GB2589802A

GB2589802A - Earphone system

Info

Publication number: GB2589802A
Application number: GB2101907.0A
Authority: GB
Inventors: Darlington Paul
Original assignee: Soundchip SA
Current assignee: Soundchip SA
Priority date: 2014-12-01
Filing date: 2015-11-24
Publication date: 2021-06-09
Anticipated expiration: 2035-11-24
Also published as: GB2534662A; GB201520733D0; GB2534662B; GB201421291D0; GB2589802B; GB202101907D0

Abstract

The earphone system 100 comprises an active earphone driver module 30 operable in a plurality of configurations with filters 32, 33, 34 and a controller 110 operative to monitor at least one parameter capable of influencing behaviour of the earphone system and alter the configuration of the driver module in response to a change in the parameter(s). The driver module is an active noise reduction (ANR) device, and the controller can analyse the spectrum of the acoustic parameter. The system may also include an external signal pass through arrangement (figs 5 & 9). Independent claims are also included for the controller and a method of upgrading an existing earphone system.

Description

TITLE: EARPHONE SYSTEM

DESCRIPTION

The present invention relates to an earphone system (e.g. a system comprising at least one earphone), and particularly but not exclusively to an earphone system configured to provide noise reduction.

Earphones (e.g. circumaural or supra-aural earphones of the type connected together by a headband to form headphones or in-ear/in-the-canal earphones configured to be placed at the entrance to or in the auditory canal of a user's ear) are well known in the art. Active earphone systems incorporating an active earphone driver (or "active headphone driver") for providing advanced active features such as Active Noise Reduction (ANR) or binaural monitoring are also well known in the art. ANR techniques offer the capability to cancel (at least some useful portion of) unwanted external sound and/or to cancel excess pressures generated in the blocked (or "occluded") ear canal during speech. This latter phenomenon, called "the occlusion effect", makes it uncomfortable to speak whilst wearing certain earphone types. Active reduction of the occlusion effect is seen as a desirable feature of earphones used in telephony and other voice applications.

Figure 1 shows an example of a prior art earphone system 10 comprising a set of 30 earphones 20 and an Active Noise Reduction (ANR) module 30.

Set of earphones 20 comprise a binaural pair of in-the-canal earpieces 21 each including a driver (or "receiver") 22 and an internal sensing microphone 23 positioned to sense sound present in the auditory canal of the user's ear when in-the-canal earpiece 21 is in use inserted into a user's ear (for simplicity only one stereo channel is depicted). Set of earphones 20 further comprises an external sensing microphone 24 positioned to monitor external ambient acoustic noise.

ANR module 30 comprises an external audio input 31 for receiving an audio signal for reproduction and plurality of adjustable ANR filters 32, 33, 34 the outputs of which are summed before amplification by an amplifier 35 and subsequent presentation to driver 22. An internal filter adjustment unit 36 operable via an external interface 37 allows adjustable ANR filters 32, 33, 34 and amplifier 35 to be adjusted to vary the extent of ANR correction provided by ANR module 30.

Adjustable ANR filter 32 is operative to receive a feed-forward signal from external sensing microphone 24 and apply a component of ANR correction to reduce external noise. Adjustable ANR filter 33 is operative to receive a feedback signal from internal sensing microphone 23 and apply a component of ANR correction to reduce occlusion noise. Adjustable ANR filter 34 is operative to apply a degree of compensating correction 15 to an audio signal received from external audio input 31 (e.g. to compensate for a component of correction applied by the other filters).

Internal filter adjustment unit 36 is configured to recall an initial configuration of adjustable ANR filters 32, 33, 34 and switch between one of a finite set of such states in response to an input received via external interface 37. In this way, a user is able to apply 20 fine-tuning of the ANR performance of the earphone system.

The present applicant has identified the need for an improved earphone system in which limitations associated with the prior art are overcome or at least alleviated.

In accordance with a first aspect of the present invention, there is provided apparatus for use in an earphone system, the apparatus comprising: an active earphone driver module (e.g. active headphone driver module), the active earphone driver module being operable in a plurality of configurations (e.g. plurality of settings); and a controller operative to monitor (e.g. continuously monitor) at least one parameter capable of influencing behaviour of the earphone system and alter the configuration (e.g. setting) of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system.

In this way, apparatus is provided that allows automated context-sensitive adjustment of the active earphone driver module to take account of changes in the at least one parameter (with the controller acting as a "supervisor layer" and the active earphone driver module acting as a supervisee layer") Advantageously, the controller of the present invention may be added retrospectively to earphone system designs that were not originally intended to provide automatic driver module adjustment. As the controller may utilise functionality already present in the active earphone driver module, the upgrade to the design may be achieved with little or even no change to the design of the active earphone driver module thereby reducing the cost/difficulty of implementation of the new functionality.

In one embodiment, the active earphone driver module comprises an external interface for allowing adjustment of the active earphone driver module between the plurality of configurations (e.g. plurality of settings).

