Noise suppression system, method and vehicle

Abstract

Noise cancellation system (100), comprising: Noise suppression parameter selection means (110) for receiving data (150) indicative of one or more operating conditions associated with a vehicle (500) and for selecting one or more noise suppression configuration parameters (160) based thereon; and Noise suppression means (120) for receiving one or more noise signals (135), wherein a vehicle interior noise suppression signal (145) is determined based on the one or more noise signals (135) according to the one or more configuration parameters (160), and wherein the vehicle interior noise suppression signal (145) is output for noise reduction in the vehicle (500); wherein the data (150) indicating one or more operating conditions associated with a vehicle (500) comprises a driving mode of the vehicle (500), and the noise suppression parameter selection means (110) are arranged to select the one or more noise suppression configuration parameters (160) depending on the driving mode of the vehicle (500), the driving mode of the vehicle (500) corresponding to a set of driving conditions, wherein the driving mode comprises one of a plurality of driving modes, and in each driving mode, each of one or more subsystems of the vehicle (500) is set to a most suitable functional mode under those conditions.

Description

TECHNICAL FIELDThe present disclosure relates to an apparatus and method for suppressing noise. Aspects of the invention relate to a noise cancellation system, to a method of generating a noise cancellation signal, and to a vehicle including a noise cancellation system.BACKGROUNDNoise, particularly within a vehicle, is annoying to the occupants of the vehicle. Noise inside the vehicle can, for example, deflect a driver of the vehicle and be tedious for the vehicle occupants. Mechanical measures have been used to reduce noise within vehicles. However, such measures are bulky and heavy. The use of active noise suppression has been proposed. Active noise cancellation includes generating a sound wave to cancel a sound wave so that the environment becomes calmer for a listener.The document US 2012 / 0 269 358 A1 relates to an active noise control. US 2015 / 0 356 965 A1 relates to an active noise reduction device, an instrument with this device and a method for active noise reduction. US 5 758 311 A relates to an active vibration / noise control system for vehicles. US 5 493 616 A relates to an in-vehicle noise reduction system.It is an object of embodiments of the invention to at least alleviate one or more problems of the prior art.SUMMARY OF THE INVENTIONAspects and embodiments of the invention provide a noise cancellation system, a method of generating a noise cancellation signal, and a vehicle comprising a noise cancellation system as claimed in the appended claims.According to one aspect of the present invention, there is provided a noise cancellation system comprising noise cancellation parameter selection means for receiving data indicative of one or more operating conditions associated with a vehicle and for selecting one or more noise cancellation configuration parameters based thereon. Advantageously, the noise is processed in a predetermined manner tailored to the operating conditions associated with the vehicle to effectively reduce the noise.According to another aspect of the invention, there is provided noise cancelling means for receiving one or more noise signals and determining an in-vehicle noise cancelling signal from the one or more noise signals according to the one or more configuration parameters and outputting the in-vehicle noise cancelling signal to reduce noise in the vehicle. Advantageously, noise from the vehicle interior is customized to the configuration parameters.According to one aspect of the present invention, there is provided a noise cancellation system comprising noise cancellation parameter selection means for receiving data indicative of one or more operating conditions associated with a vehicle and for selecting one or more noise cancellation configuration parameters based thereon, and noise cancellation means for receiving one or more noise signals, wherein an in-vehicle noise cancellation signal is determined based on the one or more noise signals after the one or more configuration parameters, and the in-vehicle noise cancellation signal is output for noise reduction in the vehicle.According to an aspect of the present invention, there is provided a system as described above, wherein the parameter selection means for suppressing noise is a noise configuration unit. In some embodiments, the noise configuration unit includes one or more electronic processors having one or more electrical inputs for receiving the data indicative of the one or more operating conditions. The noise suppression means may be a noise suppression unit arranged to receive one or more of the noise signals and determine the vehicle interior noise suppression signal. The noise suppression unit may include one or more electronic processors. The noise configuration unit and noise suppression unit may each include an electronic storage device electrically coupled to the electronic processor and having executable instructions stored therein.Optionally, the noise cancelling parameter selection means is arranged to determine a characteristic of a surface on which the vehicle is travelling in use. The noise suppression parameter selection means may select the one or more noise suppression configuration parameters based on the characteristic. Advantageously, one deals with an influence on the noise associated with the surface on which the vehicle is travelling, which noise is perceived inside the vehicle.Optionally, the property of the surface is a roughness of the surface. The noise cancelling parameter selection means may be arranged to determine the roughness of the surface from at least one of the noise signals received from a noise detection device connected to the vehicle. The noise suppression parameter selection means may be arranged to select the one or more noise suppression configuration parameters based on the roughness of the surface. One advantageously concerns the noise associated with the roughness of the surface.Optionally, the noise detection device is connected to a suspension of the vehicle. Advantageously, the noise associated with the suspension of the vehicle is dealt with.Optionally, the noise cancelling parameter selection means is arranged to determine the surface property from either an amplitude or spectral composition of the noise signal or both. Advantageously, this allows an effective property determination.The data indicative of the one or more operating conditions includes a driving mode of the vehicle. The or each driving mode corresponds to a particular driving condition or set of particular driving conditions, and in each mode, each one or more subsystems of the vehicle is set to a most suitable function mode under those conditions. A control system for controlling the one or more subsystems of a vehicle in dependence on the driving mode is disclosed in U.S. Pat. No. U.S. Pat. No. 7,349,776 B2 and PCT Application No. WO2013 / 004764A1 by the applicant, the content of which is hereby incorporated by reference.In some embodiments, the noise suppression parameter selection means may be arranged to select the one or more noise suppression configuration parameters based on the driving mode of the vehicle. One advantageously deals with the noise associated with a particular driving condition or a set of particular driving conditions. For example, in some driving conditions, it may be desirable to minimize the noise associated therewith. Alternatively, in other driving conditions, it may be desirable for the noise associated therewith to be reduced to or held at a level audible to a user of the vehicle. Advantageously, the noise associated therewith assists the user in driving the vehicle by providing audible feedback under certain conditions, such as off road driving.In some embodiments, the amount to which the associated noise is reduced or suppressed may be selected by a user of the vehicle. Advantageously, this allows the user to maintain at least some acoustic feedback, if desired or if necessary.In an embodiment of the invention, the data indicative of the one or