US 3726025 A
An apparatus is provided for visually detecting the motion of sound waves based on macroscopic effects which ordinary sound has upon a fluid's velocity at high Reynolds numbers, such as flows from fans, in which a box-like enclosure consisting of a screen, receives fluctuating rays of light from a plurality of side-by-side multi-colored reflective strips suspended vertically in a fluid flowing from a fan situated in the box-like enclosure, said enclosure having upon a portion of its rear topside, a large number of small perforations to receive light from a lightsource in order that the light can be vertically reflected by the fluctuating strips and horizontally directed to a screen for amplification of the strips fluctuations.
Description (OCR text may contain errors)
Unite States Patent 1 Salem [451 Apr. 10, 1973 1 METHODS AND APPARATUS FOR VISUALLY ILLUSTRATING SOUND WAVES  Inventor: Kenneth G. Salem, 226 Belmont  Continuation-impart of Ser. No. 853,088, Aug. 26,
1969, Pat. No. 3,597,859.
 US. Cl. ..35/19 R, 40/106.52  Int. Cl Gi 9b 23/14, G09f 13/14  Field of Search ..35/19 R, 19 B;
1,976,093 10/1934 Raymond ..40/l38 X 2,055,910 9/1936 Rasmussen... ..40/l06.52 2,362,235 11/1944 Barnes ..35/19 B Primary Examinerl-larland S. Skogquist Attorney-Eugene F. Buell et a1.
[5 7] ABSTRACT An apparatus is provided for visually detecting the motion of sound waves based on macroscopic effects which ordinary sound has upon a fluids velocity at high Reynolds numbers, such as flows from fans, in which a box-like enclosure consisting of a screen, receives fluctuating rays of light from a plurality of side-by-side multi-colored reflective strips suspended vertically in a fluid flowing from a fan situated in the box-like enclosure, said enclosure having upon a portion of its rear topside, a large number of small per-  References Cited forations to receive light from a lightsource in order UNITED STATES PATENTS that the light can be vertlcally reflected by the fluctuatmg strips and horizontally directed to a screen for 1,131,151 3/1915 McCormick ..40/ 106.52 X amplification of the strips fluctuations. 1,240,379 9/1917 Sheppard ....40/l06.52 1,824,388 9/1931 Birch ..40/106.52 8 Chills, 3 Drawing figures 15 Q f /0 0K ////,1.u. t 1 6 16 f 2 l7 l8 I I .x"
This application is a continuation-in-part of my application, Ser. No. 853,088, Filed Aug. 26, 1969 and entitled Apparatus And Methods Of Visual Demonstration Of Sound Wave Motion now US. Pat. No. 3,597,859.
The present invention relates to apparatus for visually detecting the motion of sound waves, and more particularly relates to apparatus for observing macroscopic effects which ordinary sound has upon a fluids velocity at high Reynolds numbers such as the highly turbulent flow from an ordinary fan.
The motion of sound waves is not and has not been directly visible to the human eye. There are, however, methods of using electro'mechanical transducers which have been used to some extent for this purpose. Additionally, there are some methods which have been used, by means of which the effect of actual sound wave motion is visibly demonstrated, without the use of electro-mechanical transducers. The most significant of these methods have been based upon acoustically sensitive jets and flames. The occurrence of acoustically sensitive jets and flames was well-known in the last century, wherein it had been well established how certain flows, such as jet flows, are very sensitive acoustically, that is, sensitive to incident sound waves when the Reynolds number is in an intermediate range, so that the jet flow is only just unstable. It should be realized however, that such phenomena concerning acoustically sensitive jets and flames had been substantiated by visual observation, and proof that sound affects the flow at these intermediate Reynolds numbers was readily observable since the fluctuation of the flame or jet under observation is a type of motion which the human eye is capable of following and relating to the various sounds being made.
