Technical Field

The present disclosure relates to the incorporation of a microphone unit into a consumer device and the placement of the microphone unit so as to achieve more optimal sound reception for receipt of voice commands.

Background

Voice user interfaces (VUIs) are becoming an increasingly popular way of controlling devices around the home or office, or accessing services provided via a network such as the

Internet. For instance VUI devices may capture the user's voice locally, transport the speech to an Automatic Speech Recognition (ASR) service and then replay the responses (speech or other sounds) back to the original user. At present, the listening devices used for such purposes typically take the form of a dedicated smart speaker unit.

One of the challenges of voice user interfaces however is the capture of voice, with integrity, across living and work spaces.

Summary

Accurate capture requires careful placement of the listening device. An ideal deployment of the listening device is in a prominent place in the living space or work space (or the like), with a direct iine-of-sight to all places in the space where a person's mouth might be expected to be found. However, prominently placed devices, and associated cables, can also interfere with the utility of the living or work space, such as by taking up space on table tops or work surfaces, or cables providing trip hazards or becoming entangled with cables from other devices). Furthermore, users do not always place their listening devices in optimal places. Ideally a microphone used for voice recognition should be placed either very close to a surface or very far away. Very close surfaces result in a lot of reflections but only interfering with high frequencies above typical vocal range. Reflections from far-away surfaces affect many frequencies but with only a low magnitude of interference.

The inventors have identified that it would be beneficial to incorporate a microphone used for voice recognition into a luminaire. Luminaires are naturally placed or installed by users either very close to a surface or far away. The luminaire will be designed to rest on a surface such as a table top, work surface or floor, or to be installed on a surfaces such as a ceiling or wall. When fixed to the ceiling the luminaire is typically not close to any wall or the floor, or when fixed to a wall the luminaire is typically not placed dose to the ceiling, floor or other wall. When placed on a table top or work surface the luminaire may be placed in the middle of the room, in which case it is not dose to any other surfaces, or else is often placed up against a wail so it is close to this wall and the table top or work surface but not any other surface. Further, by being incorporated into a luminaire, the listening device naturally blends in with the environment in a device that would be present anyway.

According to one aspect disclosed herein, there is provided a luminaire for emitting illumination to illuminate an environment, the luminaire being designed to rest on or fix to a surface; wherein the luminaire incorporates microphone apparatus comprising one or more microphones for capturing audio signals from the environment, and wherein the

microphone apparatus is configured to provide the audio signals to a voice control algorithm on a signal processing apparatus in order to process one or more voice commands in the audio signals.

!n embodiments the microphone apparatus may be arranged such that when the luminaire is resting on or fixed to said surface in the manner for which it is designed, each microphone of the microphone apparatus is no more than a distance of 30mm from said surface.

In embodiments the microphone apparatus may arranged such that when the luminaire is resting on or fixed to said surface in the manner for which it is designed, each microphone of the microphone apparatus is no more than a distance of 15mm from said surface. In further embodiments, the luminaire may comprise a base designed to rest on or fix to said surface, and a body part having a connector for accepting a light-emitting element for emitting said illumination; the body part being arranged so as when the base is resting on or fixed to said surface in the manner for which it is designed and the light-emitting element is connected to the body part via the connector, the light-emitting element is held apart from the base and surface by the body part. In such embodiments the microphone apparatus may be incorporated in the base.

The inventors have identified that the base of a lamp is a particularly advantageous place to incorporate the microphone(s) since this will place them very close to the surface upon which the luminaire is placed or to which it is affixed.

In embodiments, the microphone may be arranged in the base such that when the base is resting on or fixed to said surface in the manner for which it is designed, each microphone of the microphone apparatus is no more than a distance 30mm from said surface. In embodiments the microphone may be arranged in the base such that when the base is resting on or fixed to said surface in the manner for which it is designed, each microphone of the microphone apparatus is no more than a distance 15mm from said surface

In alternative embodiments the luminaire may comprise a lamp shade, and the microphone apparatus may be disposed in the lampshade.

In embodiments the one or more microphones may be disposed on an extreme outer edge of the base or lampshade.

In embodiments the luminaire may take the form of a table lamp or a desk lamp, said surface being a table top of the table or a work surface of the desk respectively.

In embodiments the luminaire may take the form of a floor lamp, said surface being a floor.

In embodiments the luminaire may take the form of a ceiling mountable luminaire, said surface being a ceiling and the luminaire or base being designed to fix to the ceiling. In embodiments the luminaire may take the form of a wall mountable luminaire, said surface being a wall and the luminaire or base being designed to fix to the wall.

