GB2592686A

GB2592686A - An acoustic device and an acoustic system

Info

Publication number: GB2592686A
Application number: GB2003335.3A
Authority: GB
Inventors: Edward Frost Anthony
Original assignee: Narrowband Absorber Co Ltd
Current assignee: Narrowband Absorber Co Ltd
Priority date: 2020-03-06
Filing date: 2020-03-06
Publication date: 2021-09-08
Anticipated expiration: 2040-03-06
Also published as: GB202103188D0; GB2592762A; GB2592686B; GB2592762B; GB202003335D0

Abstract

The sound absorbing device is for placement on a surface in an environment. It includes a sound absorber part including a body having a cavity, an active face upon which sound from the environment is incident, and an opening provided on the active face of the body and in communication with the environment. One or more diffuser parts 30a – 30d having a convex surface are located on the external surface of the device. The cavity contains sound absorbing material (27, fig 2a). Several sound absorbing devices may be stacked together (figs 6a – 7b).

Description

Title: An acoustic device and an acoustic system

Description of Invention

This invention relates to an acoustic device.

It is widely known that when sound is generated in a room, such as a recording studio or conference room, the sound waves interact with features or characteristics of the room. The interaction between sound waves and a room may include, inter alia, absorption, transmission, reflection or diffusion of sound waves. Relevant features and characteristics of a room may include the geometry of the room, such as the dimensions of individual walls or the position of walls relative to each other. For instance, a room including two parallel walls may reflect sound waves differently to a room with two nonparallel walls. In addition, objects present in a room such as furniture may reflect or absorb sound waves. This complex relationship between sound waves and the environment is the subject of the field of acoustics.

A fundamental aspect of acoustics is that, generally speaking, sound is rarely composed of a single frequency sound wave. Instead, sound is generally composed of different frequency sound waves. The number of different frequencies is also generally dependent on the source of the sound, e.g. a musical instrument, human voice, or electronic synthesiser. The range of frequencies generated by a source of sound is often broad. For instance, the human hearing range is generally considered to be between 20 Hz and 20kHz. This range can be categorised into several bands or sub-ranges.

In an enclosed space, low frequency sound waves can be problematic, especially as the wavelength of a sound wave approaches the dimensions of the space. When a low frequency sound wave is reflected by a surface 0.e. a wall of a room), the reflected sound wave may interfere with subsequent sound waves. This interference can cause regions of high and low pressure to be created, leading to an uneven distribution of sound. An effect of this interference is that the sound as heard by a listener in the room is dependent upon their position within the room and so what is heard by the listener may actually differ from the sound at the sound source.

Sound waves residing in the mid and high frequency bands may also be problematic. Upon impacting a surface such as a wall, a portion of the energy of the sound wave may pass through the wall, i.e. some of the energy is transmitted to the wall. The remaining energy may be reflected back into the room. If the magnitude of the remaining energy is great enough, it may be audible to a listener in the room and be recognised as an echo. The consequence of this for a listener is that, upon hearing the original sound source, they may subsequently hear the reflection. This can lead to distortion and/or a lack of clarity of the sound from the sound source, and can also be distracting and unpleasant. In addition, the direction of a sound wave reflected from a surface is dependent on the angle of incidence of the source sound wave. This means that sound may not be evenly distributed throughout a room. This can lead to a different listening experiences for listeners located around a room.

Devices exist which are intended to mitigate the consequences of the complex interaction between sound waves and the environment. One type of device is an absorber, which operates by converting sound energy into another form of energy, such as heat. This may act to reduce, or eliminate, the energy of a sound wave. Another type of device is a diffuser, which may reflect an incident sound wave in a multitude of directions enhancing the distribution of sound in a room. A diffuser may be configured to only reflect sound waves that lie in a particular frequency range.

The present invention seeks to provide an improved acoustic device with respect to prior art acoustic devices.

According to a first aspect of the invention we provide an acoustic device for placement on a surface in an environment including: an absorber part including a body having a cavity, an active face on which sound from the environment is incident, and an opening provided on the active face in communication with the environment; and one or more diffuser parts including a convex surface defining a portion of an external surface of the device.

The opening may provide the only communication between the cavity and the environment.

The one or more diffuser parts may be provided on the active face.

The acoustic device may be placed into: a first configuration in which the active face is directed in a first direction; and a second configuration in which the active face is directed in a second direction.

The first direction may be horizontal or parallel with a plane defined by the surface on which the device is placed.

The second direction may be vertical or perpendicular to a plane defined by the surface on which the device is placed.

The body of the absorber part may include a first side for resting the device on the surface in its first configuration.

The body of the absorber part may a second side for resting the device on the surface in its second configuration.

The acoustic device may include a hollow neck portion extending away from the body, wherein the neck portion has a first end in communication with the opening, and a second end including a further opening for communication with the environment.

The hollow neck portion may extend in the direction of the active face.

The hollow neck portion may be located substantially centrally or centrally of the active face.

The body of the absorber part may be generally cuboid, preferably rectangular cuboid, and, optionally or preferably, the body has a square cross-section.

The body of the absorber part may have only one opening in communication with the environment.

The acoustic device may include a layer of sound absorbing material located within the cavity of the body.

The acoustic device may include a cover member for selectively covering or closing the opening or the further opening, optionally or preferably the cover member may include an external surface which includes a convex portion.

The one or more diffuser parts may be connected to the body of the absorber part.

The one or more diffuser parts may be provided on the active face and/or extend along the active face.

The convex surface of the one or more diffuser parts may be curved.

The right section of the one or more diffuser parts may extend in the direction of the active face away from the body, and/or the right section of the one or more diffuser parts may be symmetrical.

The one or more diffuser parts may include a first end face and a second end face, the diffuser part extending from the first end face to the second end face along a length axis, and, optionally, in the first configuration, the device may be selectively placed so that the length axis extends generally horizontally or generally vertically.

The diffuser part may be positioned at and/or extend along a peripheral portion of the active face.

Each of the one or more diffuser parts may extend in the direction of the active face away from the body along a height axis, and, optionally, the height axis may be horizontal in the first configuration and/or vertical in the second configuration.

The one or more diffuser parts may include first and second diffuser parts.

The first and second diffuser parts may be positioned on respective first and second opposing regions of the active face.

The one or more diffuser parts may include third and fourth diffuser parts positioned on respective third and fourth opposing regions of the active face.

The first and second diffuser pads may be the same length and/or the third and fourth diffuser parts may be the same length.

The first and second diffuser parts may be longer in length than the third and fourth diffuser parts.

The first and second diffuser parts may be identical and/or the third and fourth diffuser parts may be identical.

The first and second diffuser parts may extend parallel to each other and/or the third and fourth diffuser parts may extend parallel to each other.

The first and second diffuser parts may surround a portion of the opening of the body of the absorber part and/or the third and fourth diffuser parts surround a portion of the opening of the body of the absorber part.

The opening of the body of the absorber part may be positioned substantially centrally, or centrally with respect to the first and second diffuser parts and/or the third and fourth diffuser parts.

The length axes of the first and second diffuser parts may be arranged transversely, optionally or preferably perpendicularly, to the length axes of the third and fourth diffuser parts.

The height dimension of each the right sections of the first and second diffuser parts may be generally the same, or may be the same, as the height dimension of each of the right sections of the third and fourth diffuser pads.

The opening at the second end of the hollow neck portion of the absorber part may be at a height lying in a plane in which the diffuser parts terminate in a height direction.

The volume of the cavity of the body of the absorber part may be preferably between 0.03 m3 and 1 m3, more preferably between 0.03 m3 and 0.8 m3, and most preferably between 0.05 m3 and 0.5 m3.

According to a second aspect of the invention we provide an acoustic system including a plurality of acoustic devices according to any preceding aspect of the invention, wherein the system is operable in: a) a first mode of operation in which the acoustic and diffuser devices form an array that extends vertically wherein the active face of each device is directed in a first direction which is horizontal; and b) a second mode of operation in which the acoustic and diffuser devices form an array that extends horizontally wherein the active face of each device is directed in a second direction which is vertical.

For the first mode of operation, a portion of the devices may be stacked on top of one another and/or a portion of the devices may be positioned side-by-side with one another.

For the second mode of operation, a portion of the devices may positioned side-by-side with one another to extend along a first axial direction and a portion of the devices may be positioned side-by-side with one another to extend along a second axial direction which is perpendicular to the first axial direction.

The devices may be selectively configured to place the system from its first or second mode of operation into the other of first or second mode of operation.

The devices may be selectively configured in the first and second modes of operation so that corresponding diffusers parts of adjacent devices are parallel 30 to one another.

The devices may be selectively configured in the first and second modes of operation so that corresponding diffusers pads of adjacent devices are transverse, optionally or preferably perpendicular, one another.

Embodiments of the invention will be set out below by way of example only with reference to the accompanying figures, of which: Figure 1 is a perspective view of a device in accordance with embodiments of the present invention; Figures 2a and 2b are a side cross-section view, showing a certain part, and a front view respectively, of a device in accordance with embodiments of the present invention; Figures 3a and 3b are a perspective view and a side view respectively of a component part of a device in accordance with embodiments of the present invention; Figures 4a and 4b are perspective views of a device in accordance with embodiments of the present invention in a first configuration and a second configuration respectively; Figures 5a and 5b are front views of a device in accordance with embodiments of the present invention placed in different orientations of a first configuration 25 respectively; Figures 6a and 6b are front views of a system of devices in accordance with embodiments of the present invention in certain respective configurations of a first mode of operation; Figures 7a and 7b are plan views of a system of devices in accordance with embodiments of the present invention in certain respective configurations of a first mode of operation; Figures 8a and 8b and Scare images showing the test conditions for a device / system of devices in accordance with embodiments of the present invention; Figure 9 is a graph of results of an absorption test of a device in accordance with embodiments of the present invention under certain test conditions; Figure 10 is a graph of results of an absorption test of a device in accordance with embodiments of the present invention under certain test conditions; Figure 11 is an image showing a test environment for testing a system of devices in accordance with embodiments of the present invention; Figures 12a and 12b are graphs of results under certain respective test conditions of a system of devices; Figures 13a -e are graphs of results under certain respective test conditions of a system of devices; Figures 14a -e are graphs of results under certain respective test conditions of a system of devices; and Figures 15a -c are graphs of results under certain respective test conditions of a system of devices With reference to figure 1, an acoustic device 10 in accordance with embodiments of the present invention is shown. The acoustic device 10 will now be described with reference to the figures. As it will be readily understood on reading the description, the acoustic device forms an acoustic absorber and diffuser device.

With reference to figures 1, 2a and 2b, the acoustic device 10 includes an absorber part 20, and first, second, third and fourth diffuser parts 30a, 30b, 30c, 30d. The absorber part 20 includes a body 21 having a cavity 22, an active face 11 on which sound from the environment is incident, and an opening 23 provided on the active face 11 in communication with the environment. Each of the diffuser parts 30a, 30b, 30c, 30d includes a convex surface 33a, 33b, 33c, 33d which defines a portion of an external surface of the acoustic device 10. In embodiments, the diffuser parts 30a, 30b, 30c, 30d define portions of the external surface of the active face. In embodiments, acoustic device 10 may only include a single diffuser part, or, in embodiments, acoustic device 10 may include a greater or fewer number of diffuser pads.

Body 21 may be a rectangular cuboid shape, and may have a square cross-section. Body 21 may include a front wall 21a which defines the active face 11 and an opposing rear wall 21b, a first side wall 21c and an opposing second wall 21d, a top wall 21e and an opposing bottom wall 21f. In embodiments, body 21 may take other shapes or forms, e.g. a triangular prism, cube, and/or pad spheroid, as would be readily appreciated by the skilled person.

Body 21 may be generally hollow, and the internal cavity 22 may be defined by the walls 21a-f in embodiments. Opening 23 may be located on the front wall 21a, and may be positioned generally centrally thereon. In embodiments, the opening 23 may be positioned elsewhere. Opening 23 permits communication between the internal cavity 22 and the surrounding environment. The opening 23, in embodiments, may provide the only communication between the internal cavity 22 and the surrounding environment. Opening 23 may be generally circular in embodiments, and may be other shapes in embodiments.

With reference to figure 2a in particular, body 21 may include a hollow neck portion 24 extending away from the rest of the body 21 and which is in communication with the opening 23. The neck portion 24 indirectly provides communication between the opening 23 and the surrounding environment.

Neck portion 24 is provided on the active face 11 and may be connected to the front wall 21a or integrally formed as part of the front wall 21a in embodiments. The neck portion 24 may be provided generally centrally on the active face 11 and extend in the same direction as the active face 11. In embodiments, the hollow neck portion 24 may extend away from the front wall 21a in a direction which is transverse, e.g. perpendicular thereto. Neck portion 24 may be generally cylindrical in embodiments or be of different shapes in embodiments. Neck portion 24 may include a first end 24a positioned adjacent the front wall 21a. The first end 24a defines a first opening 25 which is in communication with the opening 23, and a second end 24b defining a further opening 26 for communication with the environment. In embodiments, first opening 25 and/or opening 26 may be aligned with opening 23. In embodiments, the first opening 25 and further opening 26 are identical in size and shape to the opening 23 provided on the active face 11. In embodiments, the first opening 25 and/or further opening 26 may not be the same size or shape as the opening 23.

The active face 11 is used to denote the side or region of the acoustic device 10 which is primarily configured for effecting acoustic absorption and/or diffusion of sound waves incident thereon. In operation, the active face 11 is directed towards a source of sound waves or a desired direction from which sound waves are incoming and which require acoustic treatment.

Further opening 26 is in communication with the surrounding environment, and, due to the neck portion 24 being hollow, it is also in communication with the first opening 25 and the opening 23 provided on the active face 11. In this manner, the hollow neck portion 24 provides communication between the opening 23 and the surrounding environment. The hollow neck portion 24 may be formed as an integral part of the body 21, or it may formed as a separate component that is either permanently or temporarily connected to the front wall 21a to form a part of the active face 11 by methods readily apparent to the skilled person. For example, the neck portion 24 may be joined to the front wall 21 by a suitable adhesive.

The acoustic device 10 may also be provided with a cover member 40 (see figure 1), which may be used to selectively cover or close the further opening 26 from communication with the surrounding environment. The cover member 40 thus permits the absorption functionality of the acoustic device 10 to be "switched" between on (cover member 40 not covering or closing the further opening 26) or off (cover member 40 covering or closing the further opening 26). The cover member 40 thus effectively seals the internal cavity 22 of the body 21 with respect to the surrounding environment. The cover member 40 may be circular in shape, or any other shape suitable for covering the further opening 26. The cover member 40, when applied to the further opening 26, includes at least one external surface which faces away from the device 10. This external surface may be flat. In embodiments, the external surface may include a convex portion, and the convex portion may be curved. The cover member 40 may also include a protrusion extending from the cover member, which enables the cover member 40 to be connected to the further opening 26 by a push interference fit and removed therefrom by simply pulling the cover member 40 away from the further opening 26. In embodiments, the cover member 40 may be connected in different ways, e.g. it may be pivotally connected. In embodiments for which the device 10 has no neck portion 24, the cover member 40 may cover the opening 23 in a similar manner to that described in relation to further opening 26. In embodiments for which the external surface of the cover member 40 is convex in shape, the cover member 40 may provide an additional surface for the diffusion of sound.

With reference to figure 2a, a layer of sound absorbing material 27 may be provided within the internal cavity 22. The material may be positioned adjacent the inner surface of the rear wall 21b to cover the entire wall. For example, the sound absorbing material may be one or more layers of sheep's wool. In embodiments, other sound absorbing materials may be provided within the internal cavity 22.

The diffuser parts 30 are provided on the active face 11 of the body 21 of the absorber part 20 and extend along respective portions or regions of the active face 11. The diffuser parts may be formed as an integral pad of the body 21 of the absorber part 20, or may be formed as separate components that are either permanently or temporarily connected to the front wall 21a so as to form part of the active face 11. For example, they may be joined by adhesive for a permanent connection thereto, or connected by fasteners for permanent or temporary connection thereto.

In embodiments, each of the diffuser parts 30a, 30b, 30c, 30d may have the same shape or differ in other embodiments. The diffuser parts 30a, 30b, 30c, 30d will be explained by way of example, with reference to figures 3a and 3b, which show an example diffuser part 30. Part 30 includes a first end face 31 and a second end face 32, and a side wall which extends from the first end face 31 to the second end face 32 along a length axis L. End faces 31, 32 may be planar or non-planar, e.g. curved, in embodiments. Part 30 includes convex surface 33 that is provided by the external surface of the side wall. In embodiments, the convex surface 33 may be curved, or may be formed of, for example, inclined planar surfaces that combine to form a convex surface. The curvature of convex surface 33 does not change as the convex surface 33 extends in the direction of the length axis L, though this need not necessarily be the case in other embodiments. The first end face 31 and second end face 32 may have respective right sections 31a, 31b that are identical, and/or symmetrical. The right sections may each extend in the direction of the active face 11 away from the body 21 along a height axis H when the part 30 is connected to the body 21. Height axis H is perpendicular to the length axis L. For each of the first diffuser part 30a, the second diffuser part 30b, the third diffuser part 30c and the fourth diffuser part 30d, the first end face 31, the second end face 32, the convex surface 33, the length axis L and the height axis shall hereafter be denoted by the corresponding suffixes a,b,c or d of the respective diffuser parts.

With reference to figure 2b, in embodiments, one or more of the diffuser parts 30a-d may extend along respective, e.g. peripheral, regions of the active face 11, e.g. one or more of the diffuser parts 30a-d may be located away from the centre of the active face 11. The diffuser parts 30a-d may surround the opening 23, and the hollow neck portion 24 where provided in embodiments.

In embodiments, the first diffuser part 30a and second diffuser part 30b may be identical in length and/or height, and are positioned along generally opposing top and bottom peripheral portions of the active face 11 respectively such that their respective length axes La, Lb are parallel.

The third diffuser part 30c and fourth diffuser part 30d may be identical in length and/or height, and may be positioned in opposing left and right, e.g. peripheral, regions of the active face 11 such that their respective length axes Ld are generally parallel or parallel.

In embodiments having first and second diffuser parts 30a, 30b, and, third and second diffuser parts 30c, 30d, the length axes La, Lb of the first and second diffuser parts may extend transversely, e.g. perpendicularly, to the length axes Lb, Ld of the third and fourth diffuser parts 30c, 30d. The first diffuser part 30a and second diffuser part 30b may each be greater in length than the third diffuser part 30c and fourth diffuser part 30d. In embodiments, the respective heights of each diffuser part 30a-d, i.e. of the right sections thereof, may be the same. In embodiments, the diffuser parts 30 may terminate in a height direction in a plane in which the further opening 26 of the neck portion 24 lies.

Use of the acoustic device 10 will now be described.

The acoustic device 10 is of a size and weight that permits a user to manually handle the device 10 for use in treating the acoustics in an environment. With reference to figure 4a, the device 10 has been placed on a surface into a first configuration in which the active face 11 is directed in a first direction 100, and with reference to figure 4b, the device 10 has been placed on the surface into a second configuration in which the active face 11 is directed in a second direction 200. The first direction 100, in embodiments, may be transverse, optionally perpendicular, to the second direction 200. The first direction 100 may be horizontal, or parallel with the plane defined by the surface. The second direction 200 may be vertical, or perpendicular, to the plane defined by the surface.

The first configuration includes two orientations that are defined with respect to the respective wall of the device 10 that is placed on the surface. For example, by resting the acoustic device 10 on either of the side walls 21c, 21d, or on the top wall 21e or bottom wall 21f.

With reference to figure 5b, for embodiments including at least one of the diffuser parts 30a, 30b and at least one of the diffuser parts 30c, 30d, when the side wall 21c or side wall 21d is chosen as a resting surface, the length axes La, Lb of the first diffuser part 30a and the second diffuser part 30b will be oriented horizontally with respect to the surrounding environment (i.e. in front view), whilst the length axes Lc, Ld of the diffuser parts 30c, 30d will be oriented vertically (i.e. in front view). With reference to figure 5a, when the top wall 21e or bottom wall 21f is chosen as a resting surface, the length axes La, Lb of the first diffuser part 30a and the second diffuser part 30b will be orientated vertically with respect to the surrounding environment, i.e. they will point in a direction transverse to the ground or floor, whilst the length axes L, Ld of the diffuser parts 30c, 30d will be oriented horizontally. Advantageously, the characteristics of the sound diffusion effected by the device 10 can be selectively varied because the characteristics may differ depending on how the device 10 has been orientated in its first configuration.

In a second configuration, as shown in figure 4b, the active face 11 of the acoustic device 10 may be directed in a second direction 200 by resting the acoustic device 10 on rear wall 21b. The device 10 may also be rotated about a central axis of the neck portion 24, so as to vary the orientation of the respective length axes La, Lb, L, Ld and similarly vary the diffusion characteristics of the device 10.

With reference to figures 6a, 6b, 7a and 7b, a plurality of acoustic devices 10 may be arranged to form a system 100 of acoustic devices 10. The system is selectively configurable so that the plurality of acoustic devices 10 may form an array of acoustic devices 10, and may be arranged in several possible modes.

Each acoustic device 10 of the system may be identical in embodiments. For the purpose of the present description, the acoustic devices that form the system 100 are identical. Each acoustic device and its respective features is denoted by the same reference numerals as used for the previously described embodiments for acoustic device 10 with the addition of ', ", "1, and so on for the individual devices of the system.

In a first mode of operation, two acoustic devices 10', 10" are arranged in an array, with each acoustic device 10' being in its first configuration. In other words the respective active faces 11', 11" of each device is directed in a first direction which is horizontal Possible arrays in the first mode of operation are shown in figures 6a and 6b.

With reference to figure 6a, in the first mode of operation, the acoustic devices 10 may be arranged in a vertical array, with the bottom wall 21f' of acoustic device 10" resting on the top wall 21e' of acoustic device 10' positioned below it i.e., in a stacked formation with one of the devices stacked on top of the other device. In the example shown in figure 6a, each acoustic device 10', 10" may be oriented so that the first and second diffuser parts 30a', 30a", 30b', 30b" of each acoustic device 10', 10" extend in a vertical direction, i.e. their respective length axes extend vertically and may be aligned for corresponding diffuser parts 30a', 30a" and 30b', 30b". Similarly, the third and fourth diffuser parts 30c', 30c", 30d', 30d" of each acoustic device 10', 10" may extend in a horizontal direction, with their respective length axes being parallel to each other.

With reference to figure 6b, in the first mode of operation, it is also possible to arrange the acoustic devices 10', 10" in a vertical array in a similar manner to figure 6a but with the first and second diffuser parts 302', 30b' of the acoustic device 10' extending in a vertical direction, i.e. their respective length axes extend vertically, and with the first and second diffuser parts 30a", 30b" of the acoustic device 10" extending in a horizontal direction, i.e. their respective length axes extend horizontally. In this configuration, the respective length axes of the corresponding first diffuser parts 30a', 30a" are transverse, e.g. perpendicular to each other, and similarly the respective length axes of the corresponding second diffuser parts 30b', 30b" are transverse, e.g. perpendicular, to each other. Similarly, it can be seen that the respective length axes of the corresponding third diffuser parts, 30c' 30c" are transverse, e.g. perpendicular, to each other, as is the case for the corresponding fourth diffuser parts 30d', 30d'.

With reference to figures 7a and 7b, in a first mode of operation, four acoustic devices 10', 10", 10", 10" may similarly be arranged to what is shown in figures 6a and 6b, but arranged to form 4 x 4 arrays which extend horizontally and vertically. In other words, with a portion of the acoustic devices 10', 10", 10", 10" being positioned relative to one another, e.g. side-by-side, to extend along a first axial direction, i.e. a horizontal direction, and a portion of the acoustic devices 10', 10", 10", 10" being positioned relative to one another, e.g. stacked with respect to one another, to extend along a second axial direction, i.e. a vertical direction.

In a second mode of operation, the acoustic devices 10',10",10-,10-may be configured to form an array for which each device is in its second configuration, i.e. each acoustic device is placed on a surface on its respective rear wall 21f, 21f", 21f-, 21f". It is possible to arrange the acoustic devices in this mode resembling the possible arrays of the first mode of operation, as shown in figures 6a, 6b, 7a and 7b. For example, in this mode the acoustic devices 10', 10" are positioned side-by-side with one another to extend in a first axial direction, and acoustic devices 10', 10" are positioned side-by-side with one another to extend in a second axial direction which is perpendicular to the first axial direction. Acoustic device 10" is placed next to acoustic device 10" in the first axial direction, and next to acoustic device 10-in the second axial direction. Similar to the first mode of operation, each individual acoustic device 10', 10", 10", 10" may be positioned so that their respective first and second diffuser parts 30a, 30b are arranged parallel to the first axial direction, or arranged parallel to the second axial direction.

It can be seen that the acoustic devices may be positioned to form arrays according to the requirements of an environment, and advantageously allows a plurality of acoustic devices 10 to form an array so that the system effectively has a larger active face, and/or is flexible so that it can be located according to the desired space, e.g. a corner of a room. Also, the selective configurability of the devices within the first and second modes of operations will lead to differing diffusion characteristics so that a user may target or select particularly desirable frequencies for acoustic diffusion according to the needs of the user or the characteristics / features of the environment being treated. It will be appreciated that a number of possible permutations are advantageously possible, depending on the number of acoustic devices 10 utilised in the system.

In operation, the absorber part 20 of the acoustic device 10 is configured so as to form what is known a Helmholtz resonator. Such resonators include a hollow body with a cavity, an opening leading to the cavity, and may also include a neck portion with its own opening at a distal end and provides for communication from the environment to the opening to the cavity.

Helmholtz resonators are designed to absorb sound waves, and generally absorb a narrow band of frequencies when compared to other means of absorption of sound waves, e.g. porous absorbers. As the absorption of sound waves occurs within a narrow band of frequencies, if a Helmholtz resonator is designed to absorb sound waves of a relatively low frequency (for instance, those below approximately 315 Hz) it may have a significantly negligible effect on higher frequencies. This allows for an isolated absorption of sound waves within a specific frequency range. Within this narrow band of frequencies, peak absorption of sound will be observed at the resonant frequency of the absorber part 20.

The resonant frequency of a Helmholtz resonator is dependent upon a variety of factors, including its dimensional characteristics such as the volume of the internal cavity, the dimensions (diameter, area) of the opening and any neck leading to the opening. It is possible to tune the resonant frequency of a Helmholtz resonator by modifying these dimensional characteristics.

The applicant has found absorption of low frequencies, for instance, those below 315 Hz, is attainable when the volume of the internal cavity 22 of the absorber part 20 is as low as 0.05 m3. Referring to acoustic device 10 as described in accordance with embodiments of the present invention, an example of a body 21 with this approximate volume has internal dimensions of approximately 0.5 m x 0.5 m x 0.2 m. The skilled person would understand that other combinations of dimensions are possible and that other volumes of the internal cavity 22 are possible for absorbing sound at this or other frequencies. For example, the volume of the internal cavity may be between 0.03 m3 and 0.1 m3. Advantageously, an absorber part 20 possessing this approximate volume enables the acoustic device 10 to be easily positioned within an environment, as well as easily repositioned within an environment, without necessarily requiring the use of transportation equipment e.g. trolleys, carts, trucks, dollies, etc. It is also possible to fine-tune the resonant frequency of the absorber part 20 further by modifying the area of the further opening 26 and the length of the hollow neck portion 24, whilst maintaining the volume of the internal cavity 22 at approximately 0.05 m3, or within the range of 0.03 m3and 0.1m3.

The degree of absorption may be dependent on where a Helmholtz resonator is positioned within an environment. In a room with generally parallel walls, points of maximum or minimum pressure of low frequency sound are understood to reside in the corners of a room. In this situation, locating a Helmholtz resonator in the corner of a room may result in a higher degree of absorption compared to other locations.

To test embodiments of the acoustic device 10, tests were carried out to measure its absorption and diffusion characteristics. For the absorption tests, prototype acoustic devices made from sheets of plywood, with overall external dimensions of each acoustic device including a width 0.52 m, length 0.52 m and height 0.36m. The acoustic devices included testing with and without sheets of sheep's wool approximately 50mm thick.

A first test will be described which was conducted with guidance from BS EN ISO 354: 2003. With reference to figure 8a, the test measured the absorption characteristics of a single acoustic device 10 positioned in the corner of the chamber and resting on the bottom wall 21f of the device, i.e. in a first configuration with the first diffuser part 30a and second diffuser part 30b arranged vertically. The cover member 40 was not connected to the further opening 26 so that the opening 26 was open to permit absorption to take place.

In this test, measurements were made of the rate of decay of sound in third octave bands from 40 Hz to 5000 Hz within the reverberation chamber, with and without the acoustic device 10 in place. From the measurements, the sound absorption coefficient between 40 Hz and 5000 Hz of the acoustic device was calculated as described in BS EN ISO 354: 2003. With reference to figure 9, the results of the test indicate that an acoustic device 10 with a volume of the internal cavity 22 of approximately 0.05 m3 can attain a fundamental resonant frequency of approximately 63 Hz, with an additional peak in absorption occurring at the second harmonic frequency of approximately 126 Hz. Advantageously, such absorption at the lower frequency bands is particularly suitable for acoustic treatment for environments such as recording studios and the like, particularly where sources of low frequency sound are present, such as the kick drum or floor tom of a drum kit.

A second test will be described which was conducted with guidance from BS EN ISO 354: 2003 to measure the absorption characteristics of a system of devices identical to those used for the first test, in the second mode of operation. With reference to figure 8b, six prototype acoustic devices were arranged in a 3x2 array on the floor of the reverberation chamber, with respective acoustic devices along a first axial direction being arranged so that their corresponding diffuser parts are perpendicular to each other, whilst respective acoustic devices along a second, perpendicular, axial direction being arranged so that corresponding diffuser parts are either parallel to each other or are aligned to each other. In this test, measurements were made of the rate of decay of sound in third octave bands from 40 Hz to 5000 Hz within the reverberation chamber, with and without the acoustic devices in place. From the measurements, the sound absorption coefficient between 40 Hz and 5000 Hz of the acoustic device was calculated as described in BS EN ISO 354: 2003. Additionally, from the measurements, the weighted sound absorption coefficient was also calculated, and categorised from A to E, as described in BS EN ISO 11654: 1997. Within this standard, absorbers with a weighted sound absorption coefficient within the range of 0.9 to 1 belong to category A, and absorbers with a weighted sound absorption coefficient with the range of 0.15 to 0.25 belong to category E. The results of the test are shown in figure 10 which is a graph showing the sound absorption coefficient against frequency with and without the sheep's wool. The results of the test indicate that a system of acoustic devices 10 with a volume of the internal cavity 22 of each acoustic device 10 of approximately 0.05 m3 can attain a fundamental resonant frequency of 80 Hz, with additional peaks in absorption occurring at the second harmonic frequency of approximately 160 Hz, the third harmonic frequency of approximately 240 Hz and the fourth harmonic frequency of approximately 320 Hz. Absorption of sound is also observed above approximately 800 Hz, due to the effects of the hard floor surface onto which the body 21 of the devices 10 is placed. The results of the test further indicate that providing sheep's wool within the internal cavity 22 of each device 10 of a system of devices may enhance their overall absorption characteristics. Without the presence of sheep's wool, the weighted sound absorption coefficient of the system of devices 10 was calculated as 0.55 and categorised as a 0 grade absorber of sound. With the presence of sheep's wool, the weight sound absorption coefficient of the system of devices 10 was calculated as 0.6 and categorised as a C grade absorber of sound.

Further tests will be described to measure the diffusion characteristics of the acoustic device 10.

The tests were conducted on 3D printed scale models of the acoustic device 10 produced from polylactic acid (PLA). These were produced at a scale of 1:5 relative to the full-sized unit described in relation to the absorption tests above. In addition, all scale models did not include an opening in communication with the surrounding environment because acoustic absorption cannot be readily scaled. All measurements were carried out at scale, with results reported for the full-scale equivalent.

The diffusion tests were conducted with guidance from BS EN ISO 17497-2: 2012 and measured the diffusion characteristics of an array of scale models of acoustic devices 10 in the first mode of operation. The tests included a random-incidence diffusion characteristics test and a directional diffusion characteristics test. The random-incidence characteristics test measures the uniformity of diffusion produced by the array of scale models of acoustic devices 10 for sound generated from a plurality of source positions -i.e. to test how it diffuses multiple sounds coming from different directions. The direction diffusion characteristics test measures the uniformity of diffusion produced by a surface for sound generated from one source position -i.e. to test how it diffuses a singular sound coming from on direction.

The test conditions for both the random-incidence diffusion characteristics test and directional diffusion characteristics test involved thirty-seven microphones M positioned in a semi-circular arc A spanning from -90° to +90° relative to a datum point 0 on which the array of acoustic devices 10 is positioned, with an angular step of 5° and each microphone located 1.2 m from the centre of the array. Loudspeakers S were placed at source angles of 0°, ±300, and ±60° relative to the array, and each loudspeaker S was located 2.2 m from the centre of the array. An example layout (with no sample present) is shown in Figure 11. Measurements were made of the sound pressure levels of sound in third octave bands from 40 Hz to 5000 Hz within the reverberation chamber, and the diffusion coefficients were calculated as described in BS EN ISO 17497-2: 2012.

Both the random-incidence diffusion characteristics tests and directional diffusion characteristics tests involved eight scale devices arranged in a 4x2 array, in two orientations: orientations A and B. In orientation A, the acoustic devices 10 were arranged so that their respective first and second diffuser parts 30a, 30b were arranged vertically, as shown in figure 8c. In orientation B, all acoustic devices were arranged so that their respective first and second diffuser parts 30a, 30b were arranged horizontally (not shown).

With reference to figures 122 and 12b, these are graphs of the random-incidence diffusion coefficient against frequency for the devices 10 arranged in in arrays according to orientation A and orientation B respectively. A reference line (solid black line) is shown which corresponds to the devices arranged with their back walls in the direction of the test so as to form a flat 4x2 wall. The two dashed lines correspond to normalised and non-normalised results.

It can be seen that random-incidence diffusion occurs for all frequencies above approximately 500 Hz, with no diffusion measurable below this value. This frequency is significantly higher than the resonant frequency observed in the first absorption test (approximately 63 Hz). In addition, peak random-incidence diffusion occurs at different frequencies depending on the orientation that the array is arranged in. For orientation A, peak random-incidence diffusion occurs at approximately 1600 Hz and 4000 Hz. For orientation B, peak random-incidence diffusion occurs at approximately 800 Hz, 2000 Hz and 5000 Hz.

With reference to figures 13a-e, these are the test results of a directional diffusion characteristics test for system 100 arranged in orientation A (as shown in figure Sc), and whilst figures figures 14a-e are the test results of a directional diffusion characteristics orientation B (corresponding to all acoustic devices being arranged so that their respective first and second diffuser parts 30a, 30b extend horizontally). For each of the graphs in figures 13a-e and 14a-e, the same key is used for the lines as that of the graphs in figures 12a and 12b.

Discussing the results of testing orientation A and referring to figures 13a-e, for a source angle of 0° peak directional diffusion occurs at approximately 2000 Hz and 3150Hz, with a smaller spike in diffusion occurring at approximately 800 Hz. When the source angle of the sound wave is ±30°, peak directional diffusion occurs at approximately 1600 Hz and 4000 Hz. When the source angle of the sound wave is ±60°, peak directional diffusion occurs approximately within the range of 3000-5000 Hz.

Discussing the results of testing orientation B and referring to figures 14a-e, different peaks in directional diffusion were observed during testing compared to orientation A. For a source angle of 0° peak directional diffusion occurs at approximately 800 Hz and 5000 Hz. When the source angle of the sound wave is ±30°, peak directional diffusion occurs at approximately 1250 Hz and 5000 Hz. When the source angle of the sound wave is ±60°, peak directional diffusion occurs at approximately 800 Hz, 2000 Hz and 5000 Hz.

The results of the test show that, advantageously, the acoustic devices can be configured into systems which, in accordance with embodiments, diffuse sound from a variety of source angles and, can be positioned in different orientations that have differing diffusion characteristics. This enables a user to select the most suitable orientation for their specific requirements.

With reference to figures 15a-c, these are graphs of results obtaining utilising the same testing conditions as the directional diffusion characteristic tests for orientation A but represent the results differently. The same key is used to denote the reference and sample results. The lines can be understood to represent the amplitude of a particular frequency at the various angles from -90° to 90°.

Figures 15a-c show the diffusion behaviour of the array of devices 10 for frequencies 2000 Hz, 4000Hz and 5000 Hz with respect to source angles 0°, 30° and 600 respectively. Figure 15a shows the diffusion of a sound wave with a frequency of 2000 Hz of which the source angle is 00 as being evenly diffused compared to the source angle so as to be spread across the range of angles -90° to 90°. Similar behaviour is also observed when the source angle is 30°, as shown in figure 15b, and figure 15c, when the source angle is 60°.

The test results for both the random-incidence diffusion tests and directional diffusion tests show diffusion of a broad range of frequencies above approximately 500 Hz, which is significantly higher than the resonant frequency observed in the first absorption test (approximately 63 Hz). For the directional diffusion tests in particular, peak values of directional diffusion occur at different frequencies depending on both the orientation that the array is arranged in and the direction the array is pointed in.

Advantageously, the acoustic device 10, or system 100 of devices 10, provides a combination of narrowband absorption of problematic, e.g. low. frequencies, and broadband diffusion of problematic, e.g. high, frequencies of sound. This enables a user to reduce the effects of, or eliminate, problematic frequencies that may occur due to the geometry of a room or other appropriate environment by absorbing and/or diffusing said frequencies. In embodiments, advantageously, the frequencies at which absorption and diffusion occur may be different and so the acoustic device or system provides for separate acoustic treatment of different frequencies.

Furthermore, the acoustic device 10, in embodiments, may be of a portable form that is suitable for a user to manually handle and relocate it within a room or environment without the use of transportation equipment, tools and/or without the need to mount the device on a support structure. This also enables a plurality of devices 10 to be positioned in an array of devices 10, and to be reconfigured by a user as desired. Another benefit is that the acoustic device or system can be used in an environment without necessarily having to be fixed as part of the structure defining the environment, e.g. walls or a ceiling and the like.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and/or to encompass equivalents.

Claims

CLAIMS1 An acoustic device for placement on a surface in an environment including: an absorber part including a body having a cavity, an active face on which sound from the environment is incident, and an opening provided on the active face in communication with the environment; and one or more diffuser parts including a convex surface defining a portion of an external surface of the device.
An acoustic device according to claim 1 wherein the opening provides the only communication between the cavity and the environment.
An acoustic device according to claim 1 or 2 wherein the one or more diffuser parts are provided on the active face.
An acoustic device according to claim 1, 2 or 3 wherein device may be placed into: a first configuration in which the active face is directed in a first direction; and a second configuration in which the active face is directed in a second direction.
An acoustic absorber and diffuser device according to claim 4 wherein the first direction is transverse, optionally or preferably perpendicular, to the second direction.
An acoustic absorber and diffuser device according to claim 4 or 5, wherein the first direction is horizontal or parallel with a plane defined by the surface on which the device is placed. 2. 3. 5. 6.
7. An acoustic absorber and diffuser device according to claim 4, 5, or 6, wherein the second direction is vertical or perpendicular to a plane defined by the surface on which the device is placed.
8. An acoustic absorber and diffuser device according to any one of claims 4 to 7, wherein the body of the absorber part includes a first side for resting the device on the surface in its first configuration.
9. An acoustic absorber and diffuser device according to any one of claims 4 to 8, wherein the body of the absorber part includes a second side for resting the device on the surface in its second configuration.
10.An acoustic device according to any preceding claim including a hollow neck portion extending away from the body, wherein the neck portion has a first end in communication with the opening, and a second end including a further opening for communication with the environment.
11 An acoustic absorber and diffuser device according to claim 10, wherein the hollow neck portion extends in the direction of the active face.
12.An acoustic absorber and diffuser device according to claim 10 or 11, wherein the hollow neck portion is located substantially centrally or centrally of the active face.
13. An acoustic absorber and diffuser device according to any preceding claim wherein the body of the absorber part is generally cuboid, preferably rectangular cuboid, and, optionally or preferably, the body has a square cross-section.
14. An acoustic absorber and diffuser device according to any preceding claim wherein the body of the absorber part has only one opening in communication with the environment.
15.An acoustic device according to any preceding claim further including a layer of sound absorbing material located within the cavity of the body.
16. An acoustic absorber and diffuser device according to any preceding claim further including a cover member for selectively covering or closing the opening or the further opening, optionally or preferably the cover member includes an external surface which includes a convex portion.
17.An acoustic device according to any preceding claim wherein the one or more diffuser pads are connected to the body of the absorber part.
18. An acoustic device according to any preceding claim wherein the one or more diffuser parts are provided on the active face and/or extend along the active face.
19. An acoustic device according to any preceding claim wherein the convex surface of the one or more diffuser parts is curved.
20.An acoustic device according to any preceding claim wherein the right section of the one or more diffuser parts extends in the direction of the active face away from the body, and/or wherein the right section of the one or more diffuser parts is symmetrical.
21 An acoustic device according to any preceding claim wherein the one or more diffuser parts include a first end face and a second end face, and the diffuser part extends from the first end face to the second end face along a length axis, and, optionally, in the first configuration, the device may be selectively placed so that the length axis extends generally horizontally or generally vertically.
22. An acoustic device according to any preceding claim wherein the diffuser part is positioned at and/or extends along a peripheral portion of the active face.
23. An acoustic device according to any preceding claim wherein each of the one or more diffuser parts extends in the direction of the active face away from the body along a height axis, and, optionally, the height axis is horizontal in the first configuration and/or vertical in the second configuration.
24.An acoustic device according to any preceding claim wherein the one or more diffuser parts includes first and second diffuser parts.
25.An acoustic device according to claim 24 wherein the first and second diffuser parts are positioned on respective first and second opposing regions of the active face.
26. An acoustic device according to claim 24 or 25 wherein the one or more diffuser parts includes third and fourth diffuser parts positioned on respective third and fourth opposing regions of the active face.
27.An acoustic device according to claim 26 wherein the first and second diffuser parts are the same length and/or the third and fourth diffuser parts are the same length.
28.An acoustic device according to claim 26 or 27 wherein the first and second diffuser parts are longer in length than the third and fourth diffuser parts
29.An acoustic device according to claim 26, 27 or 28 wherein the first and second diffuser parts are identical and/or the third and fourth diffuser parts are identical
30. An acoustic device according to any one of claims 26 to 29 wherein the first and second diffuser parts extend parallel to each other and/or the third and fourth diffuser parts extend parallel to each other
31. An acoustic device according to any one of claims 26 to 30 wherein the first and second diffuser parts surround a portion of the opening of the body of the absorber part and/or the third and fourth diffuser parts surround a portion of the opening of the body of the absorber part.
32.An acoustic device according to any one of claims 26 to 31 wherein the opening of the body of the absorber part is positioned substantially centrally, or centrally with respect to the first and second diffuser parts and/or the third and fourth diffuser parts.
33.An acoustic device according to any one of claims 26 to 32 wherein the length axes of the first and second diffuser parts are arranged transversely, optionally or preferably perpendicularly, to the length axes of the third and fourth diffuser parts.
34.An acoustic device according to any one of claims 26 to 33 wherein the height dimension of each the right sections of the first and second diffuser parts is generally the same, or is the same, as the height dimension of each of the right sections of the third and fourth diffuser parts.
35.An acoustic device according to claim 34 wherein the opening at the second end of the hollow neck portion of the absorber part is at a height lying in a plane in which the diffuser parts terminate in a height direction.
36. An acoustic device according to any preceding claim wherein the volume of the cavity of the body of the absorber part is preferably between 0.03 m3 and 1 m3, more preferably between 0.03 m3 and 0.8 m3, and most preferably between 0.05 m3 and 0.5 m3.
37. An acoustic system including a plurality of acoustic devices according to any preceding claim, wherein the system is operable in: a) a first mode of operation in which the acoustic and diffuser devices form an array that extends vertically wherein the active face of each device is directed in a first direction which is horizontal; and b) a second mode of operation in which the acoustic and diffuser devices form an array that extends horizontally wherein the active face of each device is directed in a second direction which is vertical.
38. An acoustic system according to claim 37 wherein for the first mode of operation, a portion of the devices are stacked on top of one another and/or a portion of the devices are positioned side-by-side with one another.
39. An acoustic system according to claim 37 or 38 wherein for the second mode of operation, a portion of the devices are positioned side-by-side with one another to extend along a first axial direction and a portion of the devices are positioned side-by-side with one another to extend along a second axial direction which is perpendicular to the first axial direction.
40. An acoustic system according to claim 37, 38 or 39 wherein the devices may be selectively configured to place the system from its first or second mode of operation into the other of first or second mode of operation.
41 An acoustic system according to any one of claims 37 to 40 wherein the 30 devices may be selectively configured in the first and second modes of operation so that corresponding diffusers parts of adjacent devices are parallel to one another.
42. An acoustic system according to any one of claims 37 to 41 wherein the devices may be selectively configured in the first and second modes of operation so that corresponding diffusers parts of adjacent devices are transverse, optionally or preferably perpendicular, one another.