EP1520447B1 - Method and device for generating data about the mutual position of at least three acoustic transducers - Google Patents

Abstract

The invention relates to a method and device for generating data about the mutual position of at least three acoustic transducers. The aim of the invention is to make it possible to continuously measure and calculate the mutual position of at least three acoustic transducers, particularly the rotation and the position of a human head wearing headphones within a room without using any additional transmitter element on the head, headphone, or body of the listener, during audio playback. This aim is achieved by connecting the acoustic transducers to a digitally operated system which comprises an output path emitting audio signals to first and second acoustic transducers, an input path receiving audio signals from the third acoustic transducer, an audio signal source that is connected to the output path, an ultrasound generator that is connected to the output path, and an information generator which indicates a position and is connected to the input path.

Description

The invention relates to a method and a device for generating data on the mutual position of at least three sound transducers.

In recent years, various inventions have been presented which serve to detect and calculate the orientation and position of a human head wearing headphones. A first class of inventions proposes a transmitter attached to said headset. This is used exclusively to send out a signal from which one can calculate the orientation and the position of the head. The emitted signal is either an infrared, an ultrasonic or a magnetic signal. A corresponding receiver forwards the received signal to a computing unit where the orientation and / or position of the human head is calculated. Such a device is under WO 92/07346 released.

A second class of inventions uses a gyrator or angular velocity meter attached to the headphone. In this case, the orientation (rotation) of the head can be determined directly from the angular velocity meter. Such devices are also used in digital cameras to compensate for unwanted shaking of the hand. However, such devices have a significant drift. Therefore, this method is preferably used in relative measurements. Such a device is in the EP-1 176 848 A2 released.

A third class of inventions relates to a combination of the two aforementioned methods. For the measurement of the head movements an angular velocity measuring device is used. Additional ultrasonic or infrared transmitters and receivers are used to calibrate the drift from the angular rate instrument.

Various other methods exist for measuring and calculating the position of a listener within a room in which speakers are installed. The most common method is to deliver an audible signal in succession over each individual speaker and then to measure the signal delay by means of one or more microphones. From this and from the known position of the speakers, the position of the listener can be calculated. So far, all methods and devices of this kind are designed to measure the position of a listener once before the actual music playback. Afterwards, the "sweet spot", ie the place of best reproduction, remains unchanged. In order to change the "sweet spot", the music or sound reproduction must be stopped and a new measurement must be made.

From the JP 06 082242 a device is known with which the position and orientation of a headphone in three-dimensional space can be determined by means of ultrasound signals. For this purpose, three additional sound transducers are mounted on the headphones in addition to the sound transducers for the sound signal, which emit only ultrasonic signals for determining the position and Orientireung. Three more, distributed in space transducers are provided for receiving these ultrasonic signals. In this case, an electrical or optical reference signal is emitted from the headphones to the receivers of the ultrasonic signals and the time delays of the ultrasonic signals are determined to each receiver. For this purpose, these reference signals are divided into different frequency bands. A disadvantage of this design is that in addition to the sound transducers for the sound signal own sound transducers still need to be provided for the position and orientation determination. For this purpose, an electrical or optical reference signal must be generated. By this arrangement and the necessary division of the ultrasonic signals into a plurality of frequency bands results in a very complex signal evaluation to determine the position and orientation of the headphone.

From the JP 01 276900 a device is known in which speakers are arranged distributed in a room and the position of a listener to be determined. To do so, the speakers send out ultrasonic signals that are received by a receiver at the location of the listener. From the different durations of these ultrasonic signals from the individual speakers to the receiver, the position of the receiver or listener can be determined. Since no own ultrasonic transducers are provided here, the determination of the position must be made before the actual sound reproduction. In addition, the speakers are arranged stationary, so that this device is suitable only for a one-time, provided before the sound reproduction position determination. The position of the handset can not be continuously measured. In addition, both of these devices use the correlation of incoming ultrasonic signals to determine the position. This means that they basically respond to those signals that have the largest signal amplitude, which is often signals reflected from objects. Therefore, the position determination with these devices by external conditions strong and unfavorable influenced.

The invention, as characterized in the claims, therefore achieves the object to provide a method and a device which enables the continuous measurement and calculation of the mutual position of at least three sound transducers, in particular the rotation and the position of a human head with headphones inside a room without an additional transmitting element on the head, headphones or body of the listener, during the sound reproduction permit.

