GB2527784A

GB2527784A - Wind noise reduction apparatus

Info

Publication number: GB2527784A
Application number: GB1411728.7A
Authority: GB
Inventors: David Herman
Original assignee: AUDIOGRAVITY HOLDINGS Ltd
Current assignee: AUDIOGRAVITY HOLDINGS Ltd
Priority date: 2014-07-01
Filing date: 2014-07-01
Publication date: 2016-01-06
Also published as: GB201411728D0; TW201607331A; WO2016001615A1

Abstract

The wind noise reduction apparatus comprises at least one transducer element having an input port 11, and at least one non-porous structure 30 covering at least a portion of the input port of the transducer element. The apparatus further comprises a housing 50 for the transducer element and nonÂporous structure, wherein the housing has a hole 51 through which wind and sound from outside the housing can enter the housing and the non-porous structure is arranged to cause a pressure differential in the housing and allow sound to be received through the input port of the at least one transducer element. The wind noise reduction apparatus may be applied to an earphone arrangement (figs 16 & 17).

Description

WIND NOISE REDUCTION APPARATUS

The present invention relates to the use of electro-acoustic transducers and more particularly to an apparatus which reduces the effects of wind noise in the case of a microphone.

The problem with wind noise in relation to microphones is well known and many solutions have been proposed. Such proposals have often required the use of complex signal processing equipment which increases the cost of the microphone and associated system quite considerably. Simpler solutions such as providing the microphone with a permeable or semi-permeable wind screen of some sort have also been proposed which can be effective, for example, WO 2008/099199 Al.

The present invention provides an apparatus comprising at least one transducer element and non-porous structure the purpose of which is to prevent the wind reaching the transducer thereby forming an obstruction to the wind. The transducer element and non-porous structure are preferably located within a housing comprising at least one hole. The arrangement is such that wind entering the housing through the hole will impinge on the structure and be prevented or blocked from reaching the transducer element whilst simultaneously reducing the effective wind pressure experienced by the diaphragm of the transducer.

The technology works with an omni-directional transducer elements having a port on one side such as the top side.

In order that the present invention be more readily understood, embodiments thereof will now be described by way of example only with reference to the accompanying drawings, in which:-Fig. 1 shows diagrammatically a first embodiment of a transducer element apparatus in accordance with the present invention; Fig. 2 shows diagrammatically a second embodiment of a transducer element apparatus of the present invention; and, Fig. 3 shows for reference purposes the wind speed in the transducer element used in Fig. 1 and 2 in a conventional configuration without the presence of a non-porous structure; Fig. 4 shows for reference purposes the wind pressure distribution in the transducer element of Fig. 3; Fig. 5 shows the wind speed in an arrangement such as Fig. 1 with a housing surrounding the transducer element's input port and non-porous structure having a single planar top surface; Fig. 6 shows the wind pressure distribution in the arrangement of Fig. 5; Fig. 7 shows the wind speed in an arrangement such as Fig. 2 with a housing surrounding the transducer element's input port and non-porous structure having a single planar top surface; Fig. 8 shows the wind pressure distribution in the arrangement of Fig. 7; Fig. 9 shows a wind noise rejection apparatus according to one embodiment; Fig. 10 shows the apparatus of Fig. 9 with a top section of the housing removed; Fig. 11 shows a transparent view of the apparatus of Fig. 9; Fig. 12 shows a cross sectional view of the apparatus of Fig. 9 with the section taken along line A-A in fig. 9; Fig. 13 shows a simplified side view of the non-porous structure of fig. 12; Fig. 14 is a non-porous structure that is the same as Fig. 13 but with rounded edges; Fig. 15 is a non-porous structure that is the same as Fig. 13 but with rounded bottom edges; Fig. 16 is an embodiment of an ear bud incorporating a non-porous structure arrangement; Fig. 17 is a simplified cross section view of the ear bud in Fig. 16 to show internal components of the main body; and Fig. 18 is optional processing means that may be used with the embodiments particularly the fig. 17 embodiment.

Embodiments of the present invention comprise an electro-acoustic transducer element and at least one shaped solid structure that is spaced from the transducer element. In one embodiment, an apparatus is provided comprising at least one transducer element in a spaced configuration with a solid wall structure that is formed of a material or in an arrangement to prevent wind passing from one surface of the structure to the surface on the opposite side thus inhibiting movement of wind through the screen. The screen can be non-porous and I or solid to achieve this purpose. If multiple layers of material with semi permeability are provided instead, they are arranged such that wind cannot pass through the arrangement.