more operating conditions comprises data indicative of a speed of the vehicle. Advantageously, the noise associated with the speed of the vehicle is dealt with.Optionally, the data indicative of the one or more operating conditions includes data indicative of a speed of either a drive motor connected to the vehicle or a motor, or both. One advantageously concerns the noise associated with the speed of the drive motor and the motor or both.Optionally, the data indicative of the one or more operating conditions includes data indicative of an operating mode of a propulsion engine and / or engine connected to the vehicle. The noise suppression parameter selection means may be arranged to select the one or more noise suppression configuration parameters depending on whether the drive motor / motor is operated in the hybrid mode, for example. Advantageously, hybrid vehicles deal with the noise associated with different operating modes of a drive motor and / or engine.Optionally, the data indicative of the one or more operating conditions includes data indicative of the operating state of the one or more subsystems of the vehicle. The one or more subsystems of the vehicle may include an anti-lock brake system (ABS) or traction control. Advantageously, the noise associated with the one or more subsystems of the vehicle is addressed.Optionally, the data indicative of the one or more operating conditions includes data indicative of a gear selection. One advantageously deals with the noise associated with different gear selections. In some embodiments, data indicative of a gear selection includes an indication that no gear is selected - i.e., the vehicle is in an idling or sliding state. One advantageously deals with the noise associated with such conditions.Optionally, the data indicative of the one or more operating conditions includes data indicative of a steering angle of the vehicle. The steering angle may include a rotational angle of a steering wheel or steerable wheel of the vehicle. One advantageously deals with the noise associated with different steering angles.Optionally, the data indicative of the one or more operating conditions includes data indicative of an orientation of the vehicle. In some embodiments, the data indicative of the orientation of the vehicle may include a yaw angle, roll angle, and / or pitch angle.Optionally, the data indicative of the one or more operating conditions includes data indicative of activation of one or more windshield wipers connected to the vehicle. Optionally, the data indicative of the one or more operating conditions includes data indicative of a speed of one or more windshield wipers connected to the vehicle. Advantageously, the activation of windshield wipers indicates that the vehicle is operating under wet conditions, which may affect the interior noise of the vehicle.Optionally, the data indicative of the one or more operating conditions includes data indicative of one or more of an ambient temperature and a configuration of a vehicle suspension. The ambient temperature may be either an interior temperature or an exterior temperature of the vehicle, or both. Advantageously, the temperature influences a flight time of the sound, while the vehicle suspension influences a transmission of noise-which causes oscillations. Optionally, the configuration of the vehicle suspension may include an operating state of a suspension pump.Optionally, the data indicative of the one or more operating conditions includes data indicative of the temperature of one or more tires of the vehicle. The sound associated with different tire temperatures is advantageously concerned, which can change the frequency content of the sound in the vehicle interior.Optionally, the data indicative of the one or more operating conditions includes data indicative of a position of one or more opening elements of the vehicle. The one or more opening elements may be configured to open, close, and / or adjust the size of one or more openings of the vehicle. The one or more openings may include a window or roof of the vehicle that may be opened, such as a sunroof or convertible roof. Additionally or alternatively, the one or more opening elements may comprise a blind or cover for a window or windshield of the vehicle. Advantageously, the sound associated with different positions of the one or more elements and / or different sizes of the openings of the vehicle is addressed, which may change the frequency or amplitude content of the sound.Optionally, the data indicative of the one or more operating conditions includes data indicative of the constituent parts of one or more components of the vehicle. For example, the one or more components may include a glass pane or windshield. In such embodiments, the data indicative of the one or more operating conditions includes the type of glass from which the or each component is formed.Optionally, the data indicative of the one or more operating conditions includes data indicative of a position of an aerodynamic device of the vehicle. The aerodynamic device may include a spoiler, such as an extendable spoiler. Advantageously, one deals with the noise associated with the position of the aerodynamic device.Optionally, the data indicative of the one or more operating conditions includes data indicative of the operating state of a heating, ventilation, and climate (HVAC) system of the vehicle. The operating condition may include a speed of one or more fans that are part of the HVAC system. The noise associated with the operation of the HVAC system is advantageously addressed.Optionally, the data indicative of the one or more operating conditions includes data indicative of an ambient noise level in the exterior environment of the vehicle. Advantageously, one deals with the ambient noise.Optionally, the data indicative of the one or more operating conditions includes data indicative of a load on a tow bar or tow point of the vehicle. One advantageously concerns the noise associated with a trailer load.Optionally, the data indicative of the one or more operating conditions includes data indicative of a tank level of the vehicle. The data indicative of the fuel level may include a fuel gauge position. One advantageously deals with the noise associated with different tank levels.In one embodiment of the invention, the noise cancelling parameter selection means is arranged to operably execute a pattern matching algorithm for selecting the one or more noise cancelling configuration parameters based on similarity to one or more predetermined operating conditions. The noise suppression is advantageously matched to a predefined configuration.Optionally, the pattern matching algorithm is one of a k-means or nearest neighbor algorithm.Optionally, the one or more noise cancellation configuration parameters are associated with at least one function for determining the vehicle interior noise cancellation signal based on the one or more noise signals. The parameters that can be associated with the at least one function are one or more filter coefficients.Optionally, the function is a speaker transfer function (STF) that displays a transfer function from one or more audio output devices.Optionally, the function is a reference transfer function (RTF) indicating a transfer function from one or more noise detection means.According to one aspect of the present invention, there is provided a method of generating a noise cancellation signal comprising receiving data indicative of one or more operating conditions associated with a vehicle. The method may include selecting one or more noise cancellation configuration parameters based on the received data. The method may include receiving one or more sound signals that generate an in-vehicle sound cancellation signal based on the one or more sound signals according to the one or more configuration parameters, and outputting the in-vehicle sound cancellation signal for noise reduction in the vehicle.In an embodiment of the invention, the method includes determining a characteristic of a surface on which the vehicle is travelling and selecting the one or more noise cancellation configuration parameters based on the characteristic.In an embodiment of the invention, the characteristic of the surface is a roughness of the surface, and the method comprises determining the roughness of the surface based