Patent Grant
10393155
The field of the invention is fluid dynamics, and especially acoustic fluid dynamics.
The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
In any device in which air or other fluid moves across a surface, there is turbulence within the boundary layer between the mean flow and the surface, especially when the airflow in a passageway becomes faster in speed. In some instances that turbulence is desirable, and in other instances that turbulence can be problematic.
In speaker port ducts, microphones, and musical instruments passageways, turbulence and associated vortex shedding is a cause of acoustical noise and unwanted distortions. The problem has been addressed to some extent by using larger diameter port ducts, this will help with limiting acoustical compression, but this will make the overall speaker box size larger. See e.g., Maximizing Performance from Loudspeaker Ports, Salvatti, Alex; Devantier, Allan; Button, Douglas J., JAES Volume 50 Issue 1/2 pp. 19-45; February 2002. But larger port bores do not eliminate turbulence within the boundary layer. The problem has also been addressed to some extent by using structures on the surface of the flaring. See for example, U.S. Pat. No. 6,019,188 to Nevill. But none of those technologies adequately addresses the root problem of distortions that a port duct has on a complex sound wave moving through or over a turbulent boundary layer.
Salvatti and Nevill, and all publications referenced herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Thus, there is still a need for systems and methods that reduce distortion and noise/or improve other sound qualities of speakers, musical instruments, microphones and other devices having an auditorily important acoustical boundary layer.
The inventive subject matter provides apparatus, systems and methods in which wavy riblets are disposed at auditorily important acoustical boundary layer of a sound producing device.
As the term is used herein, riblets are not mere scratches imparted incidentally during a manufacturing or growth process. Riblets are small grooves or protrusions, intentionally deployed onto a surface for a desired effect. It is particularly contemplated in this application that individuals and companies will deploy riblets in or on sound producing devices as a result of having received information that application of wavy riblets can improve the sound performance of such devices. In the case of a musical instrument, for example, wavy riblets may well be utilized to reduce distortion, and/or to improve transmission of desired frequencies. In the case of a fan blade, or an air conditioning duct, wavy riblets may well be utilized to merely reduce the sound of the air flow.
And whether or not those deploying wavy riblets understand the underlying physics, it appears that all of these effects are achieved by reducing turbulence and associated vortex shedding of air flowing over the boundary layer of the surface where the wavy riblets are deployed.
As used herein, the term “sound producing device” includes sound redirecting devices. Thus, in a speaker housed in a speaker housing, the driver, the diaphragm, the sound port duct, and the wooden box or other type of enclosures, are each considered to be a sound producing device. Similarly, in a guitar, violin, or cello type of instrument, the sound box (body) is considered to be a sound producing device, even though the original source of the sounds is vibration of the strings.
Among other inventive concepts herein, the current Applicant has discovered that wavy riblets are especially useful in altering acoustical properties of a sound producing device. Wavy riblets can be deployed directly onto a surface of a device, for example, by etching wavy riblets into the bell of a musical instrument, or the port duct of a speaker housing. Wavy riblets can additionally or alternatively be engraved mechanically, optically, chemically etched, or molded onto a surface of a film or other carrier, and then the carrier can be deployed onto or into an air flow passageway of the sound producing device.
Wavy riblet-enhanced surfaces can have any degree of rigidity or non-rigidity, and can be smooth or have any sort of preexisting manufactured or native pattern. All suitable methods of deploying wavy riblets on a surface are contemplated, including especially mechanically, optically or chemically etching the surface, and applying molded wavy riblets to the surface.
Wavy riblets preferably have a substantially “U” shaped primary grooves, i.e., with sides leading to a curved bottom. Less preferred riblets could have a “V”, rectangular, or other cross-sectional shape. Different wavy riblets on a surface can have different shapes. Wavy riblets can also have secondary grooves, which can advantageously be disposed longitudinally within the primary grooves.
Wavy riblets can be optimized for different purposes by having different orientations and dimensions, and by proximity to other riblets. In general it is thought that shallower and narrower riblet grooves are better for handling higher frequency sound waves, while deeper and wider riblet grooves are thought to be better for handling lower frequencies. A combination of different sizes of wavy riblets is thought to improve performance over a wide range of frequencies and Reynolds numbers. For frequencies typically used in music, 20 Hz to 15 KHz, wavy riblets are thought to be optimized where they have wavelengths of between 3 mm and 100 mm (more preferably 5-60 mm), amplitudes between 1 mm and 10 mm (more preferably 2-5 mm), lengths between 1 wavelength (3 mm) and 40 cm or more, as long as is needed for the device application size, and riblet groove depths between 0.1 μm and 300 μm, and riblet groove widths between 0.1 μm and 300 μm.
