Inducing vibrations in an environment by operation of a loudspeaker module

Abstract

There is provided a loudspeaker module for installation in an environment comprising: a module housing, a first loudspeaker attached to the module housing, and a second loudspeaker attached to the module housing. The first loudspeaker comprises a first diaphragm, a first drive unit configured to move the first diaphragm, and a first movable assembly. The first movable assembly includes the first diaphragm and a movable part of the first drive unit. The second loudspeaker comprises a second diaphragm, a second drive unit configured to move the second diaphragm, and a second movable assembly. The second movable assembly includes the second diaphragm and a movable part of the second drive unit. Front faces of the first and second diaphragms face in opposite directions. There is also provided a method of operating the loudspeaker module to induce vibration in the environment, the method comprising: providing a first signal to the first loudspeaker to move the first movable assembly in accordance with the first signal; and providing a second signal to the second loudspeaker to move the second movable assembly in accordance with the second signal. The second signal is different from the first signal so as to induce the vibration in the environment in which the loudspeaker module is installed. There is also provided a computer-readable medium comprising logic that, when executed by a signal unit, causes the signal unit to transmit the first and second signals to the first and second loudspeakers of the loudspeaker module respectively.

Description

[0001] INDUCING VIBRA TIONS IN AN ENVIRONMENT B Y OPERA TION OF A LOUDSPEAKER MODULE

[0002] This application claims priority to GB240117.3, filed 29 January 2024.

[0003] Field of the Invention

[0004] The present invention relates to methods for inducing vibrations in an environment by operation of a loudspeaker module.

[0005] Background

[0006] The present inventors have observed that when loudspeaker modules are installed into environments, a portion of the environment may effectively act as a sound board. Vibrations may be induced in the effective sound board by the vibrational energy generated from the operation of the loudspeaker module (e.g., the vibrational energy associated with a back-and-forth motion of a drive unit and / or diaphragm of the loudspeaker module). Vibrations induced in the sound board may provide a secondary acoustic source that can be heard and / or sensed by a person in the environment in which the loudspeaker module is installed.

[0007] For example, woofers may be installed into the doors of vehicles. Vehicle doors are used as the installation site for woofer loudspeaker modules because the hollow inside (e.g., the wet zone part of the door) of a vehicle door provides a sufficiently large back volume for the woofer, with a sufficiently large radiating surface and a sufficiently low resonance frequency to facilitate effective operation of the woofer. In such cases, the door trim functions as a sound board, thereby providing a secondary acoustic source that can be heard and / or sensed by an occupant of the vehicle through the structure of the vehicle (e.g., the frame of the vehicle cabin.

[0008] Recent developments in loudspeaker modules by the present inventors include:

[0009] • WO2023194163A1 , which describes a compact bass loudspeaker with a moving magnet.

[0010] • PCT / EP2023 / 067426, which describes another compact bass loudspeaker.

[0011] • PCT / EP2023 / 073013, which describes another compact bass loudspeaker

[0012] • PCT / EP2023 / 086339, which describes another compact bass loudspeaker

[0013] • GB2302099.3, which describes another compact bass loudspeaker

[0014] • GB2314913.1 , which describes a vehicle incorporating a compact bass loudspeaker

[0015] • GB2314915.6, which describes another compact bass loudspeaker

[0016] These developments benefit from a more compact and, in some cases, balanced configuration that significantly reduces (even, in some examples, substantially eliminates) the inducement of vibrations in the environment into which the loudspeaker module is installed.

[0017] However, the present inventors have observed that in certain contexts, while a user may wish to benefit from the improvements provided by the more compact and balanced configuration, the inducement of vibrations in the environment may still be desirable. The induced vibrations (i.e., the secondary acoustic source) may be subjectively desirable as it may contribute to a sensation of a so-called warm blanket of bass sound in the environment, wherein a person within the environment feels surrounded by the bass sounds produced by the secondary acoustic source.

[0018] In contrast, the present inventors have observed that the absence of induced vibrations accompanying generated bass sounds have been described by listeners as corresponding to a clean, precise and / or sterile bass sound.

[0019] The present inventors have observed that different listeners may prefer different sound qualities (i.e., ranging from the warm blanket of bass to the clean / precise / sterile bass sound) generated from loudspeaker modules in different contexts.

[0020] The present invention has been devised in light of the above considerations.

[0021] Summary of the Invention

[0022] In a first aspect, there is provided a method of operating a loudspeaker module to induce vibration in an environment in which the loudspeaker module is installed. The loudspeaker module comprises: a module housing, and a first loudspeaker and a second loudspeaker attached to the module housing. The first loudspeaker comprises: a first diaphragm, a first drive unit configured to move the first diaphragm, and a first movable assembly. The first movable assembly includes the first diaphragm a movable part of the first drive unit. The second loudspeaker comprises a second diaphragm, a second drive unit configured to move the second diaphragm, and a second movable assembly. The second movable assembly includes the second diaphragm and a movable part of the second drive unit. Front faces of the first and second diaphragms (i.e. a front face of the first diaphragm and a front face of the second diaphragm) face in opposite directions. The method comprises: providing a first signal to the first loudspeaker to move the first movable assembly in accordance with the first signal; and providing a second signal to the second loudspeaker to move the second movable assembly in accordance with the second signal. The second signal is different from the first signal so as to induce the vibration in the environment in which the loudspeaker module is installed.

[0023] By providing different signals to the first and second loudspeakers comprised by the loudspeaker module, the first and second movable assemblies may be induced to move (e.g., oscillate) asynchronously (i.e., out of phase with one another). This imbalance between the relative motions of the first and second movable assemblies induces vibration in the environment in which the loudspeaker module is installed.

[0024] In some examples, the front face of the first diaphragm may face away from the first drive unit.

[0025] In some examples, the front face of the second diaphragm faces away from the second drive unit.

[0026] In some examples, the first and second signals may be electrical signals, i.e., the first signal may be a first (e.g. time-varying) electrical signal and the second signal may be a second (e.g. time-varying) electrical signal. In some examples, the first and second signals may be voltage signals. In some examples, the loudspeaker module may receive the first and second signals from respective (or a common) signal unit. The signal unit(s) may, for example, be an amplifier, a set of amplifiers, a signal generation unit, a signal processing unit, or any other suitable electric system.

[0027] In some examples, providing the first signal to the first loudspeaker may involve transmitting the first signal to the first loudspeaker from a first output of the signal unit.

[0028] In some examples, the signal unit may comprise a first amplifier configured to amplify the first signal prior to the first signal being provided (or, in other words, applied) to the first loudspeaker (e.g. prior to the first signal reaching a first output of the signal unit).

[0029] In some examples, providing the second signal to the second loudspeaker may involve transmitting the second signal to the second loudspeaker from a second output of the signal unit.

[0030] In some examples, the second output of the signal unit may comprise a second amplifier configured to amplify the second signal prior to the second signal being provided (or, in other words, applied) to the second loudspeaker (e.g. prior to the second signal reaching a second output of the signal unit).

[0031] In some examples, the first and second amplifiers may be separate amplifiers. This may be appropriate if, for example, the first and second signals have been generated prior to an amplification step (in which case the first and second amplifiers may be the same), or if the difference between the first and second signals is generated by using different first and second amplifiers to a common signal.

[0032] However, it should be appreciated that separate first and second amplifiers as defined above are not required in all examples, since, for example: differences between the first and second signals may be achieved by amplifying a common signal path signal prior to that common signal path signal being modified differently by one or more signal modifying elements to form the first and second signals. The one or more signal modifying elements may include any suitable element, including, for example, resistors, inductors, and / or capacitors arranged in any suitable configuration (e.g., in a configuration of a potential divider, a current limiter, a voltage limiter, a phase modulator, an amplitude modulator, or any other suitable configuration).

[0033] In some examples, differences between the first and second signals may be achieved by amplifying a common signal path signal and a differential signal path signal prior to those signals being combined together differently to form the first and second signals.

[0034] In some examples, amplifiers may not be needed (at all), if the first and second signals are generated with adequate power.

[0035] In some examples, the method may include forming the first signal and second signal from a common signal component and a differential signal component.

[0036] The first and second signals may be formed from the common signal component and the differential signal component using any suitable signal processing technique (e.g. time based addition and subtraction). In some embodiments, the amplitude of the differential signal component may be 70% or less of the amplitude of the common signal component. In some embodiments, the amplitude of the differential signal component may be 50% or less of the amplitude of the common signal component.

[0037] In this context, the amplitude of each signal component may be taken as, for example, the RMS amplitude, or the peak-peak amplitude. For example, the RMS amplitude of the differential signal component may be 70% or less of the RMS amplitude of the common signal component.

[0038] In some examples, the amplitude of the differential signal component may be 70% or less of the amplitude of the common signal component, 50% or less of the amplitude of the common signal component, 25% or less of the amplitude of the common signal component, 20% or less of the amplitude of the common signal component, 15% or less of the amplitude of the common signal component, may be 10% or less of the amplitude of the common signal component may be 5% or less of the amplitude of the common signal component, may be 2% or less of the amplitude of the common signal component, or may be 1% or less of the amplitude of the common signal component. Alternatively, the amplitude of the differential signal component may be 1 % or more of the amplitude of the common signal component, may be 2% or more of the amplitude of the common signal component, may be 5% or more of the amplitude of the common signal component, may be 10% or more of the amplitude of the common signal component, may be 15% or more of the amplitude of the common signal component, may be 20% or more of the amplitude of the common signal component, may be 25% or more of the amplitude of the common signal component, or may be 50% or more of the amplitude of the common signal component. Alternatively, the amplitude of the differential signal component may be between 1% and 70% of the amplitude of the common signal component, between 1% and 50% of the amplitude of the common signal component, between 1% and 25% of the amplitude of the common signal component, between 1 % and 20% of the amplitude of the common signal component, between 1% and 15% of the amplitude of the common signal component, between 1% and 10% of the amplitude of the common signal component, between 1% and 5% of the amplitude of the common signal component, between 1% and 2% of the amplitude of the common signal component, between 2% and 70% of the amplitude of the common signal component, between 2% and 50% of the amplitude of the common signal component, between 2% and 25% of the amplitude of the common signal component, between 2% and 20% of the amplitude of the common signal component, between 2% and 15% of the amplitude of the common signal component, between 2% and 10% of the amplitude of the common signal component, between 2% and 5% of the amplitude of the common signal component, between 5% and 70% of the amplitude of the common signal amplitude, between 5% and 50% of the amplitude of the common signal amplitude, between 5% and 25% of the amplitude of the common signal component, between 5% and 20% of the amplitude of the common signal component, between 5% and 15% of the amplitude of the common signal component, between 5% and 10% of the amplitude of the common signal component, between 10% and 70% of the amplitude of the common signal component, between 10% and 50% of the amplitude of the common signal component, between 10% and 25% of the amplitude of the common signal component, between 10% and 20% of the amplitude of the common signal component, between 10% and 15% of the amplitude of the common signal component, between 15% and 70% of the amplitude of the common signal component, between 15% and 50% of the amplitude of the common signal component, between 15% and 25% of the amplitude of the common signal component, between 15% and 20% of the amplitude of the common signal component, between 20% and 70% of the amplitude of the common signal component, between 20% and 50% of the amplitude of the common signal component, between 20% and 25% of the amplitude of the common signal component, between 25% and 70% of the amplitude of the common signal component, between 25% and 50% of the amplitude of the common signal component, or between 50% and 70% of the amplitude of the common signal component.

