WO2023227958A1

WO2023227958A1 - Interconnected acoustic framework for low frequency modal absorption

Info

Publication number: WO2023227958A1
Application number: PCT/IB2023/051495
Authority: WO
Inventors: Roshan GEORGE THOMAS
Original assignee: George Thomas Roshan
Priority date: 2022-05-23
Filing date: 2023-02-18
Publication date: 2023-11-30

Abstract

Interconnected acoustic framework (100) for low frequency modal absorption. The framework (100) is configured along edges of the six boundaries (4 walls, floor and ceiling of the room) of an acoustic room/environment for low frequency modal absorption in a wide range of applications. The framework (100) comprises a plurality of columns (110) that are interconnected (as shown in FIG. 1) and placed flush along the comers of the boundaries of the room wherein the framework (100) effectively handles the volume of the air behind the resistive membrane (HO) which is the primary factor that influences the effectiveness at modal frequencies, the greater the volume, the lower the frequency that can be effectively attenuated.

Description

INTERCONNECTED ACOUSTIC FRAMEWORK FOR LOW FREQUENCY MODAL ABSORPTION TECHNICAL FIELD [0001] The present invention generally relates to acoustics and sound management systems and methods. The present invention also relates to systems and methods for improving the quality of sound generated by sound sources (low frequency) in room/ environment. Further, the invention relates to mechanisms for low frequency modal absorption in a room/environment. The invention additionally relates to acoustic rooms/environments for a wide range of professional applications. Further, the present invention specifically relates to an interconnected acoustic framework along edges of the six boundaries of an acoustic room/environment for low frequency modal absorption in a wide range of 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 studio, 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, production, rehearsals, foley, and performances, 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. 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] 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.

[0010] To address the problems associated with the prior arts, the applicant of this patent has filed a patent (Patent Application no. 202241009271) on a low frequency acoustic room and environment ideal for managing and controlling low frequency sounds for a wide range of professional applications which teaches an inner wall portion comprising a plurality of porous-but-resistive membranes operatively configured along the wall portions of the inner wall portion wherein the porous-but-resistive membranes shares a communicating space with a volume of air behind the inner wall portion. An outer wall portion covering the inner wall portion wherein the outer wall portion is to create the communicating space wherein the inner volume of air communicates with the volume of air in the communicating space via the porous-but-resistive membranes and thereby effectively absorb and control the low frequencies influenced by the principles of the wave acoustics generated in the room/environment and provide a comprehensive audible and experienced frequency range suitable for a wide range of professional purposes.

[0011] However, there is an ever-growing requirement and need for achieving an interconnected acoustic framework which can handle volume of the air behind the resistive membrane that influences the effectiveness at the modal frequencies. The greater the volume, the lower the frequency that can be effectively attenuated. Thus, the interconnected columns that can create one large volume which allows for the range of absorption of low frequencies, and the effectiveness of absorption in the frequency range in the room/environment is not addressed in the prior arts and there is a need for addressing the low frequency modal absorption in a room to provide an effective sound experience for a user in an acoustic room/ environment.

[0012] Based on the foregoing, it is believed that a need exists for an improved acoustic framework balancing the low frequency in the room environment. Also, a need exists for an interconnected acoustic framework along edges of the six boundaries of an acoustic room/ environment for low frequency modal absorption in a wide range of applications, as described in greater detail herein.

SUMMARY OF THE INVENTION [0013] 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.

[0014] It is, therefore, one aspect of the disclosed embodiments to provide for an improved acoustic room/environment ideal for managing and controlling low frequency range.

[0015] It is another aspect of the disclosed embodiments to provide for an improved ideal balancing system for managing the low frequency modal absorption.

[0016] It is further aspect of the disclosed embodiments to provide for an improved an interconnected acoustic framework along edges of the six boundaries of an acoustic room/ environment for low frequency modal absorption in a wide range of applications.

[0017] The aforementioned aspects and other objectives and advantages can now be achieved as described herein. An interconnected acoustic framework (100) for low frequency modal absorption, is disclosed. The framework (100) is configured along edges of the six boundaries (4 walls, floor and ceiling of the room) of an acoustic room/ environment for low frequency modal absorption in a wide range of applications. The framework (100) comprises a plurality of columns (110) that are interconnected (as shown in FIG. 1 ) and placed flush along the comers of the boundaries of the room wherein the framework (100) effectively handles the volume of the air behind the resistive membrane (110) which is the primary factor that influences the effectiveness at modal frequencies, the greater the volume, the lower the frequency that can be effectively attenuated.

The interconnected framework (100) can create one large volume which allows for the range of absorption of low frequencies, and the effectiveness of absorption in the frequency range to be maximised. The cross-sectional square shape of the framework (100) affords more surface area and inner volume, through which air moves through on account of the pressure differential created, and where soundwaves propagate via the air in the resistive material, leading to thermal losses occurring due to vibrational dissipation. The nature of the resistive material features including but not limited to flow resistivity, thickness, and permeability of the covering material of the columns (110) that encloses the interconnected space is crucial wherein the flow resistivity determines the intensity of the drop in pressure created on either side of the membrane.

