SE2251346A1

SE2251346A1 - Parametric array loudspeaker for emitting acoustic energy to create a directional beam

Info

Publication number: SE2251346A1
Application number: SE2251346A
Authority: SE
Inventors: Josef Hansson
Original assignee: Myvox Ab
Priority date: 2022-11-16
Filing date: 2022-11-16
Publication date: 2024-04-09
Also published as: SE546011C2; WO2024104819A1

Abstract

An acoustic system (100) for controlling the emission of audible sound comprises a parametric acoustic transducer array (110, 210) with a plurality of transducer elements (ei) arranged in rows (111), wherein each row (111) extends along a row direction axis (D). For each row (111), all the transducer elements of the row 111 are controllable in response to a first control signal (C1, C11, C21, C31, C41) from a controller (120) so as to emit the acoustic energy at a wavelength and phase determined by the first control signal (C1, C11, C21, C31, C41). An actuator (130) is configured to rotate the parametric acoustic transducer array (110, 210) around a rotation axis (R) that is linearly independent of the row direction axis (D) in response to a second control signal (C2). Thereby, a parametric acoustic transducer array having N transducer elements is enabled to generate a directional acoustic beam at an arbitrary angle using less than N input signals. There is also provided a corresponding computer-implemented method for controlling the emission of audible sound from an acoustic system (100), a computer program (127) comprising software for executing the method, and a nonvolatile data carrier (125) containing the computer program (127).

Description

TECHNICAL FIELD The present invention relates generally to an acoustic system and method for emitting acoustic energy to create a directional beam of audible sound. The invention also relates to a computer program and a non-volatile data carrier storing such a computer program.

BACKGROUND A parametric array, in the field of acoustics, is a nonlinear transduction mechanism that generates narrow, nearly side lobe-free beams of low frequency sound, through the mixing and interaction of high frequency sound waves, effectively overcoming the diffraction limit associated with linear acoustics. The main beam of low frequency sound is created as a result of nonlinear mixing of two high frequency sound beams at their difference frequency. Parametric arrays can be formed in water, air, and earth materials/rock. Using the principle of parametric arrays, an audible sound signal modulated onto an ultrasonic carrier wave will, during propagation in air, spontaneously demodulate, creating a virtual end-fire array of audible sources. ln effect, this creates a highly directional beam of sound. By modulating audio onto a carrier wave, for example an ultrasonics carrier wave, an end-fire virtual array of audible sources is created due to demodulation of the combined signal in the air due to nonlinear effects. lf the primary source consists of an array of transducers, it is possible to steer the beam by adjusting the phase delay of individual transducers. The audio envelope signal is typically amplitude modulated onto the carrier signal. This technology is for example described in the article “A review of parametric acoustic array in air”, in Applied Acoustics, 73 (2012), by Gan, W-S., Yang, J., Kamakura, T.

The applications for parametric arrays, creating a highly directional beam of sound, are numerous and include among others delivery of directional audible sound that is only audible to one person located in the correct position for receiving the directional beam 1 of sound, but cannot be heard in the surroundings. A few non-limiting examples of when this is of interest are hands-free applications for vehicles, listening to music or talking over the phone in an open office environment or in public transport, information to museum visitors, presentation at fairs, etc.

There exist many solutions for how to apply directional, parametric, arrays to achieve audible sound in a specific location for applications such as the once mentioned herein. However, there are problems involved with the existing solutions. lf the primary source of acoustic energy consists of an array of acoustic transducer elements, it is possible to steer the resulting beam by adjusting the phase delay of each individual transducer. ln order to steer the beam in arbitrary directions in this manner, using beamforming, a 2D array of individually driven transducers is necessary. For large acoustic transducer arrays this requires a large number of generated drive signals, each of which needs to be generated, amplified, and connected to the corresponding transducer element. This is a severe limitation on large compact arrays. Specifically, a large number of drive signals add to the digital or software complexity, which make them computationally expensive to generate. Furthermore, a large number of drive signals make the hardware needed complex to produce and handle, because each drive signal requires separate cables and routings connecting the drive electronics to the circuit and respective transducer element that it is driving. This also leads to the resulting acoustic systems being bulky, which is a hindrance for packaging as well as miniaturization of the systems as a whole. lt further reduces the available design options for the transducer array and the acoustic system.

For a large compact array, comprising for example hundreds or even thousands of transducer elements, the problems mentioned above are of course very troublesome. As an example, arrays of micro-electro-mechanical system (MEMS) transducers often comprise a large number of transducer elements, and therefore typically are faced with the problems of both computational expensiveness/software complexity and hardware complexity, and the problem associated therewith.

There is thus a need to provide an improved solution that reduces the software and the hardware complexity for arrays of acoustic transducer elements, and problems associated therewith.

