FLAT PANEL RADIATOR WITH COVERING ABSORBING SOUND
BACKGROUND OF THE INVENTION This invention relates to systems that mask sound and absorb sound in a workplace environment. More specifically, it relates to systems that mask sound and absorb sound adapted for a suspended ceiling. Noise in a workplace is not a new problem, but one that is receiving more and more attention as workplace configurations and business models continue to evolve. A number of recent studies indicate that noise, in the form of conversational distraction, is the single most negative factor that has an impact on worker productivity. As the service sector of the economy grows, more and more workers find themselves in offices more than in manufacturing facilities. The need for reconfigurable, flexible spaces has resulted in flat, open work spaces, that is, large rooms with reduced height, mobile separations on which sound can pass. The density of the workstations is also increasing, with more workers occupying a given physical space. More workers are using service lines, conference technologies and multi-media computers with large screens that reflect sound and even voice input. All these factors tend to increase the level of noise in workplaces making noise the most difficult and costly problem for businessmen to ignore. In closed spaces, particularly in closed offices and conference room facilities, speech intelligibility and acoustic functioning are determined by a variety of factors, including the shape of the room, furniture, number of occupants and especially in treatments of the roof, walls and floor. This acoustic environment will determine how much sound intrusion will occur, as well as the level at which you will hear them within those spaces will be affected by strange noise and conversational distraction. A more general examination of the interior environment of a room reveals other aspects that play a major role as the sound is perceived by the occupants. Recent research has indicated that when the problem of sound intrusion between spaces is observed, the loss of transmission of materials from the sound absorption characteristics of the materials are not the only contributors to the perceived acoustic environment. Another factor is the background noise in a space. This includes the sounds produced by installations placed at the top such as heating, ventilation and air conditioning (HVAC) systems. Another significant factor is the sound, much of which is conversational, which is introduced from adjacent spaces. This has become the focus of much of the current research. Sound can enter a space in a variety of ways. A closed office installation or stage, the sound moves through the walls or separations; through open air spaces such as vestibules and vestibules; and through other air spaces such as HVAC pipes, registers and diffusers, and between rooms through the roof panels, through the installation / plenum space, and down through the roof. In flat open offices, the sound also moves by reflection on separations that end under the ceiling, and by reflection of the ceiling between adjacent office cubicles. The arrangement of both closed and open offices, the noise instructions also move through the roof structural platform, the installation / plenary space, and the ceiling suspended from above; and conversely through the roof, the installation space / plenum, and the platform / floor of the roof from below. There are two methods to mitigate the presence of undesirable sounds in a space. The sound can be attenuated as it moves from the source or origin and inside the room, or it can be covered by the application of masking techniques. The main role of a roof system is a promotion of privacy in a closed office is to block the transmission of sound, and absorb the sound that touches the roof and prevent it from being reflected back into the workspace. The absorption performance for critical human vocal frequencies between 500-4000 Hz is expressed in terms of the percentage of sound absorbed by the roof material. The ability of a ceiling panel to absorb sound (in closed room applications) is measured in terms of the noise reduction coefficient (NRC). An NRC of 0.60 is a recommended value to ensure the attainment of normal vocal frequency privacy and good sound quality in closed offices. In open flat offices, where the intrusion of the vocal frequency between cubicles is the main concern, the performance of the applicable ceiling is provided by the AC (Articulation Class) value of the roof. An AC ceiling of a minimum of 170, and preferably of 200 or more is recommended for a good design of privacy of the vocal frequency. Conversational distraction and uncontrolled noise are the main causes of lost productivity within office work spaces. The principle of sound masking involves the introduction of sound at a specific frequency interval. The addition of sound at an appropriate level in the occupancy frequency spectrum by the human voice provides a masking effect, essentially drowning undesirable sounds in such a way that they are not noticed by the listener. A typical sound masking system includes the following elements: 1. a signal of * pink noise "; 2. means to filter the signal to provide the desired sound spectrum: 3. amplification means; and 4. means to create a uniform sound field in the area that is being treated. A pink noise signal contains equal amounts of sound energy in each one-third octave band, and covers a wide frequency range that includes the vocal frequency spectrum. Sound masking is usually achieved by introducing a band-width sound, accurately profiled that is constant in level with time, and strong enough to mask conversational distraction and unwanted noise, but not so loud as to be annoying. per se. This sound is similar to that attributed to the air diffuser of the HVAC system. The system usually consists of electronic devices which generate a sound signal, form or equalize a signal and amplify a signal. This signal is then distributed to an array of loudspeakers that are normally placed over the roof or over centers of 12 to 15 feet (3.66 to 4.57 m). Sound masking systems in open flat offices are typically calibrated at a sound level which corresponds to 48 dBA (weighted dB)