Different types of transducer element may be used such as electret condenser microphones or MicroElectrical-Mechanical System(MEMS) microphones. It is preferable to utilise omni-directional transducer elements and these can be omni-directional microphones. An omni-directional transducer element is one where there is a port in only one side a housing of the transducer with the diaphragm of the transducer disposed within the housing such that it responds equally to sounds from different directions.

Referring now to Fig. 1, this shows an arrangement which comprises a electro-acoustic transducer which in this embodiment is an electret condenser microphone 10 (ECM) having at least one input port 11 and wires 12 to provide appropriate conventional electrical connections to the microphone. A two-wire transducer is shown, but not limited to any number of wires that the transducer requires. No specific updating of the electrical connections is required for the arrangement to operate as only changes relating to the mechanical properties of the arrangement are made compared to conventional microphone arrangements.

Positioned away from the input port 11 of the microphone 10 is a solid non-porous rigid structure 20 that creates a cover for the microphone 10 and obstruction to prevent wind from directly impinging the microphone 10. The structure 20 is positioned sufficiently close to the microphone 10 to keep the arrangement compact but not close enough to completely block the port 11 of the microphone 10 from receiving sound and acoustic energy. The structure 20 is positioned between a source of wind (depicted as A") and the microphone 10 thereby acting as a screen or shield to the wind. The source of the wind can enter via an exposed hole of a housing within which the microphone 10 and non-porous structure is contained or some other source. Sound can enter through the same exposed hole but can reach the microphone 10. The sound may be somewhat attenuated but the attenuation will be relatively minimal compared to the reduction in wind on the microphone.

In this embodiment, the structure 20 is flat with a similar shape to the transducer which in this embodiment is circular. It may be a disc, however, the member is not limited to this shape and may be other shapes not necessarily matching that of the microphone but of an appropriate shape to prevent wind impinging on the microphone 10. The size of a major surface of non-porous structure 20 may be smaller than a major surface of the transducer but the size of the structure 20 at least covers the input port 11 of the microphone 10. With this arrangement, areas of turbulence are created by wind adjacent the side edges of the screen member. The structure 20 has sufficient rigidity to not fluctuate when wind impinges on the surface in wind conditions that are not excessive. The structure may be formed of plastic, metal or other suitable material.

Referring now to Fig. 2, this shows another embodiment which uses the same microphone 10 as that in Fig. 1 but a variation to the shape of the non-porous structure.

The arrangement comprises the microphone 10 of Fig. 1. The microphone is an electret condenser microphone (ECM) or MEMS having at least one input port 11 and any number of appropriate wires 12 to provide appropriate conventional electrical connections to the microphone. No specific updating of the electrical connections is required for the arrangement to operate as only changes relating to the mechanical properties of the arrangement are made compared to conventional microphone arrangements. This type of ECM or MEMS will be known to those skilled in the art and therefore will not be described in detail.

Positioned away from the input port 11 of the microphone 10 is a solid non-porous rigid structure 30 that creates a cover for the microphone 10 and obstruction to prevent wind from directly impinging the microphone 10. The structure 30 is sufficiently close to the microphone to keep the arrangement compact but close enough to completely block the port 11 of the microphone 10. In terms of scale, a typical spacing may be around 0.3 mm and although it will be appreciated that the invention is not limited to this spacing. The structure 30 is fixedly positioned between the source of wind and the transducer element thereby acting as a rigid screen or shield of the microphone to the wind.

In this preferred embodiment, the non-porous structure 30 has a V-shaped cross section when viewed from one side with the vertex of the V" being nearest to the input port 11 of the microphone 10. This type of shape is such that there is a depression or indentation in the top surface of the structure 30 forming a dimple or a concave portion in the top surface where the vertex of the top surface is bent inwards towards the bottom surface with the dimple facing towards the transducer element. Therefore the structure is three dimensional and has an indentation which can be viewed as a V-shape or chevron shape from one side when taken in cross section. The legs of the V" (or "dimple" in 3D) extend outward away from the vertex and the input port 11. Each leg (3D surface) of the "V' (viewed in section from one side) is a disc with a similar cross sectional shape to the microphone 10 which in this embodiment is circular. The distance between the end of each leg of the "V is larger than the distance between opposing edges of the microphone 10. The member 30 is not limited to being formed of two disc shaped portions as will be appreciated by those skilled in the art and could be other shapes such as rectangular portions or other types of shapes with a dimple on the top surface. Similarly to the first embodiment, with this arrangement, areas of turbulence are created by wind adjacent the side edges of the screen member.

Therefore, the screen member is of a sufficient area and thickness to provide for these turbulent areas. Similarly to the structure 20, structure 30 has sufficient rigidity to not fluctuate when wind impinges on the surface in normal wind conditions that are not excessive. The structure may be formed of plastic, metal or other suitable material that is typically solid at room temperature.

