Patent Grant
9253556
The present invention relates to equipment structures or enclosures that are placed in proximity to humans or animals which can be a noise nuisance due to the emanating sounds of fans or buzzing transformers etc., that are mounted inside. The fans can turn on and off based on heat loading and this sound level change disturbs humans as well as causes dogs to bark due to their extended frequency range of hearing. This can greatly compound the noise nuisance issue. Heretofore this has been a necessary evil because of societal demands for electricity or cell phone service provided by the equipment enclosure or structure that is the source of the noise.
A sound wave is the mechanical movement of energy through a medium. The sound energy causes the medium to oscillate which transfers the energy through the medium, molecule to adjacent molecule. These mechanical waves can only be produced in media which possess elasticity and inertia. Sound waves are similar to the ripples on the surface of water when disturbed by a rock.
The energy entering a mechanical system, such as electricity, powers a fan motor, which spins the fan blades or armature, stimulates the surrounding equipment structure or enclosure through transmitted sound energy or vibration that travels through a medium, such as the air in the exhaust vent path, or the metal that the equipment structure or enclosure is made. This transmitted sound energy transfers to the equipment structure or enclosure as well and can modulate the external air surrounding it and cumulatively transmit audible sound away from the equipment structure or enclosure that can be heard by humans or animals.
Prior approaches to solving this problem have attempted to manipulate sound with a variety of electronic circuits, such as the “Acoustic Abatement Method and Apparatus” described in U.S. Pat. No. 3,936,606 by Ronald L. Wanke. U.S. Pat. No. 2,043,416 by Paul Luer titled “Process of Silencing Sound Oscillations” transforms acoustic oscillations into electrical signals, and then reproduces them on another apparatus suitably spaced from a microphone to reproduce the sound at a different phase which cancels the original sound. None of these electrically active methods diminish the original sound levels as simply and passively as the present method and system described herein.
This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
The Dissipative System For Increasing Audio Entropy Thereby Diminishing Auditory Perception defined herein employs construction techniques, geometry, material(s) selections, and coatings that create “audio entropy” or randomness in the sound energy being created within these equipment structures or enclosures. This diminishes the available sound energy by absorbing it or making it do work which dissipates it before it can project audible sound to humans or animals.
“Entropy” is the condition in which this sound or vibration energy is disrupted or impeded from traveling along or through the elements of the equipment structure or enclosure, such as ducting for an airflow path, thereby diminishing its auditory signature perceived by humans or animals. Entropy techniques can include “damping” of the sound traveling through the equipment structure or enclosure by applying sound absorbing material(s) or coatings to surfaces within the sometimes extremely limited space within an equipment structure or enclosure, and in the path of the air being exhausted from the equipment structure or enclosure, while still providing enough free space to allow for proper ventilation in-and-out of the equipment structure or enclosure. Forcing the airflow path to turn different directions aids in diminishing the sound's amplitude because sound does not turn as easily as air and gets absorbed in the sound absorbing materials that make up or line the airflow path.
As used herein, “at least one,” “one or more,” and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “one or more of A, B, or C,” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. When each one of A, B, and C in the above expressions refers to an element, such as X, Y, and Z, or class of elements, such as X1-Xm, Y1-Yn, and Z1-Zo, the phrase is intended to refer to a single element selected from X, Y, and Z, a combination of elements selected from the same class (e.g., X1 and X2) as well as a combination of elements selected from two or more classes (e.g., Y1 and Z3).
It is to be noted that the term “a entity” or “an entity” refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more,” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising,” “including,” and “having” can be used interchangeably.
The term “means” as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C., Section 112, Paragraph 6. Accordingly, a claim incorporating the term “means” shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts, and the equivalents thereof, shall include all those described in the summary of the invention, brief description of the drawings, detailed description, abstract, and claims themselves.
“Fiberglass board/mat material” means medium-high density (three to six pounds per square foot) fiberglass board approximately two to four inches thick that is cut down to the size and shape required for a particular application. The fiberglass board/mat material is readily available from various manufacturers including Owens Corning and Johns Manville.
“Foam” means any material that has been made porous (or spongelike) by the incorporation of gas bubbles. Foam can be obtained in sheets and rolls of various thicknesses.