In one embodiment, the controller is configured to receive an input indicative of the least 10 one parameter from a sensor (e.g. a sensor forming part of an original earphone system design). In one embodiment, the active earphone driver module is an analogue device (e.g. analogue active earphone driver module) and the controller is a digital device (e.g. digital controller). In this way, automated digital control functionality may be retrospectively added to a wholly analogue earphone system design without requiring an upgrade to the analogue 15 componentry. In one embodiment, the controller is programmable.

In one embodiment, the controller may comprise a microprocessor module (e.g. programmable processor module).

In another embodiment, the controller may comprise a software module.

In one embodiment, the active earphone driver module is an Active Noise Reduction 20 (ANR) module (e.g. analogue ANR module) operative to actively filter out unwanted noise.

In one embodiment, the at least one parameter is an acoustic parameter (e.g, sensed by a sensing microphone) and the ANR module is operable in a plurality of configurations each associated with a different available ANR filter setting (e.g. different pre-set ANR filter setting). In one embodiment, the controller is operative to determine when a change in the 25 acoustic parameter is indicative of a change in an acoustic condition experienced by the earphone system and is operative to adjust the configuration of the ANR module by changing between available ANR filter settings to take account of the change of acoustic condition.

In one embodiment, the controller is operative to evaluate the acoustic parameter by spectral analysis of the acoustic parameter (e.g. using FFT techniques and octave integration).

In one embodiment, the controller is operative to monitor an input received from a sensing microphone positioned to monitor external ambient acoustic noise and alter the extent of the ANR correction provided by the ANR module in response to determining a change between a high external noise phase and a low external noise phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of the ANR correction in response to determining a change from a high external noise phase to a low external noise phase. In one embodiment, the controller is operative to increase the extent of the ANR correction in response to determining a change from a low external noise phase to a high external noise phase.

In one embodiment, the controller is operative to additionally distinguish between a high external noise phase and a high low-frequency external noise phase where low-frequency energy content of the acoustic parameter is determined to be greater than mid-frequency energy of the acoustic parameter and alter the extent of low frequency ANR correction provided by the ANR module relative to higher frequency ANR correction in response to determining a change to or from the high low-frequency external noise phase (e.g. with the alteration of the relative extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a high low-frequency external noise phase to a lower low-frequency external noise phase. In one embodiment, the controller is operative to increase the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a lower low-frequency external noise phase to a high low-frequency external noise phase.

In one embodiment, the controller is operative to monitor an input received from an audio input to the earphone system and alter the extent of the ANR correction (e.g. altering (low frequency) loop gain) provided by the ANR module in response to a change between a sustained low frequency reproduction phase and a non-sustained low frequency reproduction phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of the ANR correction in response to determining a change from a sustained low frequency reproduction phase to a non-sustained low frequency reproduction phase. In one embodiment, the controller is operative to increase the extent of the ANR correction in response to determining a change from a non-sustained low frequency reproduction phase to a sustained low frequency reproduction phase.

In one embodiment, the controller is operative to monitor an input received from a sensing microphone positioned to sense sound present in the auditory canal of the user's ear and alter the extent of the ANR correction (e.g. alter loop gain) provided by the ANR module in response to determining a change between a high occluded pressure phase and a normal occluded pressure phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of the ANR correction in response to determining a change from a normal occluded pressure phase to a high occluded pressure phase. In one embodiment, the controller is operative to increase the extent of the ANR correction in response to determining a change from a high occluded pressure phase to a normal occluded pressure phase In one embodiment, the active earphone driver module is operative to provide a monitoring (e.g. binaural monitoring) function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds (e.g. by allowing selected external sounds received by an external microphone to be amplified and presented to a user). In this embodiment (e.g. potentially non-ANR embodiment), the controller may be configured to adjust behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.

In one embodiment, the controller includes a monitoring (e.g. binaural monitoring) function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds (e.g. by allowing selected external sounds received by an external microphone to be amplified and presented to a user).

In one embodiment, the controller is further operative to monitor at least one non-acoustic parameter (e.g. electrical impedance at a receiver, receiver velocity) or for receipt of an 25 external input signal.

In accordance with a second aspect of the present invention, there is provided a method (e.g. automated method) of controlling an active earphone driver module in an earphone system, the method comprising: providing an active earphone driver module being operable in a plurality of configurations (e.g. plurality of settings); monitoring (e.g. continuously monitoring) at least one parameter capable of influencing behaviour of the earphone system; and altering the configuration (e.g. setting) of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system.

In one embodiment, the at least one parameter is sensed by a sensor (e.g a sensor forming part of an original earphone system design).

In one embodiment, the active earphone driver module is an analogue device (e.g. analogue active earphone driver module) and the method comprises digitally analysing the at least one parameter.

In one embodiment, the method is performed by a microprocessor module (e.g. programmable processor module) or a software module In one embodiment, the active earphone driver module is an Active Noise Reduction (ANR) module (e.g. analogue ANR module) operative to actively filter out unwanted noise. In one embodiment, the at least one parameter is an acoustic parameter (e.g. sensed by a sensing microphone) and the ANR module is operable in a plurality of configurations each associated with a different available ANR filter setting (e.g. different pre-set ANR filter setting).

In one embodiment, the method comprises determining when a change in the acoustic parameter is indicative of a change in an acoustic condition experienced by the earphone system and comprises adjusting the configuration of the ANR module by changing between available ANR filter settings to take account of the change of acoustic condition.

