A microphone arrangement and a wearable hearing protection device

Abstract

The present disclosure relates to a microphone arrangement (100) adapted to be comprised in a wearable hearing protection device (110). The microphone arrangement (100) comprises an electrically conducting enclosure (220), a microphone device (231), an amplifier device (230) having at least one input port (236) connected to the microphone device (231), and audio output ports (232, 233) connected to output ports (237, 238) of the amplifier device (230). At least one respective inductive component (234, 235) is connected between each audio output port (232, 233) and a corresponding output port (237, 238) of the amplifier device (230), where the amplifier device (230), the microphone device (231) and said inductive components (234, 235) are positioned within the enclosure (220).

Description

[0001] TITLE

[0002] A microphone arrangement and a wearable hearing protection device

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a microphone arrangement adapted to be comprised in a wearable hearing protection device, and a wearable hearing protection device.

[0005] BACKGROUND

[0006] Some environments are noisy due to machinery, engines and industrial equipment. The noise produced can cause more or less permanent hearing damage to a person subject to such noise if protection is not provided.

[0007] To reduce the noise level in a noisy environment to an acceptable level, such that a person’s hearing is not affected adversely, hearing protection devices, such as muffs or ear plugs can be used. In order to alleviate communication with other persons as well as providing a possibility to listen to music and the like, hearing protection devices are often provided with speakers and at least one microphone for detecting user conversation as well as for environmental audio monitoring to provide situational awareness.

[0008] Such a microphone can be provided integrated with an earmuff or separate from an earmuff, for example on a holding arm, a so-called boom or boom arm, extending from the earmuff. The connections leading from the microphone are prone to pick up ambient electromagnetic interference (EMI), for example produced by ambient machinery, that is fed into microphone amplifier circuitry, and when amplified there, such as EMI and other types of radio frequency interference (RFI) leads to distorted microphone audio signals.

[0009] Today, this is counteracted by means of audio filters and the like provided in the microphone amplifier circuitry.

[0010] It is therefore desired to provide a more efficient means to counteract disturbances due to RFI and the like that are intercepted in hearing protection devices according to the above. SUMMARY

[0011] The object of the present disclosure is to provide a microphone arrangement that is adapted to be comprised in a wearable hearing protection device and to counteract disturbances due to RFI and the like.

[0012] This object is achieved by means of a microphone arrangement adapted to be comprised in a wearable hearing protection device. The microphone arrangement comprises an electrically conducting enclosure, a microphone device, an amplifier device having at least one input port connected to the microphone device, and audio output ports connected to output ports of the amplifier device. At least one respective inductive component is connected between each audio output port and a corresponding output port of the amplifier device. The amplifier device, the microphone device and said inductive components are positioned within the enclosure.

[0013] In this manner, RFI and other electromagnetic interference that is intercepted by the microphone device is counter-acted and minimized in an efficient manner by means of the inductive components that are positioned within the enclosure, the inductive components providing an effective attenuation of the interference within a relatively large frequency span.

[0014] According to some aspects, an output of the microphone device is connected to an amplifier input port, a first inductive component is connected to a first amplifier output port, and a second inductive component is connected to a second amplifier output port.

[0015] According to some aspects, the microphone arrangement comprises at least one filter capacitor connected between the amplifier output ports. This enables reduction of interference at relatively high frequencies, each filter capacitor being adapted to reduce interference at a certain frequency band.

[0016] According to some aspects, the second amplifier output port is connected to the electrically conducting enclosure. This means that the electrically conducting enclosure can function as a ground for the microphone arrangement as well as an interference shield. According to some aspects, the inductive components are constituted by ferrite elements. Using ferrite elements provides stable and reliable functionality, where the ferrites may work as frequency-dependent resistors.

[0017] According to some aspects, the microphone device is a capacitor microphone device. In this manner, a microphone device is provided that is well-known to provide high quality audio and uses a capacitance that varies with the incoming signal to generate a varying output voltage.

[0018] The object of the present disclosure is also achieved by means of a wearable hearing protection device that comprises at least one microphone arrangement as described herein, and which is associated with the above advantages.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present disclosure will now be described more in detail with reference to the appended drawings, where:

[0021] Figure 1 shows a schematic view of a wearable hearing protection device; and

[0022] Figure 2 shows a schematic cut-open view of a microphone arrangement and an audio unit, and

[0023] Figure 3 is a diagram showing the frequency characteristics of a ferrite element which can be used in an embodiment of the disclosure.