SUMMARY A two-dimensional beamforming array requires as many input signals as the number of transducers, which is a severe limitation for arrays with a large number of transducers. The object of the present invention is to offer a solution that mitigates the above problem and renders it possible to create an acoustic beam at an arbitrary angle using a lower number of driving signals. The inventor has realized that the problem can be solved by an array of acoustic transducer elements, preferably a 2-dimensional array with at least two rows each comprising at least two transducer elements, wherein the acoustic transducer elements are connected row-wise with each other and wherein all elements in a row are driven simultaneously using a single driving signal. Each of the rows extends along a row direction axis, and the row direction axes of all rows are parallel, or substantially parallel, to each other. Thanks to the reduced number of input signals needed to drive the transducer elements of the transducer array, this transducer array design provides a lower software complexity and hardware complexity compared to a transducer array in which each transducer element is driven individually by a separate driving signal. Thereby, it is less computationally expensive, easier to manufacture, less bulky once assembled, easier to package, easier to miniaturize, and there is further greater freedom in the design of the transducer array according to embodiments herein, as well as any system that it is to be a part of, compared to a transducer array in which each transducer element is driven individually by a separate driving signal. Using the row-wise beamforming, the invention enables generating an acoustic beam that can be arbitrarily directed in one dimension, using digital beamforming. To enable arbitrary direction of the beam also in a second dimension, the transducer array is arranged such that it can be rotated around a rotation axis that is linearly independent of the row direction axis. The result is a parametric acoustic transducer array, according to embodiments herein, having N transducer elements that can generate a directional acoustic beam at an arbitrary angle using less than N input signals.

Aspects and embodiments of the invention, and advantages obtained, are described in further detail herein.

According to one aspect of the invention, the object is achieved by an acoustic system comprising a parametric acoustic transducer array configured to emit acoustic energy 3 of periodically varying intensity in the form of an acoustic signal. The parametric acoustic transducer array comprises a plurality of transducer elements arranged in at least one row, wherein each of the at least one row extends along a row direction axis. For each row, all the transducer elements of the row are controllable in response to a first control signal so as to emit the acoustic energy at a wavelength and phase determined by the first control signal. The acoustic system further comprises an actuator being operatively connected to the parametric acoustic transducer array and being configured to rotate the parametric acoustic transducer array around a rotation axis that is linearly independent to the row direction axis, in response to a second control signal. The acoustic system further comprises a controller being communicably connected to each of the at least one row of the parametric acoustic transducer array and further being communicably connected to the actuator. The controller is configured to generate, for each of the at least one row, a first control signal such that the emitted acoustic energy of the parametric acoustic transducer array forms a directional beam of acoustic energy, and to generate a second control signal such that the actuator rotates the parametric acoustic transducer array, and thus the directional beam of acoustic energy, around the rotation axis.

Suitably, a parametric acoustic transducer array is hence achieved that has N transducer elements and can generate a directional acoustic beam at an arbitrary angle using less than N input signals. Since a single first control signal, or driving signal, is used to control, or drive, all transducer elements in a row simultaneously, the solution of the present invention provides a transducer array with lower software complexity and a lower hardware complexity compared to the prior art solutions, able to generate an acoustic beam that can be arbitrarily directed in a first dimension using beamforming. lf there are two or more rows, a respective first control signal is used for driving each of the rows. Compared to using one driving signal for each transducer element, the complexity of both software and hardware is thereby evidently greatly reduced. Also, the larger the array, the larger the gain in reduced complexity and advantages connected thereto will be. Furthermore, by rotating the parametric acoustic transducer array around the rotation axis, which is linearly independent of the row direction axis, a second dimension in which the directional beam be directed is added. ln other words, the directional beam can be directed (positioned, steered) in a first dimension by beamforming the acoustic energy emitted by the transducer elements, 4 and it can further be directed (positioned, steered) in a second dimension by mechanically rotating the parametric acoustic transducer array around the rotation axis R. Because the rotation axis R is linearly independent of the row direction axis, the directional beam can thereby be directed at an arbitrary angle in two dimensions. Advantageousiy, this is achieved using a single driving signal for each row of the transducer array.

The parametric acoustic transducer array preferably comprises at least four transducer elements. The plurality of transducer elements is preferably arranged in at least two rows, each row extending along the row direction axis or an axis parallel to the row direction axis. Thereby, the parametric acoustic transducer array is two-dimensional. Suitably, this enables improved directionality of the emitted directional beam of acoustic energy compared to using a parametric acoustic transducer array with only one row of transducer elements. Using one row of transducer elements, the acoustic energy emitted will be directional in one axis but spread along the other axis. ln other words, the acoustic energy would spread out like a disk around the row, instead of being focused in a single direction as is the case if the parametric transducer array comprises two or more rows. ln the embodiment with one row, the actuator changes the orientation of the disk of emitted acoustic energy by its rotation. ln embodiments with two or more rows, the actuator changes the direction of the directional beam of acoustic energy by its rotation.

The acoustic system may comprise an input device communicatively connected to the controller. The controller may in these embodiments be configured to receive from the input device a first input signal indicative of a three-dimensional position towards which the directional beam of acoustic energy is to be directed; and to generate the first control signal for each of the at least one row based on the first input signal, such that the emitted acoustic energy of the parametric acoustic transducer array forms a directional beam of acoustic energy towards the three-dimensional position Suitably, the position towards which the directional beam of acoustic energy is to be directed may thereby be controlled using an input device, either a user-controllable input device such as a user interface, or an input device receiving input from another unit. The position may thereby be adjusted when needed, discretely or continuously, to further improve the directionality of the parametric acoustic transducer array.

The parametric acoustic transducer array may be planar. Suitably, if the parametric acoustic transducer array is planar, the relation between each row direction axis, D, and the rotation axis, R, may be described as RH >< D i 0, where RH is the projection of R in the transducer array plane. ln other words, each of the at least one row has at least one vector component that does not coincide with the projection of the rotation axis onto the plane in which the transducer array extends.

