[0001] The present invention generally relates to acoustics and sound management systems and methods. The present invention is also related to systems and methods for improving the quality of sound generated by one or more low frequency sources in a room/environment. The present invention additionally related to low frequency active acoustic absorbers. The present invention is particularly related to low frequency acoustic room and environment ideal for managing and controlling low frequency sounds for a wide range of professional applications.

BACKGROUND OF THE INVENTION

[0002] Sound systems that transform electrical signals into acoustic signals are well-known in the art. Such sound systems may include one or more transducers that produce a range of acoustic signals, such as high, mid, and low-frequency signals. An example, a loudspeaker with a subwoofer may comprise a low frequency transducer that typically produces low-frequency signals in the range of 20 Hz to 100 Hz.

[0003] The sound systems may generate the acoustic signals in a variety of listening environments, such as, home listening rooms, home theaters, movie theaters, concert halls, vehicle interiors, and recording studios. Each of the above- mentioned environments may affect the acoustic signals, including the low, mid and high frequency signals. Depending on the acoustic characteristics of the room/environment, the position of the listener in a room and the position of the loudspeaker in the room, the loudness of the sound can vary for different frequencies. This may be especially true for low frequencies.

[0004] It is relatively easy to install passive dampening systems made of fiber material to adequately absorb frequencies above 500 Hz approximately. However, these passive absorbers are not suitable for lower frequencies as the necessary thickness of material increases with the wavelength. As an example, a minimum thickness of 1 m of material is necessary to suitably absorb frequencies of 100 Hz. In a standard sized room, the natural standing resonance frequencies are in general relatively low and therefore represent a serious problem to be controlled.

[0005] Low frequencies may be important to the enjoyment of music, movies, and other forms of audio entertainment. For example, in a recording theater, the room boundaries, including the walls, draperies, furniture, furnishings, and the like, may affect the acoustic signals as they travel from the loudspeakers to the listening positions. Furthermore, the premises used for sound measurement, recording, processing and diffusion, such as recording or postproduction studios, concert halls, sound laboratories, etc. need to be acoustically treated to obtain the adequate reverberation and echo that is required for their use.

[0006] The sound produced (for example, by a studio monitoring system or a home theatre system) inside a room leads to generation of modal resonances which particularly affect the perception of low frequencies of sound and are harder to control in smaller rooms. In particular, when a closed room is employed for critical listening, the nature of the room in which the sound energy is produced influences the quality of sound perceived by the listener. The nature of the boundary surfaces (walls, floors and ceiling) and the dimensions of the room critically affect the quality of sound in the room. The boundaries act as reflective surfaces and the representation of the music perceived by the listener is “coloured/ smeared” such that it is not an authentic representation of the sound produced by the music system.

[0007] The reverb of the room, and other significant acoustic phenomena like flutter echoes, modal resonances and comb-filtering which are undesirable and substantially change the authenticity of the sound being reproduced by a speaker system compared to how it was recorded and edited during its creation. Hence a need arises to create a listening environment that is neutral in its acoustic signature and void of all possible means by which the quality of sound perceived during playback is tarnished in any way, and thereby the listening experience be pleasant and the sonic identity and frequential authenticity of the song be retained during its reproduction. Therefore, a need exists for an acoustic solution for a closed space designated for listening with acoustic solutions that target the undesirable acoustic phenomena that degrade the quality of sound perceived in the space.

[0008] Systems and methods for managing the acoustics in a room/environment, especially in the applications for critical listening (such as studios engaging in music recording, music production, audiophile spaces, soundtesting laboratories, etc.), can be broadly categorized into “absorption” and “diffusion” and vary in terms of complexity depending on the region of the frequency spectrum taken into consideration.

[0009] One embodiment of the prior art teaches use of porous absorption material which is utilized ubiquitously as the absolute essential in the acoustic treatment of a space. Porous Absorption is effective in the treatment of the mid and high frequency regions. The porous absorption is an effective method of treatment of the undesirable phenomena that exist in these frequency regions. But as we traverse into the lower ranges of the spectrum where Wave acoustics is a contributing factor, porous absorption becomes increasingly less effective the lower the target frequency becomes, i.e., the more wave Acoustics becomes dominant in the behaviour of the sound energy. As the wave Acoustics becomes more significant and problematic in small rooms (<2500 cu. ft) and medium size rooms (2500-5000 cu. ft), the more they become a factor that creates undesirable acoustic phenomena like modal resonances.