In the device according to the invention, in which a first electrical signal for a first sound transducer is generated, which converts this into a first sound signal and a second electrical signal for a second sound transducer is generated, which converts this into a second sound signal, the object is achieved in that a first ultrasound signal is added to the first electrical signal and a second ultrasound signal is added to the second electrical signal before the signals arrive in the sound transducer, that the first and second signals with the added ultrasound signals are emitted by the first and second sound transducers, that at least a third Sound transducer detects the first and second signals with their ultrasound signals and converts back into an electrical signal that the detected ultrasonic signals are filtered and separated from the first and second signal, that and thus from the first and the second generated ultrasound signal each a first and a second delay signal is formed and from a position signal is derived from the delay signals indicating the position of at least one transducer relative to the other transducers.

In addition, in the case of a group of at least two sound transducers, where a first and a second sound transducer are at a fixed relative distance from one another, the orientation or angular position of these two sound transducers having a fixed relative distance to at least one third sound transducer can be calculated according to the described method.

Furthermore, a first group of at least two sound transducers or a first and a second sound transducer for the sound reproduction may be at a fixed relative distance from one another and a second group of at least two further or third and fourth sound transducers for sound recording at a fixed relative distance from one another stand. Finally, according to the method according to the invention, the position and the orientation of the first or second group to the other first or second group can be calculated in a planar plane.

Finally, a first group of at least three or first, second and third sound transducers for sound reproduction or sound recording may be at a fixed relative distance from each other and a second group of at least two further or fourth and fifth sound transducers for sound reproduction or sound recording in a fixed relative distance from each other. The calculation of a position signature for the position and the Orientation of the first or second group to the other first or second group takes place in three-dimensional space.

A device for carrying out the described method comprises, in addition to at least a first sound transducer, a second sound transducer and a third sound transducer. According to the invention, a digitally operating system is connected to the first, second and third sound transducers and has an output path for outputting sound signals to at least one of said first, second and third sound transducers and an input path for receiving signals from at least one of said first, second and third transducers third sound transducer. Finally, said digitally operating system includes a sound source and an ultrasonic signal generator, both of which are connected via adders on said output path for outputting audio signals. An information generator for a position indication is connected to the input path, to which also a filter for the recovery of ultrasonic signals is connected. The first and second sound transducers may be the left and right sound transducers of a headphone while the third sound transducer is, for example, a stationary microphone. In another application, said first and second transducers may each be a stationary loudspeaker while the third transducers is a portable, room-movable microphone.

According to the invention, in the example of a headphone, the built-in sound transducers of a commercially available headphone are used instead of further sound transducers or transmitters. More specifically, the sound transducers of the headphones are used both for sound reproduction and for transmitting ultrasound signals. The same applies in the example of loudspeakers: the loudspeakers of the loudspeakers are used both for sound reproduction and for transmitting ultrasound signals. Therefore, any headphones or speakers can be used and additional cables omitted. In addition, the measurements of the position and orientation of a human head during sound reproduction can be performed without interrupting the sound reproduction.

The present method and apparatus are used in mainly two different applications: head tracking and hand tracking, both during sound reproduction and both without an additional transmitting element.

The first area of application concerns all applications where head-tracking is necessary or useful in connection with headphones. Head tracking means the continuous measurement and evaluation of the movements - the rotation and position change - of a human head with headphones. More specifically, the invention relates to multimedia and gaming applications where a personal computer, game console or the like Device can use the three-dimensional position and rotation indication of a human head wearing headphones.

Moreover, the invention can be used in applications with headphones for telephony or radio communication, such as in conference calls or in Aircraft cockpits where audio sources can be "placed" in a virtual acoustic environment according to the position and rotation of the human head.

In a slightly different construction, the same invention can be used to track a listener in a room with many speakers installed. Such an installation may be a DVD system with five speakers and a subwoofer, or any other arrangement with any number of speakers mounted anywhere in the room. By tracking the listener in the room, it is possible to adjust the sweet spot to the current position of the listener. The sweet spot is the place in the room where the sound reproduction of all loudspeakers gives a balanced signal and the best listening experience is achieved. In contrast to other inventions it is possible with this method and this device to measure and evaluate the position of the listener in the room continuously and during the sound reproduction dynamically and without additional transmitting element.

Fig. 1 shows a schematic arrangement for a first application of the present invention,
Fig. 2 shows a filter characteristic as it can be used in said first application,
3 and 4 show schematic representations of the positions of different elements of said first application,
Fig. 5 shows a schematic arrangement of the elements for a second application of the present invention and
Fig. 6 shows a schematic representations of the positions of various elements of said second application.