[0039] In this way, the common portions of the first and second signals may be used to generate sound, by the loudspeaker module, while the different portions of the first and second signals may be used to induce vibrations in the environment in which the loudspeaker module is installed, without overpowering the sound generated by the common signal component.

[0040] As will be discussed in more detail below, when using a loudspeaker module having the configuration described herein, the majority of the energy in the signals (e.g., in terms of the voltage embodied in the mutually common and different portions of the first and second signals) can be directed into the common signal component, thereby maximising the efficiency with which sound can be generated by the loudspeaker module. Meanwhile a relative minority of the energy can be directed into the differential signal component, which - e.g. at the levels described above - is sufficient to induce vibrations in the environment into which the loudspeaker module is installed at levels that are perceptible by an occupant of the environment (e.g., as a warm blanket of sound).

[0041] In this way, relatively low levels of energy can be used to induce vibrations in the environment (via the differential signal component) whilst also ensuring that sound of sufficient volume and quality is generated by the loudspeaker module (via the common signal component).

[0042] In some embodiments, the method may further comprise: forming the first signal by adding the differential signal component to the common signal component; and forming the second signal by subtracting the differential signal component from the common signal component.

[0043] However, a skilled person would appreciate there are other ways of forming the first and second signals from a common signal component and a differential signal component, e.g. forming the first signal by adding the differential signal to the common signal component, and providing the common signal component as the second signal (or, alternatively, adding a second differential signal component to the common signal component to provide the second signal).

[0044] In some embodiments, the forming the first signal and second signal may be carried out by a signal unit.

[0045] In some embodiments, a difference between the first and second signals is adjustable.

[0046] In some embodiments, the difference between the first and second signals may be adjustable by adjusting a differential signal component relative to the common signal component. In some examples, the method may include adjusting the differential signal component relative to the common signal component.

[0047] In this way, the first and second signals may be adjustably controlled to selectively induce vibration (e.g., of adjustable / controllable magnitude and / or frequency) in the environment in which the loudspeaker module is installed.

[0048] Adjusting the differential signal component relative to the common signal component may involve adjusting one or more parameters of said differential signal component(s) relative to the common signal component. The one or more parameters may include any one or more of: a frequency, phase, amplitude (e.g. the RMS amplitude or peak-peak amplitude), for example.

[0049] In some embodiments, adjusting the differential signal component relative to the common signal component may include adjusting an amplitude of the differential signal component relative to an amplitude of the common signal component.

[0050] The amplitudes may, for example, be RMS amplitudes or peak-peak amplitudes.

[0051] Adjusting the amplitude of the differential signal component relative to the amplitude of the common signal component may, for example, include increasing or decreasing the amplitude of the differential signal component relative to the amplitude of the common signal component.

[0052] Adjusting the differential signal component relative to the common signal component may include adjusting aspects of the differential signal component relative to the common signal component, e.g. phase.

[0053] In some embodiments, a difference between the first and second signals may be adjustable via a user interface.

[0054] The user interface may be configured to adjust the differential signal component relative to the common signal component, for example.

[0055] The user interface may be provided as part of the environment into which the loudspeaker module is installed. As an example, if the environment is a vehicle, the user interface may be provided to be accessible to an occupant of the vehicle (e.g., the driver and / or one or more passengers of the vehicle).

[0056] Alternatively, the user interface may be provided remote from the environment into which the loudspeaker module is installed such that the operation of the loudspeaker module (to induce vibration in the environment) is instructed and / or carried out / executed by interaction of an external operator (e.g., in the case of the environment being a vehicle, a manufacturer, maintenance personnel - e.g., a mechanic - and / or vendor of the vehicle).

[0057] In some examples, the user interface may be configured to provide a user of the interface with a means for adjusting a difference between the first and second signals to selectively adjust / control the inducement of vibrations (and e.g., the strength, intensity, amplitude and / or frequency of said induced vibrations). For example, the user may select, via the user interface a desired quality (e.g., on a scale from a so-called ‘clean / sterile’ bass sound to a so-called ‘warm blanket of bass’) and / or intensity (e.g., in terms of the amplitude of the vibrations) of the induced vibrations. The user interface may be provided by a display of a computer configured to execute logic that is able to determine a necessary difference between the first and second signals based on the user-input selection of the desired parameters (e.g., quality and / or intensity) of the induced vibration.

[0058] Additionally or alternatively, a user may be able to directly select, via an appropriately configured user interface, a desired difference between the first and second signals.

[0059] In response to receiving input via the user interface, a computer (e.g., a processor communicatively connected to the user interface) may be configured to execute logic that causes the required difference between the first and second signals to be implemented, and have those first and second signals transmitted respectively to the first and second loudspeakers so as to induce the desired / selected vibrations in the environment.

[0060] In some embodiments, the first and second signals may have a frequency bandwidth. A difference between the first and second signals may vary across at least a portion of the bandwidth.

[0061] For example, a difference in amplitude (e.g. the RMS amplitude or peak-peak amplitude) between the first and second signals may vary across a portion (or all) of the bandwidth.

[0062] This may be required and / or desirable to induce vibrations in the environment of the desired / necessary amplitude at relevant frequencies, with the different differences in amplitude at different frequencies being tuned to achieve a desired acoustic result for a given environment (e.g. to achieve a desired acoustic result for a loudspeaker module installed in specific location within a car).

[0063] In some examples, adjusting the differential signal component relative to the common signal component may include, across the bandwidth of frequencies, adjusting one or more parameters of said differential signal component(s) relative to the common signal component differently at different frequencies (e.g. different frequency bands) within the bandwidth. The one or more parameters may include amplitude (e.g. the RMS amplitude or peak-peak amplitude) and / or phase, for example.

[0064] In some embodiments, the environment may be a part of a vehicle.

[0065] For example, the environment may be a cabin of a vehicle. In this way, induced vibrations may reverberate around a frame of the cabin to provide one or more occupants of the vehicle with the sensation of the induced vibrations (e.g., via haptic or tactile feedback by being in physical contact with a seat, door, or trim of the vehicle cabin).

[0066] In a second aspect, there is provided a loudspeaker module for installation in an environment. The loudspeaker module comprises: a module housing; a first loudspeaker attached to the module housing; and a second loudspeaker attached to the module housing. The first loudspeaker comprises a first diaphragm, a first drive unit configured to move the first diaphragm, and a first movable assembly. The first movable assembly includes the first diaphragm and a movable part of the first drive unit. A front face of the first diaphragm faces away from the first drive unit. The first loudspeaker is configured to receive a first signal and to move the first movable assembly in accordance with the first signal when the loudspeaker module is in use. The second loudspeaker comprises a second diaphragm, a second drive unit configured to move the second diaphragm, and a second movable assembly. The second movable assembly includes the second diaphragm and a movable part of the second drive unit. A front face of the second diaphragm faces away from the second drive unit. The second loudspeaker is configured to receive a second signal and to move the second movable assembly in accordance with the second signal when the loudspeaker module is in use. Front faces of the first and second diaphragms (i.e. a front face of the first diaphragm and a front face of the second diaphragm) face in opposite directions. The second signal provided to the second loudspeaker is different from the first signal provided to the first loudspeaker so as to induce the vibration in the environment in which the loudspeaker module is installed when the loudspeaker module is in use.

[0067] In some embodiments, the front faces of the first and second diaphragms may respectively face away from the first and second drive units.

[0068] For avoidance of any doubt, features described below in connection with the loudspeaker module may be applied to the method according to the first aspect or the loudspeaker module according to the second aspect.

[0069] The loudspeaker module may have a resonant frequency in a range of 30-100Hz (Hertz), optionally 40- 80Hz. The resonant frequency of the loudspeaker module may be referred to as the “in-box” resonant frequency of the loudspeaker module (since it is the resonant frequency that occurs when the acoustic volume is enclosed by the diaphragm and the module housing).

[0070] The loudspeaker module may be a subwoofer configured to produce sound with frequencies in a bass frequency range. The bass frequency range may include 60-80Hz, more preferably include 40-100Hz. By way of example, the bass frequency range may be 20Hz-100Hz.

[0071] In some examples, the first and second diaphragms may each (respectively) be suspended from the module housing of the loudspeaker module by one or more suspension elements.

[0072] In some examples, the first and second loudspeakers may each (respectively) further comprise a loudspeaker frame from which the corresponding diaphragm is suspended by the corresponding one or more suspension elements, wherein the loudspeaker frame is attached to the module housing. In such examples, each diaphragm can be viewed as being suspended from the module housing via the corresponding loudspeaker frame.

[0073] For each of the first and second loudspeakers, the one or more suspension elements may (respectively) include a first suspension element, e.g., a roll suspension (that may also be referred to as the “surround”), which attaches to the corresponding loudspeaker frame at a first landing surface on said loudspeaker frame. The first suspension element may be attached directly or indirectly to the corresponding diaphragm. In some examples, the first suspension element may attach (directly) to an outer edge of said diaphragm. In other examples, the first suspension element may be attached to another element of the corresponding movable assembly. In some examples, the first and second signals may be configured to receive the first and second signals from a respective signal unit. The respective signal unit from which each of the first and second signals are received may be a common signal unit or may be respectively different signal units.

[0074] For each of the first and second loudspeakers, the one or more suspension elements may (respectively) include a second suspension element, e.g., a damper, which attaches to the corresponding loudspeaker frame at a second landing surface on said loudspeaker frame. The second suspension element may be attached directly or indirectly to the corresponding diaphragm. In some examples, the second suspension element may be attached (directly) to said diaphragm at a location inwardly located with respect to the outer edge of said diaphragm. In other examples, the second suspension element may be attached to another element of the corresponding movable assembly (e.g., the movable part of the corresponding drive unit, particularly where the movable part is a magnet unit of the drive unit). Typically, the surround may be non-porous and may act as a bounding surface to the acoustic volume.

[0075] In some embodiments, the first and second loudspeakers may be substantially identical.

[0076] This may simplify manufacture and also may make it easier to control vibration caused by differences in the first and second signals.

[0077] In some embodiments, each of the first and second drive units may be configured to move the corresponding diaphragm respectively along a common axis.