In one embodiment, the step of determining the change in the acoustic parameter 20 comprises spectral analysis of the acoustic parameter (e.g. using FFT techniques and octave integration).

In one embodiment, the method comprises monitoring an input received from a sensing microphone positioned to monitor external ambient acoustic noise and altering the extent of the ANR correction provided by the ANR module in response to determining a change between a high external noise phase and a low external noise phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the method comprises reducing the extent of the ANR correction in response to determining a change from a high external noise phase to a low external noise phase. In one embodiment, the method comprises increasing the extent of the ANR correction in response to determining a change from a low external noise phase to a high external noise phase.

In one embodiment, the method comprises additionally distinguishing between a high external noise phase and a high low-frequency external noise phase where low-frequency energy content of the acoustic parameter is determined to be greater than mid-frequency energy of the acoustic parameter and altering the extent of low frequency ANA correction provided by the ANR module relative to higher frequency ANR correction in response to determining a change to or from the high low-frequency external noise phase (e.g. with the alteration of the relative extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the method comprises reducing the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a high low-frequency external noise phase to a lower low-frequency external noise phase. In one embodiment, the method comprises increasing the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a lower low-frequency external noise phase to a high low-frequency external noise phase.

In one embodiment, the method comprises monitoring an input received from an audio input to the earphone system and altering the extent of the ANR correction (e.g. altering (low frequency) loop gain) provided by the ANR module in response to a change between a sustained low frequency reproduction phase and a non-sustained low frequency reproduction phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the method comprises reducing the extent of the ANR correction in response to determining a change from a sustained low frequency reproduction phase to a non-sustained low frequency reproduction phase. In one embodiment, the method comprises increasing the extent of the ANR correction in response to determining a change from a non-sustained low frequency reproduction phase to a sustained low frequency reproduction phase.

In one embodiment, the method comprises monitoring an input received from a sensing microphone positioned to sense sound present in the auditory canal of the user's ear and altering the extent of the ANR correction (e.g. alter loop gain) provided by the ANR module in response to determining a change between a high occluded pressure phase and a normal occluded pressure phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the method comprises reducing the extent of the ANR correction in response to determining a change from a normal occluded pressure phase to a high occluded pressure phase. In one embodiment, the method comprises increasing the extent of the ANR correction in response to determining a change from a high occluded pressure phase to a normal occluded pressure phase.

In one embodiment, the active earphone driver module is operative to provide a monitoring (e.g. binaural monitoring) function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds (e.g. by allowing selected external sounds received by an external microphone to be amplified and presented to a user). In this embodiment (e.g. potentially non-ANR embodiment), the method may comprise adjusting behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.

In one embodiment, the method further includes modifying operation of the earphone system in response to external sound measured by a sensing microphone to allow a user to hear selected external sounds (e.g. by allowing selected external sounds received by an external microphone to be amplified and presented to a user).

In one embodiment, the method further comprises monitoring at least one non-acoustic 15 parameter (e.g. electrical impedance at a receiver, receiver velocity) or monitoring for receipt of an external input signal.

In accordance with a third aspect of the present invention, there is provided a method of upgrading an earphone system or earphone system design, the method comprising: providing an earphone system or earphone system design including: at least one earphone; at least one sensor; and an active earphone driver module, the active earphone driver module being operable in a plurality of configurations (e.g. plurality of settings); and adding a controller operative to receive an output from the at least one sensor and monitor (e.g. continuously monitor) at least one parameter capable of influencing behaviour of the earphone system and alter the configuration (e.g. setting) of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system.

In one embodiment, the active earphone driver module is an analogue device (e.g. analogue active earphone driver module) and the controller is a digital device (e.g. digital controller). In this way, automated digital control functionality may be retrospectively added to a wholly analogue earphone system design without requiring an upgrade to the analogue componentry.

In another embodiment, the controller may comprise a software module.

In one embodiment, the active earphone driver module is an Active Noise Reduction 5 (ANR) module (e.g. analogue ANR module) operative to actively filter out unwanted noise. In one embodiment, the at least one parameter is an acoustic parameter (e.g. sensed by a sensing microphone) and the ANR module is operable in a plurality of configurations each associated with a different available ANR filter setting (e.g. different pre-set ANR filter setting). In one embodiment, the controller is operative to determine when a change in the 10 acoustic parameter is indicative of a change in an acoustic condition experienced by the earphone system and is operative to adjust the configuration of the ANR module by changing between available ANR filter settings to take account of the change of acoustic condition. In one embodiment, the controller is operative to evaluate the acoustic parameter by spectral analysis of the acoustic parameter (e.g. using FFT techniques and octave integration).

