Ultrasound based parametric loudspeaker system

• US 20020172375A1
• Filed: 04/08/2002
• Published: 11/21/2002
• Est. Priority Date: 04/07/2001
• Status: Active Grant

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Inventors: Linhard, Klaus, Kolano, Guido
• Granted Patent: US 7,181,025 B2
• Time in Patent Office: Days
• US Class Current: 381/77
• CPC Class Codes: H04R 1/323 for loudspeakers H04R1/34 and H04R1/40 take precedence
• CPC Class Codes: H04R 17/10 Resonant transducers, i.e. adapted to produce maximum output at a predetermined frequency
• CPC Class Codes: H04R 2217/03 Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves

Abstract

A parametric loudspeaker system is described which is based upon the FM-modulation of an ultrasound carrier. Known systems work with AM-modulation. The FM-modulation produces a good matching to the resonant transducer such as the conventionally employed piezo-ceramic transducers. The resonance slope of the transducers is used for FM/AM-conversion. This FM-resonance principle can advantageously be employed in a multi-path loudspeaker system, in which the transducer works in the optimal resonance range in each of the paths. With the conventional AM-modulation this is not possible. The FM-resonance principle can also be used in resonance-free or resonance-poor transducers, such as for example electrostatic transducers.

Claims

1. Process for controlling a parametric loudspeaker system, comprised of

one or more transducer elements for ultrasound, which can be driven to produce an AM-signal, which during propagation in a gaseous medium produces an audible signal by self demodulation,

one or more amplifiers associated with these transducer elements,

and one or more modulators associated therewith, which receive an input signal from a signal source,

thereby characterized,

that the transducers are driven with an FM-modulated signal (FM-modulation) in the area of the slope of their resonant characteristic lines.

2. Process according to claim 1, thereby characterized, that in the case, that the transducers exhibit no significant resonance characteristic line, the resonance characteristic line is produced by the mixing of the transducer with a resonant filter network, in the manner, that the filter network inclusive of the transducer produces a resonance slope or so modifies existing slopes of the characteristic line of the transducer, as are necessary for the satisfactory conversion of the FM-modulation into an AM-modulation by the transducer.

3. Process according to one of claims 1 through 2, thereby characterized, that the slope of the resonant characteristic line, is modified by a unit for modification of the characteristic line connected upstream of the modulator,

to the extent that the total characteristic line resulting from this change influences the translation of the FM-modulated signal into the AM-signal emitted by the transducer, in that the unit for modification of the characteristic line produces a voltage/voltage-translation.

4. Process according to claim 3, thereby characterized, that the unit for modification of the characteristic line compensates for irregularities in the characteristic line of the transducer, whereby a total characteristic line results comprised of one or more flattened out curve segments.

5. Process according to one of claims 3 through 4, thereby characterized, that the unit for modification of the characteristic line is used to linearizes the FM/AM translation occurring in the transducer, whereby in the resulting total characteristic line an ideal AM-modulation results.

6. Process according to one of claims 1 through 5, thereby characterized, that the modulation depth of the driver is adjustable, in that the smallest output voltage arriving at the transducer can be preset.

7. Process according to one of claims 1 through 6, thereby characterized, that the input signal which is supplied to the modulators is a warning signal and/or an information signal and/or a noise signal and/or a voice signal and/or a music signal.

8. Process according to one of claims 1 through 7, thereby characterized, that for adjusting a parametric multi-path loudspeaker system the total set of the transducers is subdivided into groups, wherein each group is controlled by at least one associated FM-modulator.

9. Process according to claim 8, thereby characterized, that the individual FM-modulators are respectively supplied with one signal from a multi-path separation of the input signal, wherein in the framework of the multi-path separation a frequency-based band separation of the input signal of the modulator is undertaken.

10. Process according to one of claims 8 through 9, thereby characterized, that in the case that the transducers which are subdivided into multiple groups respectively group-wise exhibit different characteristic lines, these groups respectively utilize different FM-modulators.

11. Process according to one of claims 8 through 10, thereby characterized, that as a result of the selected frequency range a power adaptation to the transducers occurs, in the manner, that the selection of the transducers of a group of transducers is matched to the power required for its associated frequency band.