[0078] In other words, the first drive unit may be configured to move the first diaphragm, and the second drive unit many be configured to move the second diaphragm.

[0079] The centre of gravity of the movable part of each of the first and second drive units may (respectively) have a position along the common axis (also referred to herein equivalently as a movement axis) that is between the first landing surface and the second landing surface of the corresponding loudspeaker frame.

[0080] By locating the centre of gravity of the magnet unit between the first landing surface and the second landing surface, rocking of the movable assembly may be inhibited. More particularly, the rocking modes of the loudspeaker module may be pushed outside of the working frequency range of the loudspeaker module.

[0081] The movable part of the first drive unit may be attached to the first diaphragm, with a stationary part of the first drive unit being attached to the module housing, and the movable part of the second drive unit may be attached to the second diaphragm, with a stationary part of the second drive unit being attached to the module housing. For avoidance of any doubt, the stationary part (of each drive unit) may be attached to the module housing directly, or indirectly (e.g., the stationary part may be attached to a corresponding loudspeaker frame, in which case the stationary part may be viewed as being attached to the module housing indirectly, via said loudspeaker frame).

[0082] The first signal may be configured to cause movement of the movable part of the first drive unit movable (and thus the first movable assembly) relative to the stationary part of said first drive unit along the movement axis of the loudspeaker module so as to move the first diaphragm to produce sound. Similarly, the second signal may be configured to cause movement of the movable part of the second drive unit (and thus the first movable assembly) relative to the stationary part of said second drive unit along the movement axis of the loudspeaker module so as to move the second diaphragm to produce sound.

[0083] The terms “stationary” and “movable” are relative terms and in principle dependent on the particular frame of reference. In this context, the terms “stationary” and “movable” are intended to refer to a conventional frame of reference according to which the first and second diaphragms are considered to be movable, and in use to be moving, whereas other parts of the loudspeaker module (e.g. stationary with respect to the module housing) are considered to be stationary. As such those parts of the loudspeaker module which in use move with the first and / or second diaphragm, such as the movable part(s) of the first and / or second drive unit, are referred to as movable, while other parts of the loudspeaker module, which in use do not move with the first and / or second diaphragm (and which may be stationary with respect to an external apparatus to which the loudspeaker module is attached), are referred to as stationary, e.g. the stationary part(s) of the first and / or second drive unit. Those parts of the loudspeaker module which are movable, i.e., the first and / or second diaphragm and parts that in use move together with said diaphragm(s), may collectively be referred to as the corresponding movable assembly.

[0084] Each of the first and second drive units may (respectively) include a magnet unit and a voice coil. The magnet unit may be included in one of the stationary part of the drive unit and the movable part of the drive unit, with the voice coil being included in the other of the stationary part of the drive unit and the movable part of the drive unit. When each of the first and second drive units is (respectively) energised (e.g., by providing the first signal and second signal thereto, respectively), the movable part of the drive unit and the stationary part of the drive unit may magnetically interact to cause the movement of the movable part relative to the stationary part.

[0085] In some examples (referred to herein as “movable voice coil” examples), for each of the first and second drive units, the movable part may be the voice coil and the stationary part may be the magnet unit. In such examples, when said drive unit is energised, magnetic flux generated by the flow of electric current in the (movable) voice coil may interact with magnetic flux generated by the (stationary) magnet unit of said drive unit to cause the movement of said movable part, which is said voice coil, relative to said stationary part, which is said magnet unit.

[0086] In other examples (referred to herein as “movable magnet unit” examples), for each of the first and second drive units, the movable part may be the magnet unit and the stationary part may be the voice coil. In such examples, when said drive unit is energised, magnetic flux generated by the flow of electric current in the corresponding (stationary) voice coil may interact with magnetic flux generated by the corresponding (movable) magnet unit of said drive unit to cause the movement of said movable part, which is said magnet unit, relative to said stationary part, which is said voice coil.

[0087] Each magnet unit may include a permanent magnet and one or more flux guiding elements for guiding magnet flux produced by the permanent magnet in a magnetic circuit and across an air gap, wherein the corresponding voice coil is configured to be located in the air gap when the corresponding movable part of the respective drive unit is at rest.

[0088] Herein, a reference to the movable part of a drive unit being at rest, or a corresponding diaphragm being at rest, may be taken to correspond to a state in which said drive unit is not energised (e.g. an electric current is not being supplied to a voice coil of the drive unit) with the movable part of said drive unit and said diaphragm having been given time to reach a state of rest.

[0089] Each magnet unit may include at least two flux guiding elements. The at least two flux guiding elements may be configured to guide magnet flux produced by the permanent magnet across the air gap. The air gap may be formed between the at least two flux guiding elements.

[0090] The at least two flux guiding elements may include a washer and a yoke. The permanent magnet may be located between the washer and the yoke. The washer and the yoke may be arranged to define the air gap between the washer and the yoke.

[0091] The yoke may include a base and an upright portion extending from the base. In some examples, the yoke may be a U-yoke wherein the upright portion is an annular sidewall. In some examples, the yoke may be a T-yoke wherein the upright portion is a central post.

[0092] Each magnet unit may form a magnetic circuit. The magnetic circuit may provide a substantially closed circuit (or loop) for the magnetic flux. The magnetic circuit may have a comparatively high magnetic reluctance. For example, the magnetic reluctance of the magnetic circuit may be at least 2.5 x 10A6 [1 / H] or even 3 x 10A6 [1 / H], where “H” represents the physical unit “Henry”. The majority of the magnetic reluctance of the magnetic circuit may be attributed to the air gap. For example, the air gap may have a magnetic reluctance of at least 2 x 10A6 [1 / H],

[0093] By utilising a magnetic circuit with high magnetic reluctance, and particularly a high-reluctance air gap, it is possible to utilise comparatively small flux guiding elements. Thus, it is possible to reduce the weight of the magnet unit. This weight reduction of the magnet unit may more than compensate for the weight of a large voice coil, meaning that the comparatively high magnetic reluctance of the magnetic circuit enables designing of particularly lightweight loudspeakers. Further detail relating to high-reluctance magnetic circuits in the context of loudspeakers is described in PCT / EP2023 / 067426.

[0094] Each voice coil may have a first perimeter and a second perimeter. The first perimeter may be an outer perimeter or an inner perimeter of the voice coil, and the second perimeter may correspondingly be the inner perimeter or the outer perimeter.

[0095] The distance between the first perimeter and the second perimeter may be referred to as a winding thickness of the voice coil. Accordingly, the magnetic flux density permeating the voice coil may drop over the winding thickness of the voice coil as specified above.

[0096] If one or more of the voice coils is generally circular, the corresponding inner perimeter of the voice coil may have a corresponding inner diameter of the voice coil, and the corresponding outer perimeter of the voice coil may have a corresponding outer diameter of the voice coil. When one or more of the voice coils is located in the air gap, i.e., the movable part of the corresponding drive unit is at rest, a magnetic flux density at the first perimeter of said voice coil may be 50% or less of a magnetic flux density at the second perimeter of said voice coil.

[0097] By having a magnetic flux density at an outer perimeter of a voice coil as 50% (percent) or less of a magnetic flux density at an inner perimeter of the voice coil, the corresponding loudspeaker is able to have a magnet unit which is smaller or lighter, thereby facilitating a lighter overall loudspeaker (even if the coil is made heavier to compensate). Further detail regarding the advantages of such an arrangement are described for example in PCT / EP2023 / 067426.

[0098] In an arrangement in which the at least two flux guiding elements include a U-yoke, the magnetic flux density at the outer perimeter of the voice coil may be 50% or less of the magnetic flux density at the inner perimeter of the voice coil.

[0099] In an arrangement in which the at least two flux guiding elements include a T-yoke, the magnetic flux density at the inside perimeter of the corresponding voice coil may be 50% or less of the magnetic flux density at the outside perimeter of said voice coil.

[0100] An extent of a voice coil as measured in direction parallel to the movement axis (which may be referred to as the ‘height’ of the voice coil) may be in a range of 85% and 100% of the separation between the first and second landing surfaces of the corresponding loudspeaker frame as measured in direction parallel to the movement axis. This configuration may enable large linear displacement of the voice coil while effectively inhibit rocking motion.

[0101] In some embodiments, the movable part of each of the first and second drive units may be a respective voice coil. The stationary part of each of the first and second drive units may be a respective magnet unit.

[0102] In some embodiments, the movable part of each of the first and second drive units may be a respective magnet unit. The stationary part of each of the first and second drive units may be a respective voice coil.

[0103] In some embodiments, a mass of the movable part of each of the first and second drive units may (respectively) be at least 60% of a mass of the corresponding movable assembly (included in that drive unit).

[0104] By providing a relatively heavy drive unit (i.e., a drive unit where a movable part of said drive unit makes up at least 60% of the mass of the movable assembly), the resonant frequency of the acoustic volume of the loudspeaker module may be reduced relative to the expected resonant frequency of another loudspeaker module of the same size having a relatively lighter drive unit. Moreover, the forces generated by the drive unit may be larger, and so the loudspeaker module is able to produce louder bass sound for a smaller size (compared with more conventional loudspeaker modules). This allows the loudspeaker module to produce adequately loud bass sound for use in a typical environment (e.g., a car), despite any imposed size restrictions.

[0105] A ratio of the mass of the first and / or second movable assembly to the effective radiating area Sd of the corresponding diaphragm may be at least 5 kilograms per square-metre, optionally at least 7 kilograms per square-metre. The ratio of the mass of said movable assembly to the effective radiating area Sd of the corresponding diaphragm may be at most 20 kilograms per square-metre, optionally at most 15 kilograms per square-metre, optionally at most 12 kilograms per square-metre. For example, the ratio of the mass of the first and / or second movable assembly to the effective radiating area Sd of the corresponding diaphragm may be in a range of 5 to 20 kilograms per square-metre, optionally in a range of 5 to 15 kilograms per square-metre, optionally in a range of 7 to 12 kilograms per square-metre.

[0106] Such a ratio, particularly when combined with the mass of the movable part of the corresponding drive unit being at least 60%, more preferably 70%, of the mass of the respective movable assembly, may represent a compact yet heavy movable assembly. Such a movable assembly may in use generate large forces, but the present inventor has observed that such forces can be absorbed by the heavy (100kg+) body of an environment such as a vehicle, leading to good sound performance (despite the significant forces), or such forces can be cancelled out by having two loudspeakers in the module mounted back-to- back (see below).

[0107] The effective radiating area Sd is a concept known in the art. For a round diaphragm, the effective radiating area Sd is quantified using the half-roll-to-half-roll diameter and hence the suspension contributes to the effective radiating area Sd. Particularly for a loudspeaker with a comparatively small diaphragm, the contribution of the suspension to the effective radiating area Sd may not be negligible. For a diaphragm having a circular perimeter which is suspended from the module housing (e.g. via a loudspeaker frame) by a roll suspension having an outer diameter do (“d_o”) and an inner diameter di (“d_i”), the effective radiating surface area of that diaphragm may be estimated as (“Sd equals pi times the square of d over the square of 2”) where d is the half-diameter of the roll suspension, (d0+ di) / 2, (“d_o dj over 2”).