The current Applicant has also discovered that it is advantageous for wavy riblets to be arranged in one or more herringbone patterns, which might or might not converge at the “spine” of the herringbone(s). The “arms” of a herringbone pattern might or might not be symmetrical, and different herringbone patterns could form different angles. As used in this application, a pattern must have at least three pairs of left and right angled wavy riblet groups, in whatever angulations, for the pattern to be considered a herringbone pattern.
The current Applicant has still further discovered that frequency responsiveness can be optimized for various frequency bands using sets of smaller riblets disposed between sets of larger riblets. Further enhancements can be achieved by superimposing other riblets over the shorter wavelength “tonal” wavy riblets.
Where a wavy riblet-enhanced film is used, an adhesive can advantageously be included on one side of a film to facilitate attachment of the film to the device, or to itself. Wavy riblet-enhanced films are preferably between 25 μm and 750 μm thick. Where films are to be rolled, thicker films are at least in part limited by the flexibility of the films, and corresponding internal stress. Contemplated film materials include polypropylene, polycarbonate, polycarbonate with any pre-surface texture, hard coated or abrasion resistant or UV grades (PC), PDMS (polydimethylsiloxane), PET, Polytetrafluoroethylene (PTFE), or other plastics, aluminum, stainless steel or other metals, wood veneers, glass, silicone or other rubbers, ceramics, etc. It is contemplated to have a pattern on one side of a film, the same pattern on opposite sides of a film, or different patterns on opposite sides of a film. for example, one side could have an optically flat surface and the other side could have a five μm texture.
Wavy riblets can be advantageously disposed in or on any device in which the effects of air moving across a surface are relevant to an auditory experience. For example, technologies disclosed herein can be advantageously utilized in or on a vast array of auditory devices, including housings of electroacoustic transducers, including for example speakers, speaker enclosures, microphones, driver cones, vent ports, headphones, earbuds, hearing aids, etc. These technologies are also thought to be useful in improving sound performance of wind or brass instruments. For example, contemplated wavy riblets can be deployed in a passageway about a mouthpiece, a passageway about the reed, a tone hole, a bore of a musical instrument, or a bell or horn of a clarinet, flute, French horn, trumpet, trombone, etc. These technologies can also be used within a resonating chamber of a box type instrument such as a guitar, piano, violin or cello. Still further, these technologies can be used in a piano or musical instrument that does not have a specific air tube or resonant chamber. In a piano, for example, wavy riblets can be deployed on the underside of the piano lid. These technologies can also be utilized on the wall of a listening room, concert venue, or other structure of a building, preferably using a wavy riblet-enhanced film.
Wavy riblets can be deployed on any suitable region of a film or other surface. For example, wavy riblets can be placed onto the surface of something as small as a postage stamp (or even smaller), which is then simply glued onto the port duct or baffle of a speaker enclosure, on a inside wall of a speaker enclosure, on the horn or bell of a wind instrument, inside the resonating chamber or side wall of an acoustic string or other musical instrument, or on a sound collecting or directing portion of a microphone.
Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Although each described embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein, and all ranges set forth herein should be interpreted as being inclusive of their endpoints.
All methods described herein can be performed in any suitable order unless otherwise indicated herein, or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
One should appreciate that the disclosed techniques provide many advantageous technical effects, including reduction of distortion and noise/or improvement of other sound qualities, by reducing, turbulence and associated vortex shedding of air flowing across an acoustical boundary layer.
In this particular instance, the left and right sides of the herringbone 105 are non-symmetrical. Also, in this particular instance, left and right sides of the herringbone 105 cross over one another approximately at the spine 120. In other contemplated embodiments the left and right sides of the herringbone might or might not be symmetrical, and might or might not touch at all. In still other embodiments, it is contemplated to use only one side (left or right) of what would otherwise be a herringbone arrangement.