As mentioned above, the microphone used in the arrangements of figures 1 and 2 is an ECM 10. Comparisons between different types of arrangements will now be described by way of example with reference to figures 3 to 8 in order to show the effect of the non-porous structure 20 and 30.

Figure 3 shows a typical wind speed fluid dynamics simulation pattern and figure 4 shows a typical wind pressure fluid dynamics simulation pattern for an omnidirectional ECM 10 such as that shown in fig. 1 with the wind travelling from left to right of the figures. The diaphragm of the microphone is not shown to simplify the figure. No non-porous structure is provided in this example arrangement. It is evident that for this type of microphone, there is significant wind speed and pressure within the ECM 10 as the wind enters through pod 11 which results in significant wind noise output from the microphone or MEMS 10. Regarding figure 3, wind disturbance is shown within the microphone or MEMS through a series of arrows and wind pressure is shown with large pressure bubbles P in the microphone.

Figure 5 shows a wind speed simulation pattern and figure 6 shows a wind pressure simulation pattern for an arrangement such as that of figure 1 which includes an ECM 10 and a solid non-porous structure 20 that is flat. As with figure 3 and 4, the wind travels from left to right of the figures. The diagrams are simplified to only show outline drawings of the various elements.

In fig. 5, the microphone 10 is an ECM with an input port 11 on a top surface of the microphone. The position of the input port 11 is coincident with the central axis of the microphone 10. The solid non-porous structure 20 is spaced away from the input port 11 of the microphone 10 and is axially aligned with the microphone such that the distance d between the surface on which the input port 11 is provided and a major surface of the non-porous structure 20 is substantially constant. These surfaces can therefore be considered to be substantially parallel to each other. The length Li of the major surface of the non-porous structure 20 may be substantially the same as the length L2 of the surface on which the input port ii of the microphone is provided.

The microphone 11 and non-porous structure 20 are contained within a casing or housing 40. An opening or hole 41 is provided in a top surface 40a of the housing 40 and the hole 41 is axially aligned with the input port ii of the microphone 10 although it may instead be axially offset from the hole 41. The non-porous structure 20 is positioned between the input port ii and the hole 41.

Side walls 40b of the housing 40 are provided with one or more vents 42 through which wind entering the hole 41 can exit the housing 40. In this embodiment, the vents 42 are adjacent the side edges of the non-porous structure 20.

A channel which acts as a passage 43 for the wind is formed in the housing 40 between an underside of the top surface of the housing 40 and the top surface of the non-porous structure 20. The ends of the passage 43 are spaced from and adjacent to the side vents 42 such that at least some wind that may be passing through the channel can be expelled from the side vents 42.

Figure 6 shows an identical arrangement to that in fig. 5 and therefore the description of the various elements is not repeated here and all the reference numerals are not shown in the figure.

If wind enters through the hole 41, it will impinge on a surface of the non-porous structure and flow through the passage 43 towards the side vents 42. A wind pressure differential will be created. However, some wind still impinges on the input port ii of the microphone 10 after entering through hole 41.

The pattern in figure 5 shows that the wind speed is high in the passage 43 and the pattern in figure 6 shows that there is a large pressure in the area P1 between the hole 41 of the housing and the surface of the non-porous structure 20. In this type of arrangement, the wind speed at the input port ii is less than that in Fig. 3. There may be some leakage in the wind speed but less than Figure 4 and this can be heard as wind noise in the microphone 10 as indicated by the pressure bubbles P2 in the figures.

Figure 7 shows a wind speed simulation pattern and figure 8 shows a wind pressure simulation pattern for an arrangement such as that of figure 2 which includes an [CM 10 and a solid non-porous structure 30 that is V (or dimple) shaped. As with figure 5 and 6, the wind travels from left to right of the figures. The diagrams are simplified to only show outline drawings of the various elements. The microphone 10 is identical to that in Figure 5.

The microphone 10 is located within a housing 50 with an input port 11 of the microphone facing towards a hole 51 in the housing 50. The housing is similar to the embodiment in Figure 5 and 6. The hole 51 is provided in a top surface 50a of the housing 40 and the hole 51 is axially aligned with the input port 11 of the microphone although it may instead be axially offset from the hole 51.

Located between the input port 11 and the hole 51 is the V-shaped (dimple shaped in three dimensions) rigid non-porous structure 30 which was described in relation to Figure 2. The orientation of the non-porous structure is similar to that in fig. 2 with the vertex of the V" (or dimple) being nearest to the input port 11 of the microphone 10. The upper surface of the legs 30a of the V-shaped non-porous structure 30 and the underside of top surface 50a of the housing 50 forms a passageway that narrows away from the vertex of the V to the ends of the legs 30a with each leg 30a thereby forming a tapering passage 53on each side of the hole 51.

