MOBILE PHONE COVER PROVIDING PASSIVE NOISE REDUCTION OF MICROPHONE AUDIO INPUT SIGNALS

Abstract

The present disclosure is related to a mobile phone cover providing passive noise reduction of at least one microphone audio input signal, comprising a supporting frame (13). The supporting frame (13) is arranged with an extension element with a compartment (15) facing upwards with a partly open surface on a same side as a display surface of the mobile phone, the compartment (15) is adapted to support a porous body (17) providing the passive noise reduction.

Claims

1. A mobile phone cover providing passive noise reduction in a wave guide like arrangement in front of at least one microphone audio input opening located on a bottom end surface of a mobile phone housing, comprising: a supporting frame having an outer periphery side face running around a periphery of the mobile phone housing when mounted onto the mobile phone; the periphery side face has an upper outer end surface, and a first outer lower end surface; wherein the mobile phone cover is arranged with an extension element extending out from the first outer lower end surface of the supporting frame, thereby providing a second lower end surface of the supporting frame running in parallel with the first outer lower end surface; the parallel first and second end surfaces defines an inner compartment in between the supporting frame and the first and second end surfaces and a covered bottom side of the compartment located opposite an upper surface side of the compartment faced upwards towards a display side of the mobile phone when the cover is mounted; the compartment is filled with a body made of a porous material covering the at least one microphone audio input opening; wherein an opening in the upper surface side of the compartment is arranged located above the at least one microphone audio input opening.

2. The mobile phone cover of claim 1, wherein at least the first lower end surface of the supporting frame is constituted by a material having an adapted acoustic impedance adapted to a typical range of frequencies of speech signals from humans.

3. The mobile phone cover of claim 1, wherein the extension element of the supporting frame is constituted by a material having an adapted acoustic impedance adapted to a typical range of frequencies of speech signals from humans.

4. The mobile phone cover of claim 1, wherein at least one cut-out is arranged on a location on the first lower end surface of the supporting frame coinciding with the location of the at least one microphone input opening on the mobile phone housing.

5. The mobile phone cover of claim 1, wherein at least one cut-out is arranged on a location on the second end surface of the supporting frame coinciding with the location of the at least one microphone input opening on the mobile phone housing.

6. The mobile phone cover of claim 1, wherein the supporting frame is arranged with at least one extension element on any side faces of the supporting frame, wherein a specific side face of the supporting frame having an extension element covering at least one microphone input opening.

7. The mobile phone cover of claim 1, wherein the supporting frame has an open backside.

8. The mobile phone cover of claim 1, wherein the supporting frame has a covered, or partly covered backside constituted by a stiff material like a steel plate or similar materials.

9. The mobile phone cover of claim 1, wherein the covered backside has at least one cut-out located above a microphone input opening on the mobile phone hosing when the cover is pulled over the mobile phone housing.

10. The mobile phone cover of claim 9, wherein a frame is arranged around the cut-out over the microphone input location holding a body made of a porous material.

11. The mobile phone cover of claim 1, wherein the porous material of the body is foam rubber, or a sponge like material.

12. (canceled)

13. The mobile phone cover of claim 9, wherein the porous material comprises a rubber foam or a sponge like material.

Description

FIGURES

[0033] The mobile phone cover according to the present invention will now be described in more detail with reference to the accompanying figures. The figures illustrates examples of embodiments of the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. Further, respective examples of embodiments may each be combined with any of the other examples of embodiment.

[0034] FIG. 1 illustrates an example of embodiment of the present invention.

[0035] FIG. 2 illustrates further details of the example in FIG. 1.

[0036] FIG. 3 illustrates the example of embodiment in FIG. 2 viewed from another perspective.

[0037] FIG. 4 illustrates a further example of embodiment of the present invention.

[0038] FIG. 5 illustrates further details of the example of embodiment illustrated in FIG. 4.

[0039] FIG. 6a illustrates use of an example of embodiment of the present invention

[0040] FIG. 6b illustrates use of another example of embodiment of the present invention.

[0041] FIG. 7 illustrates an example of a performance measurement of an example of embodiment of the present invention.

[0042] FIG. 8 illustrates another example of a performance measurement of an example of embodiment of the present invention.

[0043] FIG. 9 illustrates another example of a performance measurement of an example of embodiment of the present invention.

[0044] FIG. 10 illustrates another example of a performance measurement of an example of embodiment of the present invention.

[0045] FIG. 12 illustrates possible shapes of a noise reduction element according to the present invention.