on at least one of the noise signals received from a noise detector connected to the vehicle, and selecting the one or more noise suppression configuration parameters based on the roughness of the surface.Optionally, the noise detection device is connected to a suspension of the vehicle.Optionally, the method comprises determining the property of the surface from one or both of an amplitude and a spectral composition of the noise signal.The data indicative of the one or more operating conditions includes a driving mode of the vehicle. The or each driving mode corresponds to a particular driving condition or set of particular driving conditions, and in each mode, each of one or more subsystems of the vehicle is set to a most suitable function mode under those conditions.In some embodiments, the method includes selecting the one or more noise cancellation configuration parameters depending on the driving mode of the vehicle. One advantageously deals with the noise associated with a particular driving condition or a set of particular driving conditions. For example, in some driving conditions, it may be desirable to minimize the noise associated therewith. Alternatively, in other driving conditions, it may be desirable for the noise associated therewith to be reduced to or held at a level audible to a user of the vehicle. Advantageously, the noise associated therewith assists the user in driving the vehicle by providing audible feedback under certain conditions, such as off road driving.In some embodiments, the amount to which the associated noise is reduced or suppressed is selected by a user of the vehicle. Advantageously, this allows the user to maintain at least some acoustic feedback, if desired or if necessary.Optionally, the data indicative of the one or more operating conditions includes data indicative of a speed of the vehicle, a speed of either a propulsion motor or a motor, or both, an activation or speed of one or more windshield wipers connected to the vehicle, and / or one or more of an ambient temperature and a configuration of a vehicle suspension. The ambient temperature may be either an interior temperature or an exterior temperature of the vehicle, or both. Optionally, the configuration of the vehicle suspension may include an operating state of a suspension pump of the vehicle.Optionally, the data indicative of the one or more operating conditions includes data indicative of an operating mode of a propulsion engine and / or engine connected to the vehicle. The method may include selecting the one or more noise cancellation configuration parameters depending on whether the engine / motor is operating in hybrid mode, for example. Advantageously, hybrid vehicles deal with the noise associated with different operating modes of a drive motor and / or engine.Optionally, the data indicative of the one or more operating conditions includes data indicative of the operating state of the one or more subsystems of the vehicle. The one or more subsystems of the vehicle may include an anti-lock brake system (ABS) or traction control. Advantageously, the noise associated with the one or more subsystems of the vehicle is addressed.Optionally, the data indicative of the one or more operating conditions includes data indicative of a gear selection. One advantageously deals with the noise associated with different gear selections. In some embodiments, data indicative of a gear selection includes an indication that no gear is selected - i.e., the vehicle is in an idling or sliding state. One advantageously deals with the noise associated with such conditions.Optionally, the data indicative of the one or more operating conditions includes data indicative of a steering angle of the vehicle. The steering angle may include a rotational angle of a steering wheel or steerable wheel of the vehicle. One advantageously deals with the noise associated with different steering angles.Optionally, the data indicative of the one or more operating conditions includes data indicative of an orientation of the vehicle. In some embodiments, the data indicative of the orientation of the vehicle includes a yaw angle, roll angle, and / or pitch angle.Optionally, the data indicative of the one or more operating conditions includes data indicative of the temperature of one or more tires of the vehicle. The sound associated with different tire temperatures is advantageously concerned, which can change the frequency content of the sound in the vehicle interior.Optionally, the data indicative of the one or more operating conditions includes data indicative of a position of one or more opening elements of the vehicle. The one or more opening elements may be configured to open, close, and / or adjust the size of one or more openings of the vehicle. The one or more openings may include a window or roof of the vehicle that may be opened, such as a sunroof or convertible roof. Additionally or alternatively, the one or more opening elements may comprise a blind or cover for a window or windshield of the vehicle. Advantageously, one deals with the sound associated with different positions of the one or more aperture elements and / or different sizes of the apertures, which may change the frequency or amplitude content of the sound.Optionally, the data indicative of the one or more operating conditions includes data indicative of the constituent parts of one or more components of the vehicle. For example, the one or more components may include, for example, a glass pane or windshield. In such embodiments, the data indicative of the one or more operating conditions includes the type of glass from which the or each component is formed.Optionally, the data indicative of the one or more operating conditions includes data indicative of a position of an aerodynamic device of the vehicle. The aerodynamic device may include a spoiler, such as an extendable spoiler. Advantageously, one deals with the noise associated with the position of the aerodynamic device.Optionally, the data indicative of the one or more operating conditions includes data indicative of the operating state of a heating, ventilation, and climate (HVAC) system of the vehicle. The operating condition may include a speed of one or more fans that are part of the HVAC system. The noise associated with the operation of the HVAC system is advantageously addressed.Optionally, the data indicative of the one or more operating conditions includes data indicative of an ambient noise level in the vehicle environment. Advantageously, one deals with the ambient noise.Optionally, the data indicative of the one or more operating conditions includes data indicative of a load on a tow bar or tow point of the vehicle. One advantageously concerns the noise associated with a trailer load.Optionally, the data indicative of the one or more operating conditions includes data indicative of a tank level of the vehicle. The data indicative of the fuel level may include a fuel gauge position. One advantageously deals with the noise associated with different tank levels.In one embodiment of the invention, the method includes operably executing a pattern matching algorithm for selecting the one or more noise cancellation configuration parameters based on similarity to one or more predetermined operating conditions.Optionally, the method comprises associating the noise cancellation configuration parameters with at least one function for determining the noise cancellation signal based on the one or more noise signals.Optionally, the configuration parameters associated with the at least one function are one or more filter coefficients.In an embodiment of the invention, the function is one of a loudspeaker transfer function (STF) indicating a transfer function of one or more audio output devices and a reference transfer function (RTF) indicating a transfer function of one or more sound sensing means.According to an aspect of the invention, there is provided a vehicle comprising a noise suppression system according to an aspect of the invention.According to one aspect of the invention, there is provided computer software which, when executed by a computer, is arranged to carry out a method according to one aspect of the invention. The computer software is optionally stored on a computer readable medium. The software may be tangibly stored on the computer readable medium.Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives presented in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular their individual features, may be taken into account independently of each other or in any combination. This means that all embodiments and / or features of any embodiment may be combined in any manner and / or combination, provided that these features are not incompatible. The applicant reserves the right to alter any originally filed claim or to submit any new claim accordingly, including the right to alter any originally filed claim to depend on and / or integrate any feature of any other claim, although not originally claimed in this manner.BRIEF DESCRIPTION OF THE DRAWINGSOne or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 shows a system according to an embodiment of the invention; FIG. 2 shows a system according to an embodiment of the invention arranged in use; FIG. 3 schematically shows a system according to an embodiment of the invention; FIG. 4 shows a method according to an embodiment of the invention; and FIG. 5 shows a vehicle comprising a system according to an embodiment of the invention.DETAILED DESCRIPTIONFIG. 1 shows a noise suppression system 100 according to an embodiment of the invention. The system 100 includes noise cancelling means 120 and noise cancelling parameter selection means 110. The noise cancelling parameter selection means 110 is arranged to select one or more configuration parameters of the noise cancelling means 120 from one or more inputs as will be explained. In use, the noise cancelling parameter selection means 110 is arranged to determine one or more operating characteristics and to correspondingly select the configuration parameters of the noise cancelling means 120 to improve noise cancelling. In some embodiments, the one or more configuration parameters are associated with at least one transfer function associated with the noise cancellation system, as will be explained.The noise suppression parameter selection means 110 may be provided in the form of a processor that operatively executes software instructions to determine the one or more configuration parameters of the noise suppression means 120. Hereinafter, the noise suppressing parameter selection means 110 will be referred to as a noise configuration unit 110. Likewise, the noise suppression means 120 may be one or more processing devices arranged in use to determine at least one noise suppression signal 145 for noise reduction and provide the noise suppression signal 145 to one or more audio output means 141, 142, as will be explained. The audio output means 141, 142 may be one or more acoustic devices such as speakers 141, 142. The at least one noise cancellation signal 145 may be determined from the at least one noise signal 135 input from one or more noise input means 131, 132 as one or more reference signals. The one or more sound input means 131, 132 may be one or more vibroacoustic detection devices such as microphones or accelerometers 131, 132.Hereinafter, the noise suppression means 120 will be referred to as a noise suppression unit 120.The noise suppression system 100 may be used within a vehicle such as a land vehicle, although it will be appreciated that other types of vehicles are provided, such as aircraft and watercraft.Noise is a significant problem in the interior of the vehicle. A noisy environment of the vehicle is detrimental to the vehicle occupant(s), such as the passenger(s)'s consumption and comfort. The vehicle occupant(s) may be tired, for example, by the noise load in the vehicle interior. Further, a feature of a premium vehicle is that an environment within the vehicle interior is relatively quiet. Noise suppression may be used to reduce the noise experienced by one or more vehicle occupants. However, it has been found that noise suppression may not be effective over a wide operating range of the vehicle. The noise suppression system 100 may be arranged to selectively reduce noise arising from one or more predetermined sources, such as, but not limited to, road noise, wind noise, engine noise, etc. The noise suppression system 100 is arranged to adapt to one or more operating conditions of the vehicle.The noise suppression unit 120 is arranged to reduce noise within one or more noise suppression regions 10 in the vehicle interior. In one embodiment, substantially the entire vehicle interior is set as the noise suppression region 10. That is, only one noise suppressing region 10 may be provided in the vehicle interior. However, in some embodiments, a plurality of noise suppression areas are located in the vehicle interior. In this case, the noise suppression unit 120 may provide at least one specific noise suppression signal 145 to the audio output means 141, 142 within the respective noise suppression range. That is, various noise suppression signals may be provided to each noise suppression region. The noise suppression unit 120 may use different configuration parameters to determine the noise suppression signals for each noise suppression region. Each of the one or more interior noise suppression regions 10 may be disposed proximate an expected position of at least one vehicle occupant. For example, a first noise suppression region may be disposed proximal to a designated position of a driver of the vehicle. The designated position may correspond to a head position of the occupant. A second and possibly further noise suppression region(s) may each be disposed with respect to each potential further vehicle occupant, and in some embodiments, corresponding to an expected head position of each occupant. For example, a second noise suppression region may be disposed proximal to a passenger designated position of the vehicle.One or more noise signals 135 received from the one or more noise input means 131, 132 may be provided to the noise configuration unit 110 as the parameter selection signal 155 in some embodiments. In some embodiments, the noise configuration unit 110 is arranged to determine the noise cancellation configuration parameters based, at least in part, on the parameter selection signal 155. In some embodiments, the noise configuration unit 110 is arranged to receive operational data 150 indicative of operational characteristics of a vehicle to which the system 100 is connected. In some embodiments, the noise configuration unit 110 is arranged to determine the noise suppression configuration parameters based, at least in part, on the operating data 150. Data indicative of one or more noise cancellation configuration parameters 160 is provided from the noise configuration unit 110 to the noise cancellation unit 120.FIG. 2 illustrates an embodiment of the noise suppression system 100 arranged in use. The noise suppression system 100 is shown connected to a first noise input means 131 and a first audio output means 141. However, it is to be understood that this is not limiting and that the system 100 may be connected to more than one input means 131 and output means 141, respectively. Furthermore, it is not necessary that the number of input means 131 is equal to the number of output means 141. The first audio output means 141 may be connected to a first noise suppression area 200.As noted above, the noise input means 131 is at least one acoustic sensing device for providing the reference signal. In the example shown in FIG. 2, the sound input means 131 is an accelerometer 131. The accelerometer 131 is disposed on a vehicle component to determine and output data indicative of vibrations of the vehicle structure of a portion of the vehicle in use. In one embodiment, the accelerometer 131 is disposed on a suspension component of the vehicle, such as a wheel hub carrier of the vehicle, although it is understood that the accelerometer 131 may be otherwise mounted on the vehicle, and particularly on the suspension thereof. The accelerometer 131 is arranged to output, in use, a signal 135 indicative of vibration applied thereto and thus noise caused in the vehicle interior. The signal 135 is received by the noise cancellation system 100. As will be appreciated, vibrations applied to the accelerometer 131 mounted on the suspension of the vehicle are typical of at least one road surface on which the vehicle is travelling and may also be typical of a travel speed of the vehicle on the road