When a flow is designated as having a low Reynolds number, it is considered to be laminar in nature, or very smooth flowing, and when the flow just begins to become unstable, it is then considered to be in its transition stage" from laminar to turbulent. As previously stated, this is the case with acoustically sensitive jets and flames; it is in this transition stage,. the intermediate range of Reynolds numbers in which theyhave been found to be sensitive to incident sound. The transition stage of fluid flows is not of a mixed-up chaotic motion such as the case is with its turbulent stage." The transition stage normally possesses some form of pattern ordesign having associated with it, orderly motion, which the human eye can normally follow and relate to the changing sound of the medium. It is however, in the turbulent stage," that is, flows designated as having high Reynolds numbers such as flows from fans, rivers or winds, in which no relationship has heretofore been found to existbetween the normally turbulent motions of these flowsand ordinary sound waves. Of course, there exists no apparent stable pattern, nor any form of orderly motion, in this particular stage, for the eye to observe, making it very difficult indeed, if not impossible, for an observer to relate. the turbulent motions of the fluid with any particular sound. This refers to direct observation of the flow by shadowgraph techniques or the like such as the schlieren system or interferometry, all of which are based on the variation of the index of refraction with density in the medium traversed by light.
The present invention aims to overcome the foregoing difficulties and disadvantages by providing a means in which the energy of the chaotic and so-called random nature of the turbulent fluid is transferred to a dynamical system which when properly displayed, will present to an observer a substantially more orderly and stable pattern; this in turn will enable the observer to relate the turbulent motion of the fluid, or in other words, its fluctuating velocities, with the changing sounds of the medium.
In accordance with the invention, this is accomplished by providing a box-like enclosure consisting of a front screen made of white cotton cloth or the like to receive rays of light from a plurality of side-by-side multi-colored reflective strips suspended vertically near the rear wall spaced from the screen inside the enclosure, a fluid flowing from a fan also situated in the box-like enclosure, said enclosure having upon the rear portion of its topside, a large number of small perforations to receive light from a lightsource, such as an ordinary flashlight, in order that the light can be vertically reflected by the fluctuating colored strips and then directed in a horizontal plane to the screen.
This invention is an improvement over my application, Ser. No. 853,088 in that the strips fluctuations are amplified when reflected by the screen, thereby giving the observer a better, more qualitative representation of the effect which ordinary sound waves have on high Reynolds numbers flows such as flows from fans.
Another object of the invention is to provide an image upon the screen in which various colors are displayed. This is accomplished by. using multi-colored strips. As a result, an unlimited number of moving colored patterns can be displayed upon the screen simply by repositioning lightsource over the perforated section located at the top of the box-like enclosure which contains fan, strips and screen.
In the foregoing general description of my invention, I have set out certain objects, purposes and advantages of my invention. Other objects, purposes and advantages of this invention will be apparent from a con sideration of the following description and accompanying drawings in which:
FIG. 1 is an isometric view of an apparatus according to my invention;
FIG. 2 is a side elevation of the apparatus of FIG. 1; and
FIG. 3 is a front elevation of the apparatus of FIG. 1.
Referring to the drawings, I have illustrated a hous ing 10 of rectangular box-like configuration having a front opening 11 which is fitted with a screen 12, preferably a translucent white material such as a white cotton sheeting. The top 13 of the housing 10 is provided with a plurality of openings or perforations 14 near the rear edge spaced from screen 12. A lightsource 15 is fitted over the openings to permit light to enter the housingtherethrough. A plurality of vertically side-by-side reflective strips 16 are suspended from the top 13 within the housing beneath openings 14 so that the light raysentering openings 14 from lightsource 15, such as a flashlight or the like will strike the strips 16. A fan 17 driven by motor 18 is placed in one front corner of the housing adjacent screen 12,
preferably directed angularly toward an opposite sidewall, top or bottom.
Preferably, the strips 16 are made of a thin flexible resin such as polyethylene, cellophane or the like with a metallized colored coating on the surfaces to provide a highly reflective, but very flexible strip,
The operation of the device is as follows. Electrical current is introduced into fan motor 18 by means of wire 19. When fan blade 17 rotates, flowing air, preferably indirectly, strikes the strips 16 causing them to move as shown in FIG. 2. Rays of light from flashlight 15 positioned above one or more selected perforations 14 at top of enclosure are vertically reflected by strips 16 and then horizontally directed to screen 12. Lightsource can be positioned to reflect an unlimited number of colorful fluctuating patterns onto screen 12, including a pattern consisting of only a single small bright spot which is most ideal for studying the motions of the strips in relation to the sounds being made. The motions of the strips are highly amplified by reflecting the rays of light from a vertical plane first, and then directing them through a horizontal plane to the screen situated a reasonable distance from the strips. The phenomenon which one can then observe will be that of changing velocities and colorful patterns of the strips motions, the velocity fluctuations representing indirectly, the actual fluctuations in RPM of the rotating fan blade 17. The fan blades fluctuation in RPM, I have found, is basically due to the microscopic changes of molecular distribution in the medium caused by ordinary sound waves; in other words, the fan blade 17 is churning air which is continuously being changed in its molecular distribution (rarefactions and compressions of molecules) due to changing acoustical pressures, thereby causing the fan blade 17 to meet with constantly changing resistance. As a result of this constantly changing resistance, and since the changes are basically due to sound waves, any fluctuation of energy imparted to the strips from the fans flow, will indirectly be some mode of the same precise fluctuations of the fans RPM; the fluctuations of the strips will then be amplified upon the screen 12 for one to observe directly, the visible effects of the energy of sound waves, based upon their macroscopic effects on high Reynolds numbers flows such as shown and described with fans.
