US 3509282 A
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April 28, 70 v w. J. ASHWORTH 3,509,282.
SOUND SYSTEM Filed Dec. 13, 1968 2 Sheets-Sheet 1 llllllllllll Ill/l v J A H6 INVENTOR United States Patent 3,509,282 SOUND SYSTEM William J. Ashworth, Rt. 2, New Albany, Miss. 58652 Continuation-impart of application Ser. No. 558,204, June 13, 1966. This application Dec. 13, 1968, Ser.
Int. Cl. H041 1/28 US. Cl. 1791 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF INVENTION This application is a continuation in part of my c0pending application, Ser. No. 558,204, filed June 13, 1966 and entitled Sound System. The present invention relates to a sound reproducing system and in particular, one utilizing a sounding board activated by an audio transducer and a conventional cone type loudspeaker operated together from a common signal source. Heretofore, other sound reproducing systems have been proposed to add the illusion of depth to sound systems. This has usually been accomplished by the use of reverberation systems of various types but these usually introduce an undesirable amount of distortion to the sound that is highly objectionable to the listener.
SUMMARY OF INVENTION The present invention provides a new and novel means of obtaining a realistic illusion of depth without objectionable distortion in sound systems that has not been possible heretofore. This may be accomplished by coupling a conventional loudspeaker together with a sounding board activated by a transducer and driving both devices from a common signal source. The sounding board and loudspeaker will operate slightly out of phase, giving an illusion of sound depth. A greater degree of sound depth illusion can be accomplished by the use of two sounding boards mounted on a frame in a spaced apart face to face relation. When one sounding board is activated by an audio transducer, the other sounding board will also vibrate along with the first sounding board. The vibrations of each sounding board is slightly out of phase with the other and the listener receives the impression of being completely surrounded with sound.
The present invention may also be coupled together with one or more conventional dynamic loudspeakers. When this is done, both sounding boards radiate sound that is also slightly out of phase with the conventiona loudspeaker giving the listener an even greater illusion of sound depth. Other objects and advantages of the pres n invention will be apparent from the following description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the present invention showing two sounding boards mounted in a frame in spaced apart relation to one another.
FIG. 2 is a front elevation view of the embodiment shown in FIG. 1.
FIG. 3 is a sectional view taken along line AA of FIG. 1.
FIG. 4 is a sectional view taken along line AA of FIG. 1 showing a modification of the rear sounding board.
FIG. 5 is a sectional view taken along line AA of FIG. 1 showing a modification of the front sounding board.
FIG. 6 illustrates a conventional type loudspeaker and the present invention where both receive their signal from the same signal source and both are driven by the same amplifier.
FIG. 7 illustrates the present invention utilizing another method of driving the transducer, loudspeaker combination.
FIG. 8 illustrates another method of driving the transducer, loudspeaker combination.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS The preferred embodiment of the invention as shown in FIGS. 1 and 3 utilizes a sound chamber 6 consisting of a frame 2 which supports sounding board 3 and a sounding board 4 in a face to, face spaced relation to one another. An audio transducer 5 is attached to sounding board 4 which is actuated by a conventional signal source, such as a radio, phonograph, tape player, etc., or by any other conventional method. When transducer 5 causes sounding board 4 to vibrate, sounding board 3 will also vibrate, because of the vibrations, primarily transmitted to it through the air, in much the same manner as the second leg of a tuning fork reacts when the first leg is activated.
Sounding board 3 does not extend all the way to the lower portion of the frame 2, which leaves an opening in the sound chamber 6. This opening is provided for two purposes. The first is to allow the sound generated within the sound chamber 6, formed by the frame 2 and sounding boards 3 and 4 to pass through the opening 7, and add to the sound generated by the outer face of sounding board 3. The second reason for the cut away opening 7 is'to make the sounding board 3 more resilient. By supporting sounding board 3 on only three sides with the lower portion left unsupported, it is much more flexible and can move considerably further when vibrating than would be possible if it were supported on all four sides. The transducer 5 may be attached to sounding board 3 instead of sounding board 4. Such an attachment is shown in FIG. 4, where transducer 5 is shown attached to sounding board 2.
In one embodiment, the forward sounding board 3 is rigidly supported by the frame 2 on only three sides and has one side that is not fastened to the frame 2. The rear sounding board 4 extends over the full length and breadth of frame 2 and is rigidly fastened in place to the frame around the entire edge. Because of the relatively small amount of movement possible with sounding board 4, a high percentage of harmonics are generated when sounding board 4 is activated at frequencies below the range of approximately 250 cycles by transducer 5. Because of the greater flexibility of sounding board 3, it wll usually, at the lower frequencies, vibrate at one half the rate of the predominate frequency at which sounding board 4 is vibrating. This places the vibratory rate of sounding board 3 at or near that of the fundamental frequency of the signal being fed into transducer 5. Normally, when operating at low frequencies, sounding board 3 and sounding board 4 will vibrate at a dilferent rate and will be slightly out of phase with one another.
The lower frequency sounds, rich in harmonics, that are generated by sounding board 4, pass through the sound chamber 6 and out through the opening 7. This sound produces an echo effect. At the same time, sound is being generated by sounding board 3, which is vibrating at a slower rate than sounding board 4, and at the same rate or near the frequency of the signal fed into the transducer 5.