surface.The noise suppression system 100 is arranged to output a noise suppression signal 145 to the audio output means 141, wherein the audio output means 141 outputs a corresponding acoustic signal. The audio output means 141, in one embodiment, is an audio output device such as a loudspeaker disposed within an occupant compartment of the vehicle, i.e., within a vehicle interior. The speaker 141 may be disposed, for example, within a dashboard, body trim, or door trim of the vehicle, although it is understood that these embodiments are not exhaustive. In one embodiment, the speaker 141 is disposed within a head restraint of the vehicle proximate an expected head position of an occupant. The speaker 141 may be located within a noise suppression region indicated by a dotted line indicated by 200 in FIG. 2.As illustrated, in the noise suppression system 100, the first noise input means 131 and the first audio output means 141 form an open loop. In some embodiments, a closed loop is formed by including one or more feedback means 210. The feedback means 210 provides a feedback signal 215 to the noise cancellation system 100. The feedback signal indicates the noise within the noise suppression region 200. Therefore, the feedback signal 215 may be an error signal indicative of residual noise present within the noise suppression region 200. The error signal may correspond to a sum of the sounds within the sound suppression region 200, the acoustic signal may correspond to the sound suppression signal 145, and in some circumstances, a designated audio signal within the sound suppression region, such as audio output by an entertainment system of the vehicle, such as music. It should be appreciated that the noise cancellation signal 145 may have a minus sign that is to cancel the noise within the noise cancellation region 200. The feedback means 210 may be at least one microphone disposed within the noise suppression region 200. In one embodiment, for example, the feedback means 210 may be a microphone disposed within the passenger compartment of the vehicle. The microphone 210 may be disposed within a head restraint of the vehicle. In a closed loop, the determined noise suppression configuration parameters may provide a starting point, the feedback signal from the feedback means 210 being used to optimize this starting point.FIG. 3 schematically illustrates a structure of the noise configuration unit 110 and the noise suppression unit 120 according to an embodiment of the present invention.The noise configuration unit 110 includes a processing unit 310 for operably executing an algorithm for determining the one or more configuration parameters of the noise suppression unit 120. The processing unit 310 includes one or more processing devices for operably executing an algorithm for determining the configuration parameters. The one or more determined configuration parameter(s) are provided to the noise configuration unit 120 as parameter 305.The processing unit 310 is communicatively connected to an interface 320 to receive acoustic data 325 from one or more sound input means 131, such as one or more acoustic sensing devices, which as discussed above may be microphones or accelerometers or a combination thereof arranged to provide reference signals. Each acoustic sensing device 131 provides respective acoustic data 325 to the processing unit 310 via the interface 320. The acoustic data 325 provided by each acoustic sensing device 131 may correspond to a predetermined portion of the vehicle, such as a respective noise suppression region 200. The interface 320 may receive data from the noise input means via a dedicated audio data communication bus.The processing unit 310 may be communicatively connected to an interface 330 for receiving operational data 335 indicative of operational characteristics of the vehicle, in some embodiments. As discussed below, the interface 330 may be arranged to communicate with one or more systems of the vehicle to determine an operating state of each system and / or operating information about the vehicle. The operating features may be, for example, information about one or more settings or the state of the vehicle or a number of vehicle occupants. The interface 330 may be communicatively coupled to a communication bus of the vehicle to receive the operational data 335 from the one or more systems of the vehicle. For example, the interface may communicate with a seatbelt monitoring system of the vehicle to determine the number of vehicle occupants from a number of seatbelts being seatbelted. Alternatively, the number of occupants may be determined by a system that uses one or more interior cameras of the vehicle. The interface 330 may receive exhaust data indicative of an exhaust setting or configuration of the vehicle, such as data indicative of a position of an exhaust control valve. The exhaust control valve may be operated by an engine management system of the vehicle based on, for example, engine speed or load. The interface 330 may receive operating data 335 from other systems of the vehicle, such as a suspension control system, a transmission control system, etc., as will be appreciated.The one or more configuration parameters 305 of the noise suppression unit 120 are determined by the processing unit 310 of the noise configuration unit 110 from either or both of the received acoustic data 325 and the operational data 335. The configuration parameters 305 may be a plurality of configuration parameters 305 provided to the noise suppression unit 120, as will be explained. The configuration parameters may be associated with one or more transfer functions of the noise suppression unit 120. In particular, the configuration parameters may be one or more coefficients of the one or more transfer functions of the noise suppression unit 120. In one embodiment, the configuration parameters 305 may include a plurality of coefficients associated with at least one transfer function of the noise suppression unit 120.The noise suppression unit 110 includes a parameter data storage 340. The parameter data storage 340 stores data representing a plurality of configurations of the noise suppression unit 110. The processing unit 310 is arranged to select one of the configurations according to the data 325, 335 received via one or both interfaces 320, 330. That is, either corresponding to acoustic data 325 or operating data 335 or both. The data representing the plurality of configurations of the noise configuration unit 110 may include a plurality of data sets for configuring the noise suppression unit 120 into a corresponding configuration. The plurality of data sets may be a plurality of tables of configuration data, although it is understood that embodiments of the invention are not limited in this respect. In one embodiment, the parameter data store stores a plurality of sets of the one or more coefficients of the one or more transfer functions of the noise suppression unit 120 selected according to one or both of the acoustic data 325 and the operational data 335.In one embodiment, the noise suppression unit 120 includes a first data store 360 storing at least one reference transfer function (RTF) and a second data store 370 storing at least one speaker transfer function (STF). Although shown as first and second data stores 360, 370, it is understood that the data stores may be collapsed, i.e., the noise suppression unit 120 may comprise only one data store that includes both RTF and STF. The noise suppression unit 120 further comprises a processing unit 350 communicatively connected to the data stores 360, 370. The processing unit 350 includes one or more processing devices for operably executing an algorithm for determining the noise cancellation signal output via an interface 355. The algorithm is based on the one or more configuration parameters received from the sound configuration unit 110.The RTF represents a transfer function from one or more sources of reference data to one or more noise suppression regions. In particular, the RTF may represent a transfer function that indicates a transformation of the reference information as provided by the one or more acoustic sensing devices 131, 132. The RTF may indicate a noise transformation from the acoustic sensing devices 131, 132 to one or more noise suppression areas 200. A corresponding RTF