The ends of the passage 53 are spaced from and adjacent to the side vents 52 such that at least some wind that may be passing through the channel can be expelled from the side vents 52.

Figure 8 shows an identical arrangement to that in fig. 7 and therefore the description of the various elements is not repeated here and not all the reference numerals are not shown in the figure.

If wind enters through the hole 51, it will impinge on a surface of the non-porous structure 30 and flow through the passages 53 towards the side vents 52. Therefore, the wind is prevented from impinging directly on the input port 11 of the microphone 10 when it enters through hole 51.

The wind speed is high in the passages 53 and the wind travels further compared to figure 5 before impinging on the surface of the non-porous structure 30.

The pattern in figure 8 shows that there is some wind pressure at an area P2 near the vertex of the V-(or dimple in 3 dimensions) shape but this is less than the pressure in Figure 6. In this type of arrangement, the wind speed and pressure show virtually no wind effect and very little or no wind speed differential or pressure differential evident at the input port 11 than in the arrangement of Fig. 5 as is indicated by no pressure bubbles being shown. The wind is better directed by the V-shaped (dimple-shaped) screen member as there is a focussed shift of the wind to the side vents 52. Note that if the wind enters the side vents then an equalization of pressure will also occur due do the top port and the effect will also be a reduction in wind speed and wind pressure at the transducer element. In this case the entry hole 51 and side vents' 52 functions will be reversed but the overall effect will be the same.

Figures 9 to 12 show schematic representations of an embodiment of a wind noise reduction apparatus based on the basic configurations described above in relation to the V-shaped non-porous structure embodiments. Figure 13 shows a schematic side view of the non-porous structure used in the embodiments.

Referring to figs. 9 to 12, a wind noise reduction apparatus having a generally circular cylindrical shape is shown comprising an omni-directional electret condenser microphone (ECM) 60 including at least one input port 61. Four are shown as representing a typical unit commonly available in this embodiment but the number of ports will depend on the specific brand of microphone. The microphone has wires 62 to provide appropriate conventional electrical connections to the microphone. This type of microphone will be known to those skilled in the art and therefore will not be described in detail.

The apparatus further comprises a housing formed of a base section 71 that has a shape corresponding to accommodate the transducer (i.e. round for most microphones or square/rectangular for most MEMS transducers). The base section 71 is annular with a hole in the middle to receive the microphone 60. The microphone 60 is received in the hole such that an upper surface of the microphone / transducer! MEMS is flush with the upper surface of the base section 71. It will be appreciated that other configurations of the microphone and base section may be provided. For example, the base section 71 may include a seat rather than having a hole and the seat receives the microphone / transducer / MEMS.

A structural arrangement 80 is provided on the base section 71. The arrangement 80 comprises a plurality of support members 81 and in this particular embodiment there are three support members although more or less could be provided. The support members 81 are generally solid cylindrical or other shaped elements and extend upwards from the base section 71 may be parallel to each other.

One end of each support member 81 is attached to the microphone 60 in the base section 71 of the apparatus. The support members support a non-porous structure 82 and, in this embodiment, through holes(not shown) are provided in the non-porous structure 82 to receive the corresponding support member 81.

The non-porous structure82 is solid structure and has a V-shaped (or dimple shaped in three dimensions) cross section as shown in figs. 12 and 13 when viewed from one side in section. In this embodiment, this is achieved with a rigid member of a constant thickness and the top surface 83 and bottom surface 84 of the rigid member being angled downwards towards the a central axis C of the disc. Taking a cross section of the rigid member such as in fig. 12 and in more detail in fig. 13, a V-shape or chevron shape is formed with legs 82a of the "V' extending outward from the vertex of the "V". The angle a" of the legs 82a of the "V' with respect to the central axis C is could be between 0 to 90 degrees although no specific value limitations are intended.

It will be appreciated that similar shaped non-porous structures may be provided.

The shape of the top surface is such that there is a point between the ends of the top surface that is lower than a plane between the ends of the top surface. With the V" or chevron shape shown in Figure 12 and 13, this lowest point is the centre point of the top surface which is also on the rotational axis of the screen member but this need not necessarily be the case. The top surface can be considered as forming a dimple in the non-porous structure. It follows that a curved surface may form the top surface of the non-porous structure where the centre point of the top surface is lower than the edges of the end of top surface such that the vertex where the top surfaces of the two legs meet may be curved rather than pointed. The edges of the legs may be rounded rather than flat and pointed (see fig. 14) or chamfered. Alternatively, only the bottom edge of the legs may be rounded with the top edges being flat and pointed (see fig. 14).