How out Fig. 1 a headphone 7, each with a sound transducer 7a and 7b for the right and left ear is connected to a digitally operating system 13, which can process sound signals and output via a connection 5, which can be configured as a cable or wireless connection. Such a digitally operating system 13 can be, for example, a personal computer, a game console, a set-top box or a similar device in this manner, which generates sound signals for a handset 6. For this, this digital system 13 includes a source 1 for generating unmodified audio signals, an ultrasonic generator 2 which produces inaudible signals above the threshold of hearing, typically above 20 kHz, and a digital-to-analog converter 4 (DAC 4) All three elements 1, 2, 4 are interconnected via lines 15 and adders 3a and 3b The source 1 for the unmodified audio signal may be, for example, a CD player, a music file or any other sound source inside or outside the system 13. This source 1 generates the one tone signal that the listener wants to hear 6. In addition, one or a plurality of sound transducers 8, such as microphones or ultrasonic receiver, mounted in front of the handset 6 and are connected via a connection 9 to the digital system 13. This connection 9 may in turn be a cable or a wireless connection. An analog-to-digital converter 10 (ADC 10) is connected via connections 16 and 17 to a filter 11 and to an information generator 12 for a position indication. The source 1 with the connections 15, the converter 4 and the connections 5 form an output path 19. The connection 9, the converter 10, the filter 11 with the connections 16 and 17 and the information generator 12 for the position indication are elements which have an input path 20 form.

During operation, the digital system 13 produces an audio signal which is sent from the source 1, passed through the lines 15 and, after the conversion in the converter 4, through the links 5 to the first and second sound transducers 7a and 7b which are connected to the headphone 7 and thus are placed on the head 6. The ultrasound generator 2 generates two separate ultrasound signals, one for each sound transducer 7a and 7b of the headphone, each above 20 kHz, which may be in adjacent frequency bands.

Another possibility is that the two ultrasound signals are temporary sequences in the same frequency band over 20 kHz, one temporary sequence for the right transducer 7a of the headphone 7 and one for the left transducer 7b. The sequences are sent out alternately for a short time.

In both cases, the ultrasonic signals are added to the said audio signal by means of the adders 3a and 3b in the lines 15. The ultrasonic signals are also converted in the converter 4 and fed to the sound transducers 7a and 7b together with the audio signal. By the way, the converter 4 can be a normal audio converter with a sampling rate of 48 kHz. Since more recently converters with a sampling frequency of 96 kHz are available, so that a significantly higher ultrasonic signal of over 24 kHz can be used. This can then be converted back to the corresponding ADC 10, which also operates at a sampling rate of 96 kHz.

The said ultrasonic signals are also transmitted continuously by the sound transducers 7a and 7b. The person wearing the headphones 7 can not hear the ultrasound signals, although the sound transducers emit them. A third sound transducer 8, which is placed in a fixed position in front of the receiver 6, for example a microphone or an ultrasonic receiver, receives the ultrasonic signals.

Depending on the characteristics of the headphone 7, the transmitted ultrasonic signal may be weak because the attenuation in the air as well as the absorption of materials is quite strong for signals above 20 kHz. In general, these signals may have some form. However, in order to achieve a good signal quality and to be able to receive the ultrasound signal even at a distance of several meters, there is a band limited pseudo white noise most suitable for this. Suitable signals are maximumlength sequences with an autocorrelation function with a well-defined, single maximum. Other possibilities are Golay sequences and sequences with aperiodic phase, whereby the signal acquisition in a noisy environment can be improved. At least two adders 3a and 3b for the signal in the output path 19 are used, in which the output signal is the sum of the input signal of the source 1 and the ultrasonic generator 2. A digital-to-analog converter (DAC) 4 has at least two digital signal inputs connected to the adders 3a and 3b, as well as two analog outputs. The connection 5, such as a cable or a wireless connection, is used to transmit the signals from the digital system 13 to the headphones 7. A human head 6 carries the standard, commercially available headphones 7. The analog-to-digital converter (ADC) 10 converts at least one analog signal received from the transducer 8 into at least one digital signal. Of course, both ultrasonic signals from the sound transducer 7a and 7b are included in this received signal. The signal at the output of the transducer 10 has the shape as shown in FIG Fig. 2 is apparent. In Fig. 2 are signals above a horizontal axis along which values of frequencies may be plotted and displayed alongside a vertical axis along which values for the amplitude of a signal may be plotted. According to Fig. 2 is an unmodified audio signal 23 in the frequency band below about 20 kHz. Two separate frequency bands 24 and 25 can be seen above 20 kHz, of which one frequency band 24 can be assigned to the right-hand sound converter 7a and the other frequency band 25 to the left sound converter 7b. The filter 11, connected to the converter 10, processes the received signal and filters the frequency band 23 below 20 kHz from the signal shape by means of a high-pass filter Fig. 2 out. The remaining signal now consists only of possibly weak frequency bands 24 and 25 from the right transducer 7a and the left transducer 7b of the headphones 7. A second filter in said filter 11 separates the two contained ultrasonic signals into two individual, reconstructed ultrasonic signals, of which one reconstructed signal Ultrasound signal 24 from the right transducer 7a and the other reconstructed signal contains the ultrasonic signal 25 from the left transducer 7b of the headphones 7. In the case where the ultrasonic signals lie in adjacent frequency bands, said second filter is a bandpass filter and is applied for each frequency band. By means of adequate cross-correlation with the known input signals, the signal-to-noise ratio can be improved. Such filter techniques by means of cross-correlation are known techniques of their kind and are therefore not explained in detail here.