[0108] In other examples, the effective radiating surface area of the diaphragm Sd may be measured using known techniques, see e.g. “Dynamical Measurement of the Effective Radiating area SD”, Klippel GmbH (https: / / www.klippel.de / fileadmin / klippel / Files / Know How / Application Notes / AN 32 Effective Radiation Area.pdf).

[0109] In some examples, the loudspeaker module may define a total acoustic volume enclosed by the module housing and one or more components of the first and second loudspeakers. In some examples, the total acoustic volume may be formed of a single common acoustic volume (e.g., as discussed below). In other examples, the total acoustic volume may be formed of a first acoustic volume and a second acoustic volume (e.g., as discussed below).

[0110] In some embodiments, the loudspeaker module may define a common acoustic volume enclosed by the module housing and one or more components of the first and second loudspeakers.

[0111] In some embodiments, the loudspeaker module may define a first acoustic volume enclosed by the module housing and one or more components of the first loudspeaker, and a second acoustic volume enclosed by the module housing and one or more components of the second loudspeaker. The loudspeaker module may comprise a barrier separating the first and second acoustic volumes. The one or more components may include, for example, the first and / or second diaphragm, one or more of the one or more suspension elements of the first and / or second loudspeaker, the loudspeaker frame of the first and / or second loudspeaker, and / or one or more walls of the module housing.

[0112] By enclosing the total acoustic volume (i.e., either the common acoustic volume or the first and second acoustic volumes) with components of the loudspeaker module itself (e.g., the diaphragm(s) and the module housing), it is possible to design and accurately calibrate the loudspeaker module with a known, predictable acoustic volume(s). This means that the same loudspeaker module can be installed across a wide variety of environments, irrespective of any variations in the dimensions and / or geometry of the environments into which loudspeaker modules are installable.

[0113] Since the or each acoustic volume is enclosed by components of the loudspeaker module itself, the loudspeaker module may be installed in a “plug-and-play” type manner because the loudspeaker module’s configuration does not need to be specifically calibrated to the environment in which the loudspeaker is installed.

[0114] The total acoustic volume (i.e., either the common acoustic volume or the combination of the first and second acoustic volumes) may be in the range 0.25 litres to 8 litres, preferably in the range of 0.5 litres to 3 litres, and more preferably in the range of 0.5 litres to 1 .5 litres. Such volumes are relatively small for subwoofers, but the present inventors have found that they are adequate with a loudspeaker (or pair of loudspeakers) having a design as set out herein.

[0115] The loudspeaker module may be operable to cause displacement of a volume VD of air by the first and second diaphragm. The volume VD displaced by a diaphragm may be defined as the volume of air displaced by said diaphragm as it moves from its rest position in the air gap to a position of maximum displacement. As such, twice the volume VD is displaced by said diaphragm when the diaphragm is moved from nominal maximum displacement inwards to nominal maximum displacement outwards or vice versa, i.e., a peak-to-peak stroke.

[0116] The volume VD of air displaced by the first and second diaphragms (in combination) may be at least 0.05 times the total acoustic volume (5 percent of the total acoustic volume). This may result in a loudspeaker module having a comparatively large first and / or second diaphragm and enclosing a comparatively small total acoustic volume.

[0117] A ratio of the total acoustic volume over the combined effective radiating surfaces Sd of the first and second diaphragms may be in a range of 0.01 to 0.5 metres. This ratio of the total acoustic volume over Sd may provide an alternative parametrisation of a comparatively large diaphragm and a comparatively small total acoustic volume.

[0118] A ratio of the total acoustic volume VB over the effective radiating surfaces Sd of the first and second diaphragms may be in a range of 0.01 to 0.5 metres. This ratio of VB over Sd may provide an alternative parametrisation of a comparatively large diaphragm and a comparatively small acoustic volume.

[0119] In some embodiments, the barrier may be an acoustically reflective barrier. The acoustically reflective barrier may cause the first and second acoustic volumes to be entirely acoustically isolated from each other. The acoustically reflective barrier may be formed from any suitable non-transmissive material (e.g., the same material as an external wall of the module housing).

[0120] In some embodiments, the barrier may be an acoustically resistive barrier. The acoustically resistive barrier may have a specific airflow resistance of 10000 Pa s m-1or less, or 5000 or less Pa s nr1.

[0121] An acoustically resistive barrier can add mechanical damping to the system when the differences in the first and second signals cause parallel movement of the first and second diaphragms (as in Fig. 6b, discussed below), thereby helping to broaden and dampen out the impedance curve around the resonance frequency. This acoustic resistance creates friction when there is net air movement from one volume to the other and thus will influence the forces acting on the application only in dipole operation.

[0122] In some implementations the thickness of the acoustically resistive barrier can be increased up to a part or even the complete width of the loudspeaker module and the material of the acoustically resistive barrier can be chosen so that it also acts as a box filler increasing the apparent box volume for a monopole mode. Suitable materials include, for example, melamine foam, reticulated polyurethane, polyester foams, unprocessed organic wool, and others alike.

[0123] In some examples, the specific airflow resistance of the acoustically resistive barrier may be 7500 Pa s nr1or less, 5000 Pa s m-1or less, 2500 Pa s m-1or less, 1000 Pa s m-1or less, 500 Pa s m-1or less, or 250 Pa s m-1or less. Alternatively, the specific airflow resistance of the acoustically resistive barrier may be 250 Pa s m-1or more, 500 Pa s m-1or more, 1000 Pa s m-1or more, 2500 Pa s m-1or more, 5000 Pa s nr1or more, or 7500 Pa s m-1or more. Alternatively, the specific airflow resistance may be between 250 and 10 000 Pa s nr1, between 250 and 7500 Pa s nr1, between 250 and 5000 Pa s nr1, between 250 and 2500 Pa s nr1, between 250 and 1000 Pa s nr1, between 250 and 500 Pa s nr1, between 500 and 10 000 Pa s nr1, between 500 and 7500 Pa s nr1, between 500 and 5000 Pa s nr1, between 500 and 2500 Pa s nr1, between 500 and 1000 Pa s nr1, between 1000 and 10 000 Pa s nr1, between 1000 and 7500 Pa s nr1, between 1000 and 5000 Pa s nr1, between 1000 and 2500 Pa s nr1, between 2500 and 10 000 Pa s nr1, between 2500 and 5000 Pa s nr1, or between 5000 and 10 000 Pa s nr1.

[0124] In a particular example, the specific airflow resistance of the acoustically resistive barrier may be 2000 Pa s nr1.

[0125] Specific airflow resistance reflects the air resistance per surface area of a material and is dependent on a number of factors such as thickness and the choice of material (two pieces of material having different thicknesses may have the same specific airflow resistance). The specific airflow resistance of the acoustically resistive barrier may be measured in accordance with ISO 9053.

[0126] ISO 9053 sets out standard methods (Method A or Method B) for conducting airflow measurements to measure Airflow Resistance - R [P s m-3], Specific Airflow Resistance - Rs [Pa s nr1], and Airflow Resistivity - r [Pa s m-2] for a material sample having a given surface area (S) and thickness (t). Such measurements are discussed in more detail in WO 2020 / 234317 (under the heading “Airflow resistance measurements”). In some examples the acoustically resistive barrier may be formed from one or more porous materials.

[0127] The one or more porous materials may be any combination of: (i) non-woven materials such as paper of felted fabric, (ii) woven fabrics, (iii) compressed foams, and / or (iv) thermoplastic fibres.

[0128] The non-woven material may have a density of below 1 g cm'3.

[0129] The paper may have a density in the range of 0.5 g cm'3to 1 g cm'3. Additionally or alternatively, the paper may have a thickness of 0.2 to 2 mm.

[0130] The felted fabric may have a density in the range of 0.3 to 0.8 g cm'3, and / or a thickness in the range 1 to 10 mm.

[0131] The felted fabric may, for example, by wool felt or needle felt. The needle felt may comprise synthetic fibres.

[0132] The woven fabric may be baked (optionally with resins or other additives to increase strength) in a tooling to be shaped.

[0133] The thermoplastic fibres may be, for example, a melt blown thermoplastic.

[0134] In a third aspect, there is provided a loudspeaker assembly including a loudspeaker module according to the second aspect, and a signal unit.

[0135] In some examples, the signal unit may include one or more processors configured to execute logic and / or instructions that cause the one or more processors to cause the signal unit to provide the first and second signals to the first and second loudspeakers respectively.

[0136] The logic and / or instructions may be embodied in an appropriately configured computer program product and / or computer-readable medium.

[0137] In a fourth aspect, there may be provided a signal unit configured to provide the first signal to the first loudspeaker, and to provide the second signal to the second loudspeaker.

[0138] In some examples, the signal unit may be configured to generate the first and second signals.

[0139] For example, the signal unit may include one or more signal paths. The one or more signal paths may include a common signal path and one or more differential signal path. Various arrangements are possible, and some of which are discussed herein.

[0140] In a fifth aspect, there may be provided a method of providing first and second signals to a loudspeaker module to induce vibrations in an environment in which the loudspeaker module is installed. The method may comprise: providing, by the signal unit described herein, the first signal (e.g. as described herein) to the first loudspeaker of a loudspeaker module as described herein; and providing, by the signal unit described herein, the second signal (e.g. as described herein) to the second loudspeaker of the loudspeaker module. The first and second signals are different from each other so as to induce the vibration in the environment in which the loudspeaker module is installed. In a sixth aspect, there is provided a computer-readable medium comprising logic and / or instructions that, when executed by a signal unit is configured to cause the signal unit to: provide a first signal to a first loudspeaker of a loudspeaker module, to move a first movable assembly of the first loudspeaker in accordance with the first signal; and provide a second signal to a second loudspeaker of the loudspeaker module, to move a second movable assembly of the second loudspeaker in accordance with the second signal. The loudspeaker module may be as described elsewhere herein. Similarly, the signal unit is as described elsewhere herein.

[0141] In some embodiments, the logic and / or instructions may further cause the signal unit to generate the first and second signals.

[0142] There may also be provided a computer program product comprising logic and / or instructions to cause a processor mounted in or on the signal unit to carry out the methods described herein.

