Allpass-Weighted Transducer Arrays for Uniform Off-Axis Response
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Linear electroacoustic arrays suffer from angle-dependent frequency responses, leading to degraded listening experiences at off-broadside positions, and existing solutions often sacrifice gain to achieve frequency invariance.
Innovation Solution
The design of generalized allpass arrays using FIR approximations of allpass filters to provide a nearly uniform response across different frequency bands, with subarrays optimized for both gain and invariance parameters, and the implementation of crossover-filtered configurations and frequency-invariant beamformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional array configurations are used to achieve higher acoustic output, then gain is improved, but frequency response uniformity deteriorates at off-broadside positions
Solution Approach 1:
The patent applies parameter changes by modifying the array weight coefficients from conventional uniform or tapered weights to allpass filter weights. This transformation changes the frequency response characteristics while maintaining the array's gain, resolving the contradiction between acoustic output and frequency response uniformity at off-broadside positions.
Solution Approach 2:
The patent implements local quality by applying frequency-dependent weight adjustments only to specific array elements based on their position and the desired beamforming characteristics. The allpass filter weights are designed to compensate for spatial variations in the frequency response, providing uniformity where needed while preserving overall gain.
2Manufacturing precision
If filter network frequency invariant beamforming or Bessel weighting is used to provide invariant response, then frequency response uniformity is improved, but gain is sacrificed
Solution Approach 1:
The patent uses FIR approximations of allpass filters to copy the desirable frequency-invariant characteristics of IIR allpass filters while avoiding their implementation complexity. This allows achieving response uniformity without the gain loss associated with conventional approaches.
Solution Approach 2:
The patent combines multiple array elements with specifically designed allpass filter weights to create a composite array structure. This composite approach achieves both response uniformity and maintained gain by leveraging the complementary strengths of individual elements with optimized weighting.
3Power
If array elements are increased to achieve higher output level, then gain is improved, but device complexity increases
Solution Approach 1:
The patent introduces dynamic weight adjustment through allpass filter design, allowing the array to adapt its frequency response characteristics. This dynamic approach enables achieving higher effective output with the same number of elements, avoiding the need to increase array size and associated complexity.
Data Source
AI summary
Allpass arrays of arbitrary order are presented. The transducers in the arrays are configured with weights corresponding to the FIR approximation of an allpass filter such that a nearly uniform array response is provided.