[0024] DETAILED DESCRIPTION

[0025] Aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The different devices, systems, computer programs and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout. The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0026] It is well known that audio system performance will be degraded due to any undesirable and interfering voltages where audio cables are sensitive to electromagnetic interference (EMI) and other types of radio frequency interference (RFI). EMI is due to magnetic fields that induce a voltage in neighboring conductors which is heard as an interfering sound, for example a buzz or hum.

[0027] This is for example a problem in hearing protection devices that are provided with speakers and at least one microphone for detecting user conversation as well as for environmental audio monitoring to provide situational awareness, where the microphone may intercept unwanted RFI.

[0028] In order to alleviate this problem, a microphone arrangement 100 will be described in the following with reference to Figure 1 and Figure 2, where Figure 1 shows a schematic view of a wearable hearing protection device, and Figure 2 shows a schematic cut-open view of a microphone arrangement and an audio unit. The microphone arrangement 100 is adapted to be comprised in a wearable hearing protection device 110.

[0029] Furthermore, the microphone arrangement 100 comprises an electrically conducting enclosure 220, a microphone device 231 , an amplifier device 230 having at least one input port 236 connected to the microphone device 231 , and audio output ports 232, 233 connected to output ports 237, 238 of the amplifier device 230.

[0030] According to the present disclosure, at least one respective inductive component 234, 235 is connected between each audio output port 232, 233 and a corresponding output port 237, 238 of the amplifier device 230, where the amplifier device 230, the microphone device 231 and said inductive components 234, 235 are positioned within the enclosure 220. For example, the enclosure is a metallic capsule or the like into which the other parts mentioned are positioned and / or mounted. In this manner, RFI and other electromagnetic interference that is intercepted by the microphone device 231 is counter-acted and minimized in an efficient manner by means of the inductive components 234, 235 that are positioned within the enclosure 220, the inductive components 234, 235 providing an effective attenuation of the interference within a relatively large frequency span.

[0031] According to some aspects, an output of the microphone device 231 is connected to an amplifier input port 236, a first inductive component 234 is connected to a first amplifier output port 237, and a second inductive component 234 is connected to a second amplifier output port 238.

[0032] For example, the amplifier input port 236 is a gate port, the first amplifier output port 237 is a drain port and the second amplifier output port 238 is a source port. This is of course only an example, the amplifier device 230 can be of any desired type and be arranged in many different ways, and may also comprise one or more separate amplifier sub-devices.

[0033] According to some aspects, the microphone arrangement 100 comprises at least one filter capacitor 239a, 239b, 239c connected between the amplifier output ports 237, 238. These filter capacitors 239a, 239b, 239c are adapted to reduce interference at relatively high frequencies, each filter capacitor 239a, 239b, 239c being adapted to reduce interference at a certain frequency band. For example, a first filter capacitor 239a may be adapted to reduce interference about 400 MHz and a second filter capacitor 239b may be adapted to reduce interference about 3,5 GHz. If not counteracted, these interfering signal components will cause interference problems in following signal processing.

[0034] According to some aspects, the second amplifier output port 238 is connected to the electrically conducting enclosure 220. This means that the electrically conducting enclosure 220 can function as a ground for the microphone arrangement 100 as well as an interference shield. According to some aspects, the inductive components 234, 235 are constituted by ferrite elements. Using ferrite elements 234, 235 provides stable and reliable functionality, where, according to some further aspects, the ferrites work as frequencydependent resistors.

[0035] According to some aspects, the microphone device 231 is a capacitor microphone device 231. The capacitor microphone device 231 , or condenser microphone device, is well-known to provide high quality audio and uses a capacitance that varies with the incoming signal to generate a varying output voltage. Normally, for the capacitor microphone device 231 to operate, it requires a direct current (DC) supply voltage to be applied. In the schematic illustration in Figure 2, no such DC supply is explicitly shown, but is considered implicitly disclosed, being well-known in the art.

[0036] According to some aspects, the capacitor microphone device 231 comprises a fixed electrode 231 a and a movable electrode 231 b, where the fixed electrode 231 a is connected to the electrically conducting enclosure 220. This means that when sound waves hit the capacitor microphone device 231 , the movable electrode 231 b vibrates, which changes the level of capacitance in a well-known manner.