[0018] If flow resistivity is too high, the movement of air through the membrane will experience more barrier to moving through, and not enough will pass through to remove the pressure within the listening area. And if the flow resistivity is too low, it will move through too easily, such that the drop in pressure on each side will be lesser, and equalization will take place without the optimum reduction in intensity of pressure. When the flow resistivity is within a nominal range that is ideal for the efficiency of the system, the air flow is met with the ideal resistance to entry, that creates the most difference in pressure on either side of the membrane until it is equalized.

[0019] The presence of the framework (100) throughout the bi-comer and tricomers of the room, the interconnected columns (HO) creating one large inner space, and the select physical attributes of the resistive membrane allows for a higher degree of low frequency modal suppression, as well as more effective absorption into the lowest ranges of low frequencies.

BREIF DESCRIPTION OF THE DRAWINGS

[0001] FIG. 1 illustrates a perspective view of the interconnected acoustic framework (100) for low frequency modal absorption, in accordance with the disclosed embodiment.

[0002] FIG. 2 illustrates a perspective view of the interconnected acoustic framework (100) along edges of the six boundaries of an acoustic room/environment for low frequency modal absorption in a wide range of applications, in accordance with the disclosed embodiment.

DETAILED DESCRIPTION

[0003] The 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.

[0004] The embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. The embodiments disclosed herein can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. As used herein, the term "and/or" includes all combinations of one or more of the associated listed items.

[0005] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. [0006] Description of the Invention: The framework (100) is configured along edges of the six boundaries (4 walls, floor and ceiling of the room) of an acoustic room/environment for low frequency modal absorption in a wide range of applications. The framework (100) comprises a plurality of columns (110) that are interconnected (as shown in FIG. 1) and placed flush along the comers of the boundaries of the room wherein the framework (100) effectively handles the volume of the air behind the resistive membrane (110) which is the primary factor that influences the effectiveness at modal frequencies, the greater the volume, the lower the frequency that can be effectively attenuated. The interconnected framework (100) can create one large volume which allows for the range of absorption of low frequencies, and the effectiveness of absorption in the frequency range to be maximised. The cross-sectional square shape of the framework (100) affords more surface area and inner volume through which air moves through on account of the pressure differential created, and where soundwaves propagate via the air in the resistive material, leading to thermal losses occurring due to vibrational dissipation. The nature of the resistive material features including but not limited to flow resistivity, thickness, and permeability of the covering material of the columns (110) that encloses the interconnected space is crucial wherein the flow resistivity determines the intensity of the drop in pressure created on either side of the membrane.

[0007] If flow resistivity is too high, the movement of air through the membrane will experience more barrier to moving through, and not enough will pass through to remove the pressure within the listening area. And if the flow resistivity is too low, it will move through too easily, such that the drop in pressure on each side will be lesser, and equalization will take place without the optimum reduction in intensity of pressure. When the flow resistivity is within a nominal range that is ideal for the efficiency of the system, the air flow is met with the ideal resistance to entry, that creates the most difference in pressure on either side of the membrane until it is equalized.

[0008] The presence of the framework (100) throughout the bi-comer and tricomers of the room, the interconnected columns (HO) creating one large inner space, and the select physical attributes of the resistive membrane allows for a higher degree of low frequency modal suppression, as well as more effective absorption into the lowest ranges of low frequencies. [0009] Working of the Invention: The construction of the columns (HO) is such that the columns (110) are hollow within, and the sides of the columns (110) are made of porous but resistive membrane. In a cuboid room of dimensions, there can 12 bicomers, 4 along the length, 4 along the width, and 4 along the height as shown in FIG. 1. Hence there are 12 columns that all meet each other at the tricomers, which are 8 in number. Since the nature of the columns (110) is that it is hollow within, all 12 columns meet each other at the tricomers, to form a single interconnected system (100) of columns (110 that all share one “air space” on the inner side of the porous but resistive membrane. [0010] FIG 2A is a diagram of one tri-corner showing the meeting of three columns (110). FIG. 2B is a cross section of the column (110), where the column (110) has 4 sides of a resistive membrane thus enclosing the inner volume containing the interconnected air space. Fig 2C is an embodiment where the column (110) has only 2 sides as resistive membrane, and the other 2 sides are flush and sealed tight with no air leakages with the wall to create the inner volume containing the interconnected air space. FIG. 2D is a representative diagram showing the 12 bicomer lines and the 8 tri-comer intersections shown in the dotted circles. When sound is produced in a closed room, pressure zones are caused by the modal resonant nature of sound waves. The intensity of the pressure zones varies from each other, but are greatest in the comers. When this interconnected system (100) of columns (110) is placed in all the comers, there is a differential of pressure between the volume outside and the volume instead the columns, which is separated by the porous but resistive membrane. This differential of pressure pushes the air from the region of higher pressure to the region of lower pressure, until there is an equalization of pressure, which depends on the volume and the capacity of the region inside the columns. And since the column is completely connected with each other and share one single air space, the intensity of the pressure within the room can be reduced significantly, which thereby tames the room modal resonances effectively.