In one embodiment, the controller is operative to additionally distinguish between a high external noise phase and a high low-frequency external noise phase where low-frequency energy content of the acoustic parameter is determined to be greater than mid-frequency energy of the acoustic parameter and alter the extent of low frequency ANR correction provided by the ANR module relative to higher frequency ANR correction in response to determining a change to or from the high low-frequency external noise phase (e.g. with the alteration of the relative extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a high low-frequency external noise phase to a lower low-frequency external noise phase. In one embodiment, the controller is operative to increase the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a lower low-frequency external noise phase to a high low-frequency external noise phase In one embodiment, the controller is operative to monitor an input received from an audio input to the earphone system and alter the extent of the ANR correction (e.g. altering (low frequency) loop gain) provided by the ANR module in response to a change between a sustained low frequency reproduction phase and a non-sustained low frequency reproduction phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to reduce the extent of the ANR correction in response to determining a change from a sustained low frequency reproduction phase to a non-sustained low frequency reproduction phase. In one embodiment, the controller is operative to increase the extent of the ANR correction in 15 response to determining a change from a non-sustained low frequency reproduction phase to a sustained low frequency reproduction phase.

In one embodiment, the controller is further operative to monitor at least one non-acoustic parameter (e.g. electrical impedance at a receiver, receiver velocity) or for receipt of an 10 external input signal.

In accordance with a fourth aspect of the present invention, there is provided a controller (e.g. controller module) for use in an earphone system comprising an active earphone driver module (e.g. active headphone driver module), the active earphone driver module being operable in a plurality of configurations (e.g. plurality of settings), the controller being operative to monitor (e.g. continuously monitor) at least one parameter capable of influencing behaviour of the earphone system and in response to a determined change in the at least one parameter of the earphone system generate an output to instruct adjustment of the configuration (e.g. setting) of the active earphone driver module.

In one embodiment, the active earphone driver module comprises an external interface 20 for allowing adjustment of the active earphone driver module between the plurality of configurations (e.g. plurality of settings) and the controller communicates the output to the active earphone drive module via the external interface.

In one embodiment, the controller is configured to receive an input indicative of the least one parameter from a sensor (e.g. a sensor forming part of an original earphone system design).

In one embodiment, the active earphone driver module is an analogue device (e.g. analogue active earphone driver module) and the controller is a digital device (e.g. digital control I er).

In another embodiment, the controller module may comprise a software module.

In one embodiment, the active earphone driver module is an Active Noise Reduction (ANR) module (e.g. analogue A NR module) operative to actively filter out unwanted noise.

In one embodiment, the at least one parameter is an acoustic parameter (e.g. sensed by

U

a sensing microphone) and the ANR module is operable in a plurality of configurations each associated with a different available ANR filter setting (e.g. different pre-set ANR filter setting). In one embodiment, the controller is operative to determine when a change in the acoustic parameter is indicative of a change in an acoustic condition experienced by the 5 earphone system and is operative to generate an output to instruct adjustment of the configuration of the ANR module by changing between available ANR filter settings to take account of the change of acoustic condition.

In one embodiment, the controller is operative to monitor an input received from a sensing microphone positioned to monitor external ambient acoustic noise and generate an output to instruct adjustment in the extent of the ANR correction provided by the ANR module in response to determining a change between a high external noise phase and a low external noise phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to generate an output to instruct a reduction in the extent of the ANR correction in response to determining a change from a high external noise phase to a low external noise phase. In one embodiment, the controller is operative to generate an output to instruct an increase in the extent of the ANR correction in response to determining a change from a low external noise phase to a high external noise phase.

In one embodiment, the controller is operative to additionally distinguish between a high external noise phase and a high low-frequency external noise phase where low-frequency energy content of the acoustic parameter is determined to be greater than mid-frequency energy of the acoustic parameter and generate an output to instruct adjustment in the extent of low frequency ANR correction provided by the ANR module relative to higher frequency ANR correction in response to determining a change to or from the high low-frequency external noise phase (e.g. with the alteration of the relative extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to generate an output to instruct a reduction in the extent of low frequency ANR correction relative to the higher frequency ANR correction in response to determining a change from a high low-frequency external noise phase to a lower low-frequency external noise phase. In one embodiment, the controller is operative to generate an output to instruct an increase in the extent of low frequency ANR correction relative to the

H

higher frequency ANR correction in response to determining a change from a lower low-frequency external noise phase to a high low-frequency external noise phase.

In one embodiment, the controller is operative to monitor an input received from an audio input to the earphone system and generate an output to instruct an adjustment in the extent 5 of the ANR correction (e.g. altering (low frequency) loop gain) provided by the ANR module in response to a change between a sustained low frequency reproduction phase and a non-sustained low frequency reproduction phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to generate an output to instruct a reduction in the extent of the ANR 10 correction in response to determining a change from a sustained low frequency reproduction phase to a non-sustained low frequency reproduction phase. In one embodiment, the controller is operative to generate an output to instruct an increase in the extent of the ANR correction in response to determining a change from a non-sustained low frequency reproduction phase to a sustained low frequency reproduction phase.

In one embodiment, the controller is operative to monitor an input received from a sensing microphone positioned to sense sound present in the auditory canal of the user's ear and generate an output to instruct an adjustment in the extent of the ANR correction (e.g. alter loop gain) provided by the ANR module in response to determining a change between a high occluded pressure phase and a normal occluded pressure phase (e.g. with the alteration of the extend of the ANR correction occurring each time a change between phases is determined). In one embodiment, the controller is operative to generate an output to instruct a reduction in the extent of the ANR correction in response to determining a change from a normal occluded pressure phase to a high occluded pressure phase. In one embodiment, the controller is operative to generate an output to instruct an increase in the extent of the ANR correction in response to determining a change from a high occluded pressure phase to a normal occluded pressure phase.