may be provided for each suppression region 200. The RTF may include a plurality of coefficients. The RTF may represent use for configuring a filter. The RTF represents how noise inside the vehicle is caused by acoustic signals at the acoustic sensing devices. For example, the RTF may focus on acoustic signals in one or more frequency ranges, resulting in sounds within the noise suppression region 200.The STF represents a transfer function from the one or more audio output devices 141, 142. The STF may represent a transfer function from an audio output device to a noise suppression area 200. A corresponding STF may be provided for each suppression region 200. Each STF may be configured according to a respective number of vehicle occupants. That is, since the number of occupants may affect a signal output through a speaker received in the noise suppression region 200, corresponding STFs may be provided for either the number of occupants or seating positions of those occupants, or both, within the vehicle. The STF may include a plurality of coefficients. For example, the STF may focus on acoustic signals in one or more frequency ranges, resulting in sounds within the noise suppression region 200.The configuration parameters 305 received at the noise suppression unit 120 may configure either at least one RTF or STF or both according to the operating conditions of the vehicle. In one embodiment, a plurality of RTF and / or STF are stored within the noise suppression unit 120 and selected according to the configuration parameters 305 received from the noise configuration unit 110.In some embodiments, the noise configuration unit 120 is operable based on a plurality of filter coefficients to determine the noise cancellation signal 145. Each acoustic device 141, 142 may be associated with one or more filter coefficients. In particular, each acoustic device may be associated with a plurality of filter coefficients, each filter coefficient corresponding to a respective reference acoustic pattern. The filter coefficients may be represented as w km[ i], which denotes a filter coefficient for driving an acoustic device m from a k-th reference acoustic pattern.In some embodiments, the configuration parameters 305 received at the noise suppression unit 120 configure use of one or more noise input means 131, 132. In particular, one or more noise input means 131, 132 may be selectively activated for use in determining one or more noise cancellation signals according to the configuration parameters. For example, when passing another vehicle, in particular a large vehicle, which may cause a large amount of noise, one or more noise input means 131, 132 may be activated or deactivated in a suitable manner in order to optimize the noise suppression within the vehicle. That is, noise signals from a subset of noise input means 131, 132 may be used to determine one or more noise cancellation signals according to the configuration parameters.The noise configuration unit 110 is arranged to determine one or more operating characteristics of the vehicle.As explained above, the noise configuration unit 110 is arranged to receive acoustic data 325. For example, the sound configuration unit 110 may receive input from at least one acoustic sensing device, such as the accelerometer 131, indicating corresponding accelerations applied thereto. The noise configuration unit 110 is arranged to determine, based on the acoustic data 325, a characteristic of a surface on which the vehicle is operably driving. The feature may be a roughness of the coating of the surface on which the vehicle is driving. The surface roughness may be determined from either an amplitude or spectral composition, or both, of a signal output by the one or more acoustic sensing devices 131, 132. The noise configuration unit 110 may process the received acoustic data 325, such as by applying a Fourier transform to the received acoustic data 325 to determine one or more frequency components of the signal from which the surface roughness may be determined.As discussed above, in some embodiments, the noise configuration unit 110 is further communicatively coupled to a communication bus of the vehicle to receive operational data 335 indicative of the operational characteristics of the communication bus. The communication bus may be, for example, a CAN bus or an Internet Protocol (IP)-based communication bus of the vehicle, such as an Ethernet-based bus, although it is understood that embodiments of the invention are not limited in this respect.An operating characteristic may be vehicle speed. The vehicle speed may be conveniently combined with information indicative of the surface roughness, as discussed above, in some embodiments. In some embodiments, one or more coefficients associated with the RTF may be selected based on surface roughness and vehicle speed.An operating feature may be a driving mode of the vehicle. As discussed above, a driving mode may correspond to a particular driving condition or set of particular driving conditions, and in each mode, each of the one or more subsystems of the vehicle is set to a most suitable function mode under those conditions. In some embodiments, one or more coefficients associated with the RTF may be selected based on the driving mode.Additionally or alternatively, the one or more coefficients associated with the RTF may be based on a request or selection of the amount of noise associated therewith to be suppressed / reduced. The request or selection may be made by a user of the vehicle.An operating characteristic may be the engine speed and / or motor speed, i.e., the motor speed of the vehicle. The drive motor and / or motor speed may cause vehicle vibrations that may be detected by the acoustic sensing devices 131, i.e., represented in the acoustic data 325. The determination of the drive motor speed and / or motor speed advantageously allows the adaptation of the noise suppression unit 120 in order to reduce an influence of the oscillations induced by the drive motor and / or motor. In some embodiments, one or more coefficients associated with the RTF may be selected based on the drive motor and / or motor speed.An operating feature may be an operating mode of a prime mover and / or motor connected to the vehicle, such as a hybrid mode. In some embodiments, one or more coefficients associated with the RTF may be selected based on the mode of operation.An operating feature may be the operating state of one or more subsystems of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the operating state of one or more subsystems of the vehicle.An operating feature may be a steering angle of the vehicle, for example, a turning angle of a steering wheel or steerable wheel of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the steering angle.An operating feature may be an orientation of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the orientation of the vehicle.An operational feature may be windshield wiper activation of the vehicle, such as activation of windshield wipers of a windshield of the vehicle. Additionally or alternatively, an operating characteristic may be a windshield wiper speed of the vehicle. The windshield wiper activation / speed may indicate that the vehicle is driving on a wet surface, even without a vehicle rain sensor being activated by rainfall. Noise may be generated on the vehicle traveling on such a wet surface due to water or other liquid and / or dirt impinging on the underbody or other surfaces of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on wiper activation and / or wiper speed.An operating characteristic may be a temperature of one or more tires of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the tire temperature.An operational feature may be the position of one or more opening elements of the vehicle and / or the size of one or more openings of the vehicle. The one or more opening elements may be configured to open or close. Such opening elements may be a cover for a window, a windshield or a sliding roof of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the position of the one or more aperture elements and / or the size of the one or more apertures.An operational feature may be the position of an aerodynamic device of the vehicle. The aerodynamic device may include a spoiler, such as an extendable spoiler.An operating