EP1543483B1

EP1543483B1 - Wireless audio monitor

Info

Publication number: EP1543483B1
Application number: EP03783995A
Authority: EP
Inventors: Adrian D. Motor. Limited CHARITY; Douglas Motorola European Intellectual EALEY
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2002-08-06
Filing date: 2003-06-30
Publication date: 2008-04-16
Anticipated expiration: 2023-06-30
Also published as: GB0218267D0; WO2004015643A1; GB2391673B; DE60320428D1; GB2391673A; ATE392686T1; EP1543483A1; AU2003242776A1

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 and a second wide bandwidth audio receiving mode. The first transceiver 60 is adapted to operate in the first narrow bandwidth audio receiving mode when listening for voice activity, and to communicate with a second transceiver 64 in wide bandwidth mode via a 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

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.
US 5812056 (Law) proposes radio frequency signal delay measurement between two devices to determine the distance of separation between the supervisory adult and child.
US 5640147 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.
US 5774038 proposes that the first (child's) transmitter may be voice activated. This provides both a level of discrimination at the transmitter and a reduction of power consumption increasing monitoring time.
DE-A-10008029 describes a unit suitable for monitoring audio sounds from an infant. The unit provides an integration of an input audio signal over a period of time to determine if the quantity of sound monitored indicates an infant crying, thereby causing a special function to be triggered. The special function may comprise recording the audio signal and dialling a predetermined telephone number.
The purpose of the present invention is to provide an improved monitoring and communication system and method of operation therein.

Summary of Invention

In a first aspect the present invention provides a system as defined in claim 1 of the accompanying claims.
In a second aspect the present invention provides a method as defined in claim 16 of the accompanying claims.
Further features of the present invention are as defined in the accompanying dependent claims.
Embodiments of the present invention will now be described by way of reference to the accompanying drawings.

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 a preferred embodiment is given.

Description of an Exemplary Embodiment

Figure 3 illustrates the scenario of a preferred embodiment. In the 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 the 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 the 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 the 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 the 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 the 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.
The transceivers are based upon current portable two-way radios. This 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 is modified with the control options and modes outlined above. The two-way radios are equipped with an audio filter that provides the two bandwidths 10 and 12 shown in figure 1. The two-way radios are able to switch between these filter modes, as described above.

Claims

A system for remotely detecting and communicating voice activity, the system comprising: at least a first transceiver (60) which is a radio transceiver and a second transceiver operable to receive communications from the first transceiver and to send communications to the first transceiver, the first transceiver having voice activity detection (20); and including a filter to screen out noise and being reversibly switchable between a first audio receiving mode adapted selectively to pick up sounds from a monitored voice source and a second audio receiving mode, the second transceiver (64) being adapted to indicate to a user the detection of voice activity (52) by the first transceiver (60); characterised in that the first (60) and second (64) transceivers are two-way portable radios forming a functionally interchangeable pair operable to provide wireless communication with one another such that the second transceiver can receive a signal transmitted from the first transceiver and the first transceiver can receive a command sent from the second transceiver, in which the filter (46) is switchable to filter sounds in each of two selectable bandwidths to provide the first and second modes of operation, the bandwidths being a first narrow audio bandwidth selected when listening for a particular voice activity, and the second bandwidth being a broader audio bandwidth incorporating the first bandwidth and providing a standard audio receiving mode, the second transceiver being operable by a command sent by wireless communication to the first transceiver to change a mode of operation of the first transceiver.
A system according to claim 1, wherein the filter is operable in the first mode to be band-limited to favour infant voice frequencies.
A system according to claim 1 or claim 2, wherein the voice activity detector of the first transceiver is operable to employ a threshold mechanism that is dependent on the level of background noise.
A system according to claim 3 wherein the voice activity detector of the first transceiver is operable to employ a threshold mechanism that can be adjusted by a user.
A system according to any one of the preceding claims wherein the first transceiver is operable to transmit audio for a limited period of time following voice activity detection.
A system according to any one of the preceding claims wherein the second transceiver is operable to indicate the detection of voice activity by the first transceiver by call alert or vibration.
A system according to any one of the preceding claims wherein the first transceiver is automatically operable to change its mode of operation upon the detection of voice activity.
A system according to 7 wherein the first transceiver is operable to automatically change its transmission mode from voice-detection based transmission to continuous transmission.
A system according to claim 7 wherein the first transceiver is operable automatically to change its audio receiving mode from the first mode to the second mode.
A system according to any one of claims 7 to 9, wherein the first transceiver is operable to change mode for a limited time period before reverting to a previous mode.
A system according to any one of the preceding claims wherein the second transceiver is operable to change a mode of its operation between a first mode indicating voice activity by the first transceiver and a second mode monitoring the audio transmission of the first transceiver, the change of mode of the second transceiver being either:
(i) by manual intervention of a user of the second transceiver; or

(ii) under control of the first transceiver by a wireless radio link.
A system according to any one of the preceding claims, wherein the second transceiver is operable to remotely alter the transmission mode of the first transceiver from voice-detection based transmission to continuous transmission.
A system according to any one of the preceding claims wherein the second transceiver is operable to change the audio receiving mode of the first transceiver from the first mode to the second mode of the first transceiver.
A system according to any one of the preceding claims wherein the second transceiver is operable to change a level of gain applied to an audio signal by the first transceiver.
A system according to any one of the preceding claims wherein the first transceiver is operable to revert from a remotely altered mode in which its mode is controlled by the second transceiver to a previous mode after a limited period of time.
A method for remotely detecting and communicating voice activity using the system according to any one of the preceding claims, the method comprising: detecting audio by the voice activity detector (20) of the first transceiver; (ii) filtering the audio by the filter of the by the first transceiver in the first mode to selectively to pick up voice sounds from a monitored infant; (iii) transmitting a communication from the first transceiver to the second transceiver indicating selectively monitored voice activity detected by the first transceiver; (iv) detecting the communication indicating voice activity by the second transceiver; (v) indicating by the second transceiver to a user the detection of voice activity by the first transceiver (60); sending by the second transceiver a command by wireless communication to the first transceiver to change a mode of operation of the first transceiver; and switching the first transceiver by the command between the first audio receiving mode and the second audio receiving mode.