GB2369522A

GB2369522A - A waterproof microphone

Info

Publication number: GB2369522A
Application number: GB0028808A
Authority: GB
Inventors: John Davies
Original assignee: Davies Industrial Communications Ltd
Current assignee: Davies Industrial Communications Ltd
Priority date: 2000-11-25
Filing date: 2000-11-25
Publication date: 2002-05-29
Anticipated expiration: 2020-11-25
Also published as: GB2369522B; GB0028808D0

Abstract

A weatherproof microphone 1 comprising a watertight rigid housing 2A,2B and a microphone transducer 18 within the housing. A smooth continuous receiver portion 6 is sealed by a waterproof membrane 7 to protect the transducer from water. The outer surface of the housing 2A and the membrane 7 finish flush with each other to reduce noise caused by air moving over the surface of the microphone. The housing is also smoothly contoured to reduce turbulence. Preferably the receiver portion 6 consists of a thin circular diaphragm that is formed integrally with the casing, being defined by a region in which the thickness of the housing is thinner than that of the case portion. An actuator 20 may be incorporated between the diaphragm and the transducer 18 to convey sound waves (see fig 6). The diaphragm itself may be a transducer, being formed of a piezo-electric material covered by a waterproof film (see fig 7).

Description

A MICROPHONE

The present invention relates to a microphone and particularly, but not exclusively, to a weatherproof hand-held microphone of the type designed to be exposed to severe weather conditions, as for example may be encountered on an inshore life boat where wind noise and water are particularly problematic.

Microphones have been designed for the reduction of ambient noise. A common technique employs noise cancelling, whereby ambient noise strikes both sides of a diaphragm in equal intensity and is therefore cancelled. However the microphone is arranged such that speech from a user only strikes one side of the diaphragm and is thus not cancelled, causing the microphone to respond and produce an output signal from the speech. Waterproof microphones are also known employing either a waterproof transducer or waterproof membrane.

Prior art noise cancelling microphones work well in helping to reduce ambient noise to acceptable levels in certain applications. However when such a microphone is used in a high velocity air flow, which may be either naturally occurring wind or induced by the microphone being mounted on a moving vehicle or craft, it has been found that traditional noise cancelling microphones do not suppress the"wind"noise. Indeed performance in high wind or at speed may be poorer than for an ordinary microphone.

One particularly effective way of reducing wind noise on a microphone is to use a foam rubber windsock over a conventional microphone. However this only works whilst the windsock remains dry. If the windsock is exposed to excessive water it may become

saturated, impeding transmission to the microphone transducer. Furthermore certain applications may preclude the use of a windsock, such an application would be a hand held microphone for use in radio communications where a windsock would be impracticable.

One particularly problematic application with which the present inventor is concerned is the use of a hand-held microphone for use on an inshore life boat, typically a fast inflatable open decked craft which in operation is often deluged with not only sea spray but also large quantities of sea water. For such an application there is a requirement for a hand-held microphone through which clear communication can be made whilst travelling at speed or in inclement weather, where the microphone often held by the operator of the craft who will normally be fully exposed to high winds and airflow induced by the speed of the craft. The microphone will also be exposed for long periods of time to seawater, and must be robust enough to cope with such an application where it could be left lying on a saturated deck.

An object of the present invention is to provide an improved microphone particularly, but not exclusively applicable to environments as described above.

According to the present invention there is provided microphone for the reception of airborne acoustic sound waves. The microphone comprises a housing having a relatively rigid case portion and a smooth continuous receiver portion for the reception of sound waves, wherein the outer surface of the receiver portion is substantially flush with the outer surface of the case portion.

It has been found that the majority of wind noise received by a microphone normally results from turbulence of airflow across the microphone. This can be greatly reduced by employing the present invention and having the outer surface of the receiver portion arranged flush with the outer surface of the case portion of the housing. Preferably the receiver portion forms an outer most component with no outer protective guard.

Preferably the housing is waterproof, preventing the ingress of water and making it possible to provide a weatherproof and watertight microphone.

Preferably the housing of the microphone has smooth contours on all edges bordering the face in which the receiver portion is located, this having been found to significantly further smooth the flow of air over the surface of the membrane.