[00010] With the increase in real estate costs, the sizes of studios are becoming smaller and an increase in demand for high quality and precision acoustic solutions for small rooms has risen. This has led to a need for an effective solution to handle and control low frequencies influenced by the principles of wave acoustics, but also comprehensively address the entire audible and experienced frequency range beyond the currently accepted limits of 20 Hz to 20,000 Hz.

[00011] Based on the foregoing a need therefore exists for low frequency acoustic rooms and environment ideal for managing and controlling low frequency sounds for a wide range of professional applications, as discussed in greater detail herein.

SUMMARY OF THE INVENTION

[00012] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiment and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

[00013] Therefore, one aspect of the disclosed embodiment is to provide for an acoustic room/environment ideal for managing and controlling low frequency range.

[00014] It is another aspect of the disclosed embodiment to provide for improved low frequency active acoustic absorbers that work efficiently in regions of pressure.

[00015] It is further aspect of the disclosed embodiment to provide for an improved low frequency acoustic room and environment ideal for managing and controlling low frequency sounds for a wide range of professional applications.

[00016] The aforementioned aspects and other objectives and advantages can now be achieved as described herein. Low frequency acoustic room and environment. An inner wall portion (120) comprising a plurality of porous-but- resistive membranes (125) operatively configured along the wall portions (130) of the inner wall portion (120) wherein the porous-but-resistive membranes (125) shares a communicating space (140) with a volume of air behind the inner wall portion (120). An outer wall portion (110) covering the inner wall portion (120) wherein the outer wall portion (110) is to create the communicating space (140) wherein the inner volume of air communicates with the volume of air in the communicating space (140) via the porous-but-resistive membranes (125) and thereby effectively absorb and control the low frequencies influenced by the principles of the wave acoustics generated via the porous-but-resistive membrane (125) in the room/environment (150) and provide a comprehensive audible and experienced frequency range suitable for a wide range of professional purposes. [00017] When sound is produced in the inner volume, pressure zones are created in accordance to the nature of how low frequency sound waves behave in a closed environment (wave acoustic principles), which thereby creates a pressure differential between the inner volume of air and the volume of air in communicating space (140). Thus, the air in the inner volume at the higher pressure is pushed to the air in the communicating space which is at a lower pressure through the porous but resistive membrane until either the pressure equalizes or the sound source ceases. This process attenuates the severity of the pressure zones that existed within the inner wall portion (120), and with it the intensity of the low frequency modal resonances and “flattens” the room’s acoustic response.

[00018] In an alternate embodiment of the present invention, the outer wall portion (110) can represent an open space [without any outer boundary] where inner volume of air communicates with the infinite volume of air in the communicating space (140) via the porous-but-resistive membranes (125) of the inner wall portion (120).

[00019] The acoustic room/environment (100) can be constructed in a wide range of shapes, including but not limited to, a square, a rectangle, a circle, a pentagon and the like. The inner wall portion (120) can be configured with the porous-but- resistive membranes (125) between the wall portions (130) depending on the shape of the acoustic room/environment (100) wherein the inner volume of air communicates with the volume of air in the communicating space (140) via the porous-but-resistive membranes (125) and thereby effectively absorb and control the low frequencies influenced by the principles of the wave acoustics generated in the room/environment (150) [covering all shapes] and provide a comprehensive audible and experienced frequency range suitable for a wide range of professional purposes.

[00020] In FIG 4, which is an alternative embodiment of the present invention, the acoustic room/environment (100) has gaps only at the 4 bicomers extending solely along the height dimension and are covered by the porous resistive material (125) and a communicating space is thus created by the volume behind the inner wall portion (120). A further augment of the embodiment of FIG 4 therefore would also have a raised floor, and a dropped ceiling, both providing a gap behind them constituting a greater volume of communication space. Further, the other 8 bicomers (410) too are configured so that they do not meet, and gaps are created, and those gaps covered by porous resistive material (125) as well.

BRIEF DESCRIPTION OF DRAWINGS

[00021] The drawings shown here are for illustration purpose and the actual system will not be limited by the size, shape, and arrangement of components or number of components represented in the drawings.

[00022] FIG. 1(a) and FIG. 1(b) illustrates low frequency acoustic room and environment (100) ideal for managing and controlling low frequency sounds for a wide range of professional applications, in accordance with the disclosed embodiments.