The housing further comprises a side wall 72 of predetermined thickness that extends up from the base section 71 to a height above that of the non-porous structure 82 such that the side wall surrounds the side of the non-porous structure arrangement 80. A cover 73 is provided on the side wall 72 to seal the housing and form a compact structure. It will be appreciated that the housing can be formed of a unitary structure in that the base section, side walls and cover are an integral unit. The non-porous structure is thus contained in a chamber 74 formed by the housing and microphone 60.

An aperture or through hole 75 is provided in the cover 73 and the hole 75 is axially aligned with the central axis C of the non-porous structure as is the input port 61 of the microphone 60. However, the skilled person will appreciate that a minor radial misalignment between the through hole 75, central axis C and input 61 is conceivable but not preferable.

Side vents 76 are provided as outlets in the side wall 72. In this embodiment, there are four side vents 76 circumferentially spaced in the same orthogonal plane to the central axis C of the non-porous structure. That is, there are more side vents 76 than there are input holes 75 on the top surface of the housing. The side vents extend radially through the side wall 72 orthogonally to the central axis C until reaching the outer surface of the side wall. The side vent may have a diameter of around 1 mm. As shown in the simplified drawing in fig. 13, the side venting holes' 76 radially extending central axes are aligned with the top edge of the top surface 83 of the non-porous structure 82 such that at least a portion of the side vent is above the non-porous structure 82 top surface 83 edge. However, it will be appreciated that the number of vents may vary. Where there is more than one input hole in the top surface, there may be more or less side vents. In some embodiments, the side vents may have a constant cross section or increasing cross section along their length towards the outer surface of the side wall. Even if wind enters through the one or more side walls, it would be released through other side walls or through the through hole 75.

With an arrangement such as in Fig. 9 to 12, the wind will enter through the hole and pass through the passage created by the non-porous structure in a similar way to that shown in Fig. 7. Turbulence is created in the passage and at the end of the passage and the wind is expelled through the side vents 76. It may also be explained as a mechanism of pressure equalization rather than a flow of wind. Thus the functions of vent and entry ports may be reversed and still achieve the same effect -a reduction of wind pressure at the diaphragm of the transducer element.

The inventors have found that the non-porous structure shown in Fig 15 aligned with the side vents as shown in Fig. 13 can provide around an 11 dB reduction in wind noise reading by the microphone compared to a conventional arrangement having no non-porous structure at all (such as shown in Fig. 3). 1]

Where more than one transducer is provided, a further wind noise reduction effect may be achieved by summing the outputs of the transducer elements to produce a single output.

Embodiments will now be described which show at least one application of the above concept with at least one transducer and non-porous structure. In this embodiment, two transducers are provided in fixed positions and the transducers are ECM microphones arranged in a speaker arrangement which in this case is an ear bud.

The disposition of the transducers with respect to one another is not significant as the further wind noise reduction effect achieved by summing the outputs can be obtained irrespective of the direction that the transducers face with respect to the sound source, although optimal performance is achieved when the elements face with their input ports generally towards the hole of the housing within which they are contained with at least one screen member between the transducers and the hole of the housing. There may be circumstances in which the transducers are positioned relative to each other such that their input ports are equidistant from the hole of the housing which receives the sound from outside the housing. In one such arrangement, the elements can be located on the surface of an imaginary sphere so that they are all equidistant from the desired sound source.

Referring to fig. 16, an embodiment of an ear bud 90 is shown incorporating a non-porous structure arrangement to reduce wind noise. Only one ear bud is shown but it will be appreciated that two may be provided and the second will be the same or similar to that shown in Fig. 16. The ear bud 90 comprises a cylindrical body which forms a main body 91 of the ear bud 90, an ear phone portion 92 attached to one end (top part) of the main body and wiring 93 extending from the base at the other end of the main body 91. The ear phone portion 92 contains a speaker in a similar way to conventional ear buds or ear phones and will therefore be not be described in further detail. The ear phone portion 92 can be received at one end of the main body section 91 as shown in fig. 17 such as in an interference fit. An inlet 94 is provided on a side wall of the main body 91 to receive sound from outside the main body 91. The inlet can be nearer the wiring end of the main body rather than the end of the earphone portion.

This may allow sound outside the main body to enter through the inlet when the earphone portion is in a user's ear.

As shown in the side sectional view of the main body 91 of fig. 17, below the inlet 94 in a direction orthogonal to the central longitudinal axis of the main body is provided a wind resistive arrangement 95 of foam or felt and mesh. The foam or felt reduces the wind velocity but this may cause wind turbulence in that there will be wind interaction in different directions. The mesh will be located below the form or felt and can have a hole size of around 40 microns to provide some further wind resistance.