[0037] With continued reference to Figure 1 and Figure 2, the present disclosure also relates to a wearable hearing protection device 110 comprising a first earmuff 111 and a second earmuff 112. The earmuffs 111 , 112 are connected by a holding means 113 and are adapted to cover the ears 120, 121 of a user 122, where each earmuff 111 , 112 comprises a speaker 114, 115. In accordance with the present disclosure, the hearing protection device 110 comprises at least one microphone arrangement 100 as described herein.

[0038] In this manner, a wearable hearing protection device 110 is provided having speakers and at least one microphone for detecting user conversation, as well as for environmental audio monitoring to provide situational awareness. Undesired RFI and other electromagnetic interference is reduced to a larger extent than in previous such wearable hearing protection devices. According to some aspects, the microphone arrangement 100 is positioned in a protective casing 116 attached to a holding arm 117 that runs from one earmuff 112 to the protective casing 116 and comprises an audio connection 118; 118a, 118b. The holding arm is in the form of a so-called boom or boom arm. The audio connection 118 is only schematically indicated in Figure 1 , while two signal connections 118a, 118b, constituting the audio connection 118, are shown in the more detailed Figure 2. This means that the microphone arrangement 100 can be of the type boom microphone arrangement where the microphone arrangement 100 is held relatively close to a user’s mouth, enabling a user’s speech to be easily intercepted by the microphone arrangement 100.

[0039] According to some aspects, the audio connection 118; 118a, 118b connects the audio output ports 232, 233 to a sound signal treatment unit 119 that is comprised in the wearable hearing protection device 110.

[0040] According to some aspects, the microphone arrangement 100’ is positioned within one earmuff 111 and the audio output ports 232, 233 are connected to a sound signal treatment unit 119’ that is comprised in the wearable hearing protection device 110.

[0041] This means that the microphone arrangement 100’ may be positioned farther away from a user’s mouth, but is more protected and enables the wearable hearing protection device 110 to be more compact. It is of course conceivable that the wearable hearing protection device 1 10 both comprises a microphone arrangement 100 that is positioned in a protective casing 116 attached to a holding arm 117 as described above, and a microphone arrangement 100’ that is positioned within one earmuff 111. It is also conceivable that the holding arm 117 can be removed from, and re-attached to, the earmuff 112. This means that the microphone arrangement 100’ that is positioned within one earmuff 111 can be used during certain circumstances, and that the microphone arrangement 100 that is positioned in a protective casing 116 attached to a holding arm 117 is attached during other circumstances. When the holding arm 117 is attached, the microphone arrangement 100’ that is positioned within one earmuff 111 may be disengaged. It is to be noted that, as schematically indicated in Figure 1 , the sound signal treatment unit 119, 119’ is either connected to a microphone arrangement 100 that is positioned in a protective casing 116 attached to a holding arm 117, or to a microphone arrangement 100’ that is positioned within one earmuff 111. The type of microphone arrangement 100, 100’ does not, however, need to affect the structure of the corresponding sound signal treatment unit 119, 119’.

[0042] It is also conceivable that the wearable hearing protection device 110 comprises one microphone arrangement 100 attached to a holding arm 117 for each one earmuff 111 , 112, providing a more accurate sound reception.

[0043] It is also conceivable that all microphone arrangements 100, 100’ are connected, or connectable, to one and the same sound signal treatment unit.

[0044] According to some aspects, the sound signal treatment unit 119, 119’ comprises input ports 240, 241 , an audio processing part 242 and at least one respective inductive component 243, 244 that is connected between each input port 240, 241 and the audio processing part 242. This means that further interference reduction is provided, in particular for interference that has been intercepted by the audio connection 118; 118a, 118b. According to some further aspects, the inductive components 243, 244 are constituted by ferrite elements that provide stable and reliable functionality. As mentioned above, the ferrites may work as frequency-dependent resistors.

[0045] According to some aspects, the ferrite elements 234, 235 which are used in the arrangement according to this disclosure have a high inductance for RF frequencies. According to such embodiments, the ferrite elements 234, 235 will protect the preamplifier 230 connected to the microphone 231 from RF signals picked up in the wires 118a and 118b, i.e. the audio connections to the microphone arrangement. The inductance of each one of the ferrite elements 234, 235 is consequently adapted for reducing unwanted noise due to said RF signals (i.e. EMC interference and noise) which are picked up in the wires 118a, 118b between the microphone arrangement 100 and the signal treatment unit 119, 119’. The actual inductance value of a ferrite element may in practice depend on various parameters such as its material properties and geometry. Also, the impedance of a ferrite element consists of a frequencydependent resistance and a frequency-dependent inductance.