In the case where the two ultrasonic signals are temporary sequences with a sequence for the right transducer 7a and another sequence for the left transducer 7b of the headphones 7, said second filter is a decoder of said sequences.

According to the above explanations, the filter 11 reconstructs and separates, for each receiver 8, an ultrasound signal for the right and left sound transducers 7a and 7b. Subsequently, said signals are forwarded to the information generator 12.

Since such devices are usually used in closed rooms, it is to be expected that in the receiver 8 several signals arrive, which were emitted by a specific transducer 7a or 7b as an ultrasonic signal. By reflection on a wall or other object, a first signal can arrive directly at the receiver 8, and a second signal can arrive indirectly at the receiver 8 after reflection by the same signal converter 7a, 7b. In addition, with a strong directional characteristic of the sound transducer 7a, 7b to be expected in the headphone, which can lead to the strongest signal that arrives at the receiver 8, the reflected signal. The filter 11 is therefore designed and arranged to separate and reprocess, of several possible signals, that which arrives first and not that which has the largest signal amplitude.

The information generator 12 may also receive the original ultrasonic signal from the ultrasonic generator 2 via a connection 18, along with the reconstructed ultrasonic signal arriving from the filter 11 via the connection 17. He compares the two ultrasonic signals by means of a digital cross-correlation. Two delays, one for the right and one for the left ultrasound signal arise for each receiver or microphone 8 depending on the distance of the transducers 7a and 7b to the third transducer or receiver 8. If a receiver or microphone 8 is used, the rotation or the orientation of the head 6 can be determined by the distance differences from the receiver 8. This is done by means of Fig. 3 The difference between the two mentioned delays provides the information about the differences between distances 37 and 38 of the right transducer 7a to the microphone 8 and the left transducer 7b to the microphone 8. The rotation or angular position of the head 6, expressed in angle α, 39, can be calculated by means of triangulation in a manner known per se and therefore not explained in more detail here, if one knows the width of the head or the average width of a human head, which is also assumed to be known. An accurate calibration of the individual head width is easily possible by means of personal measurements. The average of the two distances 37 and 38 gives the information about the absolute distance from the center of the head 6 to the receiver 8.

In the case of two receivers 8a and 8b, shown in FIG Fig. 4 , the rotation and a two-dimensional, exact position indication of the head 6 with respect to the receivers 8a and 8b can be calculated. As above, the position indication can be determined by triangulation with the additional knowledge of the distances 41 and 42 to the second receiver 8b and the distance 40 between the two receivers. In this case as well as in the case mentioned above, the sound transducers involved are in a planar plane, which in this case coincides with the plane of the drawing or a parallel plane thereto.

In the case of three or more receivers, the rotation and the exact position can also be calculated in three-dimensional space. Again triangulation is applied with the added knowledge of all distances to all receivers as well as all distances between all receivers.

After the just described calculation of the mutual position of the sound transducer in the information generator 12, the information about the rotation and position of the head 6 in digital form as a signal 14 (FIG. Fig. 1 ) available at one output. It can be used in an application that runs on the digital system. In most cases, the audio-visual content offered to the user via speakers, headphones, etc., will be changed depending on the rotation and position of the user.

A second application of the invention is in Fig. 5 shown. According to Fig. 5 can the same digital system 13, which can process sound signals, as previously in Fig. 1 used to track a listener in a room with two or more speakers 51a and 51b. In this case, the two loud speakers 51a and 51b replace the sound transducers 7a and 7b of the headphone, which are off Fig. 1 is known. As already described in the last section, at least two ultrasonic signals are generated by the ultrasonic generator 2 and added to the unmodified audio signal of the source 1 in the adders 3a and 3b. The digital-to-analog converter (DAC) 4 converts the digital signals into analog signals. A connection 5, either cable based or wireless, is used to give the analog signals to the two or more speakers 51a and 51b. The same receivers 8 as in the last section can be used to detect the sound signals and ultrasonic signals. A connection 9, again cable based or wireless, brings the received signals to the analog-to-digital converter (ADC) 10. The filter 11 filters out the sound signal and extracts the ultrasonic signals. In this case, the position of the speakers is known and stored in the information generator 12 after this position has been measured and entered by means of a keyboard. The information generator 12 calculates from the said ultrasonic signals the position of the receiver 8, which is unknown in this case. This is again achieved via triangulation with the given positions of the loudspeakers 51a and 51b and the given distance between the loudspeakers 51a and 51b.