The mesh provides laminar flow through the material. Other sizes of mesh can be provided or this material can be dispensed with altogether. However, improved wind noise reduction can be provided with the form or felt and mesh wind resistive arrangement 95 being located at the inlet 94 of the main body 91. A further mesh (not shown) with larger hole size compared to that in the arrangement 95 may be optionally provided above the wind resistive arrangement 95, for example, at the inlet and flush with the side wall of the main body 91 of the ear bud to help protect the foam of the wind resistive arrangement from the user poking objects into it accidently (i.e. finger nail). It will be appreciated that the arrangement 95 can be varied to provide more or less layers of material or no foam / felt or mesh, however, this may not be an optimal solution.

Below the inlet 94 and wind resistive arrangement 95 is an aperture or through hole 96 which can be of a small diameter than the inlet 94. The foam material 95 covers the through hole 96. In terms of functionality, the through hole is similar to hole 51 shown in figure 7. One end of the through hole 96 is directly below the foam member 95. If no foam member is provided, the hole 96 may be below the inlet 94 or the wider inlet 94 may not be needed. The other end of the hole 96 is above a chamber 97. In normal use, sound which can be ambient noise from outside the main body and any wind can enter the inlet 94, through the arrangement 95 and then enters the chamber 97 via the through hole 96. The mesh of the arrangement 95 provides a laminar flow.

Similarly to the embodiments of Figs. 2, 7 and 9, at least one non-porous structure 99 with a concave surface or dimple is provided between the hole 96 and a microphone 98. In this embodiment, two microphones each which are the same omnidirectional ECMs to the previous embodiments are located with their respective input ports (not shown) facing each other. That is, the microphone 98 on the left of the figure has its input port facing generally right and the microphone on the right of the figure has its input port facing generally left. It will be appreciated that a single microphone arrangement may instead be provided. The microphones are each orientated substantially orthogonally to the axis of the through hole such that the microphones central axis is substantially parallel to the central longitudinal axis of the main body.

Facing each microphone 98 is a non-porous structure 99 oriented such that its major axis (the axis that is orthogonal to the central rotational axis of the non-porous structure) is substantially parallel to the microphone 98 which is also substantially parallel to the central longitudinal axis of the ear bud main body. Therefore, in this embodiment, two non-porous structures 99 are provided. It will be appreciated that other numbers of non-porous structure, orientations of non-porous structure or types of non-porous structure can be provided. In some embodiments (not shown), a single non-porous structure could be provided and the major axis of the single screen member could be substantially parallel to the central axis of the main body of the ear bud 90 such that screen member is common to the two microphones. Therefore, the chamber 97 forms a common cavity for the plurality of microphones 98 and non-porous structures 99.

Separate side vents 100 are positioned in a similar way to the previous embodiments where they are above at least one end of the non-porous structure such that wind pressure can be reduced. In the case of a common non-porous structure, one or more outlet vents with the same functionality as the side vents would be provided at a located at or above the non-porous structure.

Optional processing circuitry may be provided at an appropriate position either in the ear bud 90 or in a separate section (not shown) that is attached to another part of the wiring 93. Instead of hardware, software can be embedded in a processor to carry out the various processing. The outputs of the microphones 98 are buffered and then summed together in any convenient manner with equal weighting or gain using any suitable analogue or digital technique. After summation, the output may be passed through a high pass or band pass filter whose lower cut off frequency is about 200 or 600 Hz (depending on application -such as ambient wind noise for safety applications or communications application) to further improve the wind noise rejection. The filtered output is fed to a driver and amplifier circuit. The filtering may also be done before the addition process if desired or, in an arrangement having only a single microphone, in the absence of any addition process.

Fig 18 shows a block diagram of the microphones 98 with processing means for carrying out signal processing if such is desired for any particular application e.g. should one or more of the elements be producing an inappropriate signal and it be desired to exclude it from the summed output. There are many other methods for achieving this using either analogue or digital solutions. As mentioned above, also a software implementation via a DSP can be provided and may be preferable as it eliminates the added circuitry. The outputs of the microphone 98 are fed to controllable buffers where the signals are compared with a reference voltage so that the signal from the worst affected element(s) is/are inhibited. Thereafter, the signals are added together at a summation means 111 and fed to an output buffer means 113 after processing by a filtering means 112 which applies high pass or band pass filtering with a lower cut-off frequency about 200 Hz. Other notch and band pass filtering can be provided to compensate for any slight loss of speech fidelity. Similar filtering techniques may also be applied to the output from a single transducer such as a transducer shown in previous embodiments such as fig. 2, 7, and 9, in which case no summation is required. The filtering may be supplemented by some amplification to improve the level of desired sound (non-wind related) received by the microphone where necessary.

