WO2002054610A1

WO2002054610A1 - Telephone headsets

Info

Publication number: WO2002054610A1
Application number: PCT/GB2001/005679
Authority: WO
Inventors: Roger Green
Original assignee: University Of Warwick
Priority date: 2001-01-05
Filing date: 2001-12-20
Publication date: 2002-07-11
Also published as: GB0100205D0

Abstract

A mobile telephone headset 1 comprises a microphone unit 5 adapted to be positioned in the vicinity of the user's mouth to receive speech to be transmitted by the telephone, and an earpiece 6 adapted to be positioned in the vicinity of the user's ear to transmit into the user's ear speech received by the telephone from a remote caller. The earpiece 6 does not incorporate an electromagnetic coil producing an electromagnetic field extending into the side of the user's head (as in conventional telephone headsets), but instead is connected by an audio pipe 7 to a sounder integral with the microphone unit 5. Alternatively the earpiece may incorporate a crystal loudspeaker and an optical receiver module. Such arrangements ensure that the user is not subjected to an unacceptable level of radiation directed into the side of the user's head in use of the telephone.

Description

"Telephone Headsets"

This invention relates to telephone headsets and is more particularly, but not exclusively, concerned with mobile telephone headsets and earpieces.

There is widespread public concern over the possible radiation hazards arising from the use of mobile telephones. This concern applies even when a hands-free headset is used so that the telephone does not need to be held against the user's head, since radiation from the earpiece can result in an equal quantity of, or even a greater quantity of, radiation being directed into the user's head than that from the antenna from the main part of the telephone.

It is an object of the invention to provide a novel headset or earpiece which considerably reduces the level of radiation directed into the user's head in use of a mobile telephone.

According to the present invention there is provided a mobile telephone headset comprising a microphone unit adapted to be positioned in the vicinity of the user's mouth to receive speech to be transmitted by the telephone, and an earpiece adapted to be positioned in the vicinity of the user's ear to transmit into the user's ear speech received by the telephone from a remote caller, wherein the earpiece does not incorporate an electromagnetic coil producing an electromagnetic field extending into the side of the user's head.

The invention separates the hearing assembly, that is the earpiece, from the possible radiation paths from the main section of the telephone. There are several possible embodiments in accordance with the invention which ensure that little or no radiation is transmitted into the ear, and hence the brain, of the user.

In some of these embodiments the conventional earpiece, which normally incorporates an electromagnetic device containing a coil of wire (which can radiate radio energy much like an antenna), is replaced by a crystal earpiece which operates on a different principle to an electromagnetic earpiece and hence radiates much lower amounts of radio energy. Alternatively a conventional electromagnetic loudspeaker may be used provided that it is housed in the same module as the microphone of the headset so that it is positioned remotely of the user's ear, with the sound waves being conducted to the user's ear by an audio pipe. Other embodiments in accordance with the invention are described below.

In order that the invention may be more fully understood, reference will now be made, by way of example, to the accompanying drawings, in which:

Figures 1 to 6 are diagrammatic views of various embodiments of headset in accordance with the invention;

Figures 7a and 7b show a section of light pipe in side view and axial section; and

Figures 8a and 8b show a section of optical fibre in side view and axial section.

Each of the embodiments of headset described below in accordance with the invention is designed to avoid the need for a device which is a strong emitter of radiation, such as an electromagnetic coil for example, to be incorporated in an earpiece which is held against the side of the user's head in use. Thus each of these embodiments overcomes the disadvantage of the use of conventional earpieces incorporating electromagnetic coils which may radiate radio energy in the manner of an antenna into the brain of the user.