feature may be the constituent parts of one or more components of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the components of the one or more components.An operating characteristic may be an ambient noise level of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the ambient noise level.An operating feature may be a load on a tow bar or tow point of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the present load.An operating feature may be a tank level of the vehicle. In some embodiments, one or more coefficients associated with the RTF may be selected based on the tank level.In other embodiments, the operational feature may indicate a position of one or more seats of the vehicle, vehicle occupancy, a seating position of vehicle occupants, and / or a temperature such as ambient temperature. The ambient temperature may be an interior temperature, i.e., in the vehicle interior, such as in the passenger cabin, or an exterior ambient temperature of the vehicle, i.e., the exterior temperature. The vehicle occupancy may indicate a number of vehicle occupants and the seating position indicating which of a plurality of positions in the vehicle interior, such as seats, are occupied. The temperature may affect a travel time of the sound perceived in the vehicle interior.The received operational data 335 may also indicate either a terrain setting of the vehicle or a suspension setting of the vehicle, or both. In some vehicles, in particular vehicles designed for off-road driving, the vehicle (or a unit thereof) may be arranged to determine the off-road which the vehicle crosses. Alternatively, the terrain may be manually selected by a driver of the vehicle. The terrain may be determined or selected from a variety of predetermined types such as sand / desert, mud, grass, asphalt, gravel, etc. Alternatively or additionally, in some vehicles, the suspension may be configured either automatically or manually by the driver. For example, the suspension may be configured in one of a plurality of extension or height conditions, such as low, medium (normal) or high, and / or in a strength condition of a plurality of strength conditions, such as hard or sport, normal, comfort, etc. The data may indicate the operating characteristics of either the terrain setting and / or the suspension setting, or both.As noted above, the noise configuration unit 110 operably executes an algorithm for determining the configuration parameters of the noise suppression unit 120. The algorithm is arranged to select one of the configurations stored in the parameter data store 340 corresponding to the data 325, 335 received via one or both interfaces 320, 330. That is, either or both of the acoustic data and the operating data. For example, in one embodiment, the noise configuration unit 110 may select configuration data 305 according to one or more of a number of vehicle occupants, a seating position of the occupant(s) in the vehicle, and a surface roughness of a surface on which the vehicle is traveling.The algorithm executed by the processing unit 310 of the noise configuration unit 110 may include a pattern matching algorithm for selecting the one or more configuration parameters based on similarity to previously measured operational characteristics. The pattern matching algorithm may be either a k-means or nearest neighbor algorithm. As will be appreciated, the k-means algorithm determines one of the k-clusters corresponding to n observations, the n observations being the operational characteristics input to the noise configuration unit 110. Each cluster corresponds to a respective configuration of the noise suppression unit 120. In another embodiment, the noise configuration unit 110 may comprise either a neural network or support vector machine (support vector machine) or both to select configuration parameters for providing optimal noise suppression performance according to a predetermined cost function. In some embodiments, principal component analysis may be used to reduce dimensionality of data indicative of the operational characteristics.FIG. 4 illustrates a method 400 according to an embodiment of the invention. Method 400 is a method for generating a noise cancellation signal 145. The method 400 may be performed by the noise suppression system according to an embodiment of the invention as described above.In step 410, one or more inputs are received. The inputs may include acoustic data 325 that indicates audio signals such as sounds at one or more acoustic sensing devices 131, 132. In some embodiments, the inputs may include operational data 335 indicative of operational characteristics of the vehicle.In step 420, one or more operating characteristics of the vehicle are determined based on the one or more received inputs. In one embodiment, the operational features indicate the surface on which the vehicle is traveling, such as surface roughness. The operational characteristics may be determined by processing the one or more received inputs by a predetermined algorithm.In step 430, a configuration of the noise suppression unit 120 is selected based on the determination made in step 420. The configuration may be selected from a plurality of predetermined configurations. Each configuration may be represented by one or more configuration parameters provided from the noise configuration unit 110 to the noise suppression unit 120. The one or more configuration parameters may be coefficients associated with one or more transfer functions. The configuration parameters may configure one or more filters according to the determined operating characteristics.In step 440, a noise cancellation signal 145 is generated based on the configuration selected in step 430. The noise cancellation signal 145 is generated from the output of the acoustic sensing devices 131, 132. In some embodiments, the noise cancellation signal may be further generated in a closed loop based on the feedback signal 215 to the noise cancellation system 100 indicating noise within the noise cancellation region 200.FIG. 5 illustrates a vehicle 500 according to an embodiment of the invention. The vehicle includes a noise cancellation system as described above with reference to the previous figures.Advantageously, embodiments of the invention adapt a configuration of the noise cancellation system to operating characteristics such that a noise cancellation signal responds to changes in operating environment. Thus, noise suppression can be improved.It should be understood that embodiments of the present invention may be implemented in the form of hardware, software, or a combination of hardware and software. Such software may be stored in the form of volatile or non-volatile storage, such as a storage device such as a ROM, whether erasable or rewritable or not, or in the form of memory such as RAM, memory chips, apparatus or integrated circuits, or on an optically or magnetically readable medium such as a CD, DVD, magnetic disk or magnetic tape. It should be understood that the storage devices and storage media are embodiments of machine readable memory suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method according to any preceding claim, and a machine readable memory for storing said program. Further, embodiments of the present invention may be electronically transmitted over any medium, such as a communication signal transmitted over a wired or wireless connection, and embodiments include these in any suitable manner.All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) and / or all steps of a method or process thus disclosed may be combined in any combination, except combinations in which at least some such features and / or steps are mutually exclusive.Any feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose unless expressly stated otherwise. Thus, unless expressly stated otherwise, each disclosed feature is only one example of a generic series of equivalent or similar features.The invention is not limited to the details of any of the preceding embodiments. The invention extends to any novel feature, or to any novel combination of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel step or combination of the steps of a method or process thus disclosed. The claims should not be construed to cover only the above embodiments, but rather any embodiments that fall within the scope of the claims.