With this type of ear bud, the ear bud can be connected to a sound source (eg. a music source) in a conventional way. This could be wired or wireless, via Bluetooth, for example. Advantageously, the ear bud construction can be applied to a product for use outdoors used in various sports such as jogging, skiing, cycling to name a few. The user would be listening to music via a wired or wireless source such as Bluetooth connected to their mobile phone. Because their ears are obstructed by the ear buds, hearing of sounds outside the ear bud is diminished. Thus, hearing oncoming vehicles (cars, trucks motorbikes for example) in order to get out of the way would be impeded without some type of wind noise reduction.

Therefore, wind noise reduction can be applied to a product while maintaining full fidelity for the listening experience. Thus, the user can hear the outside ambient noise (cars, trucks etc) without the wind interfering and whilst also hearing their favourite music.

This wind noise reduction technology can also be used for ambient noise cancellation and can be included if required with the relevant processing.

This design also renders the music directly and without frequency filtering.

It should be noted that this design does not eliminate non-wind related ambient noise.

Also, this design does not include echo cancelation. This means that if it is to be used to speak on the phone, then the transducers (microphones) should not feedback or loop with the audio coming from the earbud internal speaker. Solving this is well-known and available from many manufacturers of Bluetooth transceiver chips. These echo cancelation solutions will integrate well with this wind noise reduction solution.

The omni-directional transducer element(s) can be fabricated using semi-conductor techniques which allows the array of elements to occupy very little space. A MEMs microphone is sometimes referred to as a SiMIC (Silicon Microphone) and may have a rectangular shape rather than a circular shape as described above in relation to the [CM. Appropriate changes can be made where necessary as would be understood by the skilled person to account for this difference in microphone shape.

Although the drawings show a simple shape for the non-porous structure, tests have shown that utilising a special shape for the screen has advantages.

In addition to the embodiments of the invention described in detail above, the skilled person will recognize that various of the features described herein can be modified and/or combined with additional features, and the resulting additional embodiments of the invention are also within the scope of the accompanying claims.

