WO2004015643A1

WO2004015643A1 - Wireless audio monitor

Info

Publication number: WO2004015643A1
Application number: PCT/EP2003/006904
Authority: WO
Inventors: Adrian D Charity; Douglas Ealey
Original assignee: Motorola Inc
Priority date: 2002-08-06
Filing date: 2003-06-30
Publication date: 2004-02-19
Also published as: EP1543483A1; GB2391673A; DE60320428D1; GB2391673B; ATE392686T1; GB0218267D0; AU2003242776A1; EP1543483B1

Abstract

A wireless audio monitor can remotely detect voice activity. A first portable radio transceiver (60) is reversibly switchable between a first narrow-bandwidth audio receiving mode (12) and a second standard audio receiving mode (10). The first transceiver (60) is adapted to operate in the first narrow-bandwidth audio receiving mode (12) when listening for voice activity, and to communicate with a second transceiver (64) via a wireless radio communication link when voice activity has been detected. The second transceiver (64) is adapted to indicate to a user the detection of voice activity by the first transceiver (60). The detection of voice can be optimised for infant voices (52), to enable the system to function as a baby monitor.

Description

WIRELESS AUDIO MONITOR

Field of the Invention

Monitoring an audio environment via wireless devices .

Background of the Invention

Monitoring of an audio environment via wireless devices generally requires two units. The first unit is a listening device. The listening device transmits audio signals from the intended area to the second unit, which is a monitoring device. The monitoring device relays the received audio signal to a user.

A typical device may in use provide constant audio monitoring. The transmitter simply broadcasts continuously, and control is limited to adjusting the volume of the monitoring device.

Published application JP 62026965 (TOSHIBA) proposes applying a low-pass filter to transmitted signals when the audio level at the first (child) unit is at or below a prescribed threshold, and not applying said filter when the audio level is above said threshold. Such a process would reduce the amount of noise heard by the supervisory adult from a continuous transmission.

Published application US 4531115 (BLACK) uses a generated single audio frequency source at the transmitter. The receiver is notch filtered to that audio frequency so only signal energy from that source may be used to trigger an alarm. The method by which the transmitter is activated is not specified. Published application US 5812056 (LAW) proposes radio frequency signal delay measurement between two devices to determine the distance of separation between the supervisory adult and child.

Published application US 5640147 (CHEK) proposes activation control by the second (supervisory adult-held) receiver unit of a first (child-held) transmitter unit for audio monitoring of the child's environment.

Published application US 5774038 proposes that the first (child's) transmitter unit may be voice-activated. This provides both a level of discrimination at the transmitter, and a reduction of power consumption, increasing monitoring time.

However, there is still considerable scope to improve the monitoring arrangement, as the following description of the invention makes clear.

Summary of Invention

The present invention provides means for remotely detecting voice activity.

In a first aspect, the invention provides a communication system, as claimed in claim 1.

In a second aspect, the invention provides a method of operating a communication system, as claimed in claim 17

Further aspects are as claimed in the dependent claims .

Brief description of the Drawings FIG. 1 shows the frequency characteristics of two modes of operation of the invention.

FIG. 2 shows an embodiment of a transceiver 2 in accordance with the present invention.

FIG. 3 shows a preferred usage of a transceiver 60 in accordance with the present invention.

Detailed description of the invention

FIG. 1 shows the frequency characteristics of two modes of operation of the invention. There is a narrowband audio receiving mode 12. There is also a standard audio receiving mode 10.

The use of the two modes shown in figure 1 will become apparent from the description below of the operation of the invention.

FIG. 2 shows an embodiment of a transceiver 2 in accordance with the present invention. The transceiver 2 of figure 2 can transmit speech from a user of the device. The transceiver 2 comprises a microphone 34 that provides a signal and a reversibly switchable filter 46 that provides either a standard or narrowband version of the signal from the microphone 34. Hence the transceiver 2 of figure 2 is able to apply filters to the received sound that are of the general form shown in figure 1.

The transceiver 2 also has a controller 20 and a memory 32 Controller 20 may be a microprocessor. Transmission circuit 22 transmits the signal from the filter 46. Transmission circuit 22 transmits via switch 24 and antenna 26.

The transceiver 2 of figure 2 also comprises a display screen 42 and keypad 44, which serve as part of the user interface circuitry of the transceiver. At least the keypad 44 portion of the user interface circuitry is activateable by the user. Voice activation of the transceiver, or other means of interaction with a user, may also be employed.