[0143] The order of the operations of the methods described herein is exemplary, but the steps may be carried out in any suitable order, or simultaneously where appropriate. Additionally, steps may be added or substituted in, or individual steps may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

[0144] Various functions and operations described herein can be implemented in hardware, software, or any combination thereof. If implemented in software, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media may include, for example, computer-readable storage media. Computer-readable storage media may include volatile or non-volatile, removable or non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. A computer-readable storage media can be any available storage media that may be accessed by a computer. By way of example, and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, flash memory or other memory devices, CD-ROM or other optical disc storage, magnetic disc storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0145] Moreover, the acts described herein may be embodied using computer-executable instructions that can be implemented by one or more processors and / or stored on a computer-readable medium or media. The computer-executable instructions can include routines, sub-routines; programs; threads of execution, and / or the like. Still further, results of acts of the methods can be stored in a computer-readable medium, displayed on a display device, and / or the like.

[0146] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. Variants should be considered to be included into the scope of the invention.

[0147] Summary of the Figures

[0148] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0149] Figure 1 shows an exemplary loudspeaker module installed in an environment.

[0150] Figure 2 shows an alternative exemplary loudspeaker module installed in an environment.

[0151] Figure 3 shows an alternative exemplary loudspeaker module installed in an environment.

[0152] Figure 4 shows an alternative exemplary loudspeaker module installed in an environment.

[0153] Figures 5a-d show exemplary signal units.

[0154] Figure 6a schematically illustrates the effect of applying the common signal portion of the first and second signals from an exemplary signal unit to an exemplary loudspeaker module.

[0155] Figure 6b schematically illustrates the effect of applying the different signal portions of the first and second signals from an exemplary signal unit to an exemplary loudspeaker module.

[0156] Figure 7 shows a method of operating a loudspeaker module to induce vibration in an environment in which the loudspeaker module is installed.

[0157] Figure 8 shows a method of operating a signal unit to induce vibration in an environment using a loudspeaker module installed in said environment.

[0158] Figures 9a-c show graphs illustrating the displacements of the first and second loudspeakers of various exemplary loudspeaker modules.

[0159] Figures 10a-c show graphs illustrating the operating performance parameters of various exemplary loudspeaker modules.

[0160] Figures 11a-b show graphs comparing the operating performance parameters of various exemplary loudspeaker modules with the operating performance of a conventional loudspeaker module.

[0161] Figures 12a-d show graphs comparing the operating performance parameters of various exemplary loudspeaker modules with the operating performance of a conventional vented loudspeaker module.

[0162] Detailed Description of the Invention

[0163] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0164] Figure 1 shows an exemplary loudspeaker module 100 installed in an environment. The loudspeaker module 100 comprises two back-to-back loudspeakers 200 and a module housing 102a, b. The module housing 102 may comprise a plurality of housing portions 102a, 102b. Alternatively, the module housing 102 may be defined by a single housing portion.

[0165] The first loudspeaker 200 comprises a first diaphragm 202 and a first drive unit 204. The first drive unit 204 is configured to drive the first diaphragm 202 to generate sound. The first loudspeaker 200 comprises a first movable assembly that includes the first diaphragm 202 and a movable part of the first drive unit 204.

[0166] The first drive unit 204 comprises a movable part and a stationary part. In this example, the movable part is a first voice coil 206 of the first drive unit 204, while the stationary part is a first magnetic unit 208 of the first drive unit 204. In other examples, the movable part may be the first magnetic unit, while the stationary part may be the first voice coil.

[0167] In this example, the mass of the movable part of the first drive unit 204 makes up at least 60% of the mass of the first movable assembly. Preferably, the mass of the movable part of the first drive unit 204 may make up 70%, 80%, or 90% of the mass of the first movable assembly.

[0168] In this example, the first loudspeaker 200 further comprises a first frame 210 defined by one or more frame elements, and one or more suspension elements 212, 214. The first diaphragm 202 is suspended from the module housing 102 via the first frame 210 by the suspension elements 212, 214. The one or more suspension elements 212, 214 include a roll suspension 212 and a damper 214. In this example, the roll suspension 212 attaches to the first loudspeaker frame 210 at a first landing surface on the first frame 210, the damper 214 attaches to the first loudspeaker frame 210 at a second landing surface on the first frame 210. The centre of gravity of the first voice coil 206 (i.e., the movable part of the first drive unit 204) has a position along a movement axis of the loudspeaker module 100 that is between the first landing surface and the second landing surface. This helps with stability against rocking motion of the first movable assembly.

[0169] The first diaphragm 202 comprises a front face facing away from the first drive unit 204.

[0170] The first loudspeaker 200 further comprises a first connector 216 (e.g. tag) mounted on or in the first loudspeaker 200 (e.g., on a surface of the first frame 210). The first connector 216 is configured to receive a first electrical signal from a signal unit (not shown) via a first signal path 220 (e.g. provided by a wire), and to transmit the first electrical signal to the first movable assembly via a first internal signal path 218 (e.g. provided by a wire), wherein the first movable assembly is configured to move in accordance with first electrical signal received from the signal unit. Although the first internal signal path 218 and the first signal path 220 are depicted as wired paths in Figure 1 , one or more of these paths may be configured as wireless paths (e.g., using inductive coils and / or antennae configured to operate as transmitters, receivers and / or transceivers).

[0171] The second loudspeaker 300 comprises a second diaphragm 302 and a second drive unit 304. The second drive unit 304 is configured to drive the second diaphragm 302 to generate sound. The second loudspeaker 300 comprises a second movable assembly that includes the second diaphragm 302 and a movable part of the second drive unit 304. The second drive unit 304 comprises a movable part and a stationary part. In this example, the movable part is a second voice coil 306 of the second drive unit 304, while the stationary part is a second magnetic unit 308 of the second drive unit 304. In other examples, the movable part may be the second magnetic unit, while the stationary part may be the second voice coil.

[0172] In this example, the mass of the movable part of the second drive unit 304 makes up at least 60% of the mass of the second movable assembly. Preferably, the mass of the movable part of the second drive unit 304 may make up 70%, 80%, or 90% of the mass of the second movable assembly.

[0173] In this example, the second loudspeaker 300 further comprises a second frame 310 defined by one or more frame elements, and one or more suspension elements 312, 314. The second diaphragm 302 is suspended from the module housing 102 via the second frame 310 by the suspension elements 312, 314. The one or more suspension elements 312, 314 include a roll suspension 312 and a damper 314. In this example, the roll suspension 312 attaches to the second loudspeaker frame 310 at a first landing surface on the second frame 310, the damper 314 attaches to the second loudspeaker frame 310 at a second landing surface on the second frame 310. The centre of gravity of the second voice coil 306 (i.e., the movable part of the second drive unit 304) has a position along a movement axis of the loudspeaker module 100 that is between the first landing surface and the second landing surface. This helps with stability against rocking motion of the second movable assembly.

[0174] The second diaphragm 302 comprises a front face facing away from the second drive unit 304. The first and second diaphragms 302, 304 face in opposite directions. The first and second loudspeakers 200, 300 may be identical (or substantially identical). When the first and second loudspeakers 200, 300 are identical, the loudspeaker module 100 may be considered to be in a balanced configuration such that when the first and second loudspeakers 200, 300 produce sound according to an identical instructing signal, the overall loudspeaker module 100 does not (substantially) induce vibrations in the environment in which the loudspeaker module 10Ois installed because the vibrations induced by the first loudspeaker 200 cancel out the vibrations induced by the second loudspeaker 300.

[0175] The second loudspeaker 300 further comprises a second connector 316 (e.g. tag) mounted on or in the second loudspeaker 300 (e.g., on a surface of the second frame 310). The second connector 316 is configured to receive a second electrical signal from a signal unit (not shown) via a second signal path 220 (e.g. provided by a wire), and to transmit the second electrical signal to the second movable assembly via a second internal signal path 318 (e.g. provided by a wire), wherein the second movable assembly is configured to move in accordance with the second electrical signal received from the signal unit. Although the second internal signal path 318 and the second signal path 320 are depicted as wired paths in Figure 1 , one or more of these paths may be configured as wireless paths (e.g., using inductive coils and / or antennae configured to operate as transmitters, receivers and / or transceivers).

[0176] The loudspeaker module 100 is attached, by one or more attachment means 104a, 104b, to an attaching section 110 of the environment. The attachment means 104 may be any suitable mechanism. For example, the one or more attachment means 104a, 104b may includes screws, clamps, hooks, adhesive and / or any other suitable mechanism for attaching (and, for example, securing) the loudspeaker module 100 to the attaching section 110 of the environment.

[0177] The attaching section 110 of the environment may function as a soundboard, such that any differences in the oscillations of the first and second movable assemblies induce vibrations in the attaching section 110, thereby inducing vibrations that are detectable (tactilely, haptically and / or acoustically) by an occupant of the environment. As discussed above, the environment may - in some cases - be a vehicle and the attaching section 110 may be a part of the vehicle cabin such as, for example, a door panel, a pillar, a floor panel and / or any other component of the cabin.

[0178] Figure 2 shows an alternative exemplary loudspeaker module 100 installed in an environment. The loudspeaker module 100 of Figure 2 differs from that of Figure 1 in the configuration of the movable assemblies of the loudspeaker module 100, and the geometry of the attachment of the loudspeaker module 100 to the attaching section 110 of the environment. In other examples and embodiments, the geometries of Figures 1 and 2 and the configurations of the movable assemblies may be altered, modified and interchanged in any suitable combination, in addition to those depicted in the accompanying figures.

[0179] In the context of the loudspeaker of Figure 2, the first drive unit 204 comprises a movable part and a stationary part. In this example, the movable part is a first magnetic coil 208 of the first drive unit 204, while the stationary part is a first voice coil 206 of the first drive unit 204. In other examples, the movable part may be the first magnetic unit, while the stationary part may be the first voice coil.

[0180] The mass of the movable part of the first drive unit 204 makes up at least 60% of the mass of the first movable assembly. Preferably, the mass of the movable part of the first drive unit 204 may make up 70%, 80%, or 90% of the mass of the first movable assembly.

[0181] Similarly, the second drive unit 304 comprises a movable part and a stationary part. In this example, the movable part is a second magnetic coil 308 of the second drive unit 304, while the stationary part is a second voice coil 306 of the second drive unit 304. In other examples, the movable part may be the second magnetic unit, while the stationary part may be the second voice coil.

[0182] The mass of the movable part of the second drive unit 304 makes up at least 60% of the mass of the second movable assembly. Preferably, the mass of the movable part of the second drive unit 304 may make up 70%, 80%, or 90% of the mass of the second movable assembly.

[0183] In the examples shown in Figures 1 and 2, the first and second diaphragms 202, 302, the first and second loudspeaker frames 210, 310 and the module housing 102 together define a (single) common acoustic volume (or ‘back volume’) of the loudspeaker module 100. The acoustic volume may be a fully enclosed volume - in other words, the first and second diaphragms 202, 302, first and second loudspeaker frames 210, 310 and module housing 102 define the boundary of the back volume of the loudspeaker module 100.