Claims

CLAIMS: 1. A wind noise reduction apparatus comprising at least one transducer element having an input port, and at least one non-porous structure covering at least a portion of the input port of the transducer element, characterised in that the non-porous structure is arranged to divert wind away from the input port of the transducer element.
2. The apparatus as claimed in claim 1, wherein the non-porous structure is in spaced relationship with the input port of the transducer element and wherein the non-porous structure is arranged between a source of a wind and the transducer element such that the non-porous structure prevents the wind from directly impinging the transducer element through the input port thereof.
3. The apparatus as claimed in claim 1 or 2, wherein the apparatus comprises a housing surrounding the transducer element and the non-porous structure.
4. The apparatus as claimed in any of the preceding claims, wherein the housing has a hole through which wind and sound from outside the housing can enter the housing.
5. The apparatus as claimed in claim 4, wherein the hole of the housing is the source of wind.
6. The apparatus as claimed in claim 4 or 5, wherein the hole is provided in a top surface of the housing.
7. The apparatus as claimed in any of the preceding claims, wherein a passageway for the wind is provided in the housing between an underside of a top surface of the housing and a top surface of the non-porous structure.
8. The apparatus as claimed in any of claims 3 to 7, wherein at least one side wall of the housing comprises at least one vent.
9. The apparatus as claimed in claim 8, wherein the wind entering through the hole impinges on a surface of the non-porous structure and flows through the passageway towards the at least one vent.
10. The apparatus as claimed in claim 9, wherein the passageway is arranged to cause wind entering through the hole to flow through the passageway and to be expelled through the at least one vent.
11. The apparatus as claimed in any of claims 4 to 10, wherein the hole is axially aligned with the input port of the transducer element.
12. The apparatus as claimed in any of claims 4 to 10, wherein the hole is offset from the input port of the transducer element.
13. The apparatus as claimed in claim 4, wherein the non-porous structure is arranged to cause a pressure differential in the housing and allow sound to be received through the input port of the housing.
14. The apparatus as claimed in any preceding claim, wherein the non-porous structure is arranged for preventing wind from passing from the top surface of the non-porous structure to the surface of the opposite side of the non-porous structure.
15. The apparatus as claimed in any preceding claim wherein the non-porous structure is fixedly positioned between a source of wind and the at least one transducer element.
16. The apparatus as claimed in any of claims 2 to 15, wherein a space between the non-porous structure and the transducer element is approximately 0.3 millimetres.
17. The apparatus as claimed in any preceding claim, wherein the input port is on a top surface of the transducer element.
18. The apparatus as claimed in any preceding claim, wherein the non-porous structure is axially aligned with the transducer element such that a distance between the outer surface of the transducer element on which the input port is provided and a major surface of the non-porous structure is substantially constant.
19. The apparatus as claimed in any preceding claim, wherein the size of a major surface of non-porous structure is smaller than a major surface of the transducer element and wherein the size of the non-porous structure at least covers the input port of the microphone.
20. The apparatus as claimed in any of claims 1 to 18, wherein the length of the major surface of the non-porous structure is substantially the same as the length of the surface on which the input port of the microphone is provided.
21. The apparatus as claimed in any preceding claim, wherein the transducer is an omni-direcional microphone.
22. The apparatus as claimed in any preceding claim, wherein the transducer element is an electro acoustic transducer.
23. The apparatus as claimed in any preceding claim, wherein the transducer element is an electret condenser microphone.
24. The apparatus as claimed in any of claims 1 to 22, wherein the transducer element is a microElectrical-Mechanical System microphone.
25. The apparatus as claimed in any preceding claim, wherein the non-porous structure is a solid structure.
26. The apparatus as claimed in any preceding claim, wherein the non-porous structure is formed of plastic or metal.
27. The apparatus as claimed in any preceding claim, wherein the non-porous structure is flat.
28. The apparatus as claimed in any of claims 1 to 26, wherein the non-porous structure is a three dimensional structure with an indention or depression on a top surface forming a dimple or a concave portion in the top surface where the vertex of top surface is bent inwards towards the bottom surface.
29. The apparatus as claimed in claim 28, wherein the non-porous structure has a substantially V shaped cross section when viewed from one side in an orthogonal plane to the central axis of the structure.
30. The apparatus as claimed in claim 29, wherein a vertex of the V shaped structure points towards the input port of the transducer element.
31. The apparatus as claimed in claims 29 or 30, wherein V shaped legs extend outward away from the vertex and the input port of the transducer element.
32. The apparatus as claimed in claim 31, wherein the porous structure is formed of a disc.
33. The apparatus as claimed in claims 31 or 32, wherein the ends of each of the legs of the non-porous structure has rounded edges.
34. The apparatus as claimed in claims 31 or 32, wherein the non-porous structure has rounded bottom edges.
35. The apparatus as claimed in any of claims 31 to 34, wherein the distance between the end of each the legs is larger than the distance between opposing edges of the transducer element.
36. The apparatus as claimed in any preceding claim, wherein a plurality of transducer elements are provided.
37. The apparatus as claimed in claim 36, wherein a single non-porous structure is provided for the plurality of transducer elements.
38. The apparatus as claimed in claim 36, wherein a plurality of non-porous structures corresponding to the number of transducer elements is provided.
39. The apparatus as claimed in claim 38, wherein an indentation on the surface of each non-porous structure points towards an input port of its respective transducer element.36. The apparatus as claimed in any preceding claim suitable for use inside a main body of an ear bud.37. A speaker apparatus comprising a main body, the main body comprising a wind noise reduction apparatus of any of preceding claim.38. The apparatus as claimed in claim 37, wherein the speaker is an ear bud.39. The apparatus as claimed in claim 38, wherein at least part of the main body of the ear bud forms is part the housing of the wind noise reduction apparatus that houses the non-porous structure and transducer element.
40. A speaker apparatus for being receiving in an ear of a user, comprising: a main body including a bottom end, a top end and at least one side wall; and an ear phone portion attached to one end of the main body, the ear phone portion comprising a speaker to receive sound via a sound source; wherein the main body comprises: a through hole to receive sound from outside the main body; a chamber to receive sound that enters through the through hole, the chamber comprising at least one non-porous structure and one transducer element with an input port, wherein the non-porous structure is located between the hole and at least part of the transducer element. 2]41. The apparatus as claimed in claim 40, wherein the non-porous structure includes a concave surface or indentation.42. The apparatus as claimed in claim 41, wherein there are at least two transducer elements orientated with their input ports facing each other.43. The apparatus as claimed in claims 42, wherein there are at least two non-porous structures and each non-porous structure is associated with a respective transducer element, and each non-porous structure is oriented such that the vertex of the concave surface or indentation points towards the input pod of a respective transducer element.44. The apparatus as claimed in any of claims 40 to 43, wherein one or more outlets are provided for wind that enters into the main body to leave the main body.45. A wind noise reduction apparatus or speaker apparatus substantially as hereinbefore described with reference to the accompanying drawings.