In embodiments the microphone apparatus may comprise multiple microphones. In such embodiments the voice control algorithm to which the microphone apparatus is configured to provide the audio signals may comprise a beamsteering algorithm for spatially targeting a source of the voice commands and/or avoiding one or more other sources.

In embodiments the microphones may be disposed in a regular array around an outer face or edge of the base or lampshade.

In embodiments the voice control algorithm to which the microphone apparatus is configured to provide the audio signals may comprise an echo cancellation algorithm for cancelling echoes from the audio signals. in embodiments the luminaire may comprise a controller configured to control the illumination based on controls signals receive back from the voice control algorithm in accordance with the voice commands.

In embodiments, the control which the controller is configured to perform in accordance with the voice commands may comprises one or more of: switching the illumination on and/or off, dimming the elimination up and/or down, and/or controlling a colour of the illumination.

In embodiments the signal processing apparatus on which the voice control algorithm is implemented may also be incorporated in the luminaire.

Alternatively the signal processing apparatus may be external to the luminaire, in which case the luminaire comprises a communications interface, the microphone being configured to provide the audio signals to the voice control algorithm on the signal processing apparatus via said communications interface. In embodiments, the connector may take the form of a standardized socket for powering the light-emitting element; and the signal processing apparatus or communications interface may be implemented in a module which connects to the body part via the standardized socket and which comprises a further instance of the standardized socket into which the light-emitting element connects; such that the module is arranged to derive power for powering the signal processing apparatus or communications interface via the socket in the body part of the luminaire; and the light-emitting element can connect to the body part, and derive power from the body part for emitting said illumination, vicariously via the instance of the socket in the module. Thus the module may be retrofitted to a pre existing luminaire.

In embodiments the microphone apparatus may also be retrofitted to the luminaire.

In embodiments the lampshade may be a removable part of the luminaire. In such embodiments, if the microphone apparatus is also to be incorporated in the lampshade, then the microphone apparatus may be retrofitted by replacing a pre-existing lampshade with the lampshade incorporating the microphone apparatus.

In embodiments the voice control algorithm may be configured to control, based on the voice commands captured via the luminaire, one or both of: an appliance other than the luminaire, and/or a service other than controlling the illumination.

In embodiments the voice control algorithm may be configured to control, based on the voice commands captured via the luminaire, one or both of: a home or office appliance other than the luminaire; and/or a service accessed via the Internet, other than for controlling the illumination.

In embodiments, the luminaire may further comprise a speaker configured to output audible feedback on the processing of the voice commands. According to another aspect disclosed herein, there is provided a system comprising: a luminaire comprising an light-emitting element for emitting illumination to illuminate an environment, wherein the luminaire further incorporates microphone apparatus comprising one or more microphones arranged to capture audio signals from the environment; and signal processing apparatus arranged to run a voice control algorithm, the microphone apparatus being configured to provide the captured audio signals to the voice control algorithm, and the voice control algorithm being configured; wherein the luminaire is arranged resting on or fixed to a surface, and the microphone apparatus is arranged in the luminaire with each microphone of the microphone apparatus being a distance of no more than 30mm from said surface. in embodiments the system may be further configured in accordance with any of the features mentioned above in relation to the luminaire, or any other feature disclosed elsewhere herein.

According to another aspect disclosed herein, there is provided a method comprising:

resting a luminaire on a surface or fixing the luminaire to the surface, and when in a position thus resting on or fixed to said surface, using the luminaire to emit illumination to illuminate an environment; when the luminaire is in said position resting on or fixed to said surface, using a microphone apparatus comprising one or more microphones incorporated into the luminaire to capture audio signals from the environment; and providing the captured audio signals from the microphone apparatus to a voice control algorithm on a signal processing apparatus in order to process one or more voice commands in the audio signals.

In embodiments the method may comprise steps in accordance with any of the features mentioned above in relation to the luminaire or system, or any other feature disclosed elsewhere herein. Brief Description of the drawings

To assist understanding of the present disclosure and to show how embodiments may be put into effect, reference is made, by way of example only, to the accompanying drawings in which:

Figure 1 is a schematic illustration of an environment comprising a speaking user and a lamp incorporating a microphone for receiving voice commands from the user;

Figure 2 is a schematic illustration of an example placement of the microphone within the lamp;

Figure 3 schematically illustrates a number of example parts of a lamp in which the microphone may be incorporated;

Figure 4 is a schematic block diagram of a lamp with microphone, plus signal processing means for receiving and acting on the voice commands received via the microphone;

Figure 5 schematically illustrates self-interference caused by reflection from a hard surface; and

Figure 6 schematically illustrates the phenomenon of combing in the frequency domain due to reflection and self-interference.