[00023] FIG. 2 illustrates low frequency acoustic room and environment (200) in a varying shape, including but not limited to, a square, a rectangle, a circle, a pentagon and the like.

[00024] FIG. 3 illustrates an alternative embodiment of low frequency acoustic room and environment (300) ideal for managing and controlling low frequency sounds for a wide range of professional applications, in accordance with the disclosed embodiments. [00025] FIG. 4 illustrates an embodiment of the acoustic room/environment (100) where the gaps at the 4 bicomers extend only along the height dimension and are covered by the porous resistive material (125), and a communicating space is thus created by the volume behind the inner wall portion (120), in accordance with the disclosed embodiments.

DETAILED DESCRIPTION

[00026] The particular values and configurations discussed in these non- limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.

[00027] FIG. 1(a) and FIG. 1(b) illustrates low frequency acoustic room and environment (100) ideal for managing and controlling low frequency sounds for a wide range of professional applications, in accordance with the disclosed embodiments. An inner wall portion (120) comprising a plurality of porous-but- resistive membranes (125) operatively configured along the wall portions (130) of the inner wall portion (120) wherein the porous-but-resistive membranes (125) shares a communicating space (140) with a volume of air behind the inner wall portion (120). An outer wall portion (110) covering the inner wall portion (120) wherein the outer wall portion (110) is to create the communicating space (140) wherein the inner volume of air communicates with the volume of air in the communicating space (140) via the porous-but-resistive membranes (125) and thereby effectively absorb and control the low frequencies influenced by the principles of the wave acoustics generated via. The membrane (125) in the room/environment (150) and provide a comprehensive audible and experienced frequency range suitable for a wide range of professional purposes.

[00028] When sound is produced in the inner volume, pressure zones are created in accordance to the nature of how low frequency sound waves behave in a closed environment (wave acoustic principles), which thereby creates a pressure differential between the inner volume of air and the volume of air in communicating space (140). Thus, the air in the inner volume at the higher pressure is pushed to the air in the communicating space which is at a lower pressure through the porous but resistive membrane until either the pressure equalizes or the sound source ceases. This process attenuates the severity of the pressure zones that existed within the inner wall portion (120), and with it the intensity of the low frequency modal resonances and “flattens” the room’s acoustic response.

[00029] In an alternate embodiment of the present invention, the outer wall portion (110) can represent an open space [without any outer boundary] where inner volume of air communicates with the infinite volume of air in the communicating space (140) via the porous -but-resistive membranes (125) of the inner wall portion (120).

[00030] The low frequency acoustic room/environment (100) teaches acoustical space designed to effectively control and to a high degree, the region of the frequency spectrum affected by wave acoustics, especially in small rooms (which have conventionally been known to be more difficult than larger spaces). The room (100) with two wall portions (110) and (120) with a gap in between the walls wherein the gap between the walls (HO) and (120) is in communication with the space within the inner room/ environment (150). The porous-but-resistive membrane (125) creates a communicating air space that exists within the inner room and the gap in between the two rooms (inner and outer wall) (HO) and (120).

[00031] When the sound is produced by a speaker system in the closed room/environment (150), the resonant nature of the modes caused by the behaviour of sound waves create a far-from-ideal environment to perceive sound. The influence of the modes is most severe in the low frequencies, and “cloud” / “mask” the accurate perception of the sound/music being reproduced which is vehemently undesirable a phenomenon which prevents the accurate perception of the critical nuances of sound that are crucial to professionals such as sound engineers and audiophiles alike. [00032] The modal behaviour of the low frequency is related to the variations in pressure created during the playback of sound in the listening environment, and the pressure variations which cause “peaks” to “nulls” in the measured frequency response affect the perception of sound, if listeners place themselves in a position of the peaks, a boomine ss of the sound will be experienced, and conversely, a “thinning” of sound will be perceived in the nulls, the measured frequency response at these points will differ vastly from the actual frequential response of the sound being produced, and the difference in the sonic identity of the sound being reproduced (as it was recorded or created in a studio) is caused by the room’s influence which is greatly in part due to the modal nature.