[0046] FIG. 13 illustrates further possible shapes of a noise reduction element according to the present invention.

[0047] FIG. 14 illustrates an example of embodiment of the present invention.

DETAILED DESCRIPTION

[0048] Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the present examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference sign in the claims with respect to elements indicated in the figures shall also not be construed as limiting to the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

[0049] The present disclosure is related to a passive noise reduction system comprising at least a mobile phone cover. Mobile phone covers are normally used to provide increased mechanical integrity of mobile phone housings, and to protect a larger display surface of smart phones usually made of glass.

[0050] An example of a mobile phone cover according to the present invention is illustrated in FIG. 1. The example of embodiment in FIG. 1 illustrate a mobile phone cover 10 comprising a supporting frame having a peripheral side face 13 running around a mobile phone housing when mounted. The cover 10 is configured to be pulled over the circumference of the mobile phone housing thereby mounting the frame 13 onto the mobile phone. In this example of embodiment, the backside 11 is open, i.e. there is no backside. Therefore, the mobile phone cover 10 can be attached to the mobile phone housing by pulling the cover onto the phone housing from a display side (i.e. front side) of the mobile phone housing. The display side will then be accessible for a user of the phone.

[0051] It is also within the scope of the present invention that the supporting frame 13 may have a cover covering the whole backside, or just a part of the backside, for example comprising a stiff back side plate increasing the mechanical integrity of the mobile phone housing. Then the mobile phone cover 10 can be attached to the cover by pressing the mobile phone housing with the mobile phone backside first into the supporting frame 13. The display side or front side of the mobile phone will be accessible for a user of the phone

[0052] The supporting frame 13 is in either case firmly attached to the mobile phone housing due to a tight clearance between the inside side faces of the supporting frame 13 and the periphery sides of the mobile phone housing. A specific supporting frame 13 is adapted in size (and may be appearance) to a specific mobile phone model. Different sized supporting frames 13 can be adapted to other respective mobile phone models.

[0053] The peripheral side face 13 of the supporting frame is running around the outer periphery of the mobile house when mounted. The peripheral side face 13 has an upper periphery side surface 12 and a first bottom periphery side face 14. An extension of the supporting frame 13 is arranged as an extension of the cover 10 out from the first bottom periphery side face 14, which ends in a second bottom periphery side surface 16 running in parallel with the first bottom periphery side face 14, i.e. both the first and the second bottom periphery side faces 14, 16 are running in parallel with the bottom periphery side of the mobile phone. In between the first and second bottom periphery side surfaces 14, 16 there is constituted an empty compartment 15. The backside of the cover 10 can be open or be arranged with a plate as discussed above. In any case, the bottom of the compartment 15 is always covered with a plate while the front side of the compartment 15 faced upwards on a same side as the front side (display side) of the mobile phone is at least always partly open, i.e. a part of the opening of the front side of the compartment 15 may be partly covered, but always a part of the front side of the compartment 15 is not covered.

[0054] When a mobile phone with a mobile phone cover 10 according to the present invention is in use, the upper periphery side surface 12 is located close to the ear of the mobile phone user while the compartment 15 is located close to the mouth of the mobile phone user. It is common to have at least one microphone located on the bottom end surface of the mobile phone housing since this part is close to the mouth of a user of the phone. Therefore, the at least one microphone of the mobile phone will be located inside the compartment 15 of the extension to the mobile phone cover 10.

[0055] In FIG. 2, the compartment 15 of FIG. 1 is filled or arranged with a body 17 made of a porous material. For example a sponge like material or foam rubber. The purpose of the porous body 17 is to mitigate the effect of wind-noise as discussed above. FIG. 3 depicts the example of embodiment in FIG. 2 viewed from above.

[0056] In FIG. 4, the first bottom end surface 14 of the supporting frame 10 as disclosed in FIG. 2 and FIG. 3 is arranged with some defined openings. The locations of these openings are correlated with corresponding located loudspeaker openings and/or microphone openings 24 arranged on the bottom end surface of the mobile phone housing. The second bottom end surface 16 is also arranged with openings corresponding with the openings on the first bottom end surface 14.

[0057] FIG. 5 illustrate a perspective view of the example of embodiment in FIG. 4, wherein a body 17 comprising a porous material is located inside the compartment 15 as discussed above.