12. Process according to one of claims 8 through 11, thereby characterized, that for each individual of the group of transducers the respective directionality of the loudspeaker system is optimized, in that the selection of the transducers of a group of transducers occurs on the basis of the directionality of the individual transducers in the respective frequency band.

13. Process according to one of claims 8 through 12, thereby characterized, that for each individual of the group of transducers the respective directional effect of the loudspeaker system is optimized, in that the individual groups of transducers, in particular depending upon the frequency band of the input signal of the modulator associated with them, are arranged differently geometrically.

15. Device according to claim 14, thereby characterized, that in the case that the transducers exhibit no significant resonance characteristic line, a filter network is provided, which includes the transducer and thereby produces a resonance slope as necessary for the satisfactory conversion of the FM-modulation into an AM-modulation by the transducer.

17. Device according to claim 16, thereby characterized, that the unit for modification of the characteristic line compensates for irregularities in the characteristic line of the transducer, whereby a total characteristic line results comprised of one or more flattened out curve segments.

14. Device for controlling a parametric loudspeaker system, comprised of

one or more transducer elements for ultrasound, which can be driven to produce an AM-signal, which during propagation in a gaseous medium produces an audible signal by self demodulation,

one or more amplifiers associated with these transducer elements,

and one or more modulators associated therewith, which receive an input signal from a signal source,

thereby characterized,

that means are provided for driving transducers with an FM-modulated signal (FM-modulation) in the area of the slope of their resonant characteristic lines.

16. Device according to one of claims 14 through 15, thereby characterized, that a unit is connected upstream for modification of the modulator, whereby the slope of the resonant characteristic line is modified,

to the extent that the total characteristic line resulting from this change influences the translation of the FM-modulated signal into the AM-signal emitted by the transducer, in that the unit for modification of the characteristic line produces a voltage/voltage-translation.

18. Device according to one of claims 16 through 17, thereby characterized, that the unit for modification of the characteristic line is adapted to linearize the FM/AM translation occurring in the transducer, whereby in the resulting total characteristic line an ideal AM-modulation results.

19. Device according to one of claims 14 through 18, thereby characterized, that a means is provided for adjusting the modulation depth of the driver, in that the smallest output voltage arriving at the transducer can be preset.

20. Device according to one of claims 14 through 19, thereby characterized, that for adjusting a parametric multi-path loudspeaker system the total set of the transducers is subdivided into groups, wherein each group is controlled by at least one associated FM-modulator.

21. Device according to claim 20, thereby characterized, that means are provided for multi-path separation of the input signal, wherein in the framework of the multi-path separation a frequency-based band separation of the input signal of the modulator is undertaken.

22. Device according to one of claims 20 through 21, thereby characterized, that in the case that the transducers which are subdivided into multiple groups respectively group-wise exhibit different characteristic lines, these groups are respectively provided with different FM-modulators.

23. Device according to one of claims 20 through 22, thereby characterized, that as a result of the selected frequency range a power adaptation to the transducers occurs, in the manner, that the selection of the transducers of a group of transducers is matched to the power required for its associated frequency band.

24. Device according to one of claims 20 through 23, thereby characterized, that for each individual of the group of transducers the respective directionality of the loudspeaker system is optimized, in that the selection of the transducers of a group of transducers occurs on the basis of the directionality of the individual transducers in the respective frequency band.

25. Device according to one of claims 20 through 24, thereby characterized, that for each individual of the group of transducers the respective directional effect of the loudspeaker system is optimized, in that the individual groups of transducers, in particular depending upon the frequency band of the input signal of the modulator associated with them, are arranged differently geometrically.

26. Device according to one of claims 20 through 25, thereby characterized, that the transducers are so arranged, that the transducers which are associated with the lower frequencies of the input signal are positioned at the outer area of the device and that the transducers which are associated with the, high frequencies of the input signal are positioned at the inner area of the device.

27. Device according to one of claims 20 through 26, thereby characterized, that the transducers which are associated with the high frequencies of the input signal are tightly clustered and that the transducers which are associated with the lower frequencies of the input signal are relatively more spread out.