[00033] When the sound is produced in the closed room/environment (150), the modal resonances created cause varying pressure zones wherein the pressure variations vary from peaks to nulls. These variations are influenced by the nature of the sound energy that excites them, most appreciable by the low frequency energy that catalyzes the modal nature of the room/environment (150). Normally in a closed room (150), when activate by these low frequency content, the modes create very comparably high-pressure region in the comers (the wall corners and the tri-comers which are the meeting points of two walls and either the floor or the ceiling). Pressure in the comers and other wall portions is synonymous with the air being forced into the comers by the propagation of sound as a transfer of vibrational energy from one air molecule to another, and builds at the comers having no place to go and no means to equalize, and does not equalize until the sound source ceases.

[00034] The room/environment (150) where the regions of high pressure in the room (150) are encountered with a resistive but porous membrane (125) that shares a communicating space with a volume of air (the gap between the inner room’s wall and outer room’s wall) (110 and 120) behind the membrane. Almost instantaneously, the pressure that forced the air into the comers and along the boundaries of the inner room (150), now has a communicating passage with a volume behind it which is at the lower of a pressure differential, and as the air is thereby pushed through the resistive membrane (125), the pressure is equalized, and the modal nature is tamed. Further, there is also a conversion of sound energy into thermal energy by the resistive membrane (125) that assists the process, because the air molecules vibrating are pushed through the interconnected microporous nature of the resistive membrane and there thermal losses occur via dissipation because of friction of the air molecules being pushed through the interconnected pores of the resistive-but-porous membrane (125). The process of equalization of pressure across the membrane (125) occurs until the sound source has ceased.

[00035] Fig 1(b) teaches an embodiment of the proposed invention where the design shares a common floor and ceiling of the outer wall (110). In comparison to FIG 1 (b), it is seen that FIG. 1 (a) of the proposed invention shows where the design would be extending the volume of the communication air space (140) (withing the gaps of the outer and inner rooms to the ceiling and the floor as well. This can be executed by raising the floor on stilts and suspending the ceiling from a separate ceiling of the outer room. So thereby, both the inner wall portion (120) and outer wall portion (110) have separate floors and ceilings as well, and the volume includes the gap between the floors and ceilings as well as just the walls (110 and 120). Additionally, decoupling measures for the inner wall (120) can be employed, as this adds to the noise isolation factors and helps in reducing sound energy transfer as vibrational loses to the outer wall (110).

[00036] The acoustic room/ environment ( 100) can be constructed in a wide range of shapes, including but not limited to, a square, a rectangle, a circle, a pentagon and the like. FIG. 2 illustrates low frequency acoustic room and environment (200) in a varying shape, including but not limited to, a square, a rectangle, a circle, a pentagon and the like.

[00037] The inner wall portion (120) can be configured with the porous-but- resistive membranes (125) between the wall portions (130) depending on the shape of the acoustic room/environment (100) wherein the inner volume of air communicates with the volume of air in the communicating space (140) via the porous-but-resistive membranes (125) and thereby effectively absorb and control the low frequencies influenced by the principles of the wave acoustics generated in the room/environment (150) [covering all shapes] and provide a comprehensive audible and experienced frequency range suitable for a wide range of professional purposes.

[00038] FIG. 4 illustrates an embodiment of the acoustic room/environment (100) where the gaps at the 4 bicomers (410) extend only along the height dimension and are covered by the porous resistive material (125), and a communicating space is thus created by the volume behind the inner wall portion (120). The system (100) therefore would also have a raised floor, and a dropped ceiling, both providing a gap behind them constituting a greater volume of the communicating space. Further, the other 8 bicomers (410) too are configured so that they do not meet, and gaps are created, and those gaps covered by porous resistive material (125) as well. FIG. 5 (a) illustrates a top view of the low frequency acoustic room and environment (100), in accordance with the disclosed embodiments. FIG. 5(b) illustrates a top view low frequency acoustic room and environment (100) with additional “acoustic elements” (510) that bring about increased low frequency absorption, in accordance with the disclosed embodiments.

[00039] FIG. 6 illustrates the spectrogram of the acoustic room/environment (100) when empty, showing long decays, in accordance with the disclosed embodiments. The low frequency acoustic room and environment (100) is employed in the empty room, by creating an inner rigid non porous wall with a communicating space behind it, and with gaps in the 4 comers that extend the entire length of the height. These gaps in the comers are installed with a porous but resistive membrane (125) that extend from floor to ceiling, effectively acting as a partition separating the inner volume of air, and the air in the communicating space behind the inner rigid wall. The boundaries of both the length and width dimension meet the porous resistive membrane in their respective comers, along the entire height. But the floor and the ceiling do not meet the porous-but resistive membrane (125) along the edges of their dimension’s boundaries. Thus, the modal activity corresponding to the height dimension does not have the means to be suppressed effectively by pressure equalization between the inner volume and the communicating space across the resistive membrane. Hence the fundamental modal activity will only be meagerly suppressed along this height dimension.