[0058] FIG. 6a illustrates how soundwaves 23 form a human mouth is propagating through space from the mouth to towards the compartment 15. The sound waves 23 will partly enter the compartment 15 through the front side opening of the compartment 15 facing towards the mouth of the user. A microphone 24 of the phone is located adjacent to the compartment 15 on the bottom end surface of the mobile phone housing. With reference to FIGS. 4 and 5, it may also be arranged cut-outs on the first and second bottom periphery side surfaces 14, 16 corresponding with the microphone positions on the bottom periphery end surface of the mobile phone housing.

[0059] FIG. 6b illustrate how the bottom surface of the compartment 15 can be arranged with a 45° inclination angel from the bottom of the cover 10. The effect is that incoming sound waves will be reflected towards the microphone openings 24 on the mobile phone housing as illustrated in the figure.

[0060] The inventor has performed several test of exemplary embodiments of the present invention.

[0061] The purpose has been to identify how well wind induced noise is reduced or mitigated by a cover according to the present invention. The porous body 17 stops or mitigate wind induced noise as discussed above. At the same time the porous body 17 let audible sound waves pass through the pores of the porous media. In addition, the compartment 15, as depicted in FIGS. 1 to 5, constitutes a wave guide like channel from the open front surface of the compartment 15 towards a microphone opening 24 located on the bottom periphery side surface of the mobile phone housing.

[0062] The testing was performed on an iPhone XS Max and a Samsung S10+ with approximately the same results. The sound source used in the measurements was a Tivoli Pal radio and a frequency sweep generator. The Tivoli Pal radio has a single membrane speaker, having no phase issues between bass and treble. The frequency response is uneven, but only relative differences were to be measured, thereby compensating uneven frequency responses. The sound received by the phone was measured at a loudspeaker of the phone.

[0063] FIG. 7 illustrate a measurement of the effect of a cover 10 according to the present invention wherein the compartment 15 is empty and the cover is as illustrated in FIG. 6a.

[0064] FIG. 7 illustrates the result of using an iPhone XS Max wherein the compartment was empty and a frequency sweep from 60 Hz to 30.0 kHz was provided by sound from the connected Tivoli Pal radio. Normal human speech is in the frequency range from about 1 kHz to around 4.5 kHz.

[0065] The curve 30 in FIG. 7 reveals the wave guide like performance of the channel constituted by the compartment 15. The sound amplitude increased in general with one dB across the whole frequency range, and especially providing a significant increase inside the frequency range of normal human speech.

[0066] Clarity of speech is also an important factor when evaluating the effect of the present invention. In a measurement setup the test standard C50 was used to estimate clarity of speech with and without the cover 10 mounted, and wherein the compartment 15 was empty, i.e. without the porous body 17.

[0067] C50 tests compares the sound energy in early sound reflexes with those arriving later. It is expressed in dB and a high value is positive for speech clarity. The test is standardized and is available as ISO 3382-1.

[0068] FIG. 8 illustrates a relative measurement of C50 results. The graph 31 depicts the results with cover 10 mounted while the graph 32 depicts the results without the cover 10 mounted. A sound sweep was performed between the frequencies 200 Hz to 10 kHz via the Tivoli Pal radio.

[0069] The measurements illustrated in FIGS. 7 and 8 illustrates the fact that the cover itself enhance the sound received via the compartment 15, which is not only louder, but also clearer.

[0070] The effects of arranging a porous body 17 in the compartment 15 is illustrated in FIGS. 9 and 10.

[0071] FIG. 9 illustrate a situation without the cover 10 mounted, and measured with wind as illustrated in graph 33, and without wind illustrated in graph 34.

[0072] The wind effect was generated with a fan. The apparent increase of wind noise after 2 Khz is not wind noise, but the noise of the fan itself. This is most likely due to compression done by the phone itself, making the fan noise as well as the loudness of sweep measurements quieter in wind relative to a situation without wind. Compression is a process which attenuates beyond a certain threshold resulting in a lesser difference between loud and quiet sounds, hence if the sweep is quieter than before within the same measurement parameters, the total of the signal has been attenuated by an amount equal to or close to the reduction of the sweep level. To adjust for this compression, the sweep measurement was used as a reference. The measurements indicated that the sweep was about 10 dB quieter when wind is added. The relative wind noise adjusted with 10 dB is depicted in FIG. 10. The compensated measurements indicate a difference of 14 to 17 dB with and without the cover comprising a porous body 17 mounted in the compartment 15. It is probable that the cover 10 do not affects everything below 100 Hz, but in the upper frequency region this will be true.