The acoustic signal may be a modulated acoustic signal comprising a carrier wave and a modulation signal modulated onto the carrier wave. ln embodiments where the acoustic system comprise an input device, the controller may then be configured to: receive from the input device a second input signal comprising the modulation signal to be modulated onto the carrier wave of the acoustic signal; and in response to receiving the second input signal, generating a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals. The modulation signal is in embodiments an audible sound signal, wherein the directional beam is a directional beam of audible sound.

Suitably, a directional speaker is thereby achieved having the lower software complexity and lower hardware complexity as well as therewith associated advantages described herein.

The controller may be configured to generate the control signals such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. ln a non-limiting example, the controller is configured to generate the control signal such that the acoustic energy is emitted at a frequency of 160 kHz.

According to one or more embodiment of this aspect of the invention, the parametric acoustic transducer array is a micromachined ultrasonic transducer, MUT, comprising micromachined ultrasonic transducer, MUT, elements configured to emit acoustic energy in the form of ultrasonic energy, wherein the acoustic signal is a modulated ultrasonic signal. Thereby, the acoustic system may advantageously be miniaturized.

This enables application in for example handheld devices, such as mobile phones, and other applications which require small sized components.

According to one or more embodiment of this aspect of the invention, the parametric acoustic transducer array is a phased array. Suitably, a direct and simple generation and control of an acoustic-potential field is thereby enabled.

According to another aspect of the invention, the object is achieved by a computer- implemented method for controlling the emission of audible sound from an acoustic system. The system comprises a parametric acoustic transducer array configured to emit acoustic energy of periodically varying intensity in the form of an acoustic signal, wherein the parametric acoustic transducer array comprises a plurality of transducer elements arranged in at least one row, wherein each row extends along a row direction axis, and wherein, for each row, all the transducer elements of the row are controllable in response to a first control signal so as to emit the acoustic energy at a wavelength and phase determined by the first control signal. The system further comprise an actuator being operatively connected to the parametric acoustic transducer array and being configured to rotate the parametric acoustic transducer array around a rotation axis that is linearly independent of the row direction axis in response to a second control signal. The system also comprises a controller being communicably connected to each of the at least one row of the parametric acoustic transducer array and further being communicably connected to the actuator.

The method comprises generating, by the controller, for each of the at least one row a first control signal, such that the emitted acoustic energy of the parametric acoustic transducer array forms a first directional beam of acoustic energy; and generating, by the controller, the second control signal such that the actuator rotates the parametric acoustic transducer array, and thus the directional beam of acoustic energy, around the rotation axis.

Suitably, the advantageous generation of a directional acoustic beam at an arbitrary angle using a parametric acoustic transducer array having N transducer elements and using less than N input signals is thereby achieved.

The method may further comprise receiving in the controller, from an input device communicatively connected to the controller, a first input signal indicative of a three- dimensional position towards which the directional beam of acoustic energy is to be 7 directed; and generating, by the controller, the first control signal for each of the at least one row based on the first input signal such that the emitted acoustic energy of the parametric acoustic transducer array forms a directional beam of acoustic energy towards the three-dimensional position.

Generating each of the first and second control signals, by the controller, may comprise generating each of the first and second control signals such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. ln some embodiments of this aspect of the invention the parametric acoustic transducer array is a micromachined ultrasonic transducer, MUT, wherein emitting acoustic energy by the parametric acoustic transducer array comprises emitting ultrasonic energy.

The acoustic signal may be a modulated acoustic signal comprising a carrier wave and a modulation signal modulated onto the carrier wave. The method may in these embodiments further comprise: receiving in the controller, from an input device communicatively connected to the controller, a second input signal comprising the modulation signal to be modulated onto the carrier wave of the acoustic signal; and in response to receiving the second input signal, generating, by the controller, a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals. The modulation signal may be an audible sound signal, wherein the directional beam is a directional beam of audible sound. lt is presumed that the transducer elements are controllable in response to the respective first control signal so as to emit the acoustic energy at a wavelength and a phase determined by the control signal. The respective control signals are generated such that the emitted acoustic energy of the parametric acoustic transducer array forms an acoustic-potential field of acoustic waves.

According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to a processor, or processing unit. The computer program includes software for executing the above method, according to any of the embodiments presented herein, when the program is run on the processing unit.

According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.

Any advantages described herein for an embodiment of one aspects of the invention are equally applicable to the corresponding embodiments of the other aspects of the invenﬁon.

Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

Figure 1 schematically shows an acoustic system according to a first embodiment of the invention; Figure2 schematically shows an acoustic system according to a second embodiment of the invention; Figure 3a schematically shows an acoustic system according to one or more embodiment of the invention; Figure 3b embodiment of the invention; schematically shows an acoustic system according to one or more Figure 4a schematically shows an acoustic system according to one or more embodiment of the invention; Figure 4b embodiment of the invention; schematically shows an acoustic system according to one or more Figure 5a schematically shows an acoustic system according to one or more embodiment of the invention; Figure 5b embodiment of the invention; and schematically shows an acoustic system according to one or more Figure 6 illustrates, by means of a flow diagram, a method according to one or more embodiment of the invention.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Any reference number appearing in multiple drawings refers to the same object or feature throughout the drawings, unless otherwise indicated. DETAILED DESCRIPTION Introduction Audio signals are herein defined as signals having frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing.

A position is herein defined as a three-dimensional position in space (x, y, z), unless otherwise specified.

A distance is herein defined as a three-dimensional distance in space (x, y, z), unless otherwise specified.