[00040] To address the height dimension’s modal activity, the same system (as seen in FIG 4 - inner rigid wall with a communicating space behind it, and with gaps in the comers, where the gaps are covered by a porous-resistive membrane) is employed in the height dimension’s boundaries , i.e. the floor and the ceiling. So effectively here, the floor has an inner rigid wall raised from it with a communicating space behind it, with gaps in the comers, where the gaps are covered by a porous-resistive membrane. Similarly, the ceiling too has an inner rigid wall (120) dropped from it with a communicating space behind it, with gaps in the comers, where the gaps are covered by a porous-resistive membrane (125). So, in this more comprehensive design, the bicomers (the entire length of the edges of two boundaries of the inner rigid wall structure), which are 12 in number in the cuboid room, do not meet (on account of the gaps). This system can efficiently suppress the low frequency modal behaviour of the room.

[00041] FIG. 7 illustrates the spectrogram of the simplified design (FIG. 4) of the low frequency acoustic room and environment (100). As seen, it exhibits appreciable low frequency absorption, with the exception being primarily at the fundamental mode of the height dimension. This is in concordance to the working of the system, as the height dimension is not addressed with the low frequency absorption system as described earlier. FIG. 8 illustrates the waterfall graph of the empty room’s response, and FIG. 9 illustrates waterfall graph of the response after the simplified version of low frequency acoustic room and environment system (100).

[00042] FIG. 9 illustrates the waterfall graph of the room when the simplified acoustic system (100) is employed within it. From FIG. 09, appreciable low frequency modal suppression is seen over the 500ms time window, with the exception of the 56 Hz peak, which roughly corresponds to the fundamental mode of the height dimension, for which as explained above, the simplified version of the acoustic system does not address the system’s elements that bring about modal absorption. Also, it is interesting to note that the appreciable absorption seen in the spectrogram and the waterfall of the acoustic system (100) are brought about by less than 1 cubic meter of volume of porous-but-resistive material. The simplified acoustic system (100) has absorptive material only in 4 bicomers of 12, whereas the full acoustic system (FIG. 4), will have absorptive material in the other 8 bicorners as well (with the inclusion of a dropped ceiling and raised floor with gaps in those 8 bicomers covered by porous resistive material). Hence appreciable low frequency absorption can be brought about using less than 3 cubic meters in a room of such size (63.5 cu m). This presents an added advantage over conventional methods of low frequency absorption and modal suppression, which teach that much greater volumes of absorptive material in comparison would be required for desirable results to be achieved.

[00043] The RT60 (Reverberation time) values of the simplified acoustic system (FIG 4, also refer 5a) are tabulated below:

[00044] The absorption of the Low Frequency Acoustic Room and Environment, be it in its simplified or full iteration, can be increased by providing an additional acoustic elements, which is an operatively balanced increase of porous -resistive membrane in the communicating space behind the inner nonporous rigid wall.

This increases the work done by the system, as the air molecules are pushed through the additional porous resistive material during the pressure equalization across the porous resistive membrane, bringing about additional thermal and viscous losses and causing increased absorption. The selection of flow resistivity and thickness and arrangement of the additional porous resistive material is important to the operational efficiency and effectiveness of the system’s absorption.

[00045] The RT60 (Reverberation time) values of the acoustic System + additional acoustic elements (FIG. 5.b) are tabulated below:

[00046] The readings above show that the additional acoustic elements incorporated into this Simplified Low Frequency Acoustic Room and Environment (100) bring about a substantial increase in low frequency absorption and modal suppression, despite not being configured to address the fundamental modal activity in the height dimension. This can only improve when adopted to the extended acoustic system of FIG 4’s iteration (with the raised floor and dropped ceiling). While the acoustic system does bring about absorption in mid and high frequencies as well, it is more efficient at targeting the fundamental modal problems of the room. An added advantage is that the inner rigid nonporous wall retains the “liveliness” of the space, and can be customized with known methods of acoustic treatment to deliver specific acoustic results and goals.

[00047] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.