Patent Grant
9215535
1. Field of the Invention
The invention relates to a system for providing hearing assistance to a user, comprising at least one audio signal transmission unit comprising an audio signal source, typically a microphone arrangement, and means for transmitting audio signals from the audio signal source via a wireless radio frequency link to a left ear receiver unit worn at the user's left ear and a right ear receiver unit worn at the user's right ear. Typically, each of the receiver units is connected to a hearing aid, so that the user's hearing can be stimulated according to the audio signals of the audio signal source.
2. Description of Related Art
Typically, such wireless microphones are used by teachers teaching hearing impaired persons in a classroom (wherein the audio signals captured by the wireless microphone of the teacher are transmitted to a plurality of receiver units worn by the hearing impaired persons listening to the teacher) or in cases where several persons are speaking to a hearing impaired person (for example, in a professional meeting, wherein each speaker is provided with a wireless microphone and with the receiver units of the hearing impaired person receiving audio signals from all wireless microphones). Another example is audio tour guiding, wherein the guide uses a wireless microphone.
Typically, the wireless audio link is an FM (frequency modulation) radio link operating in the 200 MHz frequency band. Examples for analog wireless FM systems, particularly suited for school applications, are described in EP 1 864 320 A1 corresponds to WO 2006/104634 A2 and WO 2008/138365 A1.
In recent systems the analog FM transmission technology is replaced by employing digital modulation techniques for audio signal transmission, most of them working on other frequency bands than the former 200 MHz band.
U.S. Pat. No. 8,019,386 B2 relates to a hearing assistance system comprise a plurality of wireless microphones worn by different speakers and a receiver unit worn at a loop around a listener's neck, with the sound being generated by a headphone connected to the receiver unit, wherein the audio signals are transmitted from the microphones to the receiver unit by using a spread spectrum digital signals. The receiver unit controls the transmission of data, and it also controls the pre-amplification gain level applied in each transmission unit by sending respective control signals via the wireless link. Mixing of the received audio signals is controlled such that the signal with the highest audio power is amplified with unity gain, and the other signals are attenuated by 6 dB.
International Patent Application Publication WO 2008/098590 A1 relates to a hearing assistance system comprising a transmission unit having at least two spaced apart microphones, wherein a separate audio signal channel is dedicated to each microphone, and wherein at least one of the two receiver units worn by the user at the two ears is able to receive both channels and to perform audio signal processing at ear level, such as acoustic beam forming, by taking into account both channels.
International Patent Application Publication WO 2011/098142 A1 relates to a hearing assistance system comprising a plurality of wireless microphones, a relay unit and a left ear receiver unit and a right ear receiver unit, wherein the relay unit as adapted to mix the audio signals of the different transmission units and to transmit the mixed audio signal in a manner that a different audio signal is received by the right ear receiver unit and by the left ear receiver unit in order to enable spatial hearing by the user of the receiver units.
European Patent Application EP 2 099 236 A1 relates to a hearing aid fitting method using simulated surround sound, wherein different head related transfer functions are applied to test audio signals supplied to the hearing aid.
U.S. Pat. No. 8,369,551 B2 relates to a hearing aid receiving audio signals via a wireless audio link, wherein the distance to the audio signal transmitter is monitored by monitoring the reception quality.
European Patent Application EP 1 303 166 A2 relates to a hearing aid which is capable of determining the angular position of a speaking person.
International Patent Application Publication WO 2009/072040 A1 relates to a right ear hearing aid and a left ear hearing aid which are capable of localizing a sound source for controlling acoustic beam forming in each of the hearing aids.
U.S. Patent Application Publication 2007/0230714 A1 relates to a binaural system comprising a right ear hearing aid and a left ear hearing aid, which are capable of exchanging audio signals via a wireless link, wherein a delayed sound signal is transmitted from one of the hearing aids to the other one in order to achieve a time delay between the sound provided by the right hearing aid and the sound provided by the left ear hearing aid; this delay mimics how the ears would naturally hear a sound coming from one side from the head.
