Passive and Active Virtual Height Filter Systems for Upward Firing Drivers

• US 20170208392A1
• Filed: 06/02/2015
• Published: 07/20/2017
• Est. Priority Date: 06/03/2014
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: SMITHERS, Michael J., SEEFELDT, Alan J., CROCKETT, Brett G., BROWN, C. Phillip
• Granted Patent: US 10,313,793 B2
• Time in Patent Office: Days
• CPC Class Codes: H04R 1/26 Spatial arrangements of separate transducers responsive to two or more frequency ranges
• CPC Class Codes: H04R 3/04 for correcting frequency response
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 3/14 Cross-over networks
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04S 2400/11 Positioning of individual sound objects, e.g. moving airplane, within a sound field H04S2420/13 takes precedence
• CPC Class Codes: H04S 2420/03 Application of parametric coding in stereophonic audio systems
• CPC Class Codes: H04S 7/00 Indicating arrangements; Control arrangements, e.g. balance control
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence
• CPC Class Codes: H04S 7/308 Electronic adaptation dependent on speaker or headphone connection

Abstract

Embodiments are directed to a virtual height filter for use with or in an upward-firing speaker system that reflects sound off a ceiling to a listening location at a distance from a speaker, and that provides height cues to reproduce audio objects that have overhead audio components. A virtual height filter based on a directional hearing model is applied to the upward-firing driver signal to improve the perception of height for audio signals transmitted by the virtual height speaker to provide optimum reproduction of the overhead reflected sound. The virtual height filter is provided by any one or combination of analog or digital filter circuits, or mechanical structures including speaker grill, enclosure, or driver design or configuration.

Claims

1. An apparatus comprising:

an interface to a speaker system having at least an upward-firing driver transmitting reflected sound waves relative to a direct-firing driver; and

a virtual height filter applying a frequency response curve to a signal transmitted to the upward-firing driver to create a target transfer curve that imparts a frequency response to the reflected sound waves that accentuates a perception of virtual height to a listener in the listening environment.

2. The apparatus of claim 1, wherein the virtual height filter compensates for height cues present in sound waves transmitted directly through the listening environment in favor of height cues present in the reflected sound waves projected off a surface of the listening environment.

3. The apparatus of claim 1, wherein the virtual height filter comprises an active system including at least one of an analog filter circuit and a digital filter circuit, and wherein the digital filter circuit comprises a digital signal processing (DSP) circuit.

4. The apparatus of claim 3 further comprising a crossover having a low-pass section configured to transmit low frequency signals to a direct-firing driver and a high-pass section configured to transmit high frequency signals above to the upward-firing driver.

5. The apparatus of claim 1 further comprising a grill covering at least a portion a speaker driver having a cone producing the reflected sound waves, and affixed at a defined distance proximate the driver, the grill configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter.

6. The apparatus of claim 5 wherein the configuration of the grill designed to impart the frequency response includes at least one of:

a shape and contour of the grill, a distance from the grill to the speaker driver, and a number, size, and pattern of perforations or mesh pattern of the grill.

7. The apparatus of claim 1 wherein the one or more components comprises a structural component of an enclosure enclosing the upward-firing driver and configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter.

8. The apparatus of claim 7 wherein the structural component comprises one of:

a shape and size of the enclosure, interior baffling of the enclosure, interior resonance chambers of the enclosure.

9. The apparatus of claim 1 wherein the virtual height filtering function applied by the virtual height filter comprises a pinna filter response curve that compensates for height cues present in the sound waves transmitted directly through the listening environment in favor of height cues present in the reflected sound waves reflected off the surface of the listening environment.

10. The apparatus of claim 9 wherein the virtual height filter is configured to produce a peak response in the response curve, and another of the components is configured to produce a dip in the response curve.

11. The apparatus of claim 10 wherein the peak response is at approximately 7 kHz, and the dip is at approximately 12 kHz.

12. The apparatus of claim 9 further comprising a monotonic boost component to augment the response curve with a high frequency boost in order to achieve a flatter overall frequency response at a listening position within the listening environment.

13. The apparatus of claim 12 wherein the monotonic boost component is configured to provide a high frequency boost into a target frequency response of a reference-axis measurement of the upward firing driver to compensate for attenuation of high frequencies due to differential directional radiation and reflection off of the surface.

14. The apparatus of claim 12 wherein the monotonic boost component is configured to provide 4 dB per octave boost starting at 5 kHz.

15. The virtual height filter of claim 1 further comprising one or more components configured to produce a broad frequency response curve generally defining the virtual height speaker, and another component is configured to correct for errors and conform the broad frequency response to a closer approximation of the virtual height filter.