Detailed Description of Embodiments

The present invention combines a microphone apparatus comprising one or more microphones with a component of an otherwise-conventional luminaire, e.g. incorporating the microphone apparatus in a lamp-shade or a base of the luminaire. For example the luminaire may be a floor or table standing device, or may be hanging from a ceiling.

Preferably the microphone apparatus takes the form of a far-field microphone array capable of isolating sound at a distance in a reverberant environment. As mentioned, voice user interfaces (VUI) are becoming an increasingly popular way of accessing services provided on the internet. One of the challenges of voice user interfaces is the capture of voice, with integrity, across living and work spaces. Accurate capture requires careful placement of the listening device, preferably in combination high quality sensors and algorithms. An ideal deployment of the listening device is in a prominent place in the living or work space. However, prominent technology, and associated cables, can affect the utility of the space.

As identified herein, luminaires offer a compelling deployment scenario for VUI. They can be used to hide the microphones, cabling and associated equipment within a cover of the luminaire, e.g. in a base of the luminaire or within the cover of the lampshade. In embodiments this can solve the cabling problem by exploiting the power and infrastructure provided by the existing lighting circuit. But moreover, it also solves the positioning problem as lamps are typically prominently placed within a living space and are aesthetically acceptable.

Embodiments provide a luminaire with customized base portion for resting on or affixing to a surface such as a table top, work surface, floor, ceiling or wall, with one or more microphones incorporated in the base portion so as to be situated close to the surface (and preferably far from any other surfaces of the room or environment in which the luminaire is placed}. Alternative embodiments provide a customised lamp shade, with microphones placed either at the top (for floor or table standing applications) or at the bottom (for ceiling mounted applications) of the lampshade.

Either way, the microphones are preferably arranged so that the sound ports are clear of any obstruction presented by any parts of the luminaire itself, such as the lampshade; i.e. the path between any potential speaking users in the room and the microphones is not blocked by any of parts of the luminaire. This may be achieved by arranging the

microphones to protrude very slightly from the outer surface of the luminaire, e.g. from the face of the lampshade or base portion. The luminaire further comprises a VU1 module associated with the microphone(s), comprising signal processing logic for processing the captured audio signals to recognize voice commands, or alternatively a communications interface (e.g. wireless interface) for sending the captured audio signals to another, external device to perform the processing (e.g. a server). The wires to each microphone are preferably run on or through the existing frame (body), to avoid additional shadowing of the light source when in operation, and terminate at the VUI module. In some embodiments, the VUI module may mount onto the existing luminaire body using a standard fitting for a removable lighting component such as a bulb or fluorescent tube (e.g. screw fit or bayonet). This will provide power to the VUI module. In turn, the VUI module may contain a similar fitting so that the lighting

component can be powered from this unit - either directly, or optionally under the control of the module. The module may provide microphone processing, voice processing, and networking capabilities such as Wi-Fi. Optionally, the VUI module may also provide an output path for audio responses from the internet, including a loudspeaker.

Embodiments are now discussed in more detail with reference to Figures 1 to 4.

Figure 1 illustrates an environment 101 occupied by at least one user 102, and in which is disposed at least one luminaire 103. The environment 101 may take the form of an indoor space such as a room of a building (e.g. living room, kitchen, office or corridor), or the interior of a vehicle (e.g. car interior, train carriage or ship cabin). Alternatively the environment 101 may be an outdoor space such as a yard with one or more walls, or may be a semi-covered space such as a porch. A luminaire refers to a lighting device for emitting illumination, i.e. light on a scale suitable for illuminating an environment. The luminaire may take any of a variety of forms, e.g. a free-standing luminaire such as a table lamp or desk lamp, or a ceiling mounted luminaire which couid be screwed or hung from the ceiling, or a wall-mounted luminaire such as a wall-washer. The luminaire 103 comprises a light-emitting element or "bulb" 301, which may take the form of a traditional filament bulb, or a gas- discharge element such as a fluorescent tube, or an LED-based lighting element comprising one or more LEDs (see Figures 3 and 4, to be discussed in more detail later). E.g. the light- emitting element may take the form of a halogen or LED-based replacement for a traditional bulb. Note that in lighting terminology, strictly the overall lighting device 103 is referred to as the luminaire or lighting fixture, whilst the constituent light-emitting element (typically a removable, replaceable component) is referred to as the lamp. Strictly the term "bulb" should only used in relation to filament bulbs. However in common, everyday parlance the overall device 103 is often referred to as the "lamp", e.g. as in the case of a table lamp or desk lamp, and what is strictly the lamp is often referred to as the bulb or tube, even in the case of an LED or halogen based replacement for a filament bulb, and such terminology is often even adopted in the lighting industry itself. For avoidance of doubt the overall device will be referred to herein as the luminaire, except in the case of a desk, table or floor lamp where the term "lamp" may be used in its more everyday sense to refer to the overall device 103. The constituent lighting component such as the bulb, tube or LED array will be referred to herein as the fight-emitting element. The term "bulb" may also be used in its broader sense to refer to what is strictly called a lamp, e.g. a replacement or analog of a filament bulb based on another technology such as LEDs.