International Patent Application Publication WO 2009/056922 A1 relates to a telephone system, wherein the voices of different participants of a telephone conference are supplied as a mixed stereo signal to two ears of a listener in order to create a spatial perception of the different voices, thereby supporting the listener in distinguishing the different persons.
Various methods are known for estimating the angular localization of a source of a radio frequency (RF) signal with regard to a RF receiver. International Patent Application Publication WO 2009/147662 A1 relates to a method for determining whether a target is within a direction sector of interest of a direction finder, wherein the direction finder comprises two antennas arranged in a broad-side configuration. U.S. Pat. No. 6,748,324 B2 relates to a method of estimating the angular localization of a wireless device by a direction of arrival (DOA) measurement. European Patent Application EP 2 000 816 A2 relates to a communication system comprising a mobile phone in a LAN, wherein the angle of arrival of a RF signal and a receiver device is estimated, wherein the transmitting device includes two directional antennas which are tilt relative to each other and with regard to the front of the transmitting device, and wherein the receiving device includes a directional antenna having directivity toward the front of the receiving device. International Patent Application Publication WO 2008/112765 A1 relates to a car finder, wherein the car is provided with a RF signal source and wherein the direction finding device is provided with a directional receiver antenna, and wherein the omni-directional field created by the RF signal transmitter is analyzed by a direction sweep of the receiver antenna, with the RSSI (received signal strength indication) being measured during the sweep.
U.S. Pat. No. 5,905,464 relates to a binaural system comprising two ear phones and an RF antenna having a single analysis axis which is parallel to a line connecting the two ears, which system is used for estimating the angular localization of a source of an RF signal representing a spatial mark and which generates an audio signal representative of the angular direction of the RF signal source; the audio signal may be distributed on to the two ear phones in such a manner that a spatial hearing impression is created which indicates the direction of the RF signal source. The system may be used, for example, by persons working in a dangerous, low-visibility zone, such as firemen.
It is an object of the invention to provide for a hearing assistance system for wireless RF audio signal transmission from at least one audio signal source to ear level receivers, wherein a close-to-natural hearing impression is to be achieved. It is a further object to provide for a corresponding hearing assistance method.
According to the invention these objects are achieved by a hearing assistance system and a hearing assistance method as described herein.
The invention is beneficial in that, by estimating the angular localization of each transmission unit by comparing, for each transmission unit, the left ear RF signal measurement data and the right ear RF signal measurement data obtained from measuring at least one parameter of the RF signal as received from each transmission unit at the respective receiver unit and by distributing the audio signals onto a left ear channel to be supplied via the left ear receiver unit to the left ear stimulating means and a right ear channel to be supplied via the right ear receiver unit to the right ear stimulating means according to the estimated angular localization of each transmission unit in a manner so that the angular localization impression of the audio signals from each transmission unit as perceived by the user corresponds to the estimated angular localization of the respective transmission unit, it is possible to mimic the natural hearing impression which would result from acoustic transmission of the audio signals from the respective audio signal source. Thereby a closed-to-natural hearing impression is created; in particular, if in case that the transmission units are formed by a plurality of wireless microphones used by different persons, the user's capability to distinguish the different voices is enhanced due to the spatial separation of the voices in the sound perceived by the user. Estimating the angular localization of the transmission unit(s) by comparing RF signal measurements at the left ear and at the right ear of the user is a particularly simple and nevertheless reliable method which avoids the need for bulky system components, such as rotating directional antennas, or the need for the electrical combination of signals of a plurality of antennas which would result in complex and power hungry circuitry, thereby enabling a relatively simply design of the system.
These and further objects, features and advantages of the present invention will become apparent from the following description when taken in connection with the accompanying drawings which, for purposes of illustration only, show several embodiments in accordance with the present invention.