16. A virtual height filter for use in a speaker system reflecting sound waves off a room ceiling to a listening position in the room, comprising:

an active virtual height filter circuit configured to generate at least part of a frequency response curve to a signal transmitted to an upward-firing driver to create a target transfer curve that compensates for height cues present in sound waves transmitted directly through the room in favor of height cues present in the sound reflected off the ceiling by at least partially removing directional cues from the speaker location and at least partially inserting directional cues from the reflection point; and

a passive virtual height filter system configured to generate at least part of the frequency response curve, and incorporated in a mechanical aspect of the upward-firing driver or an enclosure enclosing the upward-firing driver.

17. The virtual height filter of claim 16, wherein the active virtual height filter circuit comprises at least one of an analog filter circuit and a digital filter circuit, and wherein the digital filter circuit comprises a digital signal processing (DSP) circuit.

18. The virtual height filter of claim 17 further comprising a crossover having a low-pass section configured to transmit low frequency signals to a direct-firing driver and a high-pass section configured to transmit high frequency signals above to the upward-firing driver.

19. The virtual height filter of claim 16 wherein the passive virtual height filter system comprises at least one of:

a grill covering at least a portion a speaker driver having a cone producing the sound waves, and affixed at a defined distance proximate the driver, the grill configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter; and

a structural component of the enclosure configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter.

20. The virtual height filter of claim 19 wherein the configuration of the grill designed to impart the frequency response includes at least one of:

a shape and contour of the grill, a distance from the grill to the speaker driver, and a number, size, and pattern of perforations or mesh pattern of the grill.

21. The virtual height filter of claim 20 wherein the structural component comprises one of:

a shape and size of the enclosure, interior baffling of the enclosure, interior resonance chambers of the enclosure.

22. The virtual height filter of claim 16 wherein the virtual height filtering function applied by the one or more components comprises a pinna filter response curve that compensates for height cues present in the sound waves transmitted directly through the listening environment in favor of height cues present in the sound reflected off the surface of the listening environment.

23. The virtual height filter of claim 22 wherein at least one of the one or more components is configured to produce a peak response of the virtual height filter, and another of the components is configured to produce a dip in the response of the virtual height filter.

24. The virtual height filter of claim 22 wherein at least one of the one or more components is configured to produce a broad frequency response curve generally defining the virtual height speaker, and another component is configured to correct for errors and conform the broad frequency response to a closer approximation of the virtual height filter.

25. A method for providing a virtual height filter transfer function to speaker system having an upward-firing driver reflecting sound off of a surface in a room, the method comprising:

providing an active virtual height filter circuit configured to generate at least part of a frequency response curve to a signal transmitted to an upward-firing driver to create a target transfer curve that compensates for height cues present in sound waves transmitted directly through the room in favor of height cues present in the sound reflected off the surface by at least partially removing directional cues from the speaker location and at least partially inserting directional cues from the reflection point; and

providing a passive virtual height filter system configured to generate at least part of the frequency response curve, and incorporated in a mechanical aspect of the upward-firing driver or an enclosure enclosing the upward-firing driver.

26. The method of claim 25 wherein the speaker system plays back audio content comprises object-based audio having height cues representing sound emanating from an apparent source located above a listener in a room encompassing the speaker.

27. The method of claim 25 wherein the active virtual height filter circuit comprises at least one of an analog filter circuit and a digital filter circuit, and wherein the digital filter circuit comprises a digital signal processing (DSP) circuit.

28. The method of claim 25 wherein the passive virtual height filter

system comprises at least one of:

a grill covering at least a portion a speaker driver having a cone producing the sound waves, and affixed at a defined distance proximate the driver, the grill configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter; and

a structural component of the enclosure configured to impart a frequency response to the sound waves and that provides at least some of the functions of the virtual height filter.

29. The method of claim 28 wherein the configuration of the grill designed to impart the frequency response includes at least one of:

a shape and contour of the grill, a distance from the grill to the speaker driver, and a number, size, and pattern of perforations or mesh pattern of the grill.

30. The method of claim 29 wherein the structural component comprises one of:

a shape and size of the enclosure, interior baffling of the enclosure, interior resonance chambers of the enclosure.

31. The method of claim 25 wherein the virtual height filtering function applied by the one or more components comprises a pinna filter response curve that compensates for height cues present in the sound waves transmitted directly through the listening environment in favor of height cues present in the sound reflected off the surface of the listening environment.

32. The method of claim 25 further comprising providing a high frequency boost to augment the response curve in order to achieve a flatter overall frequency response at a listening position within the listening environment.

33. The method of claim 32 wherein the high frequency boost is provided in a target frequency response of a reference-axis measurement of the upward firing driver to compensate for attenuation of high frequencies due to differential directional radiation and reflection off of the surface.

34. The method of claim 32 wherein the high frequency boost provides 4 dB per octave boost starting at 5 kHz.