Signals received by the transceiver are routed by the switch 24 to receiving circuitry 28. From there, the received signals are routed to controller 20 and audio processing circuitry 38. A loudspeaker 40 is connected to audio circuit 38. Loudspeaker 40 forms a further part of the user interface.

A data terminal 36 may be provided. Terminal 36 provides a signal comprising data for transmission by transmitter circuit 22, switch 24 and antenna 26.

In operation, the transceiver 2 is capable of storing in the memory 32 the data defining the modes of operation of the transceiver 2.

FIG. 3 shows a preferred usage of a transceiver 60 in accordance with the present invention. An infant 50 emits a sound 52 that is detected by the transceiver 60. If the sound exceeds a threshold determined by controller 62 of transceiver 60, a signal is transmitted.

The first transceiver 60 contains reversibly switchable audio receiving modes, the first being a narrow-bandwidth audio receiving mode, and the second a standard audio receiving mode .

A second of possibly many transceivers 64 receives the transmission of the first transceiver 60. Transceiver 64 provides a call alert and/or vibrates to alert user 54. User 54 may then send a command using the second transceiver 64 to change modes of operation of the first transceiver 60.

The general operation of the invention is therefore clear, from the above example. Below a more detailed description of two preferred embodiments is given.

Description of Exemplary Embodiments

Embodiment 1 :

Figure 3 illustrates the scenario of the first preferred embodiment. In this embodiment an infant 50 emits a sound 52 that is detected by the transceiver 60. If the sound exceeds a threshold determined by controller 62 of transceiver 60, a signal is transmitted.

In this embodiment a second transceiver 64 receives the transmission of the first transceiver 60 and provides a call alert and/or vibrates to alert user 54. In this embodiment, user 54 may then send a command using the second transceiver 64 to change modes of operation of the first transceiver 60. Additional optional transceivers are not shown for simplicity.

In this embodiment, the first narrow bandwidth audio receiving mode is designed to be most sensitive to infant voice frequencies, in accordance with figure 1. See plot 12 of figure 1. It would be expected that this mode would be the default monitoring mode in this embodiment.

Employing either the first narrow-bandwidth audio receiving mode, or the second standard audio receiving mode, the first transceiver 60 would employ a voice level threshold based on comparison between current signal levels and long term or prior signal levels constituting background noise. This threshold level may optionally be made user- adjustable.

The first narrow-bandwidth audio receiving mode can operate with a bandwidth that is optimal for detecting the frequencies of an infant . These frequencies may be those in which the volume of sound is greatest when a baby is crying. In comparison to a prior art listening device of broader bandwidth:

(i) This narrow bandwidth may help to screen out noises other than a babies' cries, making more precise the selection of instances at which a listening adult is notified of noise at the baby's location; (ii) It may also require less battery power to operate in the narrow-bandwidth receiving mode; (iii) Finally, the first and second portable units 60 and 64 may also require less battery power, because the first unit 60 will be triggered less often to communicate with the second transceiver 64.

Upon detecting speech that exceeds the voice level threshold, the first transceiver 60 may automatically employ any or all of the following modes of operation: (i) The first transceiver 60 transmits audio for a limited period of time following voice activity detection; (ii) The first transceiver 60 changes its transmission mode from voice-detection based transmission to continuous transmission;

(iii) The first transceiver 60 changes its audio receiving mode from the narrow bandwidth audio receiving mode to the standard audio receiving mode, or vice-versa, depending on the current audio receiving mode .

Any automatic change of mode may optionally last for only a limited period, before reverting to the previous mode.

The second transceiver 64 can be reversibly changed between indicating voice detection and continuously monitoring the transmissions of the first transceiver 60, either by the user by direct intervention, setting an automatic mode change, or under control of the first transceiver 60 via a wireless radio link.

The second transceiver 64 may additionally remotely control modes of the first transceiver 60, either as a consequence of user intervention, or automatically. These modes may comprise any or all of the following:

(i) The second transceiver 64 can remotely alter the transmission mode of the first transceiver between voice- detection based transmission and continuous transmission;

(ii) The second transceiver 64 can remotely alter the audio receiving mode of the first transceiver between a narrow bandwidth audio receiving mode and a standard audio receiving mode; (iii) The second transceiver 64 can remotely alter the level of gain applied to the audio signal in the first transceiver.

Any remote change of mode may optionally last for only a limited period, before reverting to the previous mode. In this embodiment, it is envisaged that the first and second transceivers are functionally interchangeable, with each comprising the necessary means to perform the role of either first or second transceiver as described herein.