[0011] In the proposed system the inner space does not have sound absorbing material. While the embodiment of Fig 2C brings about substantial absorption, the design of Fig 2B brings about increased modal suppression and more effective absorption. The thermal losses incurred while air propagates through the increased surface area of the porous-but-resistive membrane of Fig 2B help in bringing about the increased absorption. An increase in efficiency and absorption of the system can be brought about by also adding thin partitions of porous but resistive material (of select thickness and flow resistivity) within the inner volume of the interconnected framework of columns, or loosely filling the inner volume with a porous-resistive material of low flow resistivity.

[0012] FIG. 3 illustrates the spectrogram for a room measured first when empty, and then FIG. 4 illustrates the Spectrogram after the Interconnected Acoustic Framework (System) is employed in the room. The Spectrogram, when the room is empty, is showing long decays. The IAF System employed here is a square column 2 ft x 2 ft in cross sectional inner area, and the porous-but-resistive membrane that encloses this volume is of select flow resistivity and thickness. The Spectrogram shows effective low frequency modal suppression from that of the empty room as well as some attenuation of mid and high frequencies as well. [0013] FIG. 4 illustrates the spectrogram that of the Interconnected Acoustic Framework (IAF) system (100) when employed in the room. FIG. 5 illustrates the Waterfall graphs showing the empty room’s response, and FIG 6. Shows the

Waterfall graph response after the system (100) is employed in the room. [0014] FIG. 6 illustrates the Waterfall Graph of the Room when the System is employed within it. The effective low frequency modal suppression is seen more clearly. The low frequency modal suppression is more significant compared to the mid and high frequencies, which can be easily treated with conventional methods. In both graphs, a time range of 300 milliseconds is chosen to highlight the significant modal suppression and low frequency absorption.

[0015] The RT60 (Reverberation time) values of the IAF System are tabulated below:

[0016] FIG. 7 illustrates the spectrogram included below is the measurement of an alternate design of low frequency absorber, that is based on prior art. It consists of a cylindrical tube of a porous but resistive material, with a volume enclosed within it. The volume may be left empty or filled with resistive material of certain kinds. The system that was tested was a cylindrical tube of a porous by resistive material, with the inner volume empty. 12 such cylindrical tube absorbers, 3 in each comer of the rectangular room, extending approximately 10 feet in height are utilized to achieve the results of the spectrogram in FIG 7.

[0017] FIG. 8 illustrates the Waterfall graph of the 12 cylindrical tube absorbers, 3 in each comer of the rectangular room, extending approximately 10 feet in height. The difference of the degree of low frequency absorption and modal suppression between the Cylindrical Absorbers, and the interconnected Framework is better seen in the comparisons of their respective Waterfall graphs. A zoomed in comparison (10 Hz to 600 Hz) is provided below [0018] FIG. 9 illustrates the Waterfall of Interconnected Acoustic Framework

System (10 Hz to 600 Hz range - 300 ms window). FIG. 10 illustrates the

Waterfall of Cylindrical Tube Absorbers (10 Hz to 600 Hz range - 300 ms window). The increased low frequency absorption and modal suppression is seen in the IAF system and is especially pronounced in the region below 100 Hz. The RT60 (Reverberation time) values of the Cylindrical Tube Absorber System are tabulated below:

[0019] The comparison of the tabulated data between the Interconnected

Acoustic Framework System and the Cylindrical Tube system shows the increased low frequency absorption achieved by the IAF system. Thus, the

Interconnected Acoustic Framework System achieves effective low frequency absorption and modal suppression and is particularly advantageous in small rooms and rooms non-optimal dimensions where modal behaviour is challenging to treat.

[0020] 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.

Claims

UWe CLAIM

1. An interconnected acoustic framework for low frequency modal absorption, comprising: a framework (100) is configured along edges of the six boundaries (4 walls, floor and ceiling of the room) of an acoustic room/environment for low frequency modal absorption in a wide range of applications wherein the framework (100) comprises a plurality of columns (110) that are interconnected (as shown in FIG. 1 ) and placed flush along the comers of the boundaries of the room wherein the framework (100) effectively handles the volume of the air behind the resistive membrane (110) which is the primary factor that influences the effectiveness at modal frequencies, the greater the volume, the lower the frequency that can be effectively attenuated. 2. The framework as claimed in claim 1 wherein the interconnected framework

(100) can create one large volume which allows for the range of absorption of low frequencies, and the effectiveness of absorption in the frequency range to be maximised.

3. The framework as claimed in claim 1 wherein the cross-sectional square shape of the framework (100) affords more surface area and inner volume, through which air moves through on account of the pressure differential created, and where soundwaves propagate via the air in the resistive material, leading to thermal losses occurring due to vibrational dissipation. 4. The framework as claimed in claim 1 wherein the framework (100) throughout the bi-comer and tri-comers of the room, the interconnected columns (110) creating one large inner space, and the select physical attributes of the resistive membrane allows for a higher degree of low frequency modal suppression, as well.