The luminaire 103 is designed to be supported, when in use in normal operation, by a surface 105 such as a table top, work surface, shelf, floor, ceiling or wall; either in a free standing manner or fixedly.

The luminaire 103 also comprises microphone apparatus 104 comprising one or more constituent microphones 106 (see also Figures 2, 3 and 4, discussed in more detail shortly). Preferably the microphone apparatus 104 takes the form of a directional microphone array comprising an array of constituent microphones. This enables receive beamforming techniques based on the different phases and/or amplitudes of a given sound as received by the different microphones in the array. Receive beamforming in itself will be familiar to a person skilled in the art. The user 102 speaks one or more voice commands aloud in the environment 101, and the luminaire 103 is arranged so that its microphone apparatus 104 is able to capture such commands, preferably when spoken from anywhere in the

environment 101, and supply these to a voice recognition algorithm to be processed. Figure 3 shows some example luminaire designs in accordance with embodiments disclosed herein. In each case, the luminaire 103 comprises a base 201, a body part 202 and a lampshade 203.

The base 201 is the part of the luminaire designed for resting the luminaire in a freestanding manner upon a supporting, upward-facing surface beneath the luminaire 103, such as a table top, shelf or work surface (e.g. desktop); or for fixing the luminaire 103 to any type of supporting surface such as the ceiling or a wall. In the former case the base part 201 may comprise for example, on its underside, a flat surface for resting against the supporting surface, possibly with a gripping layer such as felt or rubber on the underside of the base 201. And/or, the base 201 may comprise one or more feet, such as rubber feet, for standing the base 201 on the surface 105 beneath. In the other embodiments where the base 201 is for fixing the luminaire 103 to the surface 105 (as opposed to standing it freely on the surface), the base 105 may comprise any suitable fixing means. For example the fixing means on the base 201 may comprise one or more holes for screwing, bolting, nailing or riveting the luminaire 103 to the surface 105; or one or more hooks, hoops, chords or wires for hanging the luminaire 103 from said surface 105; or one or more dips, connectors or brackets for clipping or attaching the luminaire 103 to the surface 105 or such like; or a complementary surface for accepting an adhesive for adhering the luminaire 103 to the surface 102 in question.

The body part 202 forms the main trunk of the luminaire 103. The body part 202 connects the light emitting-element 301 to the base 201, preferably via a socket in the body part 202. Thus the body part 202 provides separation between the light-emitting element 301 and the base 201 (and thus when stood on or fixed to the desired surface 105, also a separation between the light-emitting element 301 and the surface 105). In embodiments the base 201 is located at one and of the body part 202 and the light-emitting element 301 is connected at the other end, such as in embodiments where the body part 202 takes the form of a rod, pole, shaft, column or such like, or otherwise defines and axis or other expanse having two distinct ends. The socket may for instance take the form of a standardized socket for accepting a light- emitting element 301 (a lamp in the strict technical sense) such as a bulb or fluorescent tube or LED-based replacement therefor.

In embodiments, the body part defines a straight-line axis. For example, the body part 202 may be rotationally symmetric with the centre of the rotational symmetry defining the axis of the body part (i.e. a "lathed" type of shape or in the form of a lathed shape, though not necessarily actually manufactured with a lathe). As another example, the axis may be defined by the centre-of-mass of a uniform cross-sectional laminate taken through body part 202, in a plane perpendicular to the axis, at different points along the length of the body part (e.g. the centre line through a straight rod with square or rectangular cross- section). In embodiments, the body part 202 is formed and connected to the base 201 in a manner such that, when the base 201 is rested upon or fixed to the surface 105 in the manner for which it is designed, the axis of the body part 202 is vertical, in embodiments the body part 202 may take the form of a vertical rod, pole, shaft, column or the like, either completely straight or optionally instead with undulations. The base 201 may be arranged to fall substantially in the horizontal plane, or at least with its underside substantially flat in the horizontal plane, whilst the axis of the body part 202 is vertical. The base 201 may be symmetrical in the horizontal plane about the vertical axis of the body part 202, or the base 201 may have its centre of mass at the foot of the vertical axis of the body part 202.