"A" + / 1 2 dB. This level of sound generally ensures a conversational privacy without causing distraction itself. Typical electrodynamic cone speakers have a pattern of acoustic radiation that depends a lot on the excitation frequency. At low frequencies, these speakers radiate sound almost uniformly over a wide range of angles. When the frequency of the input wave increases, the radiation pattern induced by the loudspeaker becomes more focused and directed on the axis (like an electric torch as opposed to a high intensity lamp). A standard 6.5-inch (16.51 cm) loudspeaker, for example, can have a frontal radiation pattern approaching 180 degrees unidirectional at 250 Hz, but when excited at 4 KHz, most of the frontal sound energy produced is concentrated in a highly directional beam that is approximately 15 degrees wide. Some conventional dynamic speakers produce a coherent sound field, aimed at the frequencies of interest in the masking, its use to create a diffuse reverberant field, uunniiffoorrmmee represents a challenge. A solution that has been used frequently uses traditional dynamic loudspeakers mounted on top of a roof. An array of conventional dinaanaic loudspeakers is mounted on top of a suspended ceiling and excited by electric convection wires. The loudspeakers are oriented to dispense upward into the top of the hard tile. This provides a longer reflector path. so that the sound moves in this way more uunniiformemente, dispersing the sound in the space of the plenary session. The reflected sound passes through the suspended ceiling system, where it can be further dispersed. The penalty for pointing the loudspeakers upwards, however, is that considerable additional energy is required to excite the loudspeakers to realize the desirable sound levels to the listener. Pointing the speakers directly down through the ceiling, or mounting conventional speakers on top of the ceiling panels, would create a non-uniform sound field at the movable frequencies of interest, in some areas sounding louder and other areas sounding smoother . The compensation of this non-uniform sound field would require the use of many more speakers at a considerably higher cost. What is needed is a better way to provide sound to the desired space, and do this in such a way with a system that is easily installed and easy to set up and change. In an open flat office design it is desirable to make the entire ceiling highly absorbent of sound, in this way any disturbances in the plane of the roof such as those caused by the supply and air return devices, lighting devices and loudspeakers, they have a negative effect on the privacy of the vocal frequency due to the increase in sound reflections. It would be advantageous to have a system that can introduce sound into a room without adding a sound reflector component in the plane of the ceiling.
BRIEF DESCRIPTION OF THE INVENTION This specification describes a system for mounting a flat panel radiator on a suspended ceiling system. The flat panel radiator comprises a rigid radiant panel and a transducer that is composed of a magnet attached to a radiant panel, a voice coil voltage also attached to the panel, an optimized sound absorbing coating attached to the front side of the radiator frame , and wired to a source of excitation. The flat-panel sound radiators work on the principle that the exciter hanging from the flat channels causes the panels to vibrate, generating sound. The sound field generated by the flat panel radiator is not restricted to the sound cone generally generated by the speakers. The vibration of the panel generates a complex random waves waveform on the surface of the panel, which in an ideal model radiates sound in a wide circular pattern as much as a high intensity lamp would radiate light over a wide area. This differs from a standard cone speaker which can be considered as a piston, which produces a sound beam, much like a point light would radiate light in a closed beam. The circular distribution pattern of the flat panel radiator means that sound levels are equal across a large listening area. Flat panel radiators have broad acoustic radiation patterns at the frequencies required to mask sound. As noted, the flat panel radiator includes a light, a rigid radiant panel of arbitrary size and a transducer. The transducer has a magnet attached to the radiant panel, a voice coil assembly, also attached to the panel, and wires connected to an excitation source. When electrical current is passed through the voice coil, the resultant combination of electromagnetic field forces with the magnetic field will induce a relatively very small displacement, or bending, of the panel material at the mounting points. More than the coherent movement similar to a cone speaker piston, the movement of the flat panel is decidedly incoherent, containing many new different complexes scattered over the entire surface of the radiator. This effect contributes significantly to the broad radiation pattern and lacks the behavior characteristic of this technology. This can best be achieved through a flat panel made of honeycomb cell type material, which is lightweight and non-oxidizable. The honeycomb material provides minimal loss and a uniform sound pressure response at low, medium or high frequency intervals. The presence of a standard flat-panel sound radiator in a ceiling plane that in other circumstances is highly sound absorbing will tend to compromise the achievement of vocal frequency privacy in specific cases where a panel radiator is directly located, and in line, between two adjacent office spaces since the sound waves would be reflected outside the flat panel radiator and towards the adjacent office space. This invention provides a mounting configuration with an optimized sound absorption feature as the visual surface of a flat panel radiator. In this configuration a flat panel radiator is placed inside a frame element within a suspended ceiling system, and a specific acoustic coating is attached to the frame element enclosing a layer of air between the coating and the flat panel radiator . If the radiant panel is directly finished with a lamination or coating, or if an acoustically porous coating is attached with a deflection of the radiator surface, then the radiator panel will act as a sound reflector to sounds within the room. The specific coating has specific acoustic characteristics and is strategically placed under the surface of the flat panel radiator in such a way that it provides an effective sound absorption. The coating and the air layer function as a sound absorber, and can use the acoustic value of the flat panel radiator. The coating also has aesthetic functions.
DESCRIPTION OF THE DRAWINGS The invention is better understood by reading the following detailed description of the invention in conjunction with the accompanying drawings, wherein: Figure 1 illustrates a prior art sound system arranged to create a uniform, diffuse, reverberant sound field. Figure 2 illustrates a cross section of a flat panel radiator that can be used in the present invention.
Figure 3 illustrates the mounting of a flat-panel radiator on an inverted * T "roof grid Figure 4 illustrates a form of a" C "shaped frame with a variable-size joint and a acoustically resistant coating for a flat panel radiator Figures 5A-5B illustrate an alternative embodiment of a C-shaped frame with a restraining element of variable size and an acoustically resistant coating for a flat panel radiator Figure 6 illustrates A cross-sectional view of a flat-panel radiator assembly centered on a C-shaped frame with an acoustically resistant lining and equally sized retaining elements, Figure 7 illustrates an embodiment of a frame in the form of * L "with an insulating element of variable size and an acoustically resistant coating. Figure 8 illustrates a cross-sectional view of a flat panel radiator assembly centered on a C-shaped frame with an insulating element and matching elements of equal size. Figure 9 illustrates one embodiment of a regular "A" shaped frame with a restraining element of variable size and an acoustically resistant coating for a flat panel radiator, Figure 10 illustrates a "regular" A-frame mode. with an insulating element of variable size and an acoustically resistant coating for a flat panel radiator.
DETAILED DESCRIPTION OF THE INVENTION Referring now in more detail to the drawings in which similar numbers refer to similar parts through the different views, Figure 1 illustrates a prior art speaker array for producing masking noise signals. The current-technique loudspeaker arrangement uses traditional dynamic loudspeakers mounted on top of a roof, centered at 12 to 15 feet (3.66 to 4.57 m), as shown in the diagram in Figure 1. An array of conventional dynamic loudspeakers 100 it is mounted on top of a suspended ceiling 101, fed through conventional wires 105. The loudspeakers are oriented to fire upwards toward the upper crockery 102. This arrangement provides a longer thinning path to the sound, and also disperses the sound of the sound field 103, depending on the surface treatment of the hard ware. The sound passes through the suspended ceiling system 101, where it can be further dispersed, so that the sound field 103 to the listener 104 is broadcast relatively and consistently, as indicated by the arrows. Pointing the speakers directly down through the ceiling or mounting conventional speakers on top of the roof panels would create a non-uniform sound field at the frequencies of interest, with some areas sounding louder and some sounding smoother. The compensation of this would require the use of many more speakers at a considerably higher cost. The penalty for pointing or firing the loudspeakers upwards, however, is that considerable additional power is required to steer the loudspeakers to realize the desired sound levels to the listener 104. An alternative method to generate sound masking has been the development of a flat panel radiator technology. Historical attempts to make high-quality flat-panel radiators have focused on duplicating the behavior of cone speakers. Those efforts have not been very successful until very recently. No flat panel radiators are now available that have broad acoustic radiation patterns at the frequencies required to mask sound in an open work environment. The flat panel radiator shown in Figure 2, includes a rigid, light radiant panel 200 of arbitrary size, and a transducer. The transducer contains a magnet 201 that is fastened to the radiant panel 200, the voice coil assembly 202, also attached to the radiant panel 200, an electrical wire 203 connected to an excitation source 204 that is not part of the radiator system. There are at least two modes of the transducer that can be used in flat panel products. Figure 2 shows the held "cursor" or "exciter." When electrical current is passed through voice coil 202, the electromagnetic field of the voice coil interacts with the magnetic field produced by magnet 201, producing this mode a relatively very small displacement, or bending, of the material of the panel 200 between the mounting points of the voice coil 202 and the magnet 201. In addition to the coherent movement similar to that of the piston of a cone loudspeaker, the movement of the panel plane 200 is decidedly incoherent, containing many new different dispersion complexes over the entire surface of the radiator 200. This effect contributes significantly to the broad radiation pattern and lacks the characteristic beam behavior of this technology.
