin material bonded to the frame. 
The bridging members 26 and 28 are notched to form recesses in the top 
surfaces of the bridging members, as indicated at 32. A thin rectangular 
diaphragm 34 preferably made of a hard, rigid plastic material, such as 
Formica, spans the frame between the bridging members 26 and 28. The 
diaphragm is seated in the recesses 32 so that the top surface of the 
diaphragm is substantially flush with the top surfaces of the side members 
22 and 24. The width of the diaphragm is less than the distance between 
the inner margins of the side members 22 and 24 of the frame 20. Thus the 
air space between the diaphragm and the parallel flat surface of the 
backing plate 30 is open along the margins of the diaphragm. 
To secure the sounding device to the racket, screws 36 are provided at the 
four corners of the frame. The screws are provided with washers 38 which 
act to clamp the frame and diaphragm against the surface of the strings. 
The screw heads are recessed in the washers so that a smooth surface is 
provided on one side of the racket which does not interfere with the 
striking of the tennis ball. While the preferred embodiment has a 
rectangular shape, the diaphragm may be of other shapes if desired. 
Likewise the specific frame arrangement can be modified in shape. 
In operation, with the sounding device attached to the racket in the manner 
shown in FIG. 1, a player may practice striking the ball using only the 
side of the racket opposite the side against which the sounding device is 
clamped. When the ball strikes the strings where they engage the surface 
of the diaphragm 34, the strings and diaphragm make a distinct and sharp 
slapping sound. This sound is amplified by the backing plate 30 and is 
easily distinguished from the sound of the ball striking other areas of 
the racket. Balls struck slightly to one side of the diaphragm still 
produce a unique audible sound but the quality and intensity of the sound 
diminishes as the point of impact is moved further and further from the 
sweet spot. Thus a sounding device is provided which has been found highly 
useful in training a person to strike the ball effectively with the 
racket. 
An alternative construction is shown in FIG. 6 in which the sounding device 
is formed by a pair of thin parallel plates preferably of a rigid plastic 
material such as Formica, as indicated at 40 and 42. The plates 40 and 42 
are held in spaced parallel relationship by spacer members 44 and 46 
extending along opposite ends of the plates 40 and 42. The entire unit is 
then secured to one side of the strings by suitable bolts (not shown) 
extending through holes 48 at the respective corners. The sounding device 
of FIG. 6 is secured to the strings of the racket in the same manner as 
the embodiment described above in connection with FIGS. 1 through 5. 
A further modification is shown in FIG. 7 which is similar to the 
embodiment of FIG. 6 in that it comprises a pair of rectangaular plates 50 
and 52 of rigid plastic material which are arranged in closely spaced 
parallel relationship. However, the plates 50 and 52 are mounted with the 
strings of the racket, indicated generally at 54, passing through the 
space between the parallel plates. Each plate is provided with a thin 
strip of material, indicated respectively at 56 and 58, applied to 
opposing surfaces around the margins. The strips 56 and 58 may be made of 
felt or other similar soft material which engage the strings and hold the 
plates 50 and 52 in spaced relationship to the strings. The plates are 
bolted together by screws 60 at each of the four corners. The plates 50 
and 52 are sufficiently thin that striking the ball with the racket does 
not materially affect the trajectory even if the ball contacts the edge of 
one of the plates.