The hearing assistance system shown in
As shown in
The VAD 24 uses the audio signals from the microphone arrangement 17 as an input in order to determine the times when the person 11 using the respective transmission unit 10 is speaking. The VAD 24 may provide a corresponding control output signal to the microcontroller 26 in order to have, for example, the transmitter 28 sleep during times when no voice is detected and to wake up the transmitter 28 during times when voice activity is detected (in order to maintain synchronization with the master device—usually the relay unit 15—also during times when said speaker 11 is not speaking, the transmitter 28 of that transmission unit 10 is adapted to also wake up at least during some times when reception of beacon packets from the master device is to be expected; this will be explained in more detail below). In addition, an appropriate output signal of the VAD 24 may be transmitted via the wireless link 12. To this end, a unit 32 may be provided which serves to generate a digital signal comprising the audio signals from the processing unit 20 and the control data generated by the VAD 24, which digital signal is supplied to the transmitter 28. In addition to the VAD 24, the transmission unit 10 may comprise an ambient noise estimation unit (not shown in
In practice, the digital transmitter 28 is designed as a transceiver, so that it cannot only transmit data from the transmission unit 10 to the relay unit 15 but also receive control data and commands sent from the relay unit 15, as will be explained in more detail below.
According to one embodiment, the transmission units 10 may be adapted to be worn by the respective speaker 11 below the speaker's neck, for example as a lapel microphone or as a shirt collar microphone.
The relay unit 15, according to the example shown in
The relay unit 15 also receives, via the link 12′, for each of the transmission units 10A, 10B, 10C left ear RF signal measurement data from the left ear receiver unit 14B and right ear RF signal measurement data from the right ear receiver unit 14A, which data is demodulated by the transceiver 36 and is supplied as input to the angular localization estimation unit 40 which serves to estimate, from such data, the angular localization of each of the transmission units 10A, 10B, 10C relative to the receiver units MA, 14B and to control the audio signal processing unit 38 according to the estimated angular localization of each transmission unit. As will be explained later in more detail, such measurement data preferably is an RSSI (Radio Signal Strength Indication) value for each of the transmission units 10A, 10B, 10C for the left ear receiver unit 14B (indicated by RSSIL in
The audio signal processing unit 38 serves to process the received audio signals M1, M2, M3 in such a manner that a stereo signal is generated by distributing the audio signals onto a left ear channel (indicated by “audioL” in
For example, the angular localization impression may be created by introducing a relative phase delay between the left ear channel signal part and the right ear channel signal part of the audio signals from the respective transmission unit 14A, 14B, 14C according to the estimated angular localization of the respective transmission unit. Alternatively or in addition, the angular localization impression may be created by introducing a relative level difference between the left ear channel signal part and the right ear channel signal part of the audio signals from the respective transmission 14A, 14B, 14C according to the estimated angular localization of the respective transmission unit.
An example of the audio signal paths in the left ear receiver unit 14B is shown in
Rather than supplying the audio signals amplified by the amplifier 52 to the input of a hearing aid 16, the receiver unit 14 may include an audio power amplifier 56 which may be controlled by a manual volume control 58 and which supplies power amplified audio signals to a loudspeaker 60 which may be an ear-worn element integrated within or connected to the receiver unit 14. The receiver unit 14 also may include a microcontroller (not shown) for controlling the DSP 50 and the transceiver 48. Alternatively, this role could be taken over by the DSP 50.
The receiver unit 14B also receives the RF signals transmitted by the transmission units 10A, 10B, 10C which are demodulated by the transceiver 48 and which are separated into the respective signals M1, M2, M3 as transmitted by each of the transmission unit 10A, 10B, 10C in order to determine the RSSI value in an RF signal analyzer unit 70 which provides as an output the present RSSI value for each of the transmission units 10A, 10B and 10C. The output of the analyzer unit 70 is supplied to the transceiver 48 for being transmitted via the link 12′ to the relay unit 15 as the left ear RF signal measurement data RSSIL, which then is used by the angular localization estimation unit 40 of the relay unit 15.