The lampshade 203 is attached (in embodiments removably so) at the end or region of the body 202 where the light-emitting element 301 is connected. The lampshade 203 is arranged such that, when thus attached, to partially but not wholly obscure the illumination emitted by the light-emitting element 301 from the eyes of an occupant 102 in the environment 101. The obfuscation provided by the lampshade 203 may take the form of diffusion of the light, and/or partial blocking the light. Note that the term "lampshade" as used herein does not limit to a traditional frustroconical or textile lampshade as used in traditional home ceiling lights and table lamps (as illustrated in the right-hand example and bottom-left example of Figure 3), but more generally can refer more generally to any diffuser or partially-blocking light shield. For instance see the example in the top left of Figure 3, where a ceiling mounted luminaire comprises a lampshade in the form of a diffuser 103 forming part of the luminaire housing (in this particular example with the body part 202 taking the form of a stubby cylindrical trunk between the diffuser 203 and the ceiling 105).

In the middle-left example, the lampshade 203 takes the form of a diffuser which

completely engulfs both the light-emitting element 301 and the body part 202. It will be appreciated of course that the particular designs shown in Figure 3 are just by way of illustration.

In accordance with embodiments of the present disclosure, the luminaire 103 is used to hide a smart speaker inside a part of the housing 201,202 of the luminaire 103 or in the lampshade 203, or at least a listening device for receiving voice commands. This means that at least a microphone apparatus 104 is embedded into a part of the luminaire 103, the microphone apparatus comprising one or more individual constituent microphones 106. Preferably the embedded microphone apparatus comprises multiple such microphones at different spatial positions so as to enable spatial receive beamforming to isolate the voice of a particular user 102. Or even if beamforming is not used, the multiple microphones 106 can help in capturing the user's voice from different possible directions

In embodiments, the microphones 106 may be disposed on an extreme outer edge of the base 201 or lampshade 203, i.e. on the outside of the widest part of the base 201 or shade 203. In the case where the body part 202 defines an axis, this means at the greatest radius on the outer edge or face of the base 201 or shade 203 relative to the axis of the body part 202. This means that advantageously, the microphone apparatus 104 has the best chance of at least one of the microphones 106 having a line-of-sight to the majority of the room (or environment) 101. In a particularly preferred embodiments, the microphones 106 are placed all the way around an outer edge (most preferably the extreme outer edge) in a regular array, e.g. a ring in the case of a base or lampshade with circular cross-section, or at the same point on each side of a regular polygonal cross-section. This provides the best omnidirectional coverage and also a regular array to make the computations simpler for the purpose of the receive beamforming (if used). See the points labelled 106 in the examples of Figure 3. The number of microphones 106 is flexible. In scenarios where some of the microphones 106 are around the back (not in line of sight of the user's mouth), in embodiments the signal processing 107 (see Fig. 4) is able to ignore the inputs from such microphones 106. For example the signal processing 107 may ignore microphones 106 that are receiving below a threshold sound energy or below a threshold sound energy from the direction of the user 102.

For the purpose of receiving voice commands, in genera! there is a trade-off as to what is the best location of a microphone 106. ideally the microphone 106 should have a line-of- sight to all places in the environment 101 where people's mouths are expected to be found. But also, the microphone 106 should ideally be placed either very close to surfaces (lots of reflections, but these only affect very high frequencies), or very far away (affects many frequencies, but with a low magnitude).

The inventors have determined that a luminaire is a good place to incorporate a microphone as luminaires tend naturally to be placed by users in locations that perform well on both the above considerations (e.g. on the ceiling not close to wall, or on a wall not close to the ceiling, or on a table not close to either walls or ceiling). There are cases which compromise to some extent on one or other of the above considerations; however, this is a trade-off that can be accommodated in the signal processing 107, for example by tuning it to be aware of shading (no line of sight), or by means of a comb filter (microphones some distance away from a surface).

The idea is that the luminaire 103 and microphone(s) 106 are placed in such a way that there is little interference with respect to the speaking user 102, and little in the way of medium distance reflections, l.e. the microphones end up close to a surface (wall, table, ceiling), or far away from most other surfaces. The advantage of this is that any combing that happens is of a very high frequency, and well out of the way of frequencies used in speech.