The strength of the modulated signal herein typically refers to the amplitude of the modulated signal.

System architecture Firstly, a system 100 according to embodiments of the invention will be described in connection with Figs. 1 and 2, and further in connection with Figs. 3a to 5b. lt is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

Fig. 1 shows an acoustic system 100 according to the invention. The system 100 includes a parametric acoustic transducer array 110 configured to emit acoustic energy of periodically varying intensity in the form of an acoustic signal. The parametric acoustic transducer array 110 comprises a plurality of transducer elements ei arranged in at least one row 111. ln the non-limited example shown in Fig. 1, the plurality of transducer elements ei are arranged in one row 111.

Turning now to Fig. 2, there is illustrated an acoustic system 100 according to the invention. The parametric acoustic transducer array 210 is similar to the parametric acoustic transducer array 110 in all ways except for that in the parametric acoustic transducer array 210 the plurality of transducer elements ei of are arranged in more than one row 111. Preferably, the parametric acoustic transducer array 110, 210 comprises at least four transducer elements ei. lt is further preferable that the plurality of transducer elements ei are arranged in at least two rows 111. Thereby, the parametric acoustic transducer array is tvvo-dimensional which provides improved directionality of the emitted acoustic energy compared to having a single row 111, as described herein. ln the non-limiting example of Fig. 2, the plurality of transducer elements ei are arranged in four rows 111. Of course, the plurality of transducer elements ei can be arranged in both less and more rows 111, depending on what is suitable for the particular application. ln Fig. 2, the parametric acoustic transducer array 210 is shown in a top view, while the parametric acoustic transducer array 110 of Fig. 1 in shown in a perspective view.

For any of the embodiments of the system 100, each of the at least one row 111 extends along a row direction axis D. ln embodiments wherein the plurality of transducer elements ei are arranged in at least two rows 111, each row 111 extends along a respective row direction axis and all the row direction axes are parallel to each other. This is illustrated by the exemplary row direction axes D1, D2, D3 and D4 in Fig. 3A. That a row 111 extends along row direction axis (that is the row direction axis D or an axis parallel thereto, as exemplified by D1, D2, D3 and D4) means that the all the transducer element ei in the row 111 are arranged along the respective row direction axis of the row 111 with a maximum deviation of Å/4 from the row direction axis, where Å is the wavelength of the emitted acoustic energy. That the row direction axes of the at least two rows 111 of a parametric acoustic transducer array 210 are parallel to each other means that they are substantially parallel, or parallel within manufacturing tolerances, herein defined as within 10 degrees angular deviation. 11 For each row 111, all the transducer elements ei of the row 111 are controllable in response to a first control signal C1, C11, C21, C31, C41 so as to emit the acoustic energy at a wavelength and phase determined by the first control signal C1, C11, C21, C31, C41. ln other words, a single control signal, or drive signal, is used to simultaneously control or drive all transducer elements ei in a row 111. Suitably, this provides a low software complexity and low hardware complexity transducer array 110, 210 enabled to generate an acoustic beam that can be arbitrarily directed in a first dimension using row-wise digital beamforming. lf there are at least two rows 111, as illustrated for example in Fig. 2, a respective first control signal C11, C21, C31, C41 is used for driving each of the rows 111, respectively.

The parametric acoustic transducer array 110, 210 may be a phased array whereby a direct and simple generation and control of an acoustic-potential field is enabled.

The parametric acoustic transducer array 110, 210 may be planar. Suitably, if the parametric acoustic transducer array is planar, the relation between each row direction axis, D, and the rotation axis, R, may be described as RH >< D i 0, where RH is the projection of R in the transducer array plane. ln other words, each of the at least one row has at least one vector component that does not coincide with the projection of the rotation axis onto the plane in which the transducer array extends.

The acoustic system 100 according to any embodiment herein further comprises an actuator 130 that is operatively connected to the parametric acoustic transducer array 110, 210 and that is configured to rotate the parametric acoustic transducer array 110, 210 around a rotation axis R that is linearly independent to the row direction axis D, in response to a second control signal C2. Thereby, the acoustic system 100 enables arbitrary direction of the emitted beam B also in a second dimension.