In one embodiment, the active earphone driver module is operative to provide a monitoring (e.g. binaural monitoring) function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds (e.g. by allowing selected external sounds received by an external microphone to be amplified and presented to a user) and the controller is operative to generate an output to instruct adjustment of the behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.

N

In one embodiment, the controller includes a monitoring (e.g. binaural monitoring) function operative to generate an output to instruct adjustment of operation of the active earphone driver module in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds (e.g. by allowing selected 5 external sounds received by an external microphone to be amplified and presented to a user). In one embodiment, the controller is further operative to monitor at least one non-acoustic parameter (e.g. electrical impedance at a receiver, receiver velocity) or for receipt of an external input signal.

Embodiments of the present invention will now be described by way of example with 10 reference to the accompanying drawings in which: Figure 1 is a schematic view of a prior art earphone system; Figure 2 is a schematic view of an upgraded earphone system in accordance with a first embodiment of the present invention; Figure 3A is a schematic view of the upgraded earphone system of Figure 2 in a first 15 mode of operation; Figure 3B is flow diagram illustrating operation of the upgraded system of Figure 2 in the first mode of operation; Figure 4A is a schematic view of the upgraded earphone system of Figure 2 in a second mode of operation; Figure 4B is flow diagram illustrating operation of the upgraded system of Figure 2 in the second mode of operation; Figure 5 is a schematic view of the upgraded earphone system of Figure 2 in a third mode of operation; Figure 6 is a schematic view of the upgraded earphone system of Figure 2 in a fourth 25 mode of operation; and Figure 7 is a schematic view of an upgraded earphone system in accordance with a second embodiment of the present invention.

Figure 2 shows an upgraded earphone system 100 including set of earphones 20 and ANR module 30 from the system of Figure 1, together with a novel controller 110 intended to provide a layer of supervisory intelligence "above' the prior art device that communicates with the ANR module 30 which itself contains no "intelligence" or "programmability" to provide additional functionality to the ANR module.

As illustrated, controller 110 includes a plurality of inputs 112, 113, 114 together with an output 115 for communicating with ANR module 30 via external interface 37. Controller acts to generate signals on external interface 37 which configure ANR module 30 (by adjusting adjustable ANR filters 32, 33, 34 -the structure and implications of which are known to the controller logic) so as to bring about intended changes in behaviour of the earphone system 100. Controller 110 is given the ability to observe aspects of the overall system behaviour and/or operating context through inputs 112, 113, 114 connected respectively to external sensing microphone 24, internal sensing microphone 23, and external audio input 31 and any changes in ANR filter configuration are made in response to these observations.

The supervisory layer formed by controller 110 may be implemented by any of a number of computing platforms, ranging in complexity from a simple microcontroller, through to a more powerful microcontroller with digital signal processing capability. Controller 110 may be provided as part of the set of earphones 20 or as part of a terminal/handset to which the earphones 20 are connected.

As discussed in more detail below, controller 110 is operable in the following modes: 15 AUTO ANC MODE, DISTORTION CONTROL MODE, DYNAMIC RANGE OPTIMISATION MODE and BINAURAL MONITORING MODE.

AUTO ANC MODE

In a first mode of operation illustrated in Figures 3A and 3B, controller 110 makes continuous observations of the noise environment in which set of earphones 20 is being used. Electrical output signals from external sensing microphone 24 are tapped off and sent to controller 110 via input 112 where they are buffered and amplified by amplifier 120A prior to processing by Auto ANC module 130. Amplifier 120A both serves to minimise disturbance of the primary system's operation and to increase the otherwise small amplitude microphone signal to a level suitable for conversion and processing. In this application, the entire computational load associated with operation of the supervisory layer is handled in a simple microcontroller which has integral analogue to digital converters capable of sampling the microphone directly and an EC interface capable of generating the output signal for ANC module 30.

Auto ANR module 130 analyses the signals received from external sensing microphone 24 in octave bands using FFT methods. This produces a miming spectral decomposition of the noise describing not only noise level but also energy distribution over frequency. As the available bandwidth of control is finite, performance of ANR earphones is strongly dependent upon frequency the optimum configuration of ANR module 130 may vary depending upon the nature of the noise spectrum.

Auto ANR module 130 is operative to discriminate between three different classes of noise field on the basis of a spectral test as illustrated in Figure 3B in which the computed octave spectrum is compared to two Threshold levels, Thresl and Thres2. If the spectrum is below 5 Thres2, the system is deemed to be in "Quiet" mode. If the spectrum is above Threst, the system is either in "Loud" mode or, if the low frequency energy exceeds the energy in the mid-frequency bands by a predetermined amount, in "Low Frequency" mode. The decision boundaries dividing these three categories are encoded within Auto ANR module 130 in this example by the constants Thresl, Thres2 (each of which are vectors of octave band levels) and 10 the scalar n. The comparison is made with the vector of variable octave levels "Spectrum[ ]", one of its low frequency element (e.g. LF=Spectrum[1]) and an average over its mid-frequency elements (MF Average=0.25*(SpectrumP1+Spectrum[41+Spectrum[5]+Spectrum[6])).

Upon deciding which of the modes is most appropriate to the present noise climate, Auto ANR module 130 generates the necessary command(s) to ANR module 30 via external interface 37 to enact the new control function to embody this mode. In response to the received command(s) internal filter adjustment unit 36 causes adjustable ANR filters 32, 33, 34 and amplifier 35 to be adjusted to vary the extent of ANR correction provided by ANR module 30.

The benefits of having the "Quiet", "Loud" and "Low Frequency' modes are considerable. If a conventional (fixed) ANA earphone is used in a very quiet space (such as in a library) it is wasted and there is potential that its own self-noise may be audible to the wearer. Limiting the action of the ANR module to a configuration appropriate to the quiet surroundings will save battery life and increase wearer comfort. Similarly, a tuning of a conventional (fixed) ANR earphone designed for a general noise spectrum may fail to provide good attenuation of very low frequency signals that may be experiences in some scenarios. The ability to detect presence of these pressures and redeploy the resources of the ANR module has clear benefits to the user. As will be apparent to the skilled reader, controller 110 will operate to identify a change of external condition and automatically alter the mode of operation between the "Quiet", "Loud" and -Low Frequency" modes requiring no input from the user.

DISTORTION CONTROL MODE

In a second mode of operation illustrated in Figures 4A and 4B, controller 110 is used to monitor excess pressures generated in the blocked (or "occluded") ear canal as measured by internal sensing microphone 23.

In the deployment of active noise control measures (particularly in the context of inear/in-the-canal earphone applications using "Balanced Armature" receive technologies), it has been found difficult to avoid situations in which the control system takes the driver 22 close to the edge of its linear operating envelope. This is exacerbated by the variation in the geometry of different user's external ear canals and by the quality of the -fit" or "seal" that is achieved between the earphone and the user's ear.

In situations where i) the fit is good, ii) the ear is small and iii) the user's voice is loud, the user's own voice can generate high pressure levels inside the occluded ear canal. When the ANR module 30 attempts to control these high pressure levels, driver 22 is required to generate similarly high pressures into a radiation load lower than that for which the driver is designed. This can take the driver outside of its intended operating envelope resulting in audible distortion.

A solution has been found as illustrated in Figure 4A in which controller 110 observes the behaviour of ANR module 30 via input 113 which receives electrical output signals tapped from internal sensing microphone 23. The received signal is again buffered and amplified by amplifier 120B prior to conversion to digital representation and processing by Distortion Control module 140. In this application the sample rate is higher, as is consistent with a higher resolution of processing in a device optimised for the specific computations implicit in digital signal processing, in which a narrow-band frequency decomposition of the energy content of the signal from internal sensing microphone 23 is computed. This running observation of the narrow-band spectrum of the energy in the occluded ear is used by Distortion Control module 140 to control operation of ANR module 30 so as to minimise the impact of distortion.

As illustrated in Figure 4B, when a first spectral threshold Thresl is exceeded by the instantaneous value of the spectrum, a substantial reduction in the "loop gain" of the feedback control path is initiated. This amounts to a reduction in the gain of adjustable ANR filter 33 which acts on the output from internal sensing microphone 23 and which causes the distortion.

The loop gain reduction is communicated to ANR module 30 from output 115 via external interface 37 and implemented by means of internal filter adjustment unit 36.

Subsequent observations of the narrow-band spectrum of the energy in the occluded ear continue until the spectrum is observed to be below a second spectral threshold Thres2, at which point the loop gain is allowed to increase back towards its nominal value according to a first-order (exponential) trajectory. At any point in the process, further violations of Thresl will re-trigger the loop gain back to the substantially reduced point.

The entire process is parameterised by the following constants: Thresl (vector of narrow-band spectral threshold values) Thres2 (vector of narrow-band spectral threshold values) Factor for reduction of loop gain Factor for incremental relaxation of loop gain back to nominal value.

As modification of adjustable ANR filter 33 will change the response of the entire system to external audio input 31, adjustment to adjustable ANR filter 34 may be implemented to compensate for the effects of modifying the loop gain.

DYNAMIC RANGE OPTIMISATION MODE

An ANR earphone may -in the course of being tuned to fulfil its noise reducing functions -suffer reduction in the dynamic range available for the reproduction of program material such as music (as compared to a "passive" device using the same driver or to an active device with the same amplifier and driver but with no ANR control applied). This is particularly the case in earphones using the "feedback" control topology at frequencies close to the main cancelling peak, which usually occurs below 400 Hz, This is a disadvantage of ANR earphones in the context of a marketplace in which i) earphones are required to reproduce music from genres which includes large amounts of low frequency energy and ii) taste and fashion are driving earphone tunings to a further exaggerated response at low frequency.

ANR earphones further disadvantage themselves in attempting to cancel low-frequency noise (and -in doing so -rendering themselves less capable of reproducing low-frequency music) when, at the same time the very music they are reproducing makes the noise they would cancel to make inaudible through masking. The present applicant has identified that the resources of the earphone would be better redeployed in reproducing the music rather than handicapping itself in attempts to retain high levels of cancellation.