Wavy riblet group 110G is oriented at an angle α of between 25° and 35° with respect to the spine, and wavy riblet Group 110I is oriented at an angle θ of between about 20° and 35° with respect to the spine. It considered desirable, but not necessary, for the left and right groups of wavy riblets be oriented at different angles with respect to the spine. Preferred angles are between 15° and 45°.
Wavy riblets within a group are preferably spaced apart by 0.1 μm and 200 μm. Wavy riblet groupings are preferably spaced apart by 0.5 mm and 10 mm or even up to 25 mm or more.
Cross-sections of the riblets can be “U” shaped, triangular, rectangular, or any other suitable shapes. Different wavy riblet “grooves” on a given surface can have different shapes.
Wavy riblets are preferably between about 0.1 μm and 300 μm deep. Shallower wavy riblets are thought to be more advantageous where relatively higher frequencies are considered more important, and deeper wavy riblets are thought to be more advantageous where relatively lower frequencies are considered more important. Having wavy riblets with different depths on a given surface, both within and between groupings, is thought to be beneficial because doing so will aid in reducing boundary layer turbulence within a wide range of Reynolds numbers.
Wavy riblets can have any suitable lengths, and as with the depths, it is desirable to use riblets having differing lengths. What seems to be more important is that riblets are wavy, having what appear to be “wavelengths”. Preferred wavelengths are between 3 mm and 100 mm, more preferably between 5 mm and 75 mm. Here again it is preferred that different groups of wavy riblets have different wavelengths.
In this embodiment there is a second set 230 of wavy riblets situated between group 210G and group 210H of wavy riblets. The wavy riblets of the second set 230 are referred to herein as “tonal” riblets, because they can be customized to alter performance for selected ranges of frequencies. In preferred embodiments, the second set of wavy riblets 230 are generally deeper and wider than wavy riblets of the first sets of riblets 210A-210M, and are angled between 20° and 70° with respect to the spine. There can be additional “tonal” riblets (not shown) elsewhere on the surface 200, as for example between riblet groups 210F and 210G, between wavy riblet groups 210H and 210J, and between 210I and 210K.
As shown in
Groups of second sets of wavy riblets are preferably spaced apart by between 50 μm and 5 mm, and in any event spaced apart by distances less than spacings of groups of first sets of wavy riblets.
Other “second sets” of tonal riblets could additionally or alternatively be located on either or both sides of the spine 220.
The smaller “tonal” riblets can be similar to larger riblets width, shape, depth and spacing, except that they tend to be shorter, and have smaller “wavelengths”. Although
Any of the various arrangements of riblets depicted in, and described with respect to,
The wavy riblets in each of
Wavy riblets can be deployed on any suitable portion of a surface. On a fan blade, for example, wavy riblets could advantageously be deployed on most or all of the wind directing surfaces. Wavy riblets could also advantageously be deployed on most or all of a wave guide or driver cone of a speaker, or a mouthpiece or bell of a wind instrument, or a sound box of a string or other musical instrument. On the other hand, it is contemplated that wavy riblets could be deployed on any smaller area of a surface, even down to a postage stamp or smaller area. For example, it has been experimentally determined that applying a postage stamp size area (20 mm×20 mm) of wavy riblets to the inside of a bell of a clarinet produces an audibly significant improvement in the sound. A similar result has been experimentally determined with respect to applying a much smaller sized film (3 mm×5 mm) with wavy riblets engraved and applied to a earbud style of headphones (not shown). A similar result has been successfully performed using a very small film inside a port duct of a speaker.
Different sets of wavy riblets can have the same or different arrangements of wavy riblets. In this particular example, wavy riblets 910 are arranged differently from wavy riblets 920. As shown, wavy riblets are only along a relatively small portion of the inside wall of the guitar box 905, but it is also contemplated that wavy riblets could be placed on a larger or even smaller portion of the inside of the guitar box 905.
The reader will appreciate that throughout the drawing figures, some of the wavy riblets are drawn in a herringbone pattern, and some are drawn without a clear herringbone pattern. Except for riblets described in the text as having specific sizes, shapes, or configurations, riblets should be viewed as having either herringbone or non-herringbone patterns.
The reader will also appreciate that each of the devices of
It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context.
This application claims priority to U.S. provisional application Ser. No. 62/548,343 filed Aug. 21, 2017, which is incorporated herein in its entirety.
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