Referring to Figure 1, a headset 1 is shown connected to the telephone body 2 by a standard wire connecting cable 3 plugged into a connecting socket not shown on the body 2. The headset 1 incorporates a microphone module 5 intended to be positioned close to the user's mouth in use to pick up the user's speech for transmission by the telephone. The microphone module 5 includes an integral sounder which is intended to generate sound in response to receipt of an electrical actuating signal from the telephone indicative of speech received from a remote caller. To prevent radio energy coming close to the ear and thus close to the brain of the user, a plastic earpiece moulding 6 is connected to the microphone module 5 by a short piece of plastic audio pipe 7, which can be considered as analogous to a stethoscope tube, the pipe 7 being of high enough diameter to permit sound to travel faithfully over the short distance from the sounder of the microphone module 5 towards the earpiece moulding 6. The earpiece moulding 6 is merely a shaped element which fits in the user's ear and which is capable transmitting into the user's ear the sound waves received from the sounder by way of the pipe 7. The earpiece moulding 6 is fully contained except for a small hole into which the pipe 7 is placed.

The length of the pipe 7 can be anything up to about 100 mm or so, sufficient to distance the sounder/microphone module 5 from the user's ear. Thus any radiation originating from the telephone and radiated from the sounder and microphone does not get introduced into the ear cavity itself, and thus the brain of the user. Instead any such radiation is transmitted in the vicinity of the user's mouth. Advantages associated with this embodiment include cheapness, compatibility with existing manufacturing techniques, and reliability.

In a second embodiment of the invention shown diagrammatically in Figure 2, the headset 1 ' incorporates a short plastic optical fibre link 10, in place of the audio pipe 7 of the first embodiment, connecting the microphone module 5' to the earpiece 6', and the earpiece 6' incorporates a crystal loudspeaker which radiates low amounts of radio energy. In this case connecting the microphone module 5' incorporates an optical transmitter in the form of a light-emitting diode (not shown), and the earpiece 6' incorporates a very low power optical receiver module (not shown) built in to an otherwise standard earpiece. The optical receiver module consists of a small photocell or photodiode connected to a compact amplifier which drives the earpiece electrically to generate the sound required. The optical receiver module preferably uses low power CMOS circuitry to drive the earpiece 6'. The microphone module 5' is connected by a wire connecting cable 3 to a standard interface at the telephone body 2. ha this approach, a tiny battery may be required if the receiver module is in the form of a photodiode receiver. In operation of such an embodiment the electrical signal transmitted from the telephone body 2 by way of the cable 2 to the microphone module 5' is converted to an optical signal which is transmitted from the microphone module 5' along the optical fibre link 10 to the earpiece 6' where it is detected by the optical receiver module and converted to the sound which is transmitted into the user's ear.

This embodiment is more expensive to produce than the first embodiment, but otherwise possesses the same advantages as the first embodiment. The optical fibre link 10 may be contained within a plastic boom which supports the microphone module 5' with respect to the ear position, for example by being suspended from the earpiece 6' or a strap supporting the earpiece 6' by engaging the user's head in known manner.

In a third embodiment of the invention shown in Figure 3, the earpiece 6" and the microphone module 5" are not connected to the telephone body 2 by a wire connecting cable as in the other embodiments, but instead communicate with the telephone body 2 by means of low power infrared beams 11 and 12 or even light beams. The microphone module 5" incorporates an infrared or optical wireless transmitter (not shown), and the earpiece 6" incorporates a crystal loudspeaker (as in the embodiment of Figure 2) and an infrared or optical receiver (not shown) for receiving a signal transmitted by an infrared or optical wireless transmitter 14 on the telephone body 2. In use the earpiece 6" receives an infrared or light signal beamed to it by the telephone body 2, in much the same way as the IrDA concept can link a computer keyboard to a computer without wires, or in a similar manner to an infrared control for a television or video recorder. Conversely, the microphone unit 5" transmits an infrared or light signal towards the telephone body 2, which converts the transmitted information into conventional microphone signals for the telephone unit.

For this third embodiment to work, an optical antenna (patent pending) is mounted on both the telephone body 2 and the earpiece 6" to ensure that the transmitted infrared or visible radiation is collected and distributed sufficiently well. This embodiment possesses similar advantages to the other embodiments.