Claims

A noise cancellation system (100) comprising: noise cancellation parameter selection means (110) for receiving data (150) indicative of one or more operating conditions associated with a vehicle (500) and for selecting one or more noise cancellation configuration parameters (160) based thereon; and noise cancellation means (120) for receiving one or more noise signals (135), wherein a vehicle interior noise cancellation signal (145) is determined based on the one or more noise signals (135) according to the one or more configuration parameters (160), and wherein the vehicle interior noise cancellation signal (145) is output in the vehicle (500) for noise reduction; wherein the data (150) indicating one or more operating conditions associated with a vehicle (500) comprises a driving mode of the vehicle (500) and the noise cancelling parameter selection means (110) are arranged to select the one or more noise cancelling configuration parameters (160) depending on the driving mode of the vehicle (500), wherein the driving mode of the vehicle (500) corresponds to a set of driving conditions, wherein the driving mode comprises one of a plurality of driving modes and in each driving mode each of one or more subsystems of the vehicle (500) is set to a most suitable function mode under these conditions.The noise suppression system (100) of claim 1, wherein the noise suppression parameter selection means (110) is arranged to determine a characteristic of a surface on which the vehicle (500) travels in use and to select the one or more noise suppression configuration parameters (160) based on the characteristic.The noise cancellation system (100) of claim 2, wherein the characteristic of the surface is a roughness of the surface and the noise cancellation parameter selection means (110) is arranged to: determine the roughness of the surface based on at least one of the noise signals (135) received from a noise detection device connected to the vehicle (500); and select the one or more noise cancellation configuration parameters based on the roughness of the surface.The noise suppression system (100) of claim 3, wherein the noise detector is connected to a suspension of the vehicle (500).The noise suppression system (100) of any preceding claim, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of a speed of the vehicle (500).The noise suppression system (100) of any preceding claim, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of a speed of either a drive motor connected to the vehicle (500) or a motor or both.The noise suppression system (100) of any preceding claim, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of activation of one or more windshield wipers connected to the vehicle (500).The noise suppression system (100) of any preceding claim, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of one or more of an ambient temperature and a configuration of a vehicle suspension; optionally, the ambient temperature is one of an interior temperature and an exterior temperature of the vehicle (500), or both.A noise suppression system (100) according to any preceding claim, wherein the noise suppression parameter selection means (110) is arranged to operably execute a pattern comparison algorithm for selecting the one or more noise suppression configuration parameters based on similarity to one or more predetermined operating conditions.The noise suppression system (100) of claim 9, wherein the pattern matching algorithm is one of a k-means or nearest neighbor algorithm.The noise cancellation system (100) of any preceding claim, wherein the one or more noise cancellation configuration parameters are associated with at least one function for determining the vehicle interior noise cancellation signal (145) from the one or more noise signals.The noise suppression system (100) of claim 11, wherein the parameters associated with the at least one function are one or more filter coefficients.The noise suppression system (100) of claim 11 or 12, wherein the function is a speaker transfer function (STF) that indicates a transfer function of one or more audio output devices.The noise suppression system (100) of claim 11 or 12, wherein the function is a reference transfer function (RTF) indicative of a transfer function of one or more noise detectors.A method (400) of generating a noise cancellation signal, comprising: receiving data (150) indicative of one or more operating conditions associated with a vehicle (500); selecting one or more noise cancellation configuration parameters (160) from the received data; receiving one or more noise signals (135); generating a vehicle interior noise cancellation signal (145) from the one or more noise signals after the one or more configuration parameters; and outputting the vehicle interior noise cancellation signal (145) for noise reduction in the vehicle (500); wherein the data (150) indicative of one or more operating conditions associated with a vehicle (500) comprises a driving mode of the vehicle (500), and the method (400) further comprises: selecting the one or more noise suppression configuration parameters depending on the driving mode of the vehicle (500), wherein the driving mode of the vehicle (500) corresponds to a set of driving conditions; wherein the driving mode comprises one of a plurality of driving modes, and in each driving mode, each of one or more subsystems of the vehicle (500) is set to a most suitable function mode under these conditions.The method (400) of claim 15, comprising: determining a characteristic of a surface on which the vehicle (500) is travelling; and selecting the one or more noise cancellation configuration parameters based on the characteristic.The method (400) of claim 16, wherein the property of the surface is a surface roughness, and the method (400) comprises: determining the roughness of the surface based on at least one of the noise signals (135) received from a noise detector connected to the vehicle (500); and selecting the one or more noise cancellation configuration parameters based on the roughness of the surface.The method (400) of claim 17, wherein the noise detector is connected to a suspension of the vehicle (500).The method (400) of any of claims 15 to 18, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of a speed of the vehicle (500).The method (400) of any of claims 15 to 19, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of a speed of either a drive motor connected to the vehicle (500) or a motor or both.The method (400) of any of claims 15 to 20, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of activation of one or more windshield wipers connected to the vehicle (500).The method (400) of any of claims 15 to 21, wherein the data (150) indicative of the one or more operating conditions comprises data (150) indicative of one or more of an ambient temperature and a configuration of a vehicle suspension; optionally, the ambient temperature is one of an interior temperature and an exterior temperature of the vehicle (500), or both.The method (400) of any of claims 15 to 22, wherein the noise cancellation parameter selection means (110) is arranged to operably execute a pattern matching algorithm for selecting the one or more noise cancellation configuration parameters based on similarity to one or more predetermined operating conditions.The method (400) of any of claims 15 to 23, wherein the one or more noise cancellation configuration parameters are associated with at least one function for determining the noise cancellation signal based on the one or more noise signals.The method (400) of claim 24, wherein the noise cancellation configuration parameters (160) associated with the at least one function are one or more filter coefficients.The method (400) of claim 24 or 25, wherein the function is one of a speaker transfer function (STF) indicating a transfer function of one or more audio output devices and a reference transfer function (RTF) indicating a transfer function of one or more sound sensing devices.A vehicle (500) comprising a noise suppression system (100) according to any one of claims 1 to 14.Computer software, which when executed on a computer is arranged to carry out a method (400) according to any of claims 15 to 26; optionally the computer software is stored on a computer readable medium.

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