Virtual height filter for reflected sound rendering using upward firing drivers

• US 9,648,440 B2
• Filed: 01/07/2014
• Issued: 05/09/2017
• Est. Priority Date: 01/07/2013
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Crockett, Brett G., Chabanne, Christophe, Tuffy, Mark, Seefeldt, Alan J., Brown, C. Phillip, Turnmire, Patrick
• Primary Examiner(s): Teshale, Akelaw
• Application Number:
  US14/759,182
• Publication Number:
  US 20150304791A1
• Time in Patent Office: 1,218 Days
• Field of Search: 38 17, 38 18, 38 27, 38307, 38 80, 38 92, 38 97, 38 1, 38182, 38 19, 38 2, 38 22, 38300, 38 56, 38 61, 38 716, 38 77, 38 98, 38160, 38386, 38186, 38336, 38 99, 38335, 38387, 38303, 38350, 38152, 38 30, 38 7, 38342, 38345, 38348, 38104, 38120, 38301, 38304, 38306, 38332, 38333, 38337, 38338, 38340, 38349, 38351, 38361, 38388, 38412, 38432, 38433, 38 55, 38 57, 38 717, 38 89, 38 945
• CPC Class Codes: H04R 1/02 Casings; Cabinets ; Supports therefor; Mountings therein H04R1/28 takes precedence ; attachments for microphones H04R1/08; mounting of transducers in earpieces H04R1/1075
• CPC Class Codes: H04R 1/26 Spatial arrangements of separate transducers responsive to two or more frequency ranges
• CPC Class Codes: H04R 2205/024 Positioning of loudspeaker enclosures for spatial sound reproduction
• 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 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

Embodiments are directed to speakers and circuits that reflect sound off a ceiling to a listening location at a distance from a speaker. The reflected sound provides height cues to reproduce audio objects that have overhead audio components. The speaker comprises upward firing drivers to reflect sound off of the upper surface and represents a virtual height speaker. 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 may be incorporated as part of a crossover circuit that separates the full band and sends high frequency sound to the upward-firing driver.

Claims

1. A speaker driver for rendering sound for reflection off of an upper surface of a listening environment, comprising:

a driver cone;

a cone dust cap affixed to a central portion of the driver cone; and

a frame securing the cone for mounting within a speaker cabinet, wherein at least one of the driver cone, dust cap, and frame are configured to apply a height filter having a frequency response curve that is configured to at least partially remove directional cues from a speaker location, and at least partially insert the directional cues from a reflected speaker location, the frequency response curve based on

a first frequency response of a filter modeling sound travelling directly from the reflected speaker location to the ears of a listener at a listening position, for said inserting of directional cues from the reflected speaker location, and

a second filter frequency response of a filter modeling sound travelling directly from the speaker location to the ears of the listener at the listening position, for removing of directional cues for audio travelling along a path directly from the speaker location to the listener.

2. The speaker driver of claim 1, wherein the height filter is applied to one or more audio signals comprising height sound components transmitted to the speaker driver, and further wherein the frequency response curve is a universal height filter frequency response curve that represents an average of a plurality of individual height filter frequency responses, where each of the individual height filter frequency responses corresponds to a different combination of reflected speaker location, listening position, and physical speaker location.

3. The speaker driver of claim 1, wherein the height filter response exhibits a peak located at about 7 kHz and a notch at about 12 kHz.

4. A system for rendering sound using reflected sound elements, comprising:

a speaker placed at a speaker location and comprising a housing enclosing an upward-firing driver oriented at an inclination angle relative to the ground plane and configured to reflect sound off an upper surface of a listening environment to produce a reflected speaker location; and

a virtual height filter applying a frequency response curve to an audio signal transmitted to the upward-firing driver, wherein the virtual height filter at least partially removes directional cues from the speaker location and at least partially inserts the directional cues from the reflected speaker location, the frequency response curve based on

a first frequency response of a filter modeling sound travelling directly from the reflected speaker location to the ears of a listener at a listening position, for said inserting of directional cues from the reflected speaker location, and

a second filter frequency response of a filter modeling sound travelling directly from the speaker location to the ears of the listener at the listening position, for removing of directional cues for audio travelling along a path directly from the speaker location to the listener.