[0046] The amplifier has to be protected on the output port since especially high frequency digital signals will be down converted and amplified in the audio amplifier even if the signals are picked up in the cable connected to the output port on the amplifier An example: a digital radio at 440 MHz with a transmission slot of 30 ms and silent in 30 ms, DMR, can be picked up by the audio connections 118a, 118b. The on and off switching will end up in the audio band and amplified and the sound will be similar to the sound of a helicopter and is commonly called “chopper noise”. In this example, the ferrite elements are configured for operating in RF frequencies in the magnitude of approximately 440 MHz, but the specific frequency range may vary depending on the practical use of the microphone arrangement described above.

[0047] According to an embodiment, the ferrite elements (ferrite beads) have a high attenuation on high frequencies. The specific ferrite elements mounted in the microphone arrangement can suitably be of the type BLM03AX601 SZ1 from Murata, which have a +200 ohm impedance from 20 MHz to 2 GHz (i.e. an impedance of 200 ohms or more), and also, in the band 100 MHz to 700 Mhz an impedance of +600 ohms (i.e. an impedance of 600 ohms or more within that frequency interval). This is also indicated in Fig. 3, which is a diagram showing the frequency characteristics (i.e. the impedance in relation to the frequency) of such a ferrite element.

[0048] In this example, there is a first signal connection 118a running to a first input port 240 that is connected to a first inductive component 243. Furthermore, there is a second signal connection 118b running to a second input port 241 that is connected to a second inductive component 244.

[0049] According to some aspects, the audio processing part 242 comprises a filter arrangement 245 and an amplifier arrangement 246. In this way, the audio signal may be filtered and amplified when possible interference has been reduced by the inductive components 243, 244 in the sound signal treatment unit 119, 119’. According to some aspects, the audio processing part 242 is connected to an audio output part 247 that comprises at least one of a speaker arrangement 248 and a radio arrangement 249. The speaker arrangement 248 may be adapted to provide an output signal to the speakers 114, 115 comprised in the earmuffs 111 , 112 such that the person speaking may hear his or her own words in a noisy environment, and such that situational awareness is provided. The radio arrangement 249 may be adapted to wirelessly connect the wearable hearing protection device 110 to another wearable hearing protection device, transmitting audio signals and allowing other users to hear what the user 122 is saying.

[0050] Conveniently, as schematically illustrated in Figure 1 , the wearable hearing protection device 110 may also comprise an audio input part 123 that comprises a radio arrangement (not shown) that is arranged to receive audio signals that have been transmitted by another wearable hearing protection device, allowing the user 122 to hear what other users are saying. For this purpose, the audio input part 123 may also comprise suitable receiver circuitry.

[0051] This allows persons working and using wearable hearing protection devices 110 according to the present disclosure to communicate via wireless communication.

[0052] The present disclosure is not limited to the above, but may vary freely within the scope of the appended claims. For example, the wireless communication may be performed via Bluetooth or a WiFi system.

[0053] According to some aspects, some components 230, 232, 233, 234, 235, 239a, 239b, 239c may be mounted on a printed circuit board 224 (PCB) in the enclosure 220, while other components, such as for example the microphone device 231 , may be mounted separate from the PCB, although being positioned within the enclosure 220 and being electrically connected to the PCB 224 or to one or more components mounted to the PCB 224.

[0054] As schematically indicated in Figure 2, the sound signal treatment unit 119 comprises a voltage source Vccthat is connected to the first signal connection 118a via a resistor 250. The resistor is connected to the first signal connection 118a between a DC stop capacitor 251 and the first inductive component 243, where the DC stop capacitor 251 is connected to the audio processing part 242. Furthermore, the sound signal treatment unit 119 comprises a ground connection GND that is connected to the second signal connection 118b between the second inductive component 244 and the audio processing part 242. In the above, the signal connections 118a, 118b are considered to continue to run inside the sound signal treatment unit 119.