It may be advantageous for the microphone to comprise a transducer within the housing, with the receiver portion consisting of a relatively thin flexible membrane. This may be formed integrally of a homogeneous material with the case portion, the receiver portion being defined by a region in which the thickness of the housing is thinner than the thickness of the housing in the case portion, such as to permit sound waves to propagate there through to the transducer.

Where a transducer is mounted in the housing an actuator may be incorporated between the receiver portion and the transducer in order to convey received sound waves to the transducer.

It may be advantageous if the receiver portion is substantially circular with a surface area greater than 19cm2 and, where the receiver portion is formed separately to the case portion and comprises a membrane, it is advantageous that the membrane is bonded to the case portion. The membrane may be formed of polyvinyl chloride (PVC) and have a thickness in the range of 0. 5mm to 0. 7mm in its central region with a thicker peripheral section by which it is retained in the housing.

Advantageously the transducer and membrane are arranged to engage with each other when assembled such that the transducer retains the membrane in position. This may be arranged to prevent the membrane being accidentally pushed into the housing.

In an alternative embodiment the receiver portion of the housing may be a transducer itself, typically being formed of a layer of piezo-electric material, protected by a thin waterproof film or coating.

Four embodiments of the present invention will now be described, by way of example only, with reference to the attached figures, of which: Figure 1 is a top elevation of the microphone in accordance with the present invention; Figure 2 is a front elevation of the microphone shown in figure 1; Figure 3 is a partial sectional side elevation of the microphone of figures 1 and 2; Figure 4 is a cross section through the membrane seen in figure 3; and

Figures 5, 6 and 7 illustrate alternative embodiments of the invention.

Referring to figures 1, 2, 3 and 4, in which like numerals have been used to indicate like parts, a microphone 1 comprises a housing 2 formed from sections 2A and 2B.

Between the two sections 2A and 2B of housing 2 is a gasket 3 that is sandwiched between the two halves by screws 4 to form a watertight seal. Within the housing 2 a microphone transducer, such as a Besson R300 manufactured by Hosiden Besson of Brighton England, is mounted facing a receiver portion of the housing in the form of membrane 7. The transducer 5 is received in membrane 7, which membrane is shown in cross section in figure 4.

Referring to figure 4 the membrane 7 comprises a membrane portion 7A and a peripheral rim 7B. The rim 7B is formed to receive microphone 5 in inner rim 7C whilst having on its outer circumference a lip 7D arranged to co-operate with lip 2C of the housing 2. The microphone transducer 5 is inserted into the rim 7C and then the lip 7D is bonded to the lip 2C making a watertight seal.

In the top of the microphone housing 2 is a"push-to-talk" (PTT) switch 8 sealed by a PVC cap 9. The only other aperture to the housing is in the bottom and this receives communication lead 10.

The front portion 2A of the housing 2 is smoothly contoured to minimise turbulence due to airflow over the microphone and incorporates a protrusion 2D to assist the user in removing the microphone from its carrier, not shown.

A first alternative embodiment of a microphone employing the present invention is illustrated with reference to Figure 5. This comprises a boom microphone that can be attached to a headset and arranged to be located in front of a users mouth, without the requirement to be hand-held. The microphone comprises a moulding 11 containing a microphone transducer (not shown) in the bulbous region 12. The bulbous region 12 has a membrane 13 inserted flush in aperture 14 permitting sound waves to pass so that speech is directed at the transducer. The bulbous region 12 has flats 15 over its surface which further act to smooth airflow across the surface in the same manner as on a golf ball.

Figure 6 and 7 illustrate schematically further embodiments of microphones in accordance with the present invention. These may be employed with various types of microphone, for example the handheld microphone of the type illustrated in figures 1 to 3 or the boom microphone illustrated in figure 5.

With reference to figure 6 a PVC housing 16 comprises a relatively rigid case portion, except for the region 17. This region 17 is moulded to a thickness of less than 0.5mm and defines a receiver portion of the housing, in the form of a membrane homogeneous with the case portion of the housing 16.

The receiver section 17 permits airborne acoustic sound waves to propagate there through to a transducer 18 mounted on a non-rigid mass 19. The mass 19 acts to isolate

the transducer from acoustic and vibration signals received through the case portion of the housing 16.