“Neoprene” means any of a class of elastomers (rubberlike synthetic organic compounds of high molecular weight) made by polymerization of the monomer 2-chloro-1,3-butadiene and vulcanized (cross-linked, like rubber), by sulfur, metallic oxides, or other agents. Neoprene can be obtained in sheets and rolls of various thicknesses.
To assist in the understanding of the present disclosure the following list of components and associated numbering found in the drawings is provided herein:
The inventors have discovered that fiberglass board/mat material of the correct mechanical proportions have natural sound abating and/or damping qualities due to the material's related density and/or softness. By employing different material thicknesses and/or coatings in an equipment structure or enclosure, the sound levels at different desired frequencies can thereby be diminished by not allowing them to pass all the way through, or greatly decrease their amplitude. They can also absorb radiated energy in a gas flow like the airflow path required for one or more fans.
Acoustic waves are longitudinal waves that propagate by means of adiabatic compression and decompression (i.e., they do work without producing heat).
The fiberglass board/mat material employed can also cause these sound waves to compress, which creates a minute amount of heat energy loss which is easily distributed throughout the equipment structure or enclosure without issue. This energy is no longer available to stimulate the system and the system's audio perception is reduced to a desired and more tolerable level. This is a distinctly non-adiabatic process.
Air from the fan and its sound energy does not pass unrestricted through the equipment structure or enclosure, but through the airflow path duct formed by the fiberglass board/mat material employed within the equipment structure or enclosure. Air takes the path of least resistance and some of the sound is carried with it. The geometry of this airflow path duct is part of the entropy system described herein reduces the perceived sound by reflecting it or impinging it onto as many surfaces as possible to strip away the sound's energy.
The fiberglass board/mat material employed allows the audible sound to pass only partially through the equipment structure or enclosure, or allows the audible sound to pass all the way through the equipment structure or enclosure while diminishing it due to the fiberglass board/mat material's natural sound absorbing qualities. The sound waves “hit” the metal outer sheathing of the equipment structure or enclosure and stimulate it, using up some part of their energy, and causing loss due to its large mass. If the amplitude of the sound wave, which is the difference between its minimum and maximum value, can be reduced, it will have less energy available to stimulate the air (medium) between the equipment structure or enclosure and the external human or animal, and becomes less offensive. In other words, it diminishes the air pressure in the wave.
A sound pressure wave reflects or bounces off of a surface at the same angle that it hits the surface in one plane (see
If a semicircular sheathing is used to create the airflow path duct, it refracts sound waves at different angles and does not make a good waveguide for transmitting the sound wave, and will diminish the sound wave. Some of the sound waves pass through the outer damping material to the metal sheathing of the equipment structure or enclosure and bounce back again to the opposite wall of the metal sheathing where the sound wave encounters yet another layer of sound absorbing material, further diminishing its energy and its amplitude.
Since multi-frequency sound attenuation is realized by different absorptive density properties or mechanical size(s) of the various layers, and elements behaving differently due to the various frequencies interacting with them, there is a natural hysteresis set in motion due to past stimulation which further creates sound entropy.
The pressure reducing effects of the fiberglass board/mat material creates turbulence which reduces whistling at the vent holes in the equipment structure or enclosure by creating random air exit paths and directions.
Multiple air directional changes are employed because the air exits the noise generating fan orthogonally (0 degrees) to the main direction of the vent holes in the sheathing.
The system may also employ additional plates, tabs, tangs, helixes, or baffles to redirect or trap sound while allowing maximum airflow.
One embodiment of an equipment structure or enclosure is a monopole, which is in essence a hollow tube like a chime designed to conceal an antenna, transformer, or other electrical component. The fiberglass board/mat material glued to the interior does not allow the structure to reach a frequency or harmonic of a frequency that is offensive to the hearer.
The placement, pattern, and size of the intake vent holes and exhaust vent holes employ techniques to create a shift in the frequency of the produced sound that are of a less offensive frequency due to only non-audible frequencies being allowed to escape by changing the static pressure of the fans and reduce “whistling” caused by turbulence around each intake or exhaust opening.
The fiberglass board/mat material causes “refraction” which changes phase velocity but leaves frequency the same. Frequency shifting can also be accomplished by tightly gluing textured neoprene or other materials to the airflow path duct walls, which changes the wall's “surface phenomenon” and creates more resistance to sound at certain frequencies than others. The resistive and reactive properties of an acoustic medium form an acoustic impedance in conjunction with the fiberglass board/mat material.