The acoustic system 100 according to any embodiment herein also comprises a controller 120 that is communicably connected to each of the at least one row 111 of the parametric acoustic transducer array 110, 210 and further communicably connected to the actuator 130. The controller 120 is configured to generate, for each of the at least one row 111, a first control signal C1, C11, C21, C31, C41 such that the emitted acoustic energy of the parametric acoustic transducer array 110, 210 forms a directional beam B of acoustic energy. The controller 120 is further configured to 12 generate a second control signal C2 such that the actuator 130 rotates the parametric acoustic transducer array 110, 21 0, and thus the directional beam B of acoustic energy, around the rotation axis R. The result is thus an acoustic system 100 with a parametric acoustic transducer array 110, 210, according to embodiments herein, having N transducer elements e; that can generate a directional acoustic beam B at an arbitrary angle using less than N drive signals, the drive signals being referred to herein as control signals. The number of input signals for N transducer elements may be expressed as (NR + 1), where NR is the number of rows, and 1 is added for the input signal needed to drive an actuator rotating the transducer array. As a specific, non- limiting example, if the parametric acoustic transducer array 110, 210 is square, i.e. the N transducer elements e; are arranged in M rows 111 that each comprise M transducer elements ei, only sqrt(N) drive signals, or first control signals C1, C11, C21, C31, C41, are needed to drive the transducer elements ei in all the rows 111. To achieve arbitrary direction of the emitted beam B also in the second dimension, a single additional second control signal C2 is needed to control, or drive, the actuator 130. ln one or more embodiment, the acoustic system 100 further comprises an input device 140 communicatively connected to the controller 120. The controller 120 may in these embodiments be configured to receive from the input device 140 a first input signal S1 indicative of a three-dimensional position towards which the directional beam B of acoustic energy is to be directed. The controller 120 is then further configured to generate the first control signal C1, C11, C21, C31, C41 for each of the at least one row 111 based on the first input signal S1, such that the emitted acoustic energy of the parametric acoustic transducer array 110, 210 forms a directional beam B of acoustic energy towards the three-dimensional position. ln different embodiments, the first input signal S1 may be generated in response to a user interacting with the input device 130, or in response to input information being received or retrieved from an external device, such as a memory storing position information, a camera or sensor configured to identify a target for the directional acoustic beam in three-dimensional space, a distance measurement device indicating a distance and direction to the target for the directional acoustic beam, or any other suitable information source depending on the format of the information to be input. Suitably, the position towards which the directional beam of acoustic energy is to be directed may thereby be controlled, manually and/or automatically. Using the input device 130, the position may thereby further be adjusted 13 when needed, discretely or continuously, to further improve the directionality of the parametric acoustic transducer array.

Figs. 3a to 5b show different examples of how the parametric acoustic transducer array 110, 210 may be rotated, by the actuator 130, to achieve arbitrary direction of the beam in the second dimension. ln other words, Figs. 3a to 5b illustrate examples of how the parametric acoustic transducer array 110, 210 can be rotated around a rotation axis R that is linearly independent of each row direction axis D.

Fig. 3a illustrate a parametric transducer array 110, 210 according to embodiments herein, wherein the, in this example four, rows 111 of transducer elements extend along a respective parallel (or substantially parallel as described herein) row direction axis D1, D2, D3, D4. Each row of transducer elements is controlled using a respective first control signal, as described herein. Using the row-wise beamforming, the parametric transducer array 110, 210 is thus enabled generate an acoustic beam that can be arbitrarily directed in one dimension, as indicated by the acoustic beam B. Fig. 3b illustrates the same parametric transducer array 110, 210 after it has been rotated an angle 0 around the rotation axis R. As can be seen from the figure, the rotation of the parametric transducer array 110, 210 results in the acoustic beam B being rotated the same angle 0, using the same first control signals C1, C11, C21, C31, C41, and adding only a single second control signal C2 to control the actuator 130 to perform the rotation. ln the example of Figs. 3a and b, the actuator 130 is arranged to rotate the parametric transducer array 110, 210 around a rotation axis R that is centered in the parametric transducer array 110, 210 and is perpendicular to the plane in which the parametric transducer array 110, 210, and its transducer elements ei, have their main extension.

Fig. 4a and 4b illustrate a parametric transducer array 110, 210 similar to that of Figs. 3a and 3b, that can be rotated in different manner to achieve the same aim of generating a directional acoustic beam at an arbitrary angle using a low number of input signals. ln the example of Figs. 4a and b, the actuator130 is arranged to rotate the parametric transducer array 110, 210 around a rotation axis R that is perpendicular to the rows 111 of transducer elements e; in the parametric transducer array 110, 210 and parallel to the plane in which the parametric transducer array 110, 210, and its transducer elements ei, have their main extension. Also in this case, by rotating the 14 parametric transducer array 110, 210 an angle 0 around the rotation axis R by means of the actuator 130, the acoustic beam B is rotated the same angle 0, here indicated in Fig. 4b by the dotted arrow indicating the first position of the acoustic beam B before the rotation and the solid arrow indicating the second position of the acoustic beam B' after the rotation. Again, a directional acoustic beam at an arbitrary angle is achieved using the exact same set of first control signals C1, C11, C21, C31, C41, and adding only a single second control signal C2 to control the actuator 130 to perform the rotation.

Figs. 5a and b illustrate a parametric transducer array 110, 210 similar to that of Figs. 3a and 3b, that can be rotated in yet another manner to achieve the same aim of generating a directional acoustic beam at an arbitrary angle using a low number of input signals. ln the example of Figs. 5a and b, the actuator130 is arranged to rotate the parametric transducer array 110, 210 around a rotation axis R that is in likeness with the example in Figs. 3a and b centered in the parametric transducer array 110, 210 but in contrast to that of Figs. 3a and b is not perpendicular to the plane in which the parametric transducer array 110, 210, and its transducer elements ei, have their main extension, but rather at an angle between 0 degrees and 90 degrees from this plane. The result is that a tilted version of the parametric transducer array 110, 210 in Figs. 3a and b is rotated around the same rotation axis R. As can be seen from the figures, also in this case, by rotating the parametric transducer array 110, 210 an angle 0 around the rotation axis R by means of the actuator 130, the acoustic beam B is rotated the same angle 0, here indicated in Fig. 5b by the dotted arrow indicating the first position of the acoustic beam B before the rotation and the solid arrow indicating the second position of the acoustic beam B' after the rotation. Again, a directional acoustic beam at an arbitrary angle is achieved using the exact same set of first control signals C1, C11, C21, C31, C41, and adding only a single second control signal C2 to control the actuator 130 to perform the rotation.