The sound generated by the two sounding boards are slightly out of phase and when the twosounds are blended together, the listener has the illusion of being surrounded by the sound.
The illusion of even greater depth can be given by electrically coupling a conventional cone type loudspeaker 1 together with the present invention and operating both from a common signal source. As pointed out above, sounding board 3 and sounding board 4 generate sound out of phase with each other. The sound radiated by the conventional cone type loudspeakerwill also be slightly out of phase with both sounding board 3 and sounding board 4, therefore, both sounding boards and the loudspeaker will usually be operating out of phase with each other. At mid range and higher frequencies, the two sounding boards vibrate at the frequency that is fed into transducer 5, but are slightly out of phase with each other, and both will still operate out of phase with a conventional loudspeaker when one is used.
FIG. 4 shows a modification of the preferred embodiment where both sounding boards have the lower portion hanging free. In this embodiment, both sounding board 3 and sounding board 8 will vibrate at the same Vibratory rate but slightly out of phase with each other.
FIG. shows a further modification of the preferred embodiment where both sounding boards 4 and 9 are rigidly supported along their entire edges. There are no cut outs for the sound to pass through in this modification, therefore, the volume of the sound generated will be substantially lower than with the preferred embodiment shown in FIGS. 1 and 3 and with the modification shown in FIG. 4. In this modification both sounding boards 4 and 9 will vibrate at the same rate, and a high percentage of harmonics, at low frequency operation will be present and both sounding boards will operate slightly out of phase with each other.
In the preferred embodiment of the present invention, shown in FIGS. 1 and 3, frame 2 may be made of inch wood 3 inches wide. Sounding board 4 may be made from a 16 inch square piece of 7 inch thick plywood and sounding board 3 made from a 16 inch square piece of 7 inch plywood with the lower portion cut out as shown in FIG. 1. The two sounding boards can be rigidly fastened in place to the frame 2 with a suitable glue or cement, and may be spaced approximately 2 inches apart. A suitable transducer may be used to activate the sounding board such os described in my US. Patent No. 3,449,531.
FIG. 6 illustrates a cone type loudspeaker 1 and audio transducer 5 attached to a sounding board 4 where both receive their signal from the same signal source 11 and both are driven by the same audio amplifier 12.
FIG. 7 illustrates a cone type loudspeaker 1 and an audio transducer 5 attached to a sounding board 4 where both receive their signal from the same source 11. The audio amplifier 12 directly the cone type loudspeaker 1 and also actuates a second audio amplifier 13 which in turn drives the audio transducer 5. The audio amplifier 13 allows the listener to adjust the volume and tone of the sound produced by the audio transducer 5 to any level desired in relation to the sound output of the cone type loudspeaker 1.
FIG. 8 illustrates a cone type loudspeaker 1 and an audio transducer 5 attached to a sounding board 4 where both receive their signal from the same signalsource 11.
The cone type loudspeaker 1 is driven by the audio amplifier 14. The audio transducer 5 is driven by another audio amplifier 15 connected in parallel with audio amplifier 14.
Although several specific embodiments of this invention have been herein shown and described, it will be understood that details of the constructions shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.
, 1. A sound reproducing device comprising a first and a second sounding board with both said sounding boards being mounted to a frame in a substantially face to face spaced apart relation to form a partially enclosed sound chamber, whereby said first sounding board is activated by and wholly supports an audio transducer, with said second sounding board being primarily activated at a time interval later than said first sounding board by vibrations transmitted thru the air by said first sounding board, an opening being provided in said sound chamber for the passage of sound generated by said sounding board surfaces Within said sound chamber for the substantial blending together of said sound with the sound generated by said sounding board surfaces outside said sound chamber, wherein one of said sounding boards is rigidly supported along the entire length of its edges and the other said sounding board is rigidly supported along its outer periphery a distance equal to at least one half and not more than seven eighths of the total length of said sounding boards edges with the remaining portion of said sounding boards edges not being rigidly supported.
2. With a sound reproducing device according to claim 1, the combination of a dynamic loudspeaker electrically coupled with said sound reproducing device to a signal source common to both said sound reproducing device and said dynamic loudspeaker.
3. A sounding board for transmitting audio vibrations into the surrounding area, wherein said sounding board is rigidly supported along its outer periphery a distance equal to at least one half and not more than seven eighths of the total length of said sounding boards edges, wherein the remaining portion of said sounding boards edges is not rigidly supported, said sounding board being activated by an audio transducer with the primary vibratory element of said transducer being solidly connected to said sounding board.
4. A sounding board according to claim 3, wherein said transducer is wholly supported by said sounding board.
5. With a sound reproducing device according to claim 3, the combination of a dynamic loudspeaker electrically coupled with said sound reproducing device to a signal source common to both said sound reproducing device and said dynamic loudspeaker.
References Cited UNITED STATES PATENTS 1,819,499 8/1931 Conrad l8131.1 2,550,336 4/1951 Daniel 181-3l.1 2,978,543 4/1961 Kennedy 179-1.3 3,080,013 3/1963 Bateman 18131.1
RALPH D. BLAKESLEE, Primary Examiner U.S. Cl. X.R. 181-31