Eigen Tone Filter Loudspeaker Vent Absorbs Acoustic Resonances
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vented loudspeaker systems face challenges in achieving low tuning frequencies while minimizing port noise and turbulence, as larger cross-sectional areas are required to reduce turbulence but lead to impractical port lengths and undesirable resonances, affecting sound fidelity and efficiency.
Innovation Solution
The implementation of an Eigen Tone Filter (ETF) system within the loudspeaker vent, comprising closed-end columns placed inside the vent to absorb open pipe resonances, which are tuned to reduce unwanted acoustic resonances and port noise, and can be adapted to various shapes and configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the port cross-sectional area is increased to reduce turbulence and port noise, then the tuning frequency decreases, but the port length becomes impractically long
Solution Approach 1:
The patent places a Helmholtz resonator cavity inside the port structure, nesting one acoustic element within another. This allows the inner resonator to provide acoustic mass and tuning functionality without requiring the outer port to be excessively long, thereby reducing turbulence and port noise while maintaining practical dimensions.
Solution Approach 2:
The patent modifies the acoustic parameters by introducing a Helmholtz resonator with specific cavity volume and neck dimensions. This changes the overall acoustic mass and compliance of the port system, allowing for reduced port length while maintaining the desired tuning frequency and minimizing turbulence through optimized acoustic impedance.
2Quantity of substance
If the port length is increased to achieve lower tuning frequency, then the acoustic mass increases, but organ pipe resonances occur at audible frequencies
Solution Approach 1:
The patent introduces a Helmholtz resonator that creates a counter-resonance to cancel the unwanted organ pipe resonances of the port. The Helmholtz resonator's natural frequency is tuned to match the problematic organ pipe resonance frequency, and when properly damped, it absorbs the resonant energy, converting the harmful resonance into a beneficial cancellation effect.
Solution Approach 2:
The patent creates a composite acoustic system combining the port structure with an integrated Helmholtz resonator cavity. This composite structure provides both the required acoustic mass for low tuning frequency and simultaneous suppression of organ pipe resonances through the coupled resonator system, achieving multiple acoustic functions in a unified design.
3Loss of energy
If the port cross-sectional area is increased to reduce turbulence, then air flow improves, but mid-range frequencies are transmitted to the outside
Solution Approach 1:
The patent applies different acoustic treatments to different sections of the port system. The main port maintains a larger cross-sectional area for efficient air flow, while the integrated Helmholtz resonator cavity provides targeted acoustic filtering at specific frequencies. This local differentiation allows the system to simultaneously achieve good air flow efficiency and suppress unwanted mid-range frequency transmission through the port.
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 ETF system effectively reduces audible port noise, eliminates undesired resonances, and enhances the accuracy and fidelity of sound reproduction in loudspeaker systems by being passive, inexpensive, and adaptable, with marketing advantages due to its visible design.
Implementation Method 1
Eigen Tone Filter ('ETF') pipes placed inside the vent to absorb the 'open pipe' acoustic resonance of the vent
Implementation Method 2
a vent defining a lumen providing fluid communication between an enclosure's interior volume and an external ambient environment
Data Source
AI summary
A loudspeaker system (700 or 800) and method for tuning ported loudspeakers and reducing unwanted acoustic resonances provides reduced port noise, eliminates undesired port resonances and improves the accuracy and fidelity of reproduced sound in a loudspeaker system of relatively high efficiency with an enclosure including an Eigen Tone Filter structure (“ETF”) comprising a pipe or set of pipes 720, 820 placed inside a loudspeaker vent to absorb the “open pipe” acoustic resonance of the vent. The open-pipe resonance is unwanted and interferes with the midrange performance of the loudspeaker, when in use, if not corrected.