In the current art, a flat panel radiator is an assembler in a frame that allows its installation in a standard inverted "T" ceiling grid. Figure 3 shows a section of a roof grid, which includes inverted T-shaped main beams (te) (600), which support hanging wires 601, and T-shaped transverse beams (te) 602. The elements of the framework of the radiator panel 603 with a support element in the form of a connected bridge 604 and an enclosure 606 is placed in the grid elements according to that shown by the dotted lines 605. The enclosure 606 contains a terminal block (not shown) for Connect the transducer to an external excitation source. Figure 4 illustrates an embodiment of a C-shaped frame in which a flat panel radiator is mounted on a restraining element of variable size positioned within the C-shaped frame. The flat panel radiator 200 is supported, in the limit conditions set, by the restraining element of variable size in the form of C 212, and placed inside a C-shaped frame 210. A bridge-shaped support element 604 is placed above and through the frame 210. The bridge-shaped support element supports the box 610 which contains the electronic components, which are used to produce vibrations on the flat panel radiator 200. The frame 210 has an insulation element 214 below the underside of the overlapping frame with the rims of the grid system 600. The insulating element 214 may be made of an elastic material such as foam. The insulating element 214 isolates the flat panel radiator from the grid-shaped support elements 600 both mechanically and acoustically and prevents vibrations of the flat panel radiator being transmitted on the suspended ceiling system. A coating 236 is added as an acoustically resistant coating for the flat panel radiator, and can be manufactured to aesthetically fit the rest of the ceiling. The acoustic resistance of the coating is approximately 800 MKS raylos for the optimization of sound absorption. The acoustic resistance of the coating in general, should be between 400 and 40000 MKS raylos. As shown, the containment element 212 can vary in thickness to create a design depth different from the bottom surface of the flat panel radiator to the acoustically resistant coating. An optimum separation for sound absorption purposes in this and the following embodiments is a distance of between one and three inches from the bottom surface of the flat panel radiator to the acoustically resistant coating. In other embodiments, the distance of the acoustically resistant coating and the lower surface of the flat panel radiator may be up to four inches (10.09 cm). The depth of the lower portion of the containment element 212 is expressed as a deviation of the bottom of the radiator from the flat panel to the lower surface of the lower plate of the C-shaped frame 210. The diffusing coating or base in this and in the following Modes can have an acoustic flow resistance of approximately 800 MKS for optimization. Figures 5A-5B illustrate alternative embodiments of the C-shaped frame in which the restraining element of variable size does not itself need the C-shaped frame. The retaining elements 218, 228 are placed on the top and the lower part of the flat panel radiator 200, respectively. The containment element 228 may be of variable depth for positioning the flat panel radiator at an optimum distance for sound absorption of the acoustically resistant coating 236. In Figure 5A, the acoustically resistant coating 236 is attached to the upper surface of the insulating element 214. In Figure 5B, the acoustically resistant coating 236 is attached to the lower surface of the insulating element 214. In cases where the containment elements 218 and 228 are chosen to sufficiently insulate the flat panel radiator, then the insulating element 214 may not be necessary. Figure 6 illustrates a cross-sectional view of one embodiment of a flat panel radiator assembly including a C-shaped frame 704 and equal size containment elements 708 that center and fix the boundary conditions of the flat panel radiator 200 in frame 704. The flat panel radiator assembly is mounted in a suspended ceiling system comprising support elements in the form of a roof grid 600 surrounding the location of the radiator installation and connecting the assembly to a plurality of elements Similar. Although the grid-shaped support member 600 is described as having ridges, any type of tongue structure can be used in place of flanges to provide the same supporting function for frame members 704. The flat panel radiator 200 it is placed in a rectangular frame member 704 having a C-shaped cross section formed by an upper plate, a side plate and a lower plate. Each plate has a standard size and thickness to be placed between the support elements in the form of a roof grid 600. A bridge-shaped support element 604, which is attached along the surface of the opposite sides of the element of the rectangular frame 704, provides a mounting structure for a junction box. An acoustic transducer assembly 706 of the type shown in Figure 2, or similar design, is mounted to a flat panel radiator 200. A rectangular panel / radiant element 200 of a channel slightly smaller than the internal dimensions of the rectangular frame member 704 is centered within the rectangular frame member 704 and joined to the acoustic transducer 706. The equal size containment elements 708 that can be adhesively bonded to the internal surfaces of the rectangular frame member 704 support the perimeter edge of the radiant panel 200. An