[0055] The voltage source Vccis adapted to provide a DC supply voltage for the amplifier device 230 and possibly also for the microphone device 231 . The DC stop capacitor 251 is adapted to prevent DC from reaching the audio processing part 242.

[0056] According to some aspects, the wearable hearing protection device 110 is adapted for noise cancelling, such that ambient sound that is detected by the microphone device 231 is used for cancelling the same sound in the speakers 114, 115 in a previously well-known manner.

[0057] In the context of the present disclosure, interference is normally of the type electromagnetic interference such as RFI.

Claims

CLAIMS1 . A microphone arrangement (100) adapted to be comprised in a wearable hearing protection device (110), where the microphone arrangement (100) comprises an electrically conducting enclosure (220), a microphone device (231 ), an amplifier device (230) having at least one input port (236) connected to the microphone device (231 ), and audio output ports (232, 233) connected to output ports (237, 238) of the amplifier device (230), characterized in that at least one respective inductive component (234, 235) is connected between each audio output port (232, 233) and a corresponding output port (237, 238) of the amplifier device (230), where the amplifier device (230), the microphone device (231 ) and said inductive components (234, 235) are positioned within the enclosure (220).

2. The microphone arrangement (100) according to claim 1 , wherein an output of the microphone device (231 ) is connected to an amplifier input port (236), a first inductive component (234) is connected to a first amplifier output port (237), and a second inductive component (234) is connected to a second amplifier output port (238).

3. The microphone arrangement (100) according to claim 2, wherein the microphone arrangement (100) comprises at least one filter capacitor (239a, 239b, 239c) connected between the amplifier output ports (237, 238).

4. The microphone arrangement (100) according to any one of the claims 2 or 3, wherein the second amplifier output port (238) is connected to the electrically conducting enclosure (220).

5. The microphone arrangement (100) according to any one of the previous claims, wherein the inductive components (234, 235) are constituted by ferrite elements.

6. The microphone arrangement (100) according to any one of the previous claims, wherein the microphone device (231 ) is a capacitor microphone device (231 ).

7. The microphone arrangement (100) according to claim 6, wherein the capacitor microphone device (231 ) comprises a fixed electrode (231 a) and a movable electrode (231 b), where the fixed electrode (231 a) is connected to the electrically conducting enclosure (220).

8. A wearable hearing protection device (110) comprising a first earmuff (111 ) and a second earmuff (112), where the earmuffs (111 , 112) are connected by a holding means (113) and are adapted to cover the ears (120, 121 ) of a user (122), where each earmuff (111 , 112) comprises a speaker (114, 115), characterized in that the hearing protection device (110) comprises at least one microphone arrangement (100) according to any one of the previous claims.

9. The wearable hearing protection device (110) according to claim 8, wherein the microphone arrangement (100) is positioned in a protective casing (116) attached to a holding arm (117) that runs from one earmuff (112) to the protective casing (116) and comprises an audio connection (118; 118a, 118b).

10. The wearable hearing protection device (110) according to claim 9, wherein the audio connection (118; 118a, 118b) connects the audio output ports (232, 233) to a sound signal treatment unit (119) that is comprised in the wearable hearing protection device (110).11 . The wearable hearing protection device (110) according to any one of the claims 8-10, wherein the microphone arrangement (100’) is positioned within one earmuff (111 ) and the audio output ports (232, 233) are connected to a sound signal treatment unit (119’) that is comprised in the wearable hearing protection device (110).

12. The wearable hearing protection device (110) according to any one of the claims 10 or 11 , wherein the sound signal treatment unit (119, 119’) comprises input ports (240, 241 ), an audio processing part (242) and at least one respective inductive component (243, 244) is connected between each input port (240, 241 ) and the audio processing part (242).

13. The wearable hearing protection device (110) according to claim 12, wherein the inductive components (243, 244) are constituted by ferrite elements.

14. The wearable hearing protection device (110) according to claim 13, where said ferrite elements are designed with a relatively high inductance adapted forRF frequencies.

15. The wearable hearing protection device (110) according to any one of the claims 12-14, wherein the audio processing part (242) comprises a filter arrangement (245) and an amplifier arrangement (246).

16. The wearable hearing protection device (110) according to any one of the claims 12-15, wherein the audio processing part (242) is connected to audio output part (247) that comprises at least one of a speaker arrangement (248) and a radio arrangement (249).

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