[0184] Figure 3 shows an alternative exemplary loudspeaker module 100 installed in an environment. The loudspeaker module 100 of Figure 3 differs from those of Figures 1 and 2 in that the module housing 102 comprises an acoustically reflective separation wall 106 separating the first and second loudspeakers 200, 300. The movable assemblies and geometries of the loudspeaker module 100 may correspond to any of those described above in relation to Figures 1 and 2, in any suitable combination.

[0185] The acoustically reflective separation wall 106 may be contiguous with the other parts / sections 102a, 102b of the module housing 102.

[0186] The separation wall 106 divides the loudspeaker module 100 into two acoustically isolated acoustic volumes. The first diaphragm 202, the first loudspeaker frame 210, the module housing 102 and the separation wall 106 together define a first acoustic volume (or ‘back volume’) of the first loudspeaker 200. The first acoustic volume may be a fully enclosed volume - in other words, the first diaphragm 202, first loudspeaker frame 210, module housing 102 and separation wall 106 define the boundary of the back volume of the first loudspeaker 200. Meanwhile, the second diaphragm 302, the second loudspeaker frame 310, the module housing 102 and the separation wall 106 together define a second acoustic volume (or ‘back volume’) of the second loudspeaker 300. The second acoustic volume may be a fully enclosed volume - in other words, the second diaphragm 302, second loudspeaker frame 310, module housing 102 and separation wall 106 define the boundary of the back volume of the second loudspeaker 300.

[0187] The separation wall 106 may be formed from the same material as the rest of the module housing 102.

[0188] Figure 4 shows an alternative exemplary loudspeaker module 100 installed in an environment. The loudspeaker module 100 of Figure 4 differs from that of Figure 3 in that the separation wall of the loudspeaker module 100 of Figure 4 is an acoustically resistive barrier 108 instead of an acoustically reflective separation wall 106. The movable assemblies and geometries of the loudspeaker module 100 may correspond to any of those described above in relation to Figures 1 and 2, in any suitable combination.

[0189] The acoustically resistive barrier 108 divides the loudspeaker module 100 into two acoustic volumes with a specific airflow resistance of up to 10 000 Ps s m-1inhibiting acoustic transmission between the first and second acoustic volumes. In other words, the acoustically resistive barrier 108 may have a specific airflow resistance of up to 10 000 Pa s nr1.

[0190] In some examples the acoustically resistive barrier may be formed from one or more porous materials.

[0191] The one or more porous materials may be any combination of: (i) non-woven materials such as paper of felted fabric, (ii) woven fabrics, (iii) compressed foams, and / or (iv) thermoplastic fibres.

[0192] The non-woven material may have a density of below 1 g cm'3.

[0193] The paper may have a density in the range of 0.5 g cm'3to 1 g cm'3. Additionally or alternatively, the paper may have a thickness of 0.2 to 2 mm.

[0194] The felted fabric may have a density in the range of 0.3 to 0.8 g cm'3, and / or a thickness in the range 1 to 10 mm.

[0195] The felted fabric may, for example, by wool felt or needle felt. The needle felt may comprise synthetic fibres. The woven fabric may be baked (optionally with resins or other additives to increase strength) in a tooling to be shaped.

[0196] The thermoplastic fibres may be, for example, a melt blown thermoplastic.

[0197] As mentioned above, the acoustically resistive barrier 108 divides the loudspeaker module 100 into two acoustic volumes. The first diaphragm 202, the first loudspeaker frame 210, the module housing 102 and the acoustically resistive barrier 108 together define a first acoustic volume (or ‘back volume’) of the first loudspeaker 200. The first acoustic volume may be a fully enclosed volume - in other words, the first diaphragm 202, first loudspeaker frame 210, module housing 102 and acoustically resistive barrier define the boundary of the back volume of the first loudspeaker 200. Meanwhile, the second diaphragm 302, the second loudspeaker frame 310, the module housing 102 and the acoustically resistive barrier 108 together define a second acoustic volume (or ‘back volume’) of the second loudspeaker 300. The second acoustic volume may be a fully enclosed volume - in other words, the second diaphragm 302, second loudspeaker frame 310, module housing 102 and acoustically resistive barrier 108 define the boundary of the back volume of the second loudspeaker 300.

[0198] Figures 5a to 5d show exemplary signal units 400a-d configured to provide signals to the first and second processors 216, 316 of the loudspeaker module 100. The signal provided to the first processor 216 is referred to herein as the first signal, and the signal provided to the second processor 316 is referred to herein as the second signal.

[0199] The signal unit 400a of Figure 5a comprises a common signal path 402a and a differential signal path 404a. The common signal path 402a is configured to transmit a precursor common signal therethrough that is used to define a common signal component of the first and second signals. Meanwhile, the differential signal path 404a is configured to transmit a precursor differential signal therethrough that is used to define first and second differential signal components of the first and second signals respectively.

[0200] The first signal is defined by combining the precursor common signal and the precursor differential signal, using for example a summing engine 406a or other suitable engine configured to superpose the precursor common and differential signals by, in this example, adding the precursor common and differential signals.

[0201] Meanwhile, the second signal is defined by combining the precursor common signal and the precursor differential signal, using for example a difference engine 408a or other suitable engine configured to superpose the precursor common and differential signals by, in this example, subtracting the precursor differential signal from the precursor common signal (or vice versa).

[0202] In some examples, the signal unit 400a may be configured to generate the precursor common and / or differential signals to be transmitted through the common and differential signal paths 402a, 404a respectively. In some examples, the signal unit 400a may be configured to receive the precursor common and / or differential signals from one or more separate signal generation units.

[0203] The signal unit 400a may comprise a first amplifier 410a configured to amplify the amplitude (e.g., the voltage and / or current amplitude) of the first signal to a desired, required, and / or predetermined level. The signal unit 400a may further comprise a second amplifier 412a configured to amplify the amplitude (e.g., the voltage and / or current amplitude) of the second signal to a desired, required, and / or predetermined level.

[0204] The signal unit 400a comprises a first output 414a arranged to convey the (optionally amplified) first signal to the first loudspeaker 200 (e.g., the first connector 216) of the loudspeaker module 100. In use, the first signal causes the first movable assembly to move in accordance with the first signal.

[0205] The signal unit 400a comprises a second output 416a arranged to convey the (optionally amplified) second signal to the second loudspeaker 300 (e.g., the second connector 316) of the loudspeaker module 100. In use, the second signal causes the second movable assembly to move in accordance with the second signal.

[0206] The first and signal signals, by virtue of the first and second differential signal components, are different from each other and, therefore the first and second movable assemblies are caused to move in a different, imbalanced manner. This imbalance in the motion of the first and second movable assemblies induces vibrations in the attaching section 110 of the environment in which the loudspeaker module 100 is installed.

[0207] The precursor common and differential signals may, for example, be adjustable by a user to selectively control the frequency, and / or amplitude of the vibrations induced in the environment.

[0208] As can be seen from Figure 5b, in alternative configurations, the first amplifier 410b may be arranged and configured to amplify the precursor common signal conveyed through the common signal path 402b, prior to the combinations of the precursor common and differential signals to define the first and second signals.

[0209] Similarly, the second amplifier may be arranged and configured to amplify the precursor common signal conveyed through the differential signal path 404b, prior to the combinations of the precursor common and differential signals to define the first and second signals.

[0210] In various implementations of the signal unit 400b, any of the components thereof may be arranged in any suitable order or configuration so as to provide different first and second signals to the loudspeaker module 100 described herein.

[0211] The signal unit 400c of Figure 5c comprises a common signal path 402c. The common signal path 402c is configured to transmit a precursor common signal therethrough that is used to define the common signal component of the first and second signals, and the first and second differential signal components of the first and second signals respectively.

[0212] The first and second signals are defined by branching the common signal path 402c into separate paths, and modulating the signal in each branch differently so as to generate different first and second signals.

[0213] In some examples, the signal unit 400c is configured to generate the precursor common signal to be transmitted through the common signal path 402c. In some examples, the signal unit 400c may be configured to receive the precursor common signal from a separate signal generation unit. The signal unit 400c may comprise a first amplifier 410c configured to amplify the amplitude (e.g., the voltage and / or current amplitude) of the precursor common signal conveyed through a first branch of the common signal path 402c to a desired, required, and / or predetermined level. In this way, the first signal may be defined.

[0214] The signal unit 400c may further comprise a second amplifier 412c configured to amplify the amplitude (e.g., the voltage and / or current amplitude) of the precursor common signal conveyed through a second branch of the common signal path 402c to a desired, required, and / or predetermined level that is different from the level achieved by the first amplifier 41 Oc. In this way, the second signal may be defined.

[0215] The signal unit 400c comprises a first output 414c arranged to convey the (optionally amplified) first signal to the first loudspeaker 200 (e.g., the first connector 216) of the loudspeaker module 100. In use, the first signal causes the first movable assembly to move in accordance with the first signal.

[0216] The signal unit 400c comprises a second output 416c arranged to convey the (optionally amplified) second signal to the second loudspeaker 300 (e.g., the second connector 316) of the loudspeaker module 100. In use, the second signal causes the second movable assembly to move in accordance with the second signal.

[0217] The first and signal signals, by virtue of the difference in amplitude between the first and second signals, are different from each other and, therefore the first and second movable assemblies are caused to move in a different, imbalanced manner. This imbalance in the motion of the first and second movable assemblies induces vibrations in the attaching section 110 of the environment in which the loudspeaker module 100 is installed.

[0218] The signal unit 400d of Figure 5d differs from that of Figure 5c, in that the signal unit 400d of Figure 5c comprises a single amplifier 41 Od arranged and configured to amplify the precursor common signal prior to the branching of the common signal path 402d.

[0219] The signal unit 400d further comprises a first modulation unit 418d configured to modulate the signal conveyed through the first branch of the common signal path 402d (e.g., by amplitude modulation, frequency modulation, and / or phase modulation) so as to define the first signal.

[0220] The signal unit 400d may further comprise a second modulation unit 420d configured to modulate the signal conveyed through the second branch of the common signal path 402d (e.g., by amplitude modulation, frequency modulation, and / or phase modulation) in a different way from the first modulation unit 418d so as to define the second signal.

[0221] The first and signal signals, by virtue of the difference in their modulations by the first and second modulation units 418d, 420d respectively are different from each other and, therefore the first and second movable assemblies are caused to move in a different, imbalanced manner. This imbalance in the motion of the first and second movable assemblies induces vibrations in the attaching section 110 of the environment in which the loudspeaker module 100 is installed. Figure 6a schematically illustrates the effect of applying the common signal components of the first and second signals from the (example) signal unit 400a to a loudspeaker module 100. The common signal portion of the first and second signals contributes to synchronous motion of the first and second movable assemblies - i.e., in-phase motion wherein the vibrations induced by the motion of the first movable assembly cancel out the vibrations induced by the motion of the second movable assembly.