Figure 5 shows controller 110 set up to solve this exact problem by configuring controller 110 to observe external audio input 31 via a tapped connection to input 114. After appropriate isolation, buffering and amplification by amplifier 120C, a Dynamic Range Optimisation module 150 (which in this application can be realised by a relatively simple microcontroller) samples the observations of the external audio input 31 and makes running estimates of spectral content again using FFT techniques and octave integration. Observation of the levels of the lower octaves allows a decision to be made as to the appropriateness of noise reduction for the program material being reproduced. In cases where the program 5 material is observed to have persistent, high energy content at low frequency (i.e. a "sustained low frequency reproduction phase"), controller 110 transmits a control signal from output 115 via external interface 37 to cause operation of ANR module 30 to be modified by relaxing the tuning of adjustable filter 33 (requiring compensating adjustments to filter 34). When the program material is observed to stop or to change in style or level, controller 110 instructs ANR 10 module 30 to return adjustable filters 33 and 34 to their nominal tuning settings.

BINAURAL MONITORING MODE

Wearing ANR earphones is known to introduce a potentially dangerous degree of isolation between the user and their environment which may, for example, prevent them from hearing warning sounds of the approach of dangerous objects or situations. Techniques for allowing signals from an external microphone to be selectively routed directly to a user's ears to provide situation awareness are known in the art but require control.

With reference to Figure 6, external environmental signals may be detected on external sensing microphone 24 and tapped to controller 110 via input 112. Controller 110 includes appropriate buffering and amplification by amplifier 120D to couple the signals to a Binaural Monitoring module 160 operative to deploy an algorithm for identifying features of the external noise field which might indicate hazard sounds of which the user should be aware. The algorithm implemented in Monitoring module 160 is designed to be responsive to such hazard sounds and on identification of a candidate hazard sound controller 110 issues a command signal to ANR module 30 via external interface 37 to make external sounds -included the potential hazard sound -audible to the user (e.g. by configuring the response of adjustable ANR filter 32 to make the signals from external sensing microphone 24 audible and muting or at least reducing audio received via external audio input 31 by reducing the gain of adjustable ANR filter 34).

The algorithm implemented by Binaural Monitoring module 160 may (inter alia) respond to: Standard hazard tones (such as warning tones from reversing vehicles); Sudden rates-of-change in the ambient noise level; Sudden rates-of-change in the ambient noise spectrum.

All of which may be implemented using the frequency domain analysis strategies previously described in relation to the other modes of operation. Additionally, Binaural Monitoring module 160 may deploy more sophisticated algorithms in an attempt to recognise more subtle features of the external noise environment.

Figure 7 shows an enhanced earphone system 200 based on the system of Figure 2 and including additional functionality. Enhanced earphone system 200 again includes set of earphones 20 and ANR module 30 from the system of Figure 1, together with an advanced controller 210 and additional sensor in the form of series current sense resistor 25 and driver velocity sensor 27.

As illustrated, controller 210 includes a plurality of inputs 212, 213, 214 (corresponding to inputs 112, 113 and 114 respectively in the system of Figure 2) together with a differential amplifier input 216 and a driver velocity input 217 (together these inputs are connected to an array of amplifiers 220), an external input 218 and an output 215 for communicating with ANR module 30 via external interface 37. Controller 210 acts to generate signals on external interface 37 which configure ANR module 30 so as to bring about intended changes in behaviour of the earphone system 200. Controller 210 may be provided as part of the set of earphones 20 or as part of a terminal/handset to which the earphones 20 are connected As illustrated, controller 210 includes a processor 250 connected to the array of amplifiers 220 by means of a multiplexor (e.g. analogue multiplexing component) 260.

In a first series of modes of operation processor 250 is operative to implement the four modes discussed in relation to Figure 2, i.e. the AUTO ANC MODE, DISTORTION CONTROL MODE, DYNAMIC RANGE OPTEVINATION MODE and BINAURAL MONITORING MODE. As the operation is substantially identical to the operation in the controller of Figure 2 these modes will not be discussed again in detail.

Processor 250 is additionally operative in a second series of modes by sensing input signals received from differential amplifier input 216, driver velocity input 217 and external input 215.

In one mode of operation, controller 210 is operative to monitor operating electrical impedance of driver 22 through electrical observation of not just voltage applied to driver 22 but also voltage drop over series current sense resistor 25 and differential amplifier capability in the buffer amplifier array 220 (via differential amplifier input 216). This gives controller 210 the ability to make functional checks on driver 22 (e.g. for the purposes of providing a system self-test function) and offers the possibility for automatic detection of low-frequency radiation loads In another mode of operation, controller 210 is operative to monitor driver velocity using driver velocity sensor 27 (which may be implemented using electrodynamic means or otherwise) via driver velocity input 217. This offers the possibility of greater utility in detecting radiation load for stability control, earphone seal/fit management and automatic driver tuning.