During sound reproduction, the listener may carry or hold the receiver 8 in any suitable manner and may move freely within the space within the speakers. The handset can not hear the ultrasound signals emitted by the loudspeakers. Nevertheless, the receiver can detect them. Consequently, the information generator can keep track of the listener and determine the current position. Conversely, of course, the position of the speakers can be calculated from the known position of the listener.

As in Fig. 6 As shown, the listener may also carry two receivers 8a and 8b. In this case, not only the position of the listener in the room but also the rotation or orientation in the room with respect to the position of the speakers can be calculated. For this purpose, the receivers 8a and 8b have a fixed distance 65 and are mounted on the same portable element. The following distances are calculated from the respective delay times: the distance 61 from the first loudspeaker 51a to the first receiver 8a, the distance 62 from the first loudspeaker 51a to the second receiver 8b, the distance 63 from the second loudspeaker 51b to the first receiver 8a and the distance 64 from second speaker 51b to the second receiver 8b. By means of triangulation, the position of both receivers 8a and 8b can be calculated. In another application, the unmodified sound signal of the source 1 and the ultrasonic signal from the ultrasonic generator 2 can also be added as an analog signal after the transducer 4. In this case, another transducer is needed to convert the ultrasound signals to analog signals.

Claims (8)

1. A method for generating data relating to the relative position of a set of at least three transducers (7a,7b,8), whereby a first electric signal for a first transducer (7a) is being generated, which is transducing it to a first acoustic signal, and a second electric signal for a second transducer (7b) is being generated, which is is transducing it to a second acoustic signal, characterized in that a first ultrasonic signal is being added to the first electric signal and a second ultrasonic signal is being added to the second electric signal before such signals enter the transducers, the first and second signals with the added ultrasonic signals are being emitted by the first and second transducer respectively, a third transducer (8) converting the first and second signals with their ultrasonic signals back into an electrical signal, thereby filtering out and separating the ultrasonic signals, producing a first and a second delay signal from the first and second ultrasonic signals, and computing a positioning signal derived from the delays signals which indicates the position of at least one transducer with respect to the other transducers.
2. A method according to claim 1, wherein the first and the second transducer (7a,7b) are in a fixed positional relationship, characterized in that a positioning signal is being computed which indicates the position of the third transducer (8) with respect to the two other transducers, comprising the orientation of the first and second transducer having a fixed relative positional relationship with respect to the third transducer.
3. A method according to claim 1, wherein the first and second transducer for the emission of the acoustical signals are separated by a fixed first distance, and the third and a fourth transducer for receiving acoustical signals are separated by a fixed second distance, characterized in that a positioning signal is being computed which represents the position and orientation of the first and second transducer having a fixed distance in a plane with respect to the third and fourth transducers.
4. A method according to claim 1, whereby a first group with first, second and third transducers for the emission or recording of the acoustical signals standing in a fix first distance to each other, and a second group with fourth and fifth transducers for the emission or recording of the acoustical signals standing in a fix second distance to each other, characterized in that a signal is being computed which indicates the position of the first group of transducers in the three-dimensional space with respect to the other group of transducers.
5. Device for performing the method according to claim 1, comprising: a first transducer (7a), a second transducer (7b), and a third transducer (8), characterized in that there is a digital system (13) connected to said transducers which has an output audio path (19) for feeding audio signals to the first and the second transducer, an input audio path (20) for receiving audio signals from the third transducer, a source (1) of audio signals and an ultrasonic signal generator (2), connected with adders (3a,3b) to the output audio path, and an information generator (12) for the indication of a position, which is connected to the input audio path.
6. Device according to claim 5, characterized in that there is a filter (11) in the input path (20) said filter being connected to the information generator (12).
7. Device according to claim 5, characterized in that the first and second transducer (7a,7b) are each part of a headphone (7) and that the third transducer is a stationary microphone (8).
8. Device according to claim 5, characterized in that the first and second transducer each is a loudspeaker (51a,51b) and the third transducer is a portable microphone (8).

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