Acoustic Transducer Array Signal Processing for Loudspeaker Directivity
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Solution Overview
Problem
Existing loudspeaker systems face challenges in efficiently controlling acoustic radiation patterns across various frequency ranges, particularly in creating desired nulls and enhancing low-frequency output while maintaining high-frequency directivity, due to limitations in transducer spacing and interference patterns.
Innovation Solution
The use of filters to operate on input signals and provide output and cross-feed signals to transducer arrays, specifically configuring inverting low-pass, high-pass, and all-pass filters to achieve destructive interference in targeted frequency ranges, allowing transducers to work independently at high frequencies and together at low frequencies, thereby enhancing low-frequency output efficiency and controlling radiation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transducers are spaced closely to maintain high-frequency directivity, then high-frequency radiation control is improved, but low-frequency output efficiency deteriorates
Solution Approach 1:
The system segments the frequency spectrum into high-frequency and low-frequency ranges, applying different transducer configurations and signal processing strategies to each segment. High-frequency signals use closely-spaced transducers for directivity control, while low-frequency signals utilize widely-spaced transducer pairs for efficient radiation.
Solution Approach 2:
The system transitions from a single-array configuration to a dual-array configuration with widely-spaced transducer pairs. This spatial dimensionality change enables low-frequency signals to be radiated efficiently by the outer transducers while maintaining high-frequency directivity through the inner transducer pairs.
2Power
If transducers are spaced widely to enhance low-frequency output, then low-frequency radiation efficiency is improved, but high-frequency directivity control deteriorates
Solution Approach 1:
The signal processing system segments the frequency spectrum and routes different frequency components to different transducer pairs. Low-frequency components are directed to widely-spaced outer transducers for efficient radiation, while high-frequency components are directed to closely-spaced inner transducers for precise directivity control.
Solution Approach 2:
Different regions of the transducer array are assigned different functional qualities: inner transducers are optimized for high-frequency directivity control with close spacing, while outer transducers are optimized for low-frequency radiation efficiency with wide spacing. Each transducer pair operates with locally optimized characteristics.
3Measurement precision
If filters are added to control frequency-specific destructive interference, then radiation pattern control is improved, but system complexity increases
Solution Approach 1:
The system changes the parameter of transducer spacing to create frequency-dependent destructive interference patterns. By carefully selecting the spacing between transducer pairs, the system achieves desired radiation patterns without requiring complex filter networks, relying instead on the physical parameter of spacing to control acoustic interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the loudspeaker system's efficiency by allowing for precise control of acoustic radiation patterns, increasing low-frequency output capability, and positioning the perceptual axis beyond the physical range of the arrays, while maintaining high-frequency directivity and reducing interference.
Implementation Method 1
a plurality of transducers of the first array produce destructive interference in a first frequency range; the transducers of the first array do not produce destructive interference in a second frequency range; and a first transducer of the first array and a first transducer of the second array produce destructive interference in the second frequency range
Data Source
AI summary
A set of filters is configured to distribute input signals representing a single perceptual axis to first and second physically separate arrays of loudspeakers comprising at least first and second transducers, such that the arrays of loudspeakers will create an array pattern corresponding to the input signals when the input signals are between a first frequency and a second frequency.