element insulator 214 is fixed to the bottom plate of the frame 704 to isolate the radiator from the rectangular frame member 704. The transducer wires 203 are routed through the junction box to an external power source (not shown). Figure 7 illustrates an embodiment of an L-shaped frame as opposed to a C-shaped frame. In this case, the edge of the flat-panel radiator 200 can not be clamped, and the variable-size insulator 214 holds the flat panel radiator 200 in place with an adhesive material, and isolates the flat panel radiator mechanically and acoustically from the roof grid structure 600. More particularly, the insulating element 214 is of variable depth and is used to place the flat panel radiator 200 at a certain height above an acoustically resistant coating 236 which is attached to the lower surface of the L-shaped frame element 220. FIG. 8 illustrates an embodiment of the present invention in which the radiator of Flat panel is mounted through an insulating element in a suspended ceiling. The flat panel radiator 200 is supported by two resilient restraining members, of equal size, 708, one on each side of the flat panel radiator, and placed within a frame member 704 of the C-shaped cross section. bridge-shaped support element 606 is placed on top of and through the frame member 704. The frame member 704, which is slightly longer than the openings in the suspended ceiling system, has an elastic insulator 806 attached to its face. bottom that is superimposed as a rim of the roof system. Any type of tongue structure can be used in place of the flanges to provide the same support function for the frame member. In a modality, the elastic containment element and the insulating elements cover the entire perimeter of the flat radiator panel. An example of elastic insulator 806 and containment elements 708 are foam material. The insulating element 706 insulates around the flat panel of both support elements in the form of a grid 700 mechanically and acoustically and prevents vibrations of the vibrator panel on the suspended ceiling system. A diffusion coating or mesh 810 is added as an acoustically resistant flat panel radiator cover. Figures 3 through 8 illustrate simple internal mounting configurations. In that configuration the flat panel radiator 200 can be installed in a standard suspended ceiling system 101 (Figure 1) by placing it between the elements of the grid in the form of an inverted * T "600, as shown, for example, in FIG. Figure 6. The radiant surface 200 of the flat panel radiator is roughly released with, or even slightly above, the plane of the roof grid, an acoustically resistant diffuser 710 coating or mesh is added to cover the flat panel radiator that provides a sound absorption function Figure 9 illustrates a modality of a "C" -shaped framework with a restraining element of variable size and an acoustically resistant coating for a flat panel radiator. The C-shaped connecting element of variable size 212 is placed inside the frame element in the form of a "C" tegular 230. The element of the C-shaped frame 230 includes a lower plate, a first side plate, a plate upper, a second side plate, and an upper plate The lower plate and the first side plate extend below the bottom of the roof grid 600. The acoustically resistant coating 236 is attached to the lower surface of the lower plate of the frame 230. By varying the depth of the lower portion of the C-shaped retaining element 212, the distance between the flat panel radiator and the acoustically resistant lining can be used for sound absorption, the insulating element 214 isolates the frame from the roof grid both mechanically and acoustically Figure 10 illustrates a modality of a Tegular L-shaped frame with an insulating element of size In this embodiment, the edge of the flat panel radiator 200 can not be clamped, and the variable size insulator 214 functions to hold the flat panel radiator in place with an adhesive and provide insulation. More importantly, it serves to place the flat panel radiator 200 at an optimum height above an acoustically resistant coating for sound absorption purposes. The Tegular L-shaped frame 240 is positioned by the roof grid structure and has a side plate and a bottom plate that extends below the rims of the roof grid. The acoustically resistant coating 236 is attached to the bottom plate of the tegular L-shaped frame 240. Although the present invention has been described in the context of a roof grid system, the sound radiator and the mounting system may also be used in a grid structure of a wall or wall partition that has discrete panels similar to those used for the hardtop. In particular, the flat panel radiator would be supported in the same manner but with the radiator placed vertically, instead of horizontally between the upper or lower plates of the frame member. In addition, the acoustic diffuser mesh can be fixed to the edges of the frame element facing the listening area to again cover the opening created by the main beams and the transverse beams of a wall spacing. The diffusing mesh would be acoustically resistant as described above. It is intended that the structures, materials, acts and corresponding equivalents of any means plus functional elements in any subsequent claims include any structure, material or acts to perform the functions in combination with other elements claimed as specifically claimed. Although the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the present invention. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.