An actuator 20 extends from the inner surface of the receiver portion of the housing 16 to convey acoustic signals to the transducer 18. However inclusion of such an actuator is a matter of design choice and will depend on the type of transducer, properties of the receiver region of the housing and the type of sound (intensity) to be received. The configuration of the housing is merely given for illustrative purposes and the embodiment, with or without actuator may be appropriate to any number of applications.

The housing 21 illustrated in figure 7 is again only given for illustrative purposes as this embodiment may also be appropriate to any number of applications. Here a receiver portion comprises a layer of piezoelectric material lacquered to protect it from water and bonded into the case portion of the housing. Airborne acoustic waves incident on the transducer 22 generate electrical signals on wires 23.

Although a number of embodiments of the invention have been described above, by way of example, it will be apparent that a microphone in accordance with the present invention may have many forms whilst being within the scope of the appended claims.

Claims

CLAIMS 1. A microphone for the reception of airborne acoustic sound waves, the microphone comprising a housing, characterised in that the housing has a relatively rigid case portion and a smooth continuous receiver portion for the reception of sound waves, wherein the outer surface of the receiver portion is substantially flush with the outer surface of the case portion.
2. A microphone as claimed in claim 1 wherein the housing is waterproof.
3. A microphone as claimed in claim 1 or 2 wherein the receiver portion forms an outermost component of the microphone and has no outer protective guard.
4. A microphone as claimed in any preceding claim wherein the housing has smooth contours on all edges bordering the face in which the receiver portion is located.
5. A microphone as claimed in any preceding claim wherein the housing is arranged to permit the smooth flow of air across the surface of the receiver portion.
6. A microphone as claimed in claim 5 wherein at least part of the case portion of the housing has a substantially convex surface having a plurality of flats or recesses therein.
7. A microphone as claimed in any preceding claim wherein the receiver portion is substantially circular.
8. A microphone as claimed in any preceding claim wherein the receiver portion has a thickness in the range 0.5mm to 0. 7mm.
9. A microphone as claimed in any preceding claim wherein the receiver portion is formed separately to the case portion.
10. A microphone as claimed in claim 9 wherein the receiver portion has a thicker peripheral section by which it is retained in the case portion.
11. A microphone as claimed in claim 9 or 10 wherein the receiver portion is bonded to the case portion.
12. A microphone as claimed in any preceding claim comprising a transducer within the housing, wherein the receiver portion of the housing comprises a relatively flexible membrane.
13. A microphone as claimed in any claim 12 wherein the transducer and the membrane are arranged to engage with each other when assembled such that the transducer retains the membrane in position.
14. A microphone as claimed in any preceding claim wherein the membrane is made of polyvinyl chloride.
15. A microphone as claimed in any one of claims 9 to 11 wherein the receiver portion is a transducer.
16. A microphone as claimed in claim 15 wherein the transducer is formed from a piezo-eletric material.
17. A microphone as claimed in any one of claims 1 to 8 further comprising a transducer within the housing, wherein the receiver portion comprises a relatively flexible membrane formed integrally of a homogeneous material with the case portion, the membrane being defined by a region in which the thickness of the housing is thinner than the thickness of the housing in the case portion, such as to permit sound waves to propagate there through to the transducer.
18. A microphone as claimed in claim 17 comprising an actuator extending between the inner surface of the membrane and the transducer to transmit acoustic sound waves received by the membrane to be transmitted to the transducer.
19. A microphone as claimed in any preceding claim which is watertight.
20. A microphone as claimed in any preceding claim arranged to be hand-held.
21. A microphone as claimed in claim 20 comprising a"press to talk"switch.
22. A microphone as claimed in any preceding claim wherein the receiver portion has a surface area greater than 19 cm2.
23. A microphone as claimed in any one of claims 1 to 19 comprising a stalk arranged to be mounted on a headset of a user such that the receiver portion can be located in front of a user's mouth.
24. A microphone as claimed in claim 23 comprising a substantially spherical portion of which the receiver portion forms a part thereof.
25. A microphone substantially as hereinbefore described with reference to, and/or as illustrated in, one or more of the accompanying figures.