[0222] Meanwhile, Figure 6b schematically illustrates the effect of applying the differential signal components of the first and second signals from the (example) signal unit 400a to a loudspeaker module 100. The differential signal portion of the first and second signals contributes to asynchronous motion of the first and second movable assemblies - i.e., out-of-phase motion wherein the vibrations induced by the motion of the first movable assembly compound with (i.e., add to) the vibrations induced by the motion of the second movable assembly.

[0223] Accordingly, by adjusting the relative proportion (e.g., in terms of amplitude - that is current and / or voltage amplitude) of the first and / or second signal that is defined by the differential signal component(s), the extent of vibration induced in the environment by the motions of the first and second movable assemblies can be controllably adjusted.

[0224] Figure 7 shows a method of operating a loudspeaker module 100 to induce vibration in an environment in which the loudspeaker module 100 is installed.

[0225] The method comprises, in an operation 502, receiving a first signal - for example, by the first processor 216 of the first loudspeaker 200, via the first signal path 220. The first signal is useable / executable to cause a first movable assembly of a first loudspeaker 200 to move in accordance with the signal (e.g., in accordance with the oscillating / varying amplitude - that is the current and / or voltage amplitude - of the first signal).

[0226] The method further comprises, in an operation 504, applying the first signal to the first loudspeaker 200 - for example, to the first movable assembly of the first loudspeaker 200, e.g., by the first processor 216 via the first internal signal path 218.

[0227] The method further comprises, in an operation 506, moving the first movable assembly in accordance with the first signal - e.g., in accordance with the oscillating / varying amplitude - that is the current and / or voltage amplitude - of the first signal.

[0228] The method further comprises, in an operation 508, receiving a second signal - for example, by the second processor 316 of the second loudspeaker 300, via the second signal path 320. The second signal is useable / executable to cause a second movable assembly of a second loudspeaker 300 to move in accordance with the signal (e.g., in accordance with the oscillating / varying amplitude - that is the current and / or voltage amplitude - of the second signal).

[0229] The method further comprises, in an operation 510, applying the second signal to the second loudspeaker 300 - for example, to the second movable assembly of the second loudspeaker 300, e.g., by the second processor 316 via the second internal signal path 318. The method further comprises, in an operation 512, moving the second movable assembly in accordance with the second signal - e.g., in accordance with the oscillating / varying amplitude - that is the current and / or voltage amplitude of the second signal.

[0230] The combined, and different (i.e., partly asynchronous), motions of the first and second movable assemblies induces, in operation 514, vibrations in the environment in which the loudspeaker module 100 is installed.

[0231] Figure 8 shows a method of operating a signal unit to induce vibrations in an environment using a loudspeaker module 100 installed in said environment.

[0232] The method comprises, in an operation 602, generating the common signal component. Operation 602 may be carried out by the signal unit 400, or by a separate signal generation unit.

[0233] The method further comprises, in an operation 604, generating the differential signal component. Operation 604 may be carried out by the signal unit, or by a separate signal generation unit.

[0234] The method further comprises, in an operation 606, combining the common signal component and the differential signal component (e.g., using the summing engines 406a) to define the first signal.

[0235] The method may further comprise, in an operation 608, amplifying the first signal (e.g., by using the first amplifier 410a to amplify the voltage and / or current amplitude of the first signal) to a desired, required, and / or predetermined level.

[0236] The method further comprises, in an operation 610a, providing the first signal to the loudspeaker module 100, e.g., to the first processor 216 of the first loudspeaker 200 via the first signal path 220.

[0237] The first signal is executable / useable by the first processor 216 to cause the first movable assembly to move in accordance with the first signal, as described above with reference to Figure 7.

[0238] The method further comprises, in an operation 612, combining the common signal component and the second differential component (e.g., using the difference engine 408a) to define the second signal.

[0239] The method may further comprise, in an operation 614, amplifying the second signal (e.g., by using the second amplifier 412a to amplify the voltage and / or current amplitude of the second signal) to a desired, required, and / or predetermined level.

[0240] The method further comprises, in an operation 616, providing the second signal to the loudspeaker module 100, e.g., to the second processor 316 of the second loudspeaker 300 via the second signal path 320.

[0241] The second signal is executable / useable by the second processor 316 to cause the second movable assembly to move in accordance with the second signal, as described above with reference to Figure 7.

[0242] Figures 9a-c show graphs illustrating displacements of the first and second loudspeakers of an exemplary loudspeaker module.

[0243] Figure 9a shows an example of a common part of a displacement between first and second loudspeakers, as induced by a common signal component of first and second signals. Meanwhile, Figure 9b shows an example of a different part of the displacements between first and second loudspeakers, as induced by a differential signal component of first and second signals.

[0244] Figure 9c shows the effect of the combination of the common and different parts of the displacement to induce different vibrations in the first and second loudspeakers. As can be seen from Figure 9c, the combination of the common and different parts of the displacement result in different motions of the first and second loudspeakers such that the first and second loudspeakers generate a common sound whilst simultaneously inducing vibrations in the environment in which the loudspeaker module is installed.

[0245] Figure 10 compares the simulated acoustic output, i.e., the sound pressure level (in the case of Figure 10a), the impedance resonance (in the case of Figure 10b) and the forces generated (in the case of Figure 10c), achievable using the loudspeaker modules 100 described herein.

[0246] In the context of Figure 10, each of the loudspeaker modules was simulated with a drive powered with a rms voltage of 2V, and a total power input of 1 W, balanced as 0.5 W into each of the first and second loudspeakers 200, 300.

[0247] In Figure 10, the thinner solid line corresponds to the use of any of the loudspeaker modules 100 of Figures 1 to 4 in a monopole mode - i.e., in a mode where the first and second signals are entirely defined by the common signal from the common signal path 402. The thicker solid line corresponds to the use of the “1 -volume” loudspeaker module 100 (of Figure 1 or 2) in a dipole mode - i.e., in a mode where the first and second signals are entirely defined by the differential signal from the differential signal path 404. The dashed line corresponds to the use of the “2-volume” loudspeaker module 100 (e.g., of Figure 3) in a dipole mode - i.e., in a mode where the first and second signals are entirely defined by the differential signal from the differential signal path 404. The dotted line corresponds to the use of the resistively barricaded loudspeaker module (e.g., of Figure 4) in a dipole mode - i.e., in a mode where the first and second signals are entirely defined by the differential signal from the differential signal path 404.

[0248] As can be seen from Figures 10a-c, while the monopole mode of all three implementations produces the same response, the sound pressure levels, impedance resonance frequencies, and forces generated across the various implementations of loudspeaker module 100 are different, and therefore a different balance of the common and differential signal components in the first and second signals may be required to achieve similar acoustic outputs.

[0249] Figure 11 show graphs comparing the simulated operating performance parameters of various exemplary loudspeaker modules with the operating performance of a conventional loudspeaker module having a 8- inch (20-cm) single drive design with an effective acoustic volume of 20 litres.

[0250] The conventional loudspeaker module was simulated with the following parameters: a DC voice coil resistance, Re, of 3.4 Q; a voice coil inductance, Le, of 3 mH; a drive factor, Bl, of 5 T m; a moving parts mass, Mmd of 35 g; a stiffness of the loudspeaker suspension system, Kms, of 1.25 N mm'1; a mechanical loss factor, Rms, of 1 N s nr1; an effective radiating area, Sd, of 211 cm2; and a resonant frequency, Fs, of 30 Hz. Figure 11 a compares the simulated forces generated using the above conventional loudspeaker design with the loudspeaker modules 100 described herein, while Figure 11 b compares the corresponding peak displacements a function of frequency for each implementation shown in Figure 1 1 a.

[0251] In Figure 11 , the thinner solid lines correspond to a simulation of the conventional loudspeaker described above, with a power input of 100 W. The thicker solid line corresponds to a 1 -volume loudspeaker module 100 (e.g., as shown in Figure 1 or 2) with a power input of 10 W into the dipole mode of the loudspeaker module. The dashed line corresponds to a 2-volume loudspeaker module 100 (e.g., as shown in Figure

[0252] 3), with a power input of 4 W into the dipole mode of the loudspeaker module 100. The dotted line corresponds to the user of the resistively barricaded loudspeaker module 100 (e.g., as shown in Figure

[0253] 4), with a power input of 4 W into the dipole mode of the loudspeaker module 100.

[0254] As can be seen from Figure 11 a, only 4 to 20 W is needed from the loudspeaker modules 100 described herein to generate similar maximum forces as are generated by full-power conventional loudspeaker modules. In other words, similar forces (and consequently the inducement of similar vibrations) can be achieved using the loudspeaker modules described herein by channelling only 4-20% of the power input into the differential signal component (or the dipole mode) of the loudspeaker module 100.

[0255] Meanwhile, Figure 11 b shows that, at bass frequencies (e.g., in the range 30 to 80 Hz), the amount of displacement of the diaphragm by operation of the dipole modes is comparatively minimal relative to the displacement of the diaphragm of the conventional loudspeaker. In other words, there is ample headroom to drive the loudspeakers 200, 300 of the loudspeaker module 100 using the common signal component (or the monopole mode) of the loudspeaker module 100.

[0256] Therefore, it may be possible to achieve similar (or even improved) acoustic performance compared to the conventional loudspeaker modules by directing e.g., 4-20% of the power input into the differential (dipole) mode to induce vibrations, while directing e.g., 80-96% of the power input into the common (monopole) mode to generate sound.

[0257] Figure 12 shows graphs comparing the simulated operating performance parameters of various exemplary loudspeaker modules with the operating performance of a conventional vented loudspeaker module having a 8-inch (20-cm) single drive design with an effective acoustic volume of 20 litres, and a bass reflex port having a diameter of 5 cm, and a length of 8 cm.

[0258] The conventional vented loudspeaker module was simulated with the following parameters: Re of 3.4 Q; Le of 3 mH; Bl of 7 Tm; Mmd of 35 g; Kmsof 1.25 N mm1; Rmsof 1 Ns nr1; Sd of 211 cm2; and Fs of 30 Hz.

[0259] Figure 12a compares the simulated forces generated using the above conventional loudspeaker design with the loudspeaker modules 100 described herein, while Figure 12b compares the corresponding peak displacements a function of frequency for each implementation shown in Figure 12a.

[0260] In Figure 12, the thinner solid lines correspond to a simulation of the conventional vented loudspeaker described above, with a power input of 100 W. The thicker solid line corresponds to a 1 -volume loudspeaker module 100 (e.g., as shown in Figure 1 or 2) with a power input of 10 W into the dipole mode of the loudspeaker module. The dashed line corresponds to a 2-volume loudspeaker module 100 (e.g., as shown in Figure 3), with a power input of 4 W into the dipole mode of the loudspeaker module 100. The dotted line corresponds to the user of the resistively barricaded loudspeaker module 100 (e.g., as shown in Figure 4), with a power input of 4 W into the dipole mode of the loudspeaker module 100.