In addition, lights are typically tethered, such as to a wall socket or ceiling fitting, so power is readily available to power microphones 106, beamforming software/hardware 107, and/or a Wi-Fi connection to the cloud 407 (see Figure 4, to be discussed in more detail shortly). Figure 2 illustrates some exemplary factors in the placement of the luminaire 103 and the microphone(s) 106 within the luminaire 103. As mentioned, preferably a microphone 106 used for voice recognition should be placed either very close or very far away from any surface in the environment. Reflections from very dose-up interfere mainly with only high frequencies above the human vocal range. Reflections from further out can interfere within the vocal range, but if the reflections are from far enough away then their magnitude is relatively small.

To illustrate this phenomenon reference is also made to Figures 5 and 6. Referring to Figure 5, consider a sound source 102 (such as a person speaking) at a distance E from a

microphone 106, and a reflecting surface 105 a distance D behind the microphone 106 (e.g. a hard surface such as a wall, ceiling, wooden floor, table top or desktop), with the signal incident perpendicular to the surface 105. The microphone 106 receives the sound via the direct path from the source 102 after the sound travels a distance E from the source 102 to the microphone 106. The microphone 106 also receives the echo of the sound after it travels a distance E+2D. Thus the microphone 106 receives the direct signal and the reflected signal which is delayed, and they are added together since the microphone 106 samples the superposition of the two. Thus the reflection results in adding a delayed version of a signal to itself. This produces a phenomenon known as combing, which is illustrated in Figure 6. At some frequencies of the received signal the signal and its reflection

destructively interfere whilst at other frequencies they constructively interfere, in a regularly repeating pattern (that resembles a "comb") in the frequency spectrum. In general there will be a peak in the frequency response whenever the extra distance travelled is an integer multiple of the wavelength, i.e. where 2D = kc/f where c is the speed of sound, f is the frequency of the sound, and k is any non-negative integer (k=0, 1, 2 ...). There will be nulls (troughs) between these whenever 2D = (2k+l)c/2f. Figure 6 illustrates an example wherein D is 200mm. For completeness note that the situation illustrated is somewhat idealized. In practice the reflected signal is typically attenuated somewhat, therefore the combing effect isn't exactly as illustrated (e.g. the nulls do not go completely to zero).

Nonetheless the peaks and nulls will be approximately at the points in the frequency spectrum described. In scenarios where the signal is incident at an angle b to the surface 105, then 2D can be replaced with 2Dcos(P).

The closer the microphone 106 is to the reflecting surface 105, the further apart these combs are in the frequency spectrum. Preferably the microphone 106 is within 30mm or so from the surface 105, or more preferably within 15mm. If it is 15 mm from the surface 105, and the signal comes at right angles to the reflecting surface (e.g. straight from above or below or horizontal to a wall), then there will be a 30 mm extra path. This results in a delay of 30mm/343000mm.s ¹ (distance in mm divided by the speed of sound in mm/s) which equals 87.4ps. The first null (k=0) is thus at l/(2*87.487.4ps) = 5717 Hz; well away from speech. A 30mm distance with a perpendicular signal would have a first null at half that frequency (2853 Hz), and the signal starts to roll off in bands where human speech is present. However, when the signal comes from an angle, the effective difference in distance (2Dcos b) will be less than 60mm, so the frequency will be high enough again.

Thus the shorter the reflection distance, the larger the gap between the combs. Preferably each microphone 106 is placed so that the first peak in the comb will be above about 8 kHz or so.

Consider now other surfaces further away (e.g. a wall on the other side of the room). The longer the reflection distance, the smaller the gap between the combs. So a large number of combs may appear. For example, for at a three meter distance one gets combs that are only 100 or so hertz apart. However, a three meter distance will cause attenuation of the signal (one over distance squared), an hence, the combing will be much less visible. Rather than it going up and down between no-signal and maximum-signal, it will "wobble" a bit around the average.

Thus the further away the microphone 106 is from a surface, the further the reflection will be attenuated. So, it loses its strength, and therefore the null in the comb becomes less and less pronounced. Further is better - there is no absolute cut-off, but the inventors have found that in typical applications the signal starts to become negligible after about a separation (D) of about a foot (30cm) and more preferably about two feet (60cm). Secondly, there is the effect that the hard surface may no longer no longer be able to reflect directly into the microphone. E.g. if one places a microphone 106 above the surface of a table, but two feet away from the edge of the table, then there is no longer a direct (perpendicular) path for the reflection. Again, further away is better.