- In the operation of this embodiment it will at times be apparent that there is no relationship between the fluctuations on the screen and the sound one hears. This is somewhat evasive, and is primarily due to the fact that the flow from the fan is continuous while the flow of incident sound waves are not as continuous as the flow from the fan. In common ordinary sound, such as a musical number or a person speaking, there are usually pauses throughout, and it is primarily these pauses in sound which serve to contribute to the evasiveness which sporadically exists throughout the observations. Other factors which can contribute to some of this evasiveness concern the average number of oscillations per second of the suspended strips, for if these dynamical means which are utilized to observe the energy fluctuations of the fan blade were to oscillate at too rapid a motion, the eye will not be capable of observing the changes in relation to the changing sound. It is most desirable then to position the fan in the enclosure so that the strips oscillations, when amplified upon the screen, will be just fast enough that the eye can readily observe the changes in relation to changing sound. Important criteria for observing this phenomenon then are: Attainment of continuous sound, and constantly changing sound, at constantly changing rates of energy. In other words, the more continuously and rapidly the sounds flow, and the more radically they change from moment to moment, the more readily observable will the phenomenon be; and though these criteria serve to make the observations more interesting, they are not necessarily required, as the phenomenon exists with all velocities of fluid motion in conjunction with all types and frequencies of sound. The only disadvantage in not following the recommended criteria is that some concentration would be required in order for the observer to see this phenomenon. The results, very basically, are depen dent upon the ratio of the velocity of the flow (or the dynamical means one uses to observe the flow) to the velocity of sound in the medium; and depending on this ratio, some particular mode of the acoustical pressures present can be detected when some dynamical system, such as described here, is used in association with the flow.
While I have illustrated and described a preferred practice of my invention, it will be understood that this invention may be otherwise embodied within the scope of the following claims.
1. An apparatus for illustrating sound waves employing turbulent fluid flow comprising a vertical translucent screen, a plurality of side-by-side elongated reflective strips suspended vertically from one end in a plane generally parallel to and spaced from the screen, a lightsource above the reflective strips directing light generally lengthwise of the strips, a source of turbulent fluid flow and means directing said turbulent flow into continuing contact with said strips whereby said strips are caused to move in said fluid flow as modified by the sound waves to be illustrated and to reflect a moving strip of light reflected therefrom to the translucent screen.
2. An apparatus as claimed in claim 1 wherein the means directing the fluid flow is a housing enclosing the screen, the strips and the source of turbulent fluid flow,
3. An apparatus as claimed in claim 1 wherein the fluid flow has a high Reynolds number.
4. An apparatus as claimed in claim 1 wherein the screen is a white sheet of cloth.
5. An apparatus as claimed in claim 1 wherein the reflective strips are made of colored metallized plastic resin.
6. An apparatus as claimed in claim 1 wherein the lightsource is an electric bulb directing light through a plurality of holes above the reflective strips.
7. A method of illustrating sound waves comprising the steps of:
a. spacing a planar translucent screen and a plurality of depending flexible elongated strips lying in a plane apart in two generally parallel planes,
. directing light rays lengthwise of said depending strips,
0. subjecting said strips to a turbulent fluid flow,
d. imposing upon said fluid flow a sound wave pat:
e. viewing the movement of light on the translucent screen to follow the changing pattern of light caused by the sound wave.
8. An apparatus as claimed in claim 1 wherein the source of fluid flow is a fan. 5