In a non-illustrated, fourth embodiment of the invention, which represents a modification of the third embodiment, very low power radio transmitters are provided in place of the infrared or optical wireless transmitters of the third embodiment, with just sufficient range to reach the telephone body from the microphone module, and conversely for the earpiece to receive a signal from the telephone body. A compact dielectric antenna system can provide the necessary radiation and detection of radio signals. The radio link can be provided by the Bluetooth ™ system or any other radio frequency peripheral link system. By comparison with the infrared/visible light solution described above, the radio link approach does not require visible alignment, although it does require radio spectrum consumption, which the other systems do not.

In a fifth embodiment of the invention shown in Figure 4, the headset 20 incorporates an optoisolator 26 at its end for connection to the telephone body 2 to isolate the telephone circuitry from the audio circuitry of the earpiece 22 and the microphone 24. The optoisolator 26 is connected to the earpiece 22 and the microphone 24 by wire connecting cables 21 and 23. The earpiece 22 is a standard earpiece which, for low power consumption, may be a crystal earpiece. Such an earpiece also has the advantage of low RF (radio frequency) pickup from the telephone transmitter antenna. The optoisolator 26 is an optoelectronic link which consists of a low power light- emitting diode (LED) close to a photodiode, so that the optical signal from the LED produces an electrical signal in the photodiode without any direct electrical connection between the telephone circuitry from the earpiece/microphone audio circuitry. If required the microphone 24 may be powered by a miniature button-type battery, for example of 6 volts potential. The earpiece 22 may also be powered by the same battery in conjunction with a very low power CMOS audio amplifier contained in the microphone module. Because the earpiece 22 is crystal, very little drive power to the earpiece 22 is required, so that the battery power requirement is extremely small. In a sixth embodiment of the invention shown in Figure 5, the headset 30 incorporates a microphone module 28 which contains an ultrasound transmitter and which is connected to the telephone body 2 by a wire connecting cable 21 and a standard interface. The purpose of the ultrasound transmitter is to send signals through a very narrow bore ultrasonic waveguide 29 to the earpiece unit 31 which contains a low power CMOS ultrasound detector powered by a miniature button-type battery. The ultrasound signal transmitted from the microphone module 28 can travel in a very small bore in the ultrasonic waveguide 29, the bore being much smaller (less than 1 mm) than a conventional audio pipe would need to be, making it less bulky than the audio pipe embodiment already described.

In a seventh embodiment of the invention shown in Figure 6, the headset 40 incorporates a low power earpiece 22 connected by a wire connecting cable 23 to a microphone module 34 which contains an ultrasound interface. The ultrasound interface can receive ultrasound signals from, and transmit ultrasound signals to an ultrasound interface 35 on the telephone body 2 by way of an ultrasonic waveguide 36. The ultrasound interface 35 can also transmit and receive ultrasound. The frequency of the ultrasound transmitted along the waveguide 36 is different for each direction, so that at each end of the ultrasound link the signals can be differentiated and therefore separated in function. The ultrasonic waveguide 36 is of lesser diameter than would be a conventional audio pipe.

In the microphone module 34 the electrical signal from the microphone is transmitted with suitable amplification as modulation applied to the ultrasound signal. This modulation can be implemented by a wide variety of techniques, including amplitude modulation, frequency modulation, etc. At the ultrasound interface 35 the ultrasound signal is demodulated and converted back to an electrical signal for the transmitter of the telephone. The conventional audio signals from the telephone which would normally be sent to an earpiece are used to modulate a second ultrasound carrier at a different frequency to the ultrasound signal transmitted from the other ultrasound interface. The ultrasound signal originating from the ultrasound interface 35 is transmitted to the ultrasound interface of the microphone module 34, and this ultrasoimd signal carries the audio information which is demodulated in the ultrasound interface to provide a conventional audio signal for the earpiece 22 through the connecting cable 23.

In other non-illustrated embodiments the connection between the telephone and the headset, consisting of the microphone module and the earpiece, can be by way of an optical pipe using visible light. Such an optical pipe, which is not the same as an optical fibre can be made of cheap plastic pipe 50, such as is used for illuminating microscope slides or for visual inspection, as shown in side view and in axial section in Figures 7a and 7b. The plastic pipe 50 has a constant cross-section (which can be circular, rectangular or square). As shown in Figure 7b the light from a light source 51 used for the transmission of information passes into the pipe 50, and a proportion of the light passes along the pipe 50 as shown by the arrow 52. Some light also leaks out at reflective boundaries, as shown by the arrows 53. Eventually the transmitted light leaves the exit of the pipe 50 and can be interpreted as information (speech etc).