[0073] FIG. 11 illustrates a measurement of the frequency response in wind with the cover on and without the cover. The graph 37 is the result obtained with the cover mounted while the graph 38 illustrate the results without the cover 10 mounted on the phone.

[0074] The graphs illustrates that around t 2 KHz and above there is a reduction of 14 dB relative to a situation wherein the cover is not mounted, and 14-24 dB relative to a situation wherein the cover is mounted when there is wind blowing. This means that with the cover 10 mounted the amount of desired sound passing through is significantly higher than without the cover present.

[0075] The first lower end surface (14) of the supporting frame (10) may be constituted by a material having an adapted acoustic impedance adapted to a typical range of frequencies of speech from humans. Thereby speech can pass the material of the end surface (14) of the supporting frame (10) onto the at least one microphone without attenuation, or at least with minimal attenuation. The same material may also be used in the extension element (16) of the supporting frame (13).

[0076] FIG. 1 and FIG. 2 illustrate an example of a supporting frame 13, with a non-limiting specific shape of the porous body 17. FIG. 12 illustrates some examples of possible shapes of the porous body 17 that is adapted to shapes of different examples of the space 15 defined by the extension element 16 and the end surface 14 of the supporting frame 13. Illustration 17(a), illustration 17(b), illustration 17(c) and illustration 17(d) illustrates different shapes of the body 17 viewed from above. Illustration 17(e) is a perspective view of the body illustrated in 17(b), which is the same shape of the body 17 used in the examples illustrated in FIG. 2 and FIG. 3.

[0077] FIG. 13 illustrates other examples of embodiments of a porous body 18. In these examples, a cut-out in the centre of the body 18 is adapted to enable connection of a power cable for example to the mobile phone housing. Corresponding openings are then arranged in the side face of the extension element 16 and in the first bottom end surface 14 of the original supporting frame 13. Illustration 18(b) and illustration 18(d) illustrates the porous body 18 seen from the side of the body 18, while illustration 18(a) and illustration 18(c) illustrates the body 18 viewed from the top side of the body 18. Illustration 18 (e) is a perspective view of the example of embodiment of the porous body 18(a).

[0078] It is further within the scope of the present invention that microphones may be arranged on any of the side faces of the mobile phone housing including the side of the housing comprising the display (microphones may be located at edges of the display surface), and the backside opposite the display side. It is further within the scope of the present invention to provide a mobile phone cover comprising at least a supporting frame 13 that may comprise adapted cut-outs in the side faces of the frame 13 coinciding with openings of respective microphones. Further, microphones located on the display side, and/or on the backside, of the mobile phone may be covered by an extension of the cover stretching above the part of the display surface (in the edge regions of the display surface) and/or on the backside of the mobile phone housing. Cut-outs over the locations of respective microphones can be arranged with a material like the materials used for the porous bodies 17, 18 as discussed above.

[0079] FIG. 14 illustrates an example of a backside of the supporting frame 13 having a cut-out 20 above a camera lens of the mobile phone, a cut-out 21 above a microphone of the mobile phone, and a cut-out 22 for a LED based flashlight. Around the cut-out 21 above the microphone, there is a frame 19 arranged around the cut-out 21 providing support for a body of a porous media as discussed above (not illustrated). Then wind induced noise is also reduced for this specific microphone.

[0080] For example, an iPhone 7 from Apple as discussed above has a microphone located in between the LED providing flashlight and the camera opening of the phone. Then an extension of the supporting frame 13 may be arranged stretching down from the upper edge 12 comprising cut outs for the camera and the LED based flashlight in addition to a cut out over the microphone comprising a body of a porous media without necessarily covering the whole backside of the mobile phone housing.

[0081] SP Technical Research Institute of Sweden has also conducted experiments establishing the effect on the reduction of wind noise using porous materials like sponge like materials and/or foam rubber materials. The report dated 17 Jan. 2017 has the identification number 6P09044Rev1.

[0082] The investigation measured noise sound pressure differences between a situation without a wind noise reducing material and a situation with the noise reducing material. If the pressure is reduced, the impact on the membrane or diaphragm will be correspondingly decreased. i.e. less wind induced noise.

[0083] When the test wind had a speed of 2 m/s the reduction of the wind noise sound pressure was approximately 35%, and when the test wind had a speed of 8 m/s the reduction was 76%, and when the wind speed was 12 m/s the reduction was 71%. In the interval between 4 m/s and 8 m/s of wind speed, the reduction was on average 74%.