5. The system of claim 4, wherein the audio signal comprises height sound components, and further wherein the frequency response curve is a universal height filter frequency response curve that represents an average of a plurality of individual height filter frequency responses, where each of the individual height filter frequency responses corresponds to a different combination of reflected speaker location, listening position, and physical speaker location.

6. The system of claim 4, wherein the height filter response exhibits a peak located at about 7 kHz and a notch at about 12 kHz.

7. The system of claim 4 wherein the inclination angle is variable, the system further comprising:

a location component configured to determine an optimum listening position within the listening environment; and

a control component configured to alter the inclination angle to reflect the sound waves off of the upper surface to the optimum listening position.

8. The system of claim 4 further comprising a detection component configured to detect the presence of the virtual height filter in the listening environment.

9. The system of claim 4 further comprising a bypass switch to bypass the virtual height filter during a calibration process that prepares audio playback equipment to transmit the sound waves to the listening environment.

10. The system of claim 4 further comprising a room correction component performing a pre-emphasis filtering operation on the sound waves transmitted to the listening environment to compensate for the virtual height filtering applied to the signal transmitted to the upward-firing driver.

11. The system of claim 4 further comprising a room correction component generating a target response of the listening environment by use of a probe signal and adding a default virtual height filter response to a target response of the listening environment.

12. The system of claim 4 wherein the virtual height filter implements an algorithm using a scaling factor to compensate for height cues present in sound waves transmitted directly through the listening environment in favor of the height cues present in the sound reflected off the upper surface of the listening environment.

13. The system of claim 4 wherein the virtual height filter represents a unique frequency response curve, and wherein one or more characteristics of the frequency response curve are changed based on the value of the inclination angle.

14. The system of claim 4, wherein the housing further encloses a front-firing driver configured to transmit sound waves along an axis proximately corresponding to the ground plane.

15. The system of claim 14, wherein the speaker comprises two input terminals, wherein the first input terminal is configured to receive signals corresponding to the sound to be reflected off the upper surface of the listening environment, and the second input terminal is configured to receive signals corresponding to the sound waves to be transmitted along the axis proximately corresponding to the ground plane.

16. The system of claim 14, wherein the system further comprises a crossover filter, the crossover filter having a low-pass section configured to transmit low frequency signals below a threshold frequency to the front-firing driver, and a high-pass section configured to transmit high frequency signals above the threshold frequency to the upward-firing driver.

17. A speaker for transmitting sound waves to be reflected off an upper surface of a listening environment, comprising:

a housing;

an upward-firing driver within the housing and oriented at an inclination angle relative to a ground plane and configured to reflect sound off a reflection point on the upper surface of the listening environment; and

a virtual height filter applying a frequency response curve to a signal transmitted to the upward-firing driver, the frequency response curve based on

a first frequency response of a filter modeling sound travelling directly from a reflected speaker location to the ears of a listener at a listening position, for inserting of directional cues from the reflected speaker location, and

a second filter frequency response of a filter modeling sound travelling directly from a speaker location to the ears of the listener at the listening position, for removing of directional cues for audio travelling along a path directly from a speaker location to the listener.

18. The speaker of claim 17, wherein the signal comprises height sound components, and further wherein the frequency response curve is a universal height filter frequency response curve that represents an average of a plurality of individual height filter frequency responses, where each of the individual height filter frequency responses corresponds to a different combination of reflected speaker location, listening position, and physical speaker location.

19. The speaker of claim 17, wherein the height filter response exhibits a peak located at about 7 kHz and a notch at about 12 kHz.

20. The speaker of claim 17, further comprising a physical interface allowing the housing to be installed on a front-firing driver cabinet that is configured to transmit sound waves along an axis proximately corresponding to the ground plane.