Environmental reverberation processor

Details Environmental reverberation processor Environmental reverberation processor

1999-11-12

2001-02-13

Harvey, Minsun Oh (Department: 2747)

Electrical audio signal processing systems and devices

Sound effects

Reverberators

C381S061000

Reexamination Certificate

active

06188769

ABSTRACT:

BACKGROUND OF THE INVENTION
Virtual auditory displays (including computer games, virtual reality systems or computer music workstations) create virtual worlds in which a virtual listener can hear sounds generated from sound sources within these worlds. In addition to reproducing sound as generated by the source, the computer also processes the source signal to simulate the effects of the virtual environment on the sound emitted by the source. In a computer game, the player hears the sound that he/she would hear if he/she were located in the position of the virtual listener in the virtual world.
One important environmental factor is reverberation, which refers to the reflections of the generated sound which bounce off objects in the environment. Reverberation can be characterized by measurable criteria, such as the reverberation time, which is a measure of the time it takes for the reflections to become imperceptible. Computer generated sounds without reverberation sound dead or dry.
Reverberation processing is well-known in the art and is described in an article by Jot et al. entitled “
Analysis and Synthesis of Room Reverberation Based on a Statistical Time
-
Frequency Model
”, presented at the 103rd Convention of the Audio Engineering Society, 60 East 42nd St. New York, N.Y., 10165-2520.
As depicted in FIG. 1, a model of reverberation presented in Jot et al. breaks the reverberation effects into discrete time segments. The first signal that reaches the listener is the direct signal which undergoes no reflections. Subsequently, a series of discrete “early” reflections are received during an initial period of the reverberation response. Finally, after a critical time, the “late” reverberation is modeled statistically because of the combination and overlapping of the various reflections. The magnitudes of Reflections_delay and Reverb_delay are typically dependent on the size of the room and on the position of the source and the listener in the room.
FIG. 14 of Jot et al. depicts a reverberation model (Room) that breaks the reverberation process into “early”, “cluster”, and “reverb” phases. In this model, a single feed from the sound source is provided to the Room module. The early module is a delay unit producing several delayed copies of the mono input signal which are used to render the early reflections and feed subsequent stages of the reverberator. A Pan module can be used for directional distribution of the direct sound and the early reflections and for diffuse rendering of the late reverberation decay.
In the system of FIG. 14 of Jot et al. the source signal is fed to early block R
1
and a reverb block R
3
for reverberation processing and then fed to a pan block to add directionality. Thus, processing multiple source feeds requires implementing blocks R
1
and R
3
for each source. The implementation of these blocks is computationally costly and thus the total cost can become prohibitive on available processors for more than a few sound sources.
Other systems utilize angular panning of the direct sound and a fraction of the reverberation or sophisticated reverberation algorithms providing individual control of each early reflection in time, intensity, and direction, according to the geometry and physical characteristics of the room boundaries, the position and directivity patterns of the source, and the listening setup.
Research continues in methods to create realistic sounds in virtual reality and gaming environments.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a method and system processes individual sounds to realistically render, over headphones or 2 or more loudspeakers, a sound scene representing multiple sound sources at different positions relative to a listener located in a room. Each sound source is processed by an associated source channel block to generate processed signals which are combined and processed by a single reverberation block to reduce computational complexity.
According to another aspect, each sound source provides several feeds which are sent separately to an early reflection block and a late reverberation block.
According to another aspect of the invention, the early reflection feed is encoded in multi-channel format to allow a different distribution of reflections for each individual source channel characterized by a different intensity and spectrum, different time delay and different direction of arrival relative to the listener.
According to another aspect of the invention, the late reverberation block provides a different reverberation intensity and spectrum for each source.
According to another aspect of the invention, the intensity and direction of the reflections and late reverberation are automatically adjusted according to the position and directivity of the sound sources, relative the position and orientation of the listener.
According to another aspect of the invention, the intensity and direction of the reflections and late reverberation are automatically adjusted to simulate muffling effects due to occlusion by walls located between the source and listener and obstruction due to diffraction around obstacles located between the source and the listener.
Additional features and advantages of the invention will be apparent in view of the following detailed description and appended drawings.


REFERENCES:
patent: 4731848 (1988-03-01), Kendall et al.
patent: 4817149 (1989-03-01), Myers
patent: 5436975 (1995-07-01), Lowe et al.
patent: 5555306 (1996-09-01), Gerzon
patent: 5812674 (1998-09-01), Jot et al.
“Analysis and Synthesis of Room Reverberation Based on a Statistical Time-Frequency Model,” Jot et al., 103rd Convention of Audio Engineering Society, Sep. 26-29, 1997, N.Y., N.Y.

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