Notably, controller 210 is capable of receiving input signals from not only the electrical, electroacoustic and acoustic sensors, it is also receptive to external inputs via external input 2118 which will inform its decisions. These inputs include, but are not limited to, input from a user, inputs from other local transducer system (such a position/orientation sensors), inputs from locally connected apparatus (such as a connecting terminal/computer/in-flight entertainment system) and inputs received from remote sources. In all cases, such information may have been received in response to a specific request from the controller or may have been received independently of any request. In this way, controller 210 may operate in other system roles (e.g. implementing a user interface, supervising external digital communication, etc.) thereby emphasizing how naturally the "supervisor" function of the controller can be integrated into the contemporary understanding of an ANR earphone system to provide "housekeeping" or "system integration" tasks.

Claims

Claims: 1. Apparatus for use in an earphone system, the apparatus comprising: an active earphone driver module, the active earphone driver module being operable in a plurality of configurations; and a controller operative to monitor at least one parameter capable of influencing behaviour of the earphone system and alter the configuration of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system; characterised in that the controller is operative to monitor at least one non-acoustic parameter or for receipt of an external input signal.
2. Apparatus according to claim 1, wherein the active earphone driver module is an analogue device and the controller is a digital device.
3. Apparatus according to claim 1 or claim 2, wherein the active earphone driver module is an Active Noise Reduction (ANR) module operative to actively filter out unwanted noise.
4. A method of controlling an active earphone driver module in an earphone system, the method comprising: providing an active earphone driver module being operable in a plurality of configurations; monitoring at least one parameter capable of influencing behaviour of the earphone system; and altering the configuration of the active earphone driver module in response to a determined change in the at least one parameter ofthe earphone system; characterised in that the method comprises monitoring at least one non-acoustic parameter or monitoring for receipt of an external input signal.
5. A method according to claim 4, wherein the active earphone driver module is an analogue device and the method comprises digitally analysing the at least one parameter.
A method according to claim 4 or claim 5, wherein the active earphone driver module is an Active Noise Reduction (ANR) module operative to actively filter out unwanted noise
7. A method of upgrading an earphone system or earphone system design to form apparatus in accordance with any of claims 1-3, the method comprising: providing an earphone system or earphone system design including: at least one earphone; at least one sensor; and an active earphone driver module, the active earphone driver module being operable in a plurality of configurations; and adding a controller operative to receive an output from the at least one sensor and monitor at least one parameter capable of influencing behaviour of the earphone system and alter the configuration of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system.
8 A controller module for use in an earphone system comprising an active earphone driver module, the active earphone driver module being operable in a plurality of configurations, the controller module being operative to monitor at least one parameter capable of influencing behaviour of the earphone system and in response to a determined change in the at least one parameter of the earphone system generate an output to instruct adjustment of the configuration of the active earphone driver module; characterised in that the controller module is operative to monitor at least one non-acoustic parameter or for receipt of an external input signal.
9. Apparatus for use in an earphone system, the apparatus comprising: an active earphone driver module, the active earphone driver module being operable in a plurality of configurations; and a controller operative to monitor at least one parameter capable of influencing behaviour of the earphone system and alter the configuration of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system; wherein the active earphone driver module is operative to provide a monitoring function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds and the controller is operative to generate an output to instruct adjustment of the behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.
10. Apparatus according to claim 9, wherein the active earphone driver module is an 5 analogue device and the controller is a digital device.
11. Apparatus according to claim 9 or claim 10, wherein the active earphone driver module is an Active Noise Reduction (ANR) module operative to actively filter out unwanted noise.
12. A method of controlling an active earphone driver module in an earphone system, the method comprising: providing an active earphone driver module being operable in a plurality of configurations; monitoring at least one parameter capable of influencing behaviour of the earphone 15 system; and altering the configuration of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system; wherein the active earphone driver module is operative to provide a monitoring function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds and the method further comprise adjusting behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.
13. A method according to claim 12 wherein the active earphone driver module is an analogue device and the method comprises digitally analysing the at least one parameter.
14 A method according to claim 12 or claim 13, wherein the active earphone driver module is an Active Noise Reduction (ANR) module operative to actively filter out unwanted noise.
15. A method of upgrading an earphone system or earphone system design to form apparatus in accordance with any of claims 9-11, the method comprising: providing an earphone system or earphone system design including: at least one earphone; at least one sensor; and an active earphone driver module, the active earphone driver module being operable in a plurality of configurations; and adding a controller operative to receive an output from the at least one sensor and 5 monitor at least one parameter capable of influencing behaviour of the earphone system and alter the configuration of the active earphone driver module in response to a determined change in the at least one parameter of the earphone system.
16. A controller module for use in an earphone system comprising an active earphone driver module, the active earphone driver module being operable in a plurality of configurations and to provide a monitoring function configured to modify operation of the earphone system in response to external sound measured by a sensing microphone for the purpose of allowing a user to hear selected external sounds, the controller module being operative to monitor at least one parameter capable of influencing behaviour of the earphone system and in response to a determined change in the at least one parameter of the earphone system generate an output to instruct adjustment of the configuration of the active earphone driver module; wherein the controller module is operative to generate an output to instruct adjustment of the behaviour of the monitoring function in response to a determined change in the at least one parameter of the earphone system.