Embodiment 2 :

The second preferred embodiment is similar to embodiment 1, except that the transceivers are based upon current portable two-way radios. This second embodiment provides the additional benefit of multiple selectable transmission channels. This allows many transceiver pairs or groups to operate independently, within a locality where only a single-frequency transmission capability would cause interference between monitoring activities.

Each two-way radio's controller would be modified with the control options and modes outlined above, in connection with embodiment 1 of the invention. The two-way radios- would be equipped with an audio filter that could provide the two bandwidths 10 and 12 shown in figure 1. The two-way radios would be able to switch between these filter modes, as described above in connection with embodiment 1.

Claims

1. A system for remotely detecting voice activity, comprising:

at least a first (60) and a second (64) portable radio transceiver, the first transceiver being reversibly switchable between a first narrow-bandwidth audio receiving mode (12) , and a second standard audio receiving mode (10) ;

the first transceiver (60) being adapted to operate in the first narrow-bandwidth audio receiving mode when listening for voice activity, and to communicate with the second transceiver (64) via a wireless radio communication link when voice activity has been detected;

the second transceiver (64) being adapted to indicate to a user the detection of voice activity (52) by the first transceiver (60) ; and

wherein each of the first transceiver and second transceiver comprise the necessary means to perform the role of either first or second transceiver.

2. A system according to claim 1 , wherein the first narrow bandwidth audio receiving mode (12) of the first transceiver (60) is band-limited to favour infant voice frequencies .

3. A system according to claim 1 or claim 2 , wherein the voice activity detection of the first transceiver (60) employs a threshold mechanism that is dependent on the level of background noise.

4. A system according to claim 3, wherein the sensitivity of the voice activity detection threshold can be adjusted by a user .

5. A system according to any previous claim, wherein the first transceiver transmits audio for a limited period of time following voice activity detection.

6. A system according to any previous claim, wherein the second transceiver indicates the detection of voice activity by the first transceiver by call alert or vibration.

7. A system according to any of claims 1 to 6, wherein the first transceiver is adapted to automatically change its mode of operation upon the detection of voice.

8. A system according to claim 7, wherein the first transceiver automatically changes its transmission mode, the change being from voice-detection based transmission to continuous transmission.

9. A system according to claim 7, wherein the first transceiver automatically changes its audio receiving mode, the change being from a narrow bandwidth audio receiving mode to a standard audio receiving mode.

10. A system according to any of claims 7 to 9, wherein the first transceiver automatically changes modes for a limited time period, before reverting to the previous mode.

11. A system according to any previous claim, wherein a mode of the second transceiver is reversibly changeable between indicating voice activity detection by the first transceiver and monitoring the audio transmission of the first transceiver, the change of mode being either: (i) By manual intervention of a user of the second transceiver, or (ii) Under control of the first transceiver, via a wireless radio link.

12. A system according to any previous claim, wherein the second transceiver can remotely alter modes of the first transceiver, via a wireless radio communication link.

13. A system according to claim 12, wherein the second transceiver can remotely alter the transmission mode of the first transceiver, the change being from voice-detection based transmission to continuous transmission.

14. A system according to claim 12 or 13 , wherein the second transceiver can remotely alter the audio receiving mode of the first transceiver, the change being from a narrow bandwidth audio receiving mode to a standard audio receiving mode .

15. A system according to any of claims 12 to 14, wherein the second transceiver can remotely alter the audio receiving mode of the first transceiver, the change being the level of gain applied to the audio signal.

16. A system according to any of claims 12 to 15, wherein the first transceiver reverts from the remotely altered mode to the previous mode after a limited time period.

17. A method for remotely detecting voice activity, comprising the provision of at least a first (60) and a second (64) portable radio transceiver, the first transceiver being reversibly switchable between a first narrow bandwidth audio receiving mode (12) , and a second standard audio receiving mode (10) , whereby in operation: (i) The first transceiver (60) listens in the first narrow bandwidth audio receiving mode (12) , when listening for voice activity;

(ii) The first transceiver (60) communicates with the second transceiver (64) via a wireless radio communication link, when voice activity has been detected; and (iii) The second transceiver (64) indicates to a user the detection of voice activity by the first transceiver (60) .

18. A method according to claim 17, wherein the first narrow bandwidth audio receiving mode (12) is band-limited to favour infant voice frequencies.

19. A method according to claim 17, wherein the first transceiver provides an automatic change of a mode of operation upon the detection of voice.

20. A method according to any of claims 17 to 19, wherein the second transceiver provides a remote alteration of a mode of the first transceiver, via a wireless radio communication link.