Acoustic Scatterer Array for Low-Frequency Noise Absorption
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Solution Overview
Problem
Existing sound isolation systems in vehicles are inadequate for low-frequency noise reduction, as high reflection materials cause noise pollution and conventional porous sound absorbing materials are inefficient for frequencies below 1 kHz.
Innovation Solution
A sound isolation device featuring an acoustic scatterer with both acoustic monopole and dipole responses, having substantially similar resonant frequencies, which forms an array of equally spaced scatterers to absorb sound waves effectively across a broad frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high reflection material is used to reflect noises away from the cabin, then noise isolation performance is improved, but noise pollution is caused and performance is limited by the mass law
Solution Approach 1:
The patent converts the harmful reflected noise into beneficial absorbed energy by using acoustic scatterers that transform sound waves into resonant vibrations of Helmholtz resonators, which then dissipate energy through viscous losses in the neck regions, eliminating noise pollution while maintaining isolation performance
Solution Approach 2:
The patent changes the fundamental parameter of noise management from reflection to absorption by designing acoustic scatterers with specific monopole and dipole resonant frequencies that match the noise spectrum, enabling effective low-frequency noise control without the limitations of the mass law
2Reliability
If conventional porous sound absorbing materials are used, then high frequency noise reduction is achieved, but low frequency noise below 1 kHz cannot be effectively reduced
Solution Approach 1:
The patent changes the operating parameter from high-frequency absorption to low-frequency absorption by designing Helmholtz resonators with neck dimensions and cavity volumes tuned to resonate at low frequencies (below 1 kHz), where the resonant frequency is determined by the neck area, neck length, and cavity volume
Solution Approach 2:
The patent creates a composite acoustic structure combining multiple Helmholtz resonators with different resonant frequencies in an array, where each resonator targets specific frequency bands, achieving broad-spectrum noise reduction from low to high frequencies through the superposition of multiple resonant responses
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 device provides enhanced sound isolation performance by fully absorbing sound waves at specific frequencies, offering improved passenger comfort by reducing low-frequency noise pollution in vehicles.
Implementation Method 1
an acoustic scatterer that has an acoustic monopole response and an acoustic dipole response. The acoustic dipole response and the acoustic monopole response of the acoustic scatterer may have substantially similar resonant frequencies
Implementation Method 2
an acoustic scatterer that has an acoustic monopole response and an acoustic dipole response. The acoustic dipole response and the acoustic monopole response of the acoustic scatterer may have substantially similar resonant frequencies
Implementation Method 3
The array of acoustic scatterers can fully absorb sound waves at certain frequencies
Data Source
AI summary
A sound isolation device includes an acoustic scatterer that has an acoustic monopole response and an acoustic dipole response. The acoustic dipole response and the acoustic monopole response of the acoustic scatterer may have substantially similar resonant frequencies. The device may include a plurality of acoustic scatters forming an array of equally spaced apart acoustic scatterers.