Sound Image Localization Using Spherical Harmonic Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional sound image localization techniques require many control points and lengthy calculations to flexibly control directivity, making them inefficient.
Innovation Solution
A sound image localization device that uses a spherical harmonic function expansion to analytically calculate expansion coefficients, generates filter coefficients for a speaker array, and convolves these coefficients into speaker drive signals to achieve flexible directivity control with reduced calculation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional directivity control methods are used, then sound image localization can be achieved, but many control points are required and calculation time increases
Solution Approach 1:
The patent transforms the directivity control problem from a spatial domain optimization problem into a frequency domain problem by using spherical harmonic function expansion. This parameter transformation allows the system to control sound beam patterns efficiently without requiring numerous control points, thereby reducing calculation time while maintaining localization precision.
Solution Approach 2:
The patent replaces the conventional mechanical approach of adjusting individual speaker phases and amplitudes at multiple control points with a mathematical substitution using spherical harmonic functions. This substitution converts the complex spatial optimization into an analytical solution that can be computed efficiently in the frequency domain.
2Measurement precision
If conventional directivity control methods are used, then sound image localization can be achieved, but the system complexity increases due to many control points
Solution Approach 1:
By changing the parameter representation from spatial control point coordinates to spherical harmonic function coefficients, the patent simplifies the control system. Instead of managing numerous control points and their associated parameters, the system only needs to manage the expansion coefficients of the spherical harmonic functions, significantly reducing system complexity.
Solution Approach 2:
The spherical harmonic function expansion provides a universal mathematical framework that can represent various directivity patterns (sound beams) of different widths and orientations. This multi-functional approach allows the system to achieve precise sound image localization without requiring separate control mechanisms for each beam configuration.
Data Source
AI summary
Provided is a sound image localization device capable of flexibly controlling directivity with a short calculation time. A sound image localization device that reflects, on a reflector 50, a sound signal radiated from a speaker array 40 arranged with a plurality of speakers SP1 to SPQ on a straight line to localize a sound image includes an expansion coefficient calculation unit 10 configured to analytically calculate expansion coefficients by performing a spherical harmonic function expansion on a window function representing desired directivity, a filter coefficient generation unit 20 configured to convert the expansion coefficients into filter coefficients corresponding to each of the speakers SP1 to SPQ, and a speaker drive unit 30 configured to generate a speaker drive signal for driving each of the speakers SP1 to SPQ by convolving the filter coefficients in a voice signal.