In one embodiment, the sheathing has predetermined diameter vent holes, and it is a resistive element and/or filter because it does not allow all frequencies to pass through equally. A perforated sheet, or sheets, can also be placed within the airflow path duct to redirect the sound wave as well as hold foam materials and position them in the airflow path duct.
Sound absorbing fiberglass board/mat material(s) at the end of the airflow path duct prevent reflection of specific harmonics (waves out of phase) are designed to absorb lower frequencies having longer wavelengths that can travel down the long airflow path duct center-line.
Thin fixed vanes in the airflow path duct of different lengths that redirect and/or change the reflected airflow path spaced at unequal distances to attenuate different audio frequencies can also be employed to further diminish the sound energy.
Foam strips or fiberglass board/mat material arranged horizontally around the periphery of the structure are staggered in height to refract waves by creating “orthogonal steps” in the airflow path to redirect or bounce the air around as many times as possible before allowing it to exit the equipment structure or enclosure. Their surfaces can also form reversed inclined planes to redirect the sound rearwards or have the effect of a reverse megaphone.
Because of the difference in length from the fans to the exhaust holes, the optimal frequencies emitted must be polyphonic, and are, by definition, diminished or spread-out.
By directing the sound out of two distinct exit vents, the “focus” of the sound is divided, thereby lessening the effect in one specific location. It also doubles the available airflow path volume in the same diameter enclosure, like a tee, thereby enhancing its thermal efficiency.
Since sound waves bounce off of flat walls at the same angle at which they strike (see
The fraction of the sound absorbed is governed by the acoustic impedance of the foam/media and is a function of frequency and incidence angle and the over-all impingement area. This system takes these factors into account and maximizes the effectiveness of these sound absorbing qualities with sizes of fiberglass board/mat material that work best at the frequencies that are desired to be diminished.
The longitudinal voids of the equipment structure or enclosure can be filled with two part, expanding foam, such as Instapak Quick™ Packaging Foam available from LPS Industries, to help prevent the reactive elements of the system from being stimulated into achieving structure resonances that create sound or can add damping to the system which moves the resonant frequency away from the excitation frequency of the equipment structure or enclosure.
Referring now to the Figures, like reference numerals and names refer to structurally and/or functionally similar elements thereof, and if objects depicted in the figures that are covered by another object, as well as the tag line for the element number thereto, may be shown in dashed lines.
There is a (variable) hysteresis in the structure system due to temperature variance causes:
The foam strips or fiberglass board/mat material lining the walls of the airflow path duct not only have staggered heights but can also have inter-leaved densities that create resistance for the sound to travel from one to the next.
Rarefaction occurs when a speaker moves backward—sort of creating a sound vacuum. This happens with the foam strips or fiberglass board/mat material's surface as well. As the foam strips or fiberglass board/mat material moves minutely in one direction or the other, it has a different effect on the sound waves that it interacts with.
Resonant frequencies are multiples of length modes x, y, and z axis. In other words a 2′×3′ vent resonates at multiples of 2, i.e., 2, 4, 6, 8 etc., and also at multiples of 3, i.e., 3, 6, 9, 12, etc. The length and shape of the airflow path duct in the structure is fixed to be the worst harmonic possible, thereby impeding the sound energy and not allowing it to achieve resonance at unwanted frequencies.
The tangential modes are reflections for the lengths between the middle of the walls of the airflow path or space. When viewed from the top this would look like sound bouncing from the midpoint of each wall like a diamond. The length and shape of the airflow path duct in the structure can be specified to be the worst harmonic possible thereby impeding the sound energy.
Sound pressure level measurements of an electric component, such as electronic component 306, freestanding and within equipment section 204, has shown a reduction in sound pressure levels one meter away from between 2.5 to 10.5 db as measured in the front, back, and side of the electronic component.
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Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. It will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications will suggest themselves without departing from the scope of the disclosed subject matter.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/871,779 filed on Aug. 29, 2013 titled “Dissipative System For Increasing Audio Entropy Thereby Diminishing Auditory Perception” which is incorporated herein by reference in its entirety for all that is taught and disclosed therein.
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| Number | Date | Country | |
|---|---|---|---|
| 61871779 | Aug 2013 | US |
