Direct Field Acoustic Testing Standing Wave Reduction
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Solution Overview
Problem
Direct Field Acoustic Testing systems face deviations from uniform spectral content due to constructive or destructive interference and acoustic standing waves, leading to over or under excitation of objects under test.
Innovation Solution
A direct field acoustic testing system with at least four groups of acoustical transducers and a signal modifier that introduces separately controllable time delays or phase shifts to reduce interference and standing waves, using asymmetrical transducer arrangements and electronic time delays to ensure acoustic outputs arrive at different times, thereby minimizing spectral anomalies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple acoustic sources are used in direct field acoustic testing, then the acoustic field coverage is improved, but constructive or destructive interference and standing waves occur causing spectral deviations
Solution Approach 1:
The patent applies asymmetry by using non-uniform spacing between acoustic sources and the unit under test. Specifically, the distance from each acoustic source to the UUT is made asymmetric rather than uniform, which disrupts the formation of standing waves and reduces constructive/destructive interference patterns. This asymmetric arrangement breaks the symmetry that would otherwise create resonant modes and spectral deviations.
Solution Approach 2:
The patent implements dynamics by continuously varying the spacing between acoustic sources and the UUT during testing. The system dynamically adjusts distances or positions to ensure that at no point do standing waves form. This dynamic adjustment prevents the establishment of stable interference patterns while maintaining comprehensive acoustic field coverage throughout the test.
2Reliability
If acoustic sources are positioned to cover the unit under test, then testing effectiveness is improved, but standing waves and interference patterns cause over or under excitation
Solution Approach 1:
The patent uses asymmetric positioning of acoustic sources relative to the UUT to prevent harmful interference patterns. By ensuring that no two sources are equidistant from the UUT, the system eliminates the conditions necessary for standing wave formation, thereby preventing over or under excitation while maintaining effective test coverage.
Solution Approach 2:
The system dynamically adjusts the positions or spacing of acoustic sources during testing to continuously prevent standing wave formation. This dynamic control ensures that the acoustic field remains uniform across all frequencies, preventing both over-excitation and under-excitation of the UUT while maintaining comprehensive testing effectiveness.
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
The solution effectively reduces spectral deviations and standing waves, achieving greater spectral uniformity and reducing over or under excitation of the object under test, with improved uniformity and reduced power consumption when optimized.
Implementation Method 1
deviations result either from the constructive or destructive interference of the output of multiple acoustic sources
Implementation Method 2
acoustic standing waves related to the geometry of the direct field acoustic test setup
Data Source
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AI summary
A direct field acoustic testing system includes at least two acoustical transducer groups and a signal modifier for introducing separately controllable time delays or phase shifts for each acoustical transducer group so as to provide an acoustic field conforming to a pre-determined specification with reduced deviations due to constructive or destructive interference between the acoustical transducer groups.