Speaker Array Signal Processing for Wide Listening Area
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Solution Overview
Problem
Existing audio signal supply systems for speaker arrays struggle to broaden the area where satisfactory sound image localization is achieved, particularly outside the directivity axes of acoustic beams, without requiring architectural measures like diffusion plates.
Innovation Solution
An audio signal supply apparatus that includes an area setting device, a path identifying device, and a signal processing device to specify and adjust audio signal levels and delays based on propagation path information, allowing for wide directivities covering the entire listening area without architectural modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus is set at the intersection point of the straight line connecting the speaker array center with the virtual image listener and the side wall, then the sound image localization is satisfactory at the listener position, but the wave front becomes wider as distance from the focus increases, deteriorating localization for distant listeners
Solution Approach 1:
The patent applies local quality by setting different focuses for different spatial regions. Instead of a single focus for the entire acoustic space, multiple focuses are defined corresponding to different listener positions and directions. Each focus is optimized for its specific region, allowing satisfactory localization both near and far from the speaker array by tailoring the sound field characteristics to local listening requirements.
Solution Approach 2:
The patent extends the conventional single-focus approach to multiple focuses in three-dimensional space. By introducing additional spatial dimensions for focus placement and using multiple virtual image listeners distributed throughout the acoustic space, the system achieves broad listening area coverage while maintaining localization accuracy. This dimensional expansion allows sound waves to be properly focused in multiple directions simultaneously.
2Area of stationary object
If multiple diffusion plates are placed on wall surfaces to diffuse acoustic beams, then the listening area is broadened, but architectural modifications are required which increase complexity and cost
Solution Approach 1:
The patent replaces the mechanical/architectural approach of placing physical diffusion plates on walls with an electronic signal processing approach. By using multiple speaker units and independently controlling their output signals with different delays and amplitude ratios, the system achieves acoustic beam diffusion and listening area expansion through electronic means rather than physical modifications to the acoustic space.
Solution Approach 2:
The patent achieves diffusion of acoustic beams by dynamically changing signal parameters - specifically delay times and amplitude ratios - for each speaker unit. Instead of using physical diffusion structures, the system modifies the temporal and amplitude characteristics of audio signals to create diffuse sound fields that broaden the listening area without requiring architectural changes.
3Measurement precision
If the focus is set within the virtual image to improve localization at specific listener positions, then localization is improved in the direction of directivity axes, but localization cannot be improved at locations out of the directivity axes
Solution Approach 1:
The patent segments the acoustic space into multiple directional regions, each with its own optimized focus. By dividing the three-dimensional space and assigning different focuses to different spatial segments or directions, the system achieves satisfactory localization both along directivity axes and in directions between them. Each speaker unit contributes to multiple focuses, creating overlapping sound fields that provide comprehensive coverage.
Data Source
AI summary
An audio signal supply apparatus which can broaden a listening area in the directions of directivity axes of acoustic beams output from a speaker array and directions other than the directions of the directivity axes. A listening area is set, propagation paths to be followed by sounds output from speakers constituting the speaker array until the sounds reach the listening area are identified, propagation path information related to the propagation paths is obtained, window function information giving wide directivities covering the entire listening area to the sounds output from the speakers is identified based on the propagation path information and the listening area size, and weighting on the signal levels of audio signals to be supplied to the speakers is carried out using the window function information.