While in
The principle of the angular localization estimation employed by the present invention is illustrated in
Hence, by comparing the RF signal strength as received by the right ear receiver unit 14A and the RF signal strength received at the left ear receiver unit 14B, for example by comparing the respective RSSI values, for a given RF signal source, i.e., for one of the transmission units 10, it is possible to estimate the angular localization i.e., the angle of arrival a for each of RF signal source, i.e., for each of the transmission unit 10. Although the correlation between the signal strength and the angle of arrival in practice may be quite complex, it has been found that it will be possible to distinguish at least some coarse angular regions like “left”, “center-front” and “right”. In general, the reliability of the angle of arrival estimation will be deteriorated by the occurrence of reflected RF signals (such reflexions, for example, may occur at walls, metallic sealings or metallic white boards close to the user's head or in situations where the RF signal source is not in line of sight with regard to the user's head). The angle of arrival estimation will also be deteriorated if both receivers 14A and 14B do not provide the same RSSI reading output to a given reference signal. In practice this problem can be solved by a proper calibration of the RSSI readout during manufacturing of the receivers.
As already mentioned above, the audio signal processing unit 38 of the relay unit 15 will distribute the audio signals resulting from each of the transmission units 10 in such a manner onto the two stereo channels that the audio signals of each transmission unit 10 will create an angular localization impression corresponding to the estimated angular estimation of the transmission unit 10. For example, if the transmission unit 10A is located to the left of the user 13, the transmission unit 10B is located in front of the user 13 and the transmission unit 10C is located to the right of the user 13, the audio signals will be processed in such a manner that the audio signals from the transmission unit 10A are received at the left side, the audio signals from the transmission unit 10B are received in the center and the audio signals from the transmission unit 10C are received at the right side.
The transmission units 10 used in a hearing assistance system according to the invention are not restricted to wireless microphones as described so far. Rather, at least one of the transmission units could be a TV audio signal source. In this case, the user 13 would be enabled to recognize the angular localization of the TV system.
Typically, the carrier frequencies of the RF signals are above 1 GHz. In particular, at frequencies above 1 GHz the attenuation/shadowing by the user's head is relatively strong. Preferably, the digital audio link 12, 12′ is established at a carrier-frequency in the 2.4 GHz ISM band. Alternatively, the digital audio link 12, 12′ may established at carrier-frequencies in the 868 MHz or 915 MHz bands, or in as an UWB-link in the 6-10 GHz region.
The system shown in
The digital link 12, 12′ preferably uses a TDMA schedule with frequency hopping, wherein each TDMA slot is transmitted at a different frequency selected according to a frequency hopping scheme. In particular, each transmission unit 10 and the relay unit 15 transmit each audio data packet in at least one allocated separate slot of a TDMA frame at a different frequency according to a frequency hopping sequence, wherein certain time slots are allocated to each of the transmission unit 10 and the relay unit 15, and wherein the RF signals from the individual transmission units 10A, 10B, 10C are distinguished by the receiver units 14A, 14B and by the relay unit 15 by the time slots in which they are received.
Usually, the relay unit 15 will act as a master device and the transmission units 10 and the receiver units 14 act as slave devices. To this end, the relay unit 15 sends the necessary control data via the digital link 12, 12′ to the slave devices. For example, a beacon packet may be transmitted from the relay unit 15 in the first slot of each TDMA frame which contains information for hopping frequency synchronization and which may also contain information relevant for the audio streams 19A, 19B, 19C, 21, such as description of encoding format, description of audio content, gain parameter, surrounding noise level, information relevant for multi-talker network operation, and/or control data for all or a specific one of the transmission units 10 and/or the receiver unit 14.
An example of a TDMA schedule of the link 12, 12′ is shown in
In addition, certain time slots are allocated to each receiver unit 14A, 14B for transmitting a data packet containing the respective RF signal measurement data, i.e., the RSSI values for each transmission unit 10. For example, slot #12 may be allocated to transmission of the RSSI values of the right ear receiver unit 14A, and slot #13 may be allocated to transmission of the RSSI values of the left ear receiver unit 14B. Alternatively, the RSSI values sent from the receiver units 14A, 14B may be added to the response payload sent in slot #1, thereby saving the slots #12 and 13.