[0261] As can be seen from Figure 12a, again only 4 to 20 W is needed from the loudspeaker modules 100 described herein to generate similar maximum forces as are generated by full-power conventional vented loudspeaker modules. In other words, similar forces (and consequently the inducement of similar vibrations) can be achieved using the loudspeaker modules described herein by channelling only 4-20% of the power input into the differential signal component (or the dipole mode) of the loudspeaker module 100.

[0262] Meanwhile, Figure 12b shows that, at bass frequencies, the amount of displacement of the diaphragm by operation of the dipole modes is comparatively minimal relative to the displacement of the diaphragm of the conventional loudspeaker. In other words, there is ample headroom to drive the loudspeakers 200, 300 of the loudspeaker module 100 using the common signal component (or the monopole mode) of the loudspeaker module 100.

[0263] Meanwhile, Figures 12c and 12d demonstrate how even less power needs to be directed to the differential signal component (the dipole mode) to achieve similar operating performances at lower frequencies (e.g., in the range of 30 to 60 Hz).

[0264] Figure 12c compares the simulated forces generated using the above conventional loudspeaker design with the 1-volume loudspeaker modules 100 described herein (e.g., in relation to Figures 1 and 2), while Figure 12d compares the corresponding peak displacements a function of frequency for each implementation shown in Figure 12c.

[0265] As above, the thinner solid lines correspond to a simulation of the conventional vented loudspeaker described above, with a power input of 100 W. The thicker solid line corresponds to a 1-volume loudspeaker module 100 (e.g., as shown in Figure 1 or 2), this time with a power input of 2 W into the dipole mode of the loudspeaker module 100.

[0266] As can be seen from Figure 12c, only 2 W is needed from the 1-volume loudspeaker modules 100 described herein to generate similar maximum forces as are generated by full-power conventional vented loudspeaker modules. In other words, similar forces (and consequently the inducement of similar vibrations) can be achieved using the loudspeaker modules described herein by channelling only 2% of the power input into the differential signal component (or the dipole mode) of the loudspeaker module 100.

[0267] Meanwhile, Figure 12b shows that, at bass frequencies, the amount of displacement of the diaphragm by operation of the dipole modes is comparatively minimal relative to the displacement of the diaphragm of the conventional loudspeaker. In other words, there is ample headroom to drive the loudspeakers 200, 300 of the loudspeaker module 100 using the common signal component (or the monopole mode) of the loudspeaker module 100. Therefore, it may be possible to achieve similar (or even improved) acoustic performance compared to the conventional loudspeaker modules by directing e.g., 4-20% of the power input into the differential (dipole) mode to induce vibrations, while directing e.g., 80-96% of the power input into the common (monopole) mode to generate sound. At lower frequencies, even less power input may be provided to the differential (dipole) mode - e.g., even 2% or less of the power input - and still achieve acoustic performances comparable to the conventional vented loudspeaker modules, whilst also inducing similar vibrations in the environment in which said loudspeaker module is installed.

[0268] The features disclosed in the foregoing description, or in the following claims, or in 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 obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0269] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0270] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0271] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0272] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0273] The use of the term “comprise” and “include” to refer to the inclusion of integers, steps and / or operations nonetheless also encompasses aspects, examples and embodiments that may be analogously described with the term “consist” in respect of those integers, steps and / or operations.

[0274] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%. The terms “a” (or “an”), as well as the terms “one or more” and “at least one” can be used interchangeably herein.

[0275] The term “and / or” as used herein is to be taken as specific disclosure of each of specified listed features or components with or without one or more of the others. Thus, the term “and / or” as used in a phrase such as “A, B and / or C” encompasses each of: A and B and C; A and B; A and C; B and C; A or B or C; A or C; A or C; B or C; only A; only B; and only C.

[0276] The term 'computer' is used herein to refer to any device with processing capability such that it can execute instructions. Those skilled in the art will realise that such processing capabilities are incorporated into many different devices and therefore the term 'computer' includes PCs, servers, mobile telephones, personal digital assistants and many other devices.

[0277] Those skilled in the art will realise that storage devices utilised to store program instructions can be distributed across a network. For example, a remote computer may store an example of the process described as software. A local or terminal computer may access the remote computer and download a part or all of the software to run the program. Alternatively, the local computer may download pieces of the software as needed, or execute some software instructions at the local terminal and some at the remote computer (or computer network). Those skilled in the art will also realise that by utilising conventional techniques known to those skilled in the art that all, or a portion of the software instructions may be carried out by a dedicated circuit, such as a DSP, programmable logic array, or the like.

[0278] References

[0279] A number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein.

[0280] • WO 2023 / 194163 A1

[0281] • PCT / EP2023 / 067426

[0282] • PCT / EP2023 / 073013

[0283] • GB2219587.9

[0284] • GB2302099.3

[0285] • GB2314913.1

[0286] • GB2314915.6

[0287] PCT / EP2023 / 067426

[0288] WO 2020 / 234317

Claims

Claims:1 . A method of operating a loudspeaker module to induce vibration in an environment in which the loudspeaker module is installed, wherein the loudspeaker module comprises: a module housing, and a first loudspeaker and a second loudspeaker attached to the module housing, wherein the first loudspeaker comprises: a first diaphragm, a first drive unit configured to move the first diaphragm, and a first movable assembly, wherein the first movable assembly includes the first diaphragm and a movable part of the first drive unit, wherein the second loudspeaker comprises: a second diaphragm, a second drive unit configured to move the second diaphragm, and a second movable assembly, wherein the second movable assembly includes the second diaphragm and a movable part of the second drive unit, and wherein front faces of the first and second diaphragms face in opposite directions; and wherein the method comprises: providing a first signal to the first loudspeaker to move the first movable assembly in accordance with the first signal; and providing a second signal to the second loudspeaker to move the second movable assembly in accordance with the second signal; wherein the second signal is different from the first signal so as to induce the vibration in the environment in which the loudspeaker module is installed.

2. The method according to claim 1 , wherein the method includes forming the first signal and second signal from a common signal component and a differential signal component.

3. The method according to claim 2, wherein an amplitude of the differential signal component is 50% or less of an amplitude of the common signal component.

4. The method according to any preceding claim, wherein the method includes: forming the first signal by adding the differential signal component to the common signal component; and forming the second signal by subtracting the differential signal component from the common signal component.

5. The method according to any of claims 2 to 4, wherein forming the first and second signal is carried out by a signal unit.

6. The method according to any preceding claim, wherein a difference between the first and second signals is adjustable.

7. The method according to claim 6, as dependent on any of claims 2 to 5, wherein the difference between the first and second signals is adjustable by adjusting the differential signal component relative to the common signal component.

8. The method according to claim 7, wherein adjusting the differential signal component relative to the common signal component includes adjusting the amplitude of the differential signal component relative to the amplitude common signal component.

9. The method according to any of claims 6 to 8, wherein the difference between the first and second signals is adjustable via a user interface.

10. The method according to any preceding claim, wherein the first and second signals have a frequency bandwidth, and wherein a difference between the first and second signal varies across the at least a portion of the bandwidth.11 . The method according to any preceding claim, wherein the first and second loudspeakers are substantially identical.

12. The method according to any preceding claim, each of the first and second drive units are configured to move the corresponding diaphragm respectively along a common axis.

13. The method according to any preceding claim, wherein the movable part of each of the first and second drive units is a respective voice coil, and wherein a stationary part of each of the first and second drive units is a respective magnet unit.

14. The method according to any of claims 1 to 12, wherein the movable part of each of the first and second drive units is a respective magnet unit, and wherein a stationary part of each of the first and second drive units is a respective voice coil.

15. The method according to any preceding claim, wherein a mass of the movable part of each of the first and second drive units is at least 60% of a mass of the corresponding movable assembly.

16. The method according to any preceding claim, wherein the environment is a part of a vehicle.

17. The method according to any preceding claim, wherein the loudspeaker module defines a common acoustic volume enclosed by the module housing and one or more components of the first and second loudspeakers.

18. The method according to any of claims 1 to 16, wherein the loudspeaker module defines a first acoustic volume enclosed by the module housing and one or more components of the first loudspeaker, and a second acoustic volume enclosed by the module housing and one or morecomponents of the second loudspeaker, wherein the loudspeaker module comprises a barrier separating the first and second acoustic volumes.

19. The method according to claim 18, wherein the barrier is an acoustically reflective barrier.

20. The method according to claim 18, wherein the barrier is an acoustically resistive barrier having a specific airflow resistance of 10 000 Pa s m-1or less.21 . A loudspeaker module for installation in an environment, the loudspeaker module comprising: a module housing; a first loudspeaker attached to the module housing and comprising a first diaphragm, a first drive unit configured to move the first diaphragm, and a first movable assembly, wherein the first movable assembly includes the first diaphragm and a movable part of the first drive unit and wherein the first loudspeaker is configured to receive a first signal and to move the first movable assembly in accordance with the first signal when the loudspeaker module is in use; and a second loudspeaker attached to the module housing and comprising a second diaphragm, a second drive unit configured to move the second diaphragm, and a second movable assembly, wherein the second movable assembly includes the second diaphragm and a movable part of the second drive unit and wherein the second loudspeaker is configured to receive a second signal and to move the second movable assembly in accordance with the second signal when the loudspeaker module is in use; wherein front faces of the first and second diaphragms face in opposite directions; and wherein the second signal provided to the second loudspeaker is different from the first signal provided to the first loudspeaker so as to induce the vibration in the environment in which the loudspeaker module is installed when the loudspeaker module is in use.

22. The loudspeaker module according to claim 21 , wherein the front faces of the first and second diaphragms respectively face away from the first and second drive units.

23. A computer-readable medium comprising logic and / or instructions that, when executed by a signal unit, cause the signal unit to: provide a first signal to a first loudspeaker of a loudspeaker module, to move a first movable assembly of the first loudspeaker in accordance with the first signal; and provide a second signal to a second loudspeaker of a loudspeaker module, to move a second movable assembly of the second loudspeaker in accordance with the second signal, wherein the loudspeaker module comprises: a module housing; the first loudspeaker attached to the module housing and comprising a first diaphragm, a first drive unit configured to move the first diaphragm, and the first movable assembly, wherein the first movable assembly includes the first diaphragm and a movable part of the first drive unit; andthe second loudspeaker attached to the module housing and comprising a second diaphragm, a second drive unit configured to move the second diaphragm, and the second movable assembly, wherein the second movable assembly includes the second diaphragm and a movable part of the second drive unit; wherein front faces of the first and second diaphragms face in opposite directions; and wherein the second signal is different from the first signal so as to induce the vibration in an environment in which the loudspeaker module is installed.

24. The computer-readable medium according to claim 23, wherein the logic and / or instructions, when executed by a signal unit, cause the signal unit to generate the first and second signals.

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