The actuator 130 may be configured to rotate the parametric acoustic transducer array 110, 210 discretely from a first position to a second position, stepwise between a number of positions, or continuously along a path. The rotation may be determined based one or more preset or input parameter, including a selection of: an angle of rotation, a rotation axis R around which to rotate, rotation direction around the rotation axis R, positions (x,y,z) between which to rotate, continuous tracking information indicating a target that is moving in three-dimensional space, or information on a target position to be kept while the acoustic system 100 is moving, etc. Of course, the rotation parameters may alternate over time, whereby the second control signal C2 may be updated, upon request, at regular intervals, or continuously, so that the actuator 130 is controlled to rotate the parametric acoustic transducer array 110, 210 accordingly.

The input device 140 may be configured to receive information on any or all of these rotation parameters and to send them to the controller 120, included in the first input signal S1 or via a separate rotation input signal SR. The controller 120 is in these embodiments in turn configured to generate the second control signal C2 based on the one or more input rotation parameter indicated in the first and/or rotation input signal S1, SR from the input device 140.

The actuator 130 is preferably configured to mechanically rotate the parametric acoustic transducer array 110, 210, in any suitable manner, including but not limited to the examples of Figs. 3a to 6b. ln any embodiment herein, the controller 120 may be configured to generate the control signals C1, C11, C21, C2, C12, C22 such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. Advantageously, the exemplified frequencies are suitable for the application of delivering acoustic sound to the ear of a USGI”.

The parametric acoustic transducer array 110, 210 may be a micromachined ultrasonic transducer, MUT, comprising micromachined ultrasonic transducer, MUT, elements configured to emit acoustic energy in the form of ultrasonic energy, wherein the acoustic signal is an ultrasonic signal. Thereby, the acoustic system 100 may advantageously be miniaturized. This enables application in for example handheld devices, such as mobile phones, and other applications which require small sized components.

The acoustic signal may be a modulated acoustic signal comprising a carrier wave and a modulation signal, which comprises information to be transmitted, modulated onto the carrier wave. ln embodiments where the acoustic system 100 comprise an input device 140, the controller 120 may then be configured to receive from the input device 16 140 a second input signal S2 comprising the modulation signal to be modulated onto the carrier wave of the acoustic signal, and in response to receiving the second input signal, generating a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals C1, C11, C21, C31, C41, C2. The modulation signal is in some embodiments an audible sound signal, i.e. comprising audio information to be modulated onto the carrier wave, wherein the directional beam is a directional beam of audible sound. Suitably, a directional speaker is thereby achieved having the low software complexity and low hardware complexity as well as therewith associated advantages described herein. lf the parametric acoustic transducer array 110, 210 is a micromachined ultrasonic transducer, MUT, the carrier wave is in this case an ultrasonic carrier wave, and the modulated signal is a modulated ultrasonic signal.

Of course, the invention applies equally well to acoustic signals, such as ultrasonic signals, that are not modulated as the advantage of reducing the number of drive signals needed for a set number of transducer elements in an array is still obtained. A non-limiting example of an application that could benefit from the invention described herein that uses an un-modulated ultrasonic signal is a scanning sonar. lt is generally advantageous if the controller 120 is configured to effect the above- described procedure in an automatic manner by executing a computer program 127. Therefore, the controller 120 may include a memory unit 125, i.e. non-volatile data carrier, storing the computer program 127, which, in turn, contains software for making processing circuitry in the form of at least one processor 123 in the controller 120 exe- cute the actions mentioned in this disclosure when the computer program 127 is run on the at least one processor 123. ln one or more embodiment, the invention may therefore comprise a computer program 127 loadable into a non-volatile data carrier 125 communicatively connected to a processor 123, the computer program 127 comprising software for executing the method according any of the method embodiments presented in connection with Fig. 6 when the computer program 127 is run on the processor 123. Furthermore, the invention may comprise a non-volatile data carrier 125 containing the computer program 127.

Method embodiments 17 With reference to the flow diagram in Fig. 6, and also with reference to Figs. 1 to 5b as described above, we will now describe a computer-implemented method, according to one or more embodiment of the invention, for controlling the emission of acoustic energy from an acoustic system 100. The system 100 comprises a parametric acoustic transducer array 110, 210 configured to emit acoustic energy of periodically varying intensity in the form of an acoustic signal. lt is assumed that the parametric acoustic transducer array 110, 210 comprises a plurality of transducer elements ei arranged in at least one row 111, wherein each row 111 extends along a row direction axis D, and wherein, for each row 111, all the transducer elements of the row 111 are controllable in response to a first control signal C1, C11, C21 so as to emit the acoustic energy at a wavelength and phase determined by the first control signal C1, C11, C21. The system 100 further comprises an actuator 130 being operatively connected to the parametric acoustic transducer array 110, 210 and being configured to rotate the parametric acoustic transducer array 110, 210 around a rotation axis R that is linearly independent of the row direction axis D in response to a second control signal C2, C12, C22. The system 100 also comprises a controller 120 that is communicably connected to each of the at least one row 111 of the parametric acoustic transducer array 110, 210 and that is further communicably connected to the actuator 130. The system 100 may be the system 100 according to any embodiment described herein, in connection with Figs. 1 to 5b.

The method comprises: ln step 610: generating, by the controller 120, for each of the at least one row 111 a first control signal C1, C11, C21, C31, C41, such that the emitted acoustic energy of the parametric acoustic transducer array 110, 210 forms a directional beam B of acoustic energy. ln step 620: emitting, by the parametric acoustic transducer array 110, 210, acoustic energy of periodically varying intensity that has a wavelength and a phase delay de- termined by the first control signal, C1, C11, C21, C31, C41.