As discussed previously, the luminaire 103 is designed to stand upon, or be fixed to, a surface 105 such as a table top, work surface (e.g. desktop), floor, ceiling or wall. A given microphone 103 is placed within the luminaire 103 such that when the luminaire 103 is stood on or fixed to the surface 105 in question, in the manner for which the luminaire 103 was designed, the microphone 106 sits a distance Ds from this surface 105 (the ceiling in the case of a ceiling mounted luminaire, the wall in the case of a wall mounted luminaire, the floor in the case of a floor lamp, or the table top or desktop in the case of a table or desk lamp). Preferably Ds should be no greater than 30mm, and more preferably no greater than 15mm. Preferably each microphone 106 in the microphone apparatus 104 of the luminaire 103 should meet this requirement.

Further, the luminaire 103 is placed within the environment 103 such that a given microphone 106 in the luminaire 103 sits at a distance D _t from the next closest surface (e.g. a wall or the floor in the case of a ceiling mounted luminaire, or the ceiling or floor in the case of a wail mounted luminaire, or the wall of ceiling in the case of a floor lamp, or the wailing, floor or wall in the case of a table lamp or desk lamp). Preferably DL should be no less than 30cm, and more preferably no less than 60cm. Again, preferably each microphone 106 in the microphone apparatus 104 of the luminaire 103 should meet this requirement. Preferably this requirement should be met between each microphone 106 and each surface of the environment 101 other than the closest surface.

Or in variants, the luminaire 103, and microphone within the luminaire 130, may be placed such that it is dose to two or three surfaces but close to no others, e.g. in a corner, such as a table lamp placed on a corner of a room, or a ceiling mounted luminaire installed an upper corner of the room. Nonetheless, preferably no microphone 106 of the luminaire's microphone apparatus is placed anywhere between 30mm and 30cm from any surface of the environment 101, and more preferably no microphone 106 of the luminaire's microphone apparatus 104 is placed anywhere between 15mm and 60cm from any surface of the environment.

Note that "surface of the environment" in the above discussion means a surface in the room, or such like, other than the facia or other parts of the luminaire 103 itself. To avoid unwanted reflections or blockage from the actual parts of the luminaire 103 itself, in embodiments the microphone(s) 106 is/are placed so as to stand proud of the outer facia of the luminaire 103 (i.e. protruding slightly). Alternatively however any reflections or blockage from parts of the luminaire 103 itself may simply be considered tolerable, as this effect will only be relatively small.

Acoustically speaking the base 201 is the best place to locate the microphone(s) 106 since this will place them closest to the surface 105 upon which the luminaire 103 sits or to which it is attached. However this is not limiting to all possible embodiments, and in alternative embodiments one, more or all of the microphones 106 may be incorporated in another part such as the body part 202 or the lampshade 103. For example the lampshade 203 may provide better opportunities for retrofitting the microphone(s) 106.

Figure 4 gives a block diagram of an example implementation of the luminaire 103. In addition to the components discussed previously, the luminaire 103 comprises a controller 403 and a voice user interface (VUI) subsystem 404.

The controller 403 is arranged to control the light-emitting element 301 to emit illumination based on power from a power source 402 such as a wall socket. The controller 403 may comprise at least a switch for switching the illumination on and off. The controller 403 may also be configured to enable the intensity of the illumination to be dimmed up and down, and/or to adjust the colour of the illumination. The controller 403 may be arranged to enable any one of more of these functions to be controlled manually via a manual user control (not shown), and/or by the VUI subsystem 404.

The VUI subsystem 404 comprises the microphone apparatus 104, a signal processing block (signal processing function) 107, a communications protocol stack 406 such as an internet protocol stack, and a communications interface 407 which may comprise a wireless interface such as a Wi-Fi interface or a wired interface such as an Ethernet interface. The signal processing block 107 and the protocol stack 406 may be implemented in the form of software code stored on an embedded memory of the luminaire 103 and arranged to run on an embedded processing apparatus of the luminaire 103. The memory on which this code is stored may comprise one or more memory units employing one or more memory media, e.g. magnetic memory such as a hard drive or electronic memory such as an EEPROM {flash memory). The processing apparatus on which the code is arranged to run may comprise one or more processing units. Alternatively an implementation in hardware circuitry is not excluded, or a combination of hardware and software.