Alternatively, slot #0 may be shared by beacons and responses by time multiplexing, thus saving one slot or leaving room, for example, for an additional slot for the transmission of the mixed audio signal in order to enhance redundancy and robustness of this signal.
Typically, the TDMA schedule is structured for unidirectional broadcast transmission of the audio data packets from the relay unit 15 wherein the same audio packet of the processed stereo audio signal is transmitted preferably at least twice in the same TDMA frame (in the example of
Preferably, the TDMA slots are allocated in such a manner that for each transmission unit 10 the same number of audio data packets per frame is available and that also for the relay unit 15 at least the same number of audio data packet slots per frame is available. Typically, the TDMA schedule is kept constant, i.e., the allocation of the slots to the audio data packets is the same for each frame.
Allocation of the slots is done by the relay unit 15 by transmitting respective beacon packets. In case that more transmission units 10 are used than can be handled simultaneously by the TDMA schedule (in the example of
According to an alternative embodiment, the angular localization of transmission units 10 may be estimated by measuring the arrival times of the RF signals and the sound generated by the speaker's voice using the respective transmission unit 10 with regard to the right ear receiver unit 14A and the left ear receiver unit 14B, rather than determining the RF signal level difference as described above. This principle is illustrated in
While the invention has been described so far with reference to a hearing assistance system employing a relay unit, the invention is also applicable to systems not using such relay unit.
An example of such an embodiment is shown in
In the example of
The output of the unit 70 is also supplied to an angular localization estimation unit 140. The transceiver 48 receives the right ear RF signal measurement data, i.e., the RF signal level RSSIR of each of the transmission units 10A, 10B, 10C, from the other receiver unit, i.e., the right ear receiver unit 14A, and the respective demodulated signal is supplied to the angular localization estimation unit 140. Hence, similarly to the angular localization estimation unit 140 of the relay unit 15 of the embodiment of
Hence, in the embodiment shown in
It is to be understood that as in the receiver example shown in
It is to be mentioned that, as a alternative to the above-described methods for estimating the angular localization of the RF transmission units, in principle one could measure the RF signal time of arrival at each of the receiver units 14A, 14B and estimate the angular of arrival from the time delay obtained by comparing the time of arrival at the right ear receiver unit 14A and the left ear receiver unit 14B. However, in this case it would be necessary to provide for a precise common time base for measuring the time of flight of the RF signals. Such precise common time base requires a complex mechanism of query/answer signals exchange between the two receiver units 14A, 14B and a very precise clock in each receiver unit 14A, 14B, which, in turn, may result in relatively high power consumption and size. Alternatively, the common time base could be transmitted from another device which has to be placed at the same distance to the right ear receiver unit 14A and the left ear receiver unit 14B, which arrangement may be cumbersome in practice.
As a further alternative, one may measure the phase difference between the RF signals at the two receiver units 14A, 14B at the same frequency by using a mixer. However, in practice this may be difficult, since it requires a phase reference for both receiver units 14A, 14B.
In general, the present invention requires that at least one parameter of the RF signal (such as amplitude, phase, delay, i.e., arrival time, and correlation with the acoustic signal) is measured both at the right ear receiver unit 14A and at the left ear receiver unit 14B, in order to create right ear RF signal measurement data and left ear RF signal measurement data, which then are compared for estimating the angular localization of the transmission unit.
It is pointed out that the present invention does not require that the hearing assistance system includes a plurality of transmission units. Rather, it may include only a single transmission unit.
In the hearing assistance systems according to the invention, distances between the transmission unit(s) and the receiver units typically are from 1 to 20 m.
While various embodiments in accordance with the present invention have been shown and described, it is understood that the invention is not limited thereto, and is susceptible to numerous changes and modifications as known to those skilled in the art. Therefore, this invention is not limited to the details shown and described herein, and includes all such changes and modifications as encompassed by the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/068125 | 11/24/2010 | WO | 00 | 6/14/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/015675 | 2/10/2011 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20130259237 A1 | Oct 2013 | US |