Thereby, through the row-wise beamforming, there is generated an acoustic beam that can be arbitrarily directed in a first dimension. 18 ln step 630: generating, by the controller 120, the second control signal C2 such that the actuator 130 rotates the parametric acoustic transducer array 110, 210, and thus the directional beam B of acoustic energy, around the rotation axis R. ln step 640: rotating, by the actuator 130, the parametric acoustic transducer array 110, 210 around the rotation axis R based on the second control signal C2.

Thereby, arbitrary direction of the directional beam B also in a second dimension is enabled. The advantageous generation of a directional acoustic beam at an arbitrary angle using a parametric acoustic transducer array having N transducer elements and using less than N input signals is thereby achieved by the method.

The method may further comprise receiving, in the controller 120, from an input device 140 communicatively connected to the controller 120, a first input signal S1 indicative of a three-dimensional position towards which the directional beam B of acoustic energy is to be directed. ln these embodiments, the method further comprises generating, by the controller 120, the first control signal C1, C11, C21 for each of the at least one row 111 based on the first input signal S1 such that the emitted acoustic energy of the parametric acoustic transducer array 110, 210 forms a directional beam B of acoustic energy towards the three-dimensional position.

Generating each of the first and second control signals C1, C2, C11, C12, C21, C22, by the controller 120, may comprise generating each of the first and second control signals C1, C2, C11, C12, C21, C22 such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. Advantageously, the exemplified frequencies are suitable for the application of delivering acoustic sound to the ear of a USGI”.

The acoustic signal may be a modulated acoustic signal comprising a carrier wave and a modulation signal modulated onto the carrier wave. The modulation signal may be an audible sound signal, wherein the directional beam B is a directional beam of audible sound. ln embodiments wherein the acoustic signal is a modulated acoustic signal, the method may further comprise receiving in the controller 120, from the input device 140 communicatively connected to the controller 120, a second input signal S2 comprising 19 the modulation signal to be modulated onto the carrier wave of the acoustic signal; and in response to receiving the second input signal S2, generating, by the controller 120, a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals C1, C2, C11, C12, C21, C22. ln embodiments wherein the parametric acoustic transducer array 110, 210 is a micromachined ultrasonic transducer, MUT, comprising micromachined ultrasonic transducer, MUT, elements configured to emit acoustic energy in the form of ultrasonic energy, the acoustic signal is an ultrasonic signal, that may be a modulated ultrasonic signal as described above, and the carrier wave is an ultrasonic carrier wave. ln these embodiments, emitting acoustic energy by the parametric acoustic transducer array 110, 210 comprises emitting ultrasonic energy. lf this is suitable to the application of the invention, the computer-implemented method for controlling the emission of acoustic energy from an acoustic system 100, according to any embodiment described herein, may of course be applied to controlling an acoustic system comprising more than one parametric acoustic transducer array 110, 210 as described herein. Further embodiments All of the process steps, as well as any sub-sequence of steps, described with reference to Fig. 6 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital VideoNersatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EP- ROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

The term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components. The term does not preclude the presence or addition of one or more additional elements, features, inte- gers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. ln the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B", “B and not A” and “A and B", unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. lt is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

The invention is not restricted to the described embodiments in the figures but may be varied freely within the scope of the claims.

Claims

1. An acoustic system (100) comprising: a parametric acoustic transducer array (110, 210) configured to emit acoustic energy of periodically varying intensity in the form of an acoustic signal, wherein the parametric acoustic transducer array (110, 210) comprises a plurality of transducer elements (ei) arranged in at least one row (111), wherein each of the at least one row (111) extends along a row direction axis (D), and wherein, for each row (111), all the transducer elements of the row 111 are controllable in response to a first control signal (C1, C11, C21, C31, C41) so as to emit the acoustic energy at a wavelength and phase determined by the first control signal (C1, C11, C21, C31, C41); an actuator (130) being operatively connected to the parametric acoustic transducer array (110, 210) and being configured to rotate the parametric acoustic transducer array (110, 210) around a rotation axis (R) that is linearly independent to the row direction axis (D) in response to a second control signal (C2), and a controller (120) being communicably connected to each of the at least one row (111) ofthe parametric acoustic transducer array (110, 210) and further being communicably connected to the actuator (130), the controller (120) being configured to: generate, for each of the at least one row (111), a first control signal (C1, C11, C21, C31, C41) such that the emitted acoustic energy of the parametric acoustic transducer array (110, 210) forms a directional beam (B) of acoustic energy, and generate a second control signal (C2) such that the actuator (130) rotates the parametric acoustic transducer array (110, 210), and thus the directional beam (B) of acoustic energy, around the rotation axis (R).