In embodiments where the microphone apparatus 104 comprises an array of multiple microphones 106, the signal processing block 107 preferably comprises a beamsteering algorithm configured to apply receive beamforming techniques to the array to target the direction of the user 102 in the environment (and therefore exclude sounds from other sources). Such techniques in themselves are known in the art and will not be discussed at further length herein. In embodiments the signal processing block 107 may alternatively or additionally comprise one or more other signal processing algorithms for conditioning the received signals prior to voice recognition, e.g. other source-signal separation algorithms such as complex spectral phase evolution (CSPE), or an acoustic echo cancellation (AEC) algorithm.

The signal processing block 107 further comprises a voice recognition algorithm configured to recognise voice commands in the audio signals captured by microphone(s) 106.

Preferably this comprises a speech recognition algorithm and the voice commands comprise speech commands, though in other embodiments the use of other vocal sounds is not excluded. The signal processing block further comprises a control algorithm configured to enact control functions in dependence on the commands recognized by the voice recognition algorithm. In embodiments this may comprise controlling the illumination emitted by the light-emitting element 301 via the controller 403, such as to turn the illumination on and off, dim it up and down, and/or set its colour. Alternatively or additionally, the control enacted by the control algorithm based on the detected voice commands may be to control another appliance or service via the communications interface 407. For example this could be to control another household appliance or office appliance in the same room or building, e.g. via a local wireless area network such as a Wi-Fi network or ZigBee network, or a wired local area network such as an Ethernet network. As another example, the control may be to access a remote service via a wide area network such as the Internet or a cellular network (e.g. 3GPP network). For instance this could be to request information from an internet-based service such as a virtual digital assistant. E.g. the user could request information on focal shops, bars, restaurants, etc.; perform online shopping; or ask for the weather forecast; or such like.

In embodiments the voice commands comprise specific keywords. Alternatively or additionally the voice recognition algorithm may employ natural language processing (NPL) techniques. In embodiments the voice recognition algorithm may be configured to act upon voice commands only after detecting a predetermined wake-up word.

There are various ways in which the lighting controller 403 (e.g. switch) can be controlled. One way is that the speech signal gets interpreted by the cloud, which in turn controls the switch 403. Hence by way of illustration in Figure 4 the block 107 is shown as controlling the switch 403 via the Internet protocol stack 406. Another method however is to have a local keyword detector that can control the switch 403 directly (which would not necessarily require the Internet protocol stack 406). In embodiments the latter may not comprehend longer commands, just keywords; the former may have more deductive reasoning behind it.

In embodiments, the VU1 subsystem optionally comprises a speaker 405 arranged to give feedback on the processing of the voice commands. For example an audio confirmation may be played out to the user 102 acknowledging that the voice command has been recognized or acted upon, or in the case of requesting information from an online service, the information may be played out audibly to the user 102.

The VU1 subsystem 404 is preferably arrange to derive its power, for performing the above functions, from the same power supply 402 as the light-emitting element 301 (i.e. the main power to the luminaire 103). For example the VUI subsystem 404 may be arranged to derive its power from the same mains power connection, e.g. same wall socket.

In some embodiments, the VUI subsystem 404 may take the form of a discrete module or unit fitted into the luminaire 103. In embodiments this may take the form of a retrofit module fitted into a pre-existing luminaire 103 that did not previously have any

microphones or voice recognition functionality. For instance, in one embodiment the VUI module 404 inserts into the standard socket of the luminaire 103 where the bulb 301 would normally fit, and derives its power from this. The VUI module 404 then also comprises another instance of this same type of standardized socket, so the bulb 301 can fit into that. Power is supplied to the bulb 301 from the luminaire's socket through the VUI module 404 and the VUI module's socket. In such embodiments the microphone apparatus 104 may be connected to the rest of the VUI module 104 and may also be retrofitted. For example these may be incorporated into a replacement lampshade 203, or may be attached retrospectively onto the facia of any part of the luminaire 103 such as an existing lampshade 203 or the base 201.

Note that whilst in Figure 4 the signal processing block 107 has been shown as being implemented in the luminaire 103 itself, in alternative embodiments some or all of this functionality may be offloaded to an external source such as a server (a server herein referring to a logical entity implemented on one or more server units at one or more geographical sites). In this case the raw or partially-processed signals captured by the microphone(s) 106 are sent to the server via the communications interface 407, and based on these the server performs the speech recognition or recognize the voice commands. The server may then perform the corresponding control action(s) itself (e.g. retrieve requested information), or send the result of the speech recognition back to the luminaire 103 to perform the control (e.g. control the illumination).

It will be appreciated that the above embodiments have been described by way of example only. Other variants and/or applications may be realized by a person skilled in the art once given the disclosure herein. The scope of the present invention is not limited by the described embodiments but only by the accompanying claims.