Non-linear dynamic absorber for low-frequency acoustic isolation
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Solution Overview
Problem
Double-walled partitions exhibit high acoustic transparency at low frequencies (50-150 Hz) due to resonance, known as the 'breathing' frequency, which existing methods fail to adequately address without adding insulation or increasing wall thickness.
Innovation Solution
A non-linear dynamic absorber comprising a blade with embedded ends and a small mass, acting as a non-linear spring, is fixed to the wall to absorb vibrational energy and reduce resonance through energy pumping, a phenomenon where vibrational energy is transferred from the main structure to the absorber, thereby attenuating vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sound insulation is improved by increasing wall mass or adding layers, then acoustic insulation performance is improved, but device complexity and wall thickness increase
Solution Approach 1:
The invention extracts the sound insulation function from the wall structure itself and separates it into an independent dynamic absorber component. This absorber is attached to the wall but operates as a separate entity, taking out the complexity of mass-added insulation and replacing it with a compact, attachable device that provides the same acoustic insulation benefit without requiring structural modification of the wall itself.
Solution Approach 2:
The dynamic absorber acts as an intermediary element between the incident sound waves and the wall structure. Instead of directly increasing wall mass, the absorber mediates the acoustic energy transfer through its nonlinear oscillating mass-spring system, which converts sound energy into controlled vibrations that are then dissipated, providing insulation without adding structural complexity.
2Object-affected harmful factors
If traditional linear dampers are used to reduce resonance, then vibration attenuation is achieved, but effectiveness at low frequencies is insufficient
Solution Approach 1:
The invention employs a nonlinear dynamic absorber where the oscillating mass is connected to the wall through a nonlinear spring mechanism rather than a linear damper. This dynamic system can adapt its response characteristics based on the input frequency, enabling effective attenuation across a broader frequency range including low frequencies where traditional linear dampers fail. The nonlinear spring allows the system to maintain effectiveness as the operating conditions change.
Solution Approach 2:
The invention changes the fundamental parameters of the vibration control system by using a nonlinear spring with varying stiffness characteristics instead of a linear spring with constant stiffness. This parameter change allows the absorber to effectively target low-frequency resonances by adjusting its natural frequency response to match the problematic breathing mode of the wall, thereby improving low-frequency insulation performance.
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 non-linear dynamic absorber effectively reduces acoustic transparency at low frequencies by irreversibly transferring vibrational energy from the main structure to the absorber, enhancing acoustic insulation without adding layers or increasing wall thickness.
Implementation Method 1
The physical phenomenon underlying this attenuation of the plate's resonance is known as energy pumping (or non-linear targeted energy transfer)
Implementation Method 2
Under dynamic loading, this blade behaves like a nonlinear spring oscillating around its equilibrium position—or positions—within a frequency range encompassing the loading frