TECHNICAL FIELD

The disclosure relates to a vibratory system comprising a vibratory panel and one or more actuators, each actuator being configured to receive a signal and to drive the vibratory panel based on the signal.

BACKGROUND

Flat panel speakers, commonly known as Distributed Mode Loudspeakers (DML) are a type of loudspeakers where the sound is generated by vibrating a panel. The panel can comprise of any rigid material, for example, the first application used a shop window as the panel. Usually, one or several mechanical vibrators are used to induce vibrations in the panel, sound being generated by converting the electric signals provided to the vibrators to mechanical vibrations of the panel. The sound is generated mainly by bending waves, as opposed to conventional electrodynamic loudspeakers where the bending waves are usually avoided and piston-mode is preferred. The bending waves interact with the surrounding air and cause longitudinal waves that can be heard as sound.

The technology was available already a century ago but did not gain popularity until the 1990s. The thin structure of the DML technology is a clear advantage, however, the technology also has severe drawbacks.

One common drawback with DML speakers is the anti-resonance mode, a phenomenon caused by side reflections from the panel. The bending wave reflects from the sidewall of the panel and interferes with other waves, causing constructive as well as destructive interference. Based on the distance from the mechanical vibrator to the sidewalls of the panel, wave dips and peaks will appear in different frequency regions. Typically, issues with the frequency response are addressed via digital signal processing, i.e. by filtering or attenuating constructive waves, but the dips can usually not be improved since a fully destructive wave cannot be improved by adding power. This issue is instead addressed by optimizing the placement of the mechanical vibrator so that the effect is less severe and by using multiple mechanical vibrators to compensate for the dips. This improves the performance, however, it does not eliminate the problem completely. Furthermore, it is not always possible to arrange the mechanical vibrators optimally or to use multiple vibrators.

A further drawback is the problem of vibrations being transmitted outside the panel. Such vibration transmittal is usually unwanted and can cause many issues such as distortion, issues with sound source directivity, or unwanted vibrations that can be felt by the user These transmitted vibrations can be isolated using vibration damping material, but floating the panel, using such vibration damping material, is not always possible.

Hence, there is a need for an improved vibratory panel as well as an improved vibratory system for an electronic apparatus.

SUMMARY

It is an object to provide an improved vibratory panel. The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the figures.

According to a first aspect, there is provided a vibratory system comprising a vibratory panel and one or more actuators, each actuator being configured to receive a signal and to drive the vibratory panel based on the signal, the vibratory panel having a front surface and a back surface, the vibratory panel having an acoustic black hole feature wherein the front surface has a first height profile that is non-uniform and the back surface has a second height profile different from the first height profile. The second height profile may be uniform or non-uniform.

Such a solution allows components required for other purposes to be used to generate tactile vibrations and/or audio waves, dispensing with the need for separate vibration components. The actuators provide a simple and cost-effective way of generating vibrations. Furthermore, the placement of the actuator(s) does not have to be optimized due to the acoustically beneficial configuration of the vibratory panel.

In a possible implementation form of the first aspect, the vibratory system is a distributed mode loudspeaker and the signal is an audio signal. Such a solution facilitates a loudspeaker that has all the benefits of a distributed mode loudspeaker, such as the thinness of the panel, but which does not have the acoustic issues traditionally associated with distributed mode loudspeakers. The vibratory panel allows a thin loudspeaker that behaves more like a traditional electrodynamic loudspeaker when it comes to acoustic performance.

In a further possible implementation form of the first aspect, the vibratory panel comprises an inner region and an edge region circumscribing the inner region, the inner region and the edge region being located between the front surface and the back surface, at least one of the inner region and the edge region comprising the acoustic black hole feature, allowing a separate an edge region configured to control any bending wave side reflections from the panel.

In a further possible implementation form of the first aspect, the first height profile is configured to reduce reflections of vibrational waves in the edge region, preventing or at least reducing bending waves from interfering with other waves causing constructive and destructive interference.

In a further possible implementation form of the first aspect, the shape of the vibratory panel is asymmetrical with respect to reflection about a center plane. This facilitates simplified manufacture and assembly of the panel.

In a further possible implementation form of the first aspect, the first height is non-uniform relative to the center plane, a height z of a point of the front surface being a function of the location x,y of said point in said center plane, z=f(x,y), allowing the vibratory panel and first height profile to have a shape adapted to specific and individual prerequisites and limitations.

In a further possible implementation form of the first aspect, the vibratory panel comprises a video screen, allowing the panel to be used in electronic apparatuses such as smartphones, tablets, and TVs.

In a further possible implementation form of the first aspect, the first height profile comprises at least one recess or protrusion in the inner region. This allows the bending waves to be trapped and dampened inside the first height profile.

In a further possible implementation form of the first aspect, the first height profile comprises a gradual reduction of the thickness of the vibratory panel in the edge region. This allows bending wave side reflections to be reduced or completely removed. In a further possible implementation form of the first aspect, the gradual reduction of thickness extends at least partially along at least one edge of the edge region, allowing the vibratory panel and first height profile to be adapted to specific and individual preconditions such as the form factor of the electronic apparatus comprising the vibratory panel.

In a further possible implementation form of the first aspect, the thickness is measured in a direction perpendicular to the center plane, allowing waves to be dampened differently in different locations of the vibratory panel by means of a change in thickness.

In a further possible implementation form of the first aspect, the gradual reduction of thickness is linear in a direction from the inner region towards an outermost edge of the edge region, allowing the vibratory panel and first height profile to have a shape adapted to specific and individual preconditions such as the form factor of the electronic apparatus comprising the vibratory panel.

In a further possible implementation form of the first aspect, the gradual reduction of thickness comprises a curved area, allowing the vibratory panel and first height profile to have a shape adapted to specific and individual preconditions such as the form factor of the electronic apparatus comprising the vibratory panel.

In a further possible implementation form of the first aspect, the edge region comprises a spiral structure with a spiral axis located on a front side of the vibratory panel, the spiral structure comprising the first height profile, allowing the vibratory panel and first height profile to have a shape adapted to specific and individual preconditions such as the form factor of the electronic apparatus comprising the vibratory panel.

In a further possible implementation form of the first aspect, the first height profile comprises a vibration-damping layer, facilitating a reduction of the reflections of the bending waves from the sides of the panel.

These and other aspects will be apparent from the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments, and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Figs, la to le show perspective views of vibratory systems in accordance with examples of the embodiments of the disclosure;

Figs. 2 and 2b show cross-sectional views of vibratory panels in accordance with examples of the embodiments of the disclosure;

Fig. 3 shows a further cross-sectional view of a vibratory panel in accordance with an example of the embodiments of the disclosure;

Fig. 4a shows a perspective view of a vibratory panel in accordance with an example of the embodiments of the disclosure;

Fig. 4b shows a cross-sectional view of the vibratory panel of Fig. 4a;

Fig. 5 shows a perspective view of a vibratory panel in accordance with an example of the embodiments of the disclosure;

Fig. 6 shows a further perspective view of a vibratory panel in accordance with an example of the embodiments of the disclosure;

Fig. 7 shows a perspective view of a vibratory system in accordance with an example of the embodiments of the disclosure.

DETAILED DESCRIPTION

The present invention relates to a vibratory system comprising a vibratory panel 1 and one or more actuators 7, each actuator 7 being configured to receive a signal and to drive the vibratory panel 1 based on the signal, the vibratory panel 1 having a front surface 4 and a back surface 5, the vibratory panel 1 having an acoustic black hole feature wherein the front surface 4 has a first height profile 6a that is non-uniform and the back surface 5 has a second height profile 6b that different from the first height profile 6a. The second height profile 6b may be uniform or non-uniform. The vibratory system may be a distributed mode loudspeaker and the signal may be an audio signal.

The first height profile 6a is adapted to reduce reflections of vibrational waves at the edge region 3. The second height profile 6b may also be adapted to reduce reflections of vibrational waves at the edge region 3. The vibratory panel 1 forms a diaphragm that may be used to generate sound via airwaves or tactile vibrational signals via direct user contact.

The Figs, illustrate a vibratory panel 1 having a front surface 4 and a back surface 5. “Front” and “back” refer to two parallel outer surfaces separated by the body of the vibratory panel. When applying a body-fixed coordinate system that is fixed to the vibratory panel 1 itself, the front surface 4 may be considered a surface facing the user of an electronic apparatus comprising the vibratory system, or facing any listener, while the back surface 5 faces the interior of the electronic apparatus. However, the front surface 4 and the back surface 5 may be interchangeable. The vibratory panel 1 may be a completely flat panel, the center plane Pl of the panel 1 being completely planar. However, the vibratory panel 1 may also be curved, such that the center plane Pl of the panel 1 is curved.

An inner region 2 and an edge region 3 are located between the front surface 4 and the back surface 5. The edge region 3 may circumscribe the inner region 2, and it may comprise the same material as the inner region 2 or a different material. While the front surface 4 and the back surface 5 are two-dimensional, the inner region 2 and edge region 3 relate to the three- dimensional volumes of the panel body extending between the front surface 4 and the back surface 5.

The front surface 4 has a first height profile 6a adapted to reduce reflections of vibrational waves at the edge region 3. The first height profile 6a is non-uniform. The back surface 5 has a second height profile 6b that is different from the first height profile 6a. The second height profile may be uniform or non-uniform.

The first non-uniform height profile 6a has an acoustic black hole feature (ABH), ABH being a research area within vibroacoustics. Correspondingly, the second height profile 6b, when being non-uniform, may also have an acoustic black hole feature (ABH). If the second height profile 6b is uniform, the back surface 5 may comprise a flat surface extending in a flat two- dimensional plane or in a curved three-dimensional plane, forming a curved yet untextured surface.

At least one of the inner region 2 and the edge region 3 may comprise an acoustic black hole feature, i.e. the inner region 2 only, the edge region 3 only, or both the inner region 2 and the edge region 3. The first non-uniform height profile 6a and, optionally, the second non-uniform height profile 6b may be configured to reduce reflections of vibrational waves in the edge region 3.

The vibratory panel 1 may have a first thickness, measured as a distance between the front surface 4 and the back surface 5. The first non-uniform height profile 6a and the second non- uniform height profile 6b may facilitate a second thickness of the vibratory panel, the second thickness being smaller than the first thickness. The thickness is measured in a direction perpendicular to the center plane Pl of the vibratory panel 1.

More specifically, the height profile of the front surface 4, or correspondingly back surface 5, may be non-uniform relative the center plane Pl, a height z of a point of the front surface 4 being a function of the location x,y of the point in the center plane Pl, z=f(x,y). The height z at least partially varies across the front surface 4 in order to form a difference in thickness. In other words, the height is a result of a suitable mathematical function f(x,y) that produces the z coordinate, the height, of the surface for any point x, y of a xy-plane of a three-dimensional x,y,z coordinate system. For each position x,y, the surface will have a certain z coordinate or height, the z-coordinate being the distance from the center plane Pl of the vibratory panel 1, measured perpendicularly to the xy-plane.

The vibratory panel may, in other words, have a shape that is asymmetrical with respect to reflection about the center plane Pl of the vibratory panel, as illustrated in Figs. 2a and 2b. The center plane Pl extends between and in parallel with the front surface 4 and the back surface 5, equidistantly from the front surface 4 and the back surface 5. The back surface 5 extends completely in a plane P2 extending parallel with the center plane Pl . The front surface 4 extends partially in a plane P3 extending parallel with the center plane Pl and plane P2. The part of the front surface 4 which has a first height profile 6a does not extend in plane P3 and it does not extend in parallel with the center plane Pl, plane P2, and plane P3.

The vibratory panel 1 may comprise a video screen. The vibratory panel 1 may comprise any kind of display.

The first non-uniform height profile 6a and, optionally, the second non-uniform height profile 6b may be arranged in the inner region 2, as illustrated in Figs. 4a to 6. The first non-uniform height profile 6a may extend from the front surface 4 in a first direction DI such that the first non-uniform height profile 6a forms a recess in the inner region 2. In other words, the acoustic black hole feature may be a recess in the vibratory panel 1. The first non-uniform height profile 6a may also extend from the front surface 4 in a second direction D2 such that the first non- uniform height profile 6a forms a protrusion in the inner region 2. In other words, the acoustic black hole feature may be a protrusion in the vibratory panel 1. The second direction D2 extends from the front surface 4 away from the back surface 5, i.e., in a direction opposite to the first direction DI. Correspondingly, the second non-uniform height profile 6b may extend from the back surface 5 in the second direction D2 such that the second non-uniform height profile 6b forms a recess in the inner region 2. The second non-uniform height profile 6b may also extend from the back surface 5 in the first direction DI such that the second non-uniform height profile 6b forms a protrusion in the inner region 2.

The recess may have a symmetrical shape, as shown in Fig. 4a, or an asymmetrical shape, as shown in Figs. 5a and 5b. The symmetry/asymmetry may be with respect to reflection about a symmetry plane P4 extending perpendicular to the center plane Pl and to planes P2, P3. The first direction DI and the second direction DI may extend parallel with the plane P4.

The recess may comprise at least one curved surface, as shown in Figs. 4a to 6. The recess may comprise at least one planar surface, as shown in Figs. 5 and 6. The recess may comprise one or several curved surfaces and/or one or several planar surfaces. The recess may comprise a number of surfaces having different configurations. Furthermore, the recess may extend partially through the vibratory panel 1, forming a groove or notch. The recess may also extend completely through the vibratory panel 1, forming a throughgoing hole or channel.

The first non-uniform height profile 6a and the second non-uniform height profile 6b may be arranged in the edge region 3, as illustrated in Figs, la to 3 and in Fig. 7. The first non-uniform height profile 6a and the second non-uniform height profile 6b extends from the front surface 4 in the first direction DI such that the 6a, 6b forms a gradual reduction of thickness of the vibratory panel 1 in the edge region 3, i.e., the edge region 3 is tapered when seen in a direction from the inner region 2 to the outermost edge of the edge region 3. In other words, the acoustic black hole feature may be a gradual reduction of the thickness of the vibratory panel 1. The gradual reduction of the thickness may be linear in a direction from the inner region 2 towards an outermost edge of the edge region 3 (not shown), or the gradual reduction may comprise a curved surface as illustrated in Figs. 2a and 2b. The gradual reduction of thickness may extend at least partially along at least one edge of the edge region 3.

The edge region 3 may comprise a spiral structure 9 with a spiral axis located on the front side of the vibratory panel 1, the spiral structure 9 comprising the first non-uniform height profile 6a as illustrated in Fig. 3. The spiral structure 9 comprises a section of the edge region 3 that is bent into a spiral shape. The spiral structure 9 makes at least a part of the edge region 3 extend from the front surface 4 in the first direction DI or in a second direction D2. The second direction D2 extends from the front surface 4 away from the back surface 5, i.e., in a direction opposite to the first direction DI, such that the spiraled non-uniform height profile 6a, i.e. the spiral structure 9, constitutes a thickening of the vibratory panel 1 in the edge region 3.

The first non-uniform height profile 6a and, optionally, the second non-uniform height profile 6b may have any suitable shapes adhering to the power law. The power law states that a relative change in one quantity results in a proportional relative change in the other quantity, independent of the initial size of those quantities, i.e. one quantity varies as a power of another. This applies to the first non-uniform height profile 6a and the second non-uniform height profile 6b in that the shape of profile 6a, 6b changes, along the length of the profile 6a, 6b, in direct proportion to the change in length.

The first non-uniform height profile 6a and, optionally, the second non-uniform height profile 6b may comprise a vibration-damping layer 8, as illustrated in Figs. 2b and 4b. The vibration damping layer 8 may be a viscoelastic layer. The recess may be semispherical, as illustrated in Figs. 4a and 4b and the vibration-damping layer 8 may be arranged at the bottom area of the semi-sphere. However, the vibration damping layer 8 may be arranged in any suitable area of the first non-uniform height profile 6a or the second non-uniform height profile 6b, covering the profile 6a, 6b completely or only partially. Furthermore, the first non-uniform height profile 6a and the second non-uniform height profile 6b may comprise a throughgoing opening or a plateau section providing vibration damping.

As illustrated in Figs, la to le and Fig. 7, the vibratory panel 1 may be rectangular such that the inner region 2 comprises four edges or sides, and at least one first non-uniform height profile 6a may be arranged adjacent at least one of the four edges or sides. Furthermore, at least one second non-uniform height profile 6b may be arranged adjacent at least one of the four edges or sides. The first non-uniform height profile 6a and the second non-uniform height profile 6b may extend at least partially along the edge. Fig. la shows a vibratory panel 1 having a first non-uniform height profile 6a along one long side or edge. Fig. lb shows a vibratory panel 1 having first non-uniform height profiles 6a along two opposite short sides. Fig. 1c shows a vibratory panel 1 having first non-uniform height profiles 6a along two opposite long sides. Fig. Id shows a vibratory panel 1 having a first non-uniform height profile 6a along a part of one long side. Fig. le shows a vibratory panel 1 having first non-uniform height profiles 6a along parts of all sides, the first non-uniform height profiles 6a of two adjacent sides meeting to form an L-shape extending across the corner of the vibratory panel 1. Fig. 7 shows a vibratory panel 1 having tapering first non-uniform height profiles 6a along all sides, as well as recessed, first non-uniform height profiles 6a dispersed across the inner region 2.

The vibratory system is suitable for use in an electronic apparatus such as a smartphone, a tablet, or a tv. The vibratory panel 1 can be connected to a housing.

The actuator(s) 7 is/are arranged adjacent the front surface 4 and/or the back surface 5. The actuator may be based on a moving-mass electrodynamic or piezoelectric operating principle, however, any suitable type of actuator is possible. One moving-mass electrodynamic actuator is the voice-coil actuator which comprises a coil as well as a mass in the form of a magnet. The actuator(s) 7 may be placed adjacent the first height profile 6a and the second height profile 6b, in the edge region 3, and/or within the inner region 2 of the vibratory panel 1. Furthermore, the actuator(s) 7 may be arranged outside the vibratory panel 1 or within the vibratory panel 1, between the front surface 4 and the back surface 5. The actuator(s) 7 may be connected to an audio amplifier powered by a power supply unit that can also be a battery. The audio signal may be fed to the audio amplifier directly or through a digital signal processing unit from an audio playback device.

The vibratory system may form a distributed mode loudspeaker, the vibratory panel 1 forming a singing display. By using several actuators 7, the efficiency may be improved such that a distributed mode loudspeaker with good enough acoustic performance can be provided. By increasing the number of actuators, the sound pressure level will be increased, and any antisymmetric mode issues can be improved or resolved. The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

The reference signs used in the claims shall not be construed as limiting the scope. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this disclosure. As used in the description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.