This is in marked contrast to the use of an optical fibre 60, as shown in Figures 8a and 8b in side view and in axial section, which is more expensive and usually uses infrared energy to send data or analogue signals from one point to another. The principle of operation is total internal reflection from an optical boundary 64, as best seen in Figure 8b, defined by a core 61 of refractive index nl and a cladding 62 of refractive index n2, n2 being less than nl. When supplied with light from an infrared light source 63 the losses in the optical fibre 60, in terms of what is lost at reflections, are very small. By contrast, the optical pipe 50 has large losses, as it is a simpler structure. Nevertheless the losses over a short distance of such a pipe, say 60 cms, are small enough for a reasonable signal to pass.

Claims

CLAIMS:

1 A mobile telephone headset comprising a microphone unit adapted to be positioned in the vicinity of the user's mouth to receive speech to be transmitted by the telephone, and an earpiece adapted to be positioned in the vicinity of the user's ear to transmit into the user's ear speech received by the telephone from a remote caller, wherein the earpiece does not incorporate an electromagnetic coil producing an electromagnetic field extending into the side of the user's head.

2. A headset according to claim 1, wherein the earpiece incorporates a loudspeaker which produces only a low level of radiation extending into the side of the user's head.

3. A headset according to claim 2, wherein the earpiece incorporates a crystal loudspeaker.

4. A headset according to claim 1, wherein the earpiece is positioned at a distance from an electrical link for transmitting electrical signals from the telephone, and a nonelectrical link is provided for transmitting signals between the electrical link and the earpiece.

5. A headset according to claim 4, wherein the non-electrical link comprises a transmitting transducer driven by an electrical signal supplied by the electrical link for transmitting a non-electrical signal, and a transmitting medium for transmitting the nonelectrical signal from the transmitting transducer towards the earpiece.

6. A headset according to claim 5, wherein the transmitting transducer is formed integrally with the microphone unit.

7. A headset according to claim 5 or 6, wherein the non-electrical link includes a receiving transducer for receiving the non-electrical signal and for supplying a speech signal to the user's ear.

8. A headset according to claim 5, 6 or 7, wherein the transmitting transducer is a sounder adapted to be positioned remotely from the user's ear, and the transmitting medium is a pipe which conducts sound waves from the sounder towards the earpiece.

9. A headset according to claims 7 and 8, wherein the transmitting transducer is an ultrasound transmitter, and the receiving transducer is an ultrasound receiver.

10. A headset according to claim 7, wherein the transmitting transducer is a light transmitter adapted to be positioned remotely from the user's ear, and the receiving transducer is a light receiver.

11. A headset according to claim 10, wherein the transmitting medium is a light pipe which conducts visible light from the light transmitter to the light receiver.

12. A headset according to claim 10, wherein the transmitting medium is an optical fibre which conducts light from the light transmitter to the light receiver.

13. A headset according to claim 1, 2 or 3, wherein the earpiece is connected to the microphone unit by an electrical link for transmitting electrical signals to the earpiece, and a non-electrical link is provided for transmitting signals between the telephone and the microphone unit.

14. A headset according to claim 13, wherein the non-electrical link includes ultrasound transmitting and receiving transducers for transmitting sound waves between the telephone and the microphone unit.

15. A headset according to claim 1, 2 or 3, wherein the earpiece is adapted to receive a radio signal from the telephone or the microphone unit.

16. A headset according to claim 1, 2 or 3, wherein the earpiece incorporates a receiver for receiving a wireless signal from the telephone.

17. A headset according to claim 1, 2, 3 or 16, wherein the microphone unit incorporates a transmitter for transmitting a wireless signal to the telephone.

18. A mobile telephone having a headset according to any preceding claim.