2. The acoustic system (100) of claim 1, wherein the parametric acoustic transducer array (110, 210) comprises at least four transducer elements (ei)._ The acoustic system (100) of claim 1 or 2, wherein the plurality of transducer elements (ei) are arranged in at least two rows (111), each row (111) extending along the row direction axis (D) or an axis parallel to the row direction axis (D). _ The acoustic system (100) according to any one of the preceding claims, wherein the parametric acoustic transducer array (110, 210) is a phased array. _ The acoustic system (100) according to any one of the preceding claims, further comprising an input device (140) communicatively connected to the controller (120). _ The acoustic system (100) according to claim 5, wherein the controller (120) is configured to: receive from the input device (140) a first input signal (S1) indicative of a three- dimensional position towards which the directional beam (B) of acoustic energy is to be directed; and generate the first control signal (C1, C11, C21, C31, C41) for each of the at least one row (111) based on the first input signal (S1), such that the emitted acoustic energy of the parametric acoustic transducer array (110, 210) forms a directional beam (B) of acoustic energy towards the three-dimensional position. _ The acoustic system (100) according to any one of the preceding claims, wherein the controller (120) is configured to generate the control signals (C1, C11, C21, C31 , C41 , C2) such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. _ The acoustic system (100) according to any one of the preceding claims, wherein the parametric acoustic transducer array (110, 210) is planar. _ The acoustic system (100) according to any one of the preceding claims, wherein the parametric acoustic transducer array (110, 210) is a micromachined ultrasonic transducer, MUT, configured to emit acoustic energy in the form of ultrasonic energy, wherein the acoustic signal is an ultrasonic signal.10.The acoustic system (100) according to any one of the preceding claims, wherein the acoustic signal is a modulated acoustic signal comprising a carrier wave and a modulation signal modulated onto the carrier wave. 1 1 .The acoustic system (100) according to claim 5 and 10, wherein the controller (120) is configured to: receive from the input device (140) a second input signal (S2) comprising the modulation signal to be modulated onto the carrier wave of the acoustic signal; and in response to receiving the second input signal (S2), generating a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals (C1, C11, C21, C31, C41, C2). 12.The acoustic system (100) according to claim 10 or 11, wherein the modulation signal is an audible sound signal, and wherein the directional beam (B) is a directional beam of audible sound. 13.A computer-implemented method for controlling the emission of acoustic energy from an acoustic system (100), the system (100) comprising: a parametric acoustic transducer array (110, 210) configured to emit acoustic energy of periodically varying intensity in the form of an acoustic signal, wherein the parametric acoustic transducer array (110, 210) comprises a plurality of transducer elements (ei) arranged in at least one row (111), wherein each row (111) extends along a row direction axis (D), and wherein, for each row (111), all the transducer elements of the row 111 are controllable in response to a first control signal (C1, C11, C21, C31, C41) so as to emit the acoustic energy at a wavelength and phase determined by the first control signal (C1, C11, C21, C31, C41); an actuator (130) being operatively connected to the parametric acoustic transducer array (110, 210) and being configured to rotate the parametric acoustic transducer array (110, 210) around a rotation axis (R) that is linearlyindependent of the row direction axis (D) in response to a second control signal (C2), and a controller (120) being communicably connected to each of the at least one row (1 1 1) of the parametric acoustic transducer array (110, 210) and further being communicably connected to the actuator (130), wherein the method comprises: generating, by the controller (120), for each of the at least one row (111) a first control signal (C1, C11, C21, C31, C41), such that the emitted acoustic energy of the parametric acoustic transducer array (110, 210) forms a directional beam (B) of acoustic energy; and generating, by the controller (120), the second control signal (C2) such that the actuator (130) rotates the parametric acoustic transducer array (110, 210), and thus the directional beam (B) of acoustic energy, around the rotation axis (R)- 14.The method of claim 13, further comprising: receiving in the controller (120), from an input device (140) communicatively connected to the controller (120), a first input signal (S1) indicative of a three- dimensional position towards which the directional beam (B) of acoustic energy is to be directed; and generating, by the controller (120), the first control signal (C1, C11, C21, C31, C41 ) for each of the at least one row (111) based on the first input signal (S1) such that the emitted acoustic energy of the parametric acoustic transducer array (110, 210) forms a directional beam (B) of acoustic energy towards the three-dimensional position. 15.The method of claim 13 or 14, wherein generating each of the first and second control signals (C1, C11, C21, C31, C41, C2), by the controller (120), comprises generating each of the first and second control signals (C1, C11, C21, C31, C41, C2) such that the acoustic energy is emitted at a frequency in the interval of 30 to 300 kHz, preferably in the interval of 140 to 220 kHz, more preferably at a frequency of 160 kHz. 16.The method of claim 15, wherein the parametric acoustic transducer array (110, 210) is a micromachined ultrasonic transducer, MUT, wherein emitting acoustic energy by the parametric acoustic transducer array (110, 210) comprises emitting ultrasonic energy. 17.The method according to any one of the claims 13 to 16, wherein the acoustic signal is a modulated acoustic signal comprising a carrier wave and a modulation signal modulated onto the carrier wave. 18.The method according to claim 17, comprising: receiving in the controller (120), from an input device (140) communicatively connected to the controller (120), a second input signal (S2) comprising the modulation signal to be modulated onto the carrier wave of the acoustic signal; and in response to receiving the second input signal (S2), generating, by the controller (120), a modulated acoustic signal by modulating the modulation signal onto the carrier wave of the acoustic signal before generating the first and second control signals (C1, C11, C21, C31, C41, C2). 19.The method according to claim 17 or 18, wherein the modulation signal is an audible sound signal, and wherein the directional beam (B) is a directional beam of audible sound. 20.A computer program (127) loadable into a non-volatile data carrier (125) communicatively connected to a processor (123), the computer program (127) comprising software for executing the method according any of the claims 13 to 19 when the computer program (127) is run on the processor (123). 21 .A non-volatile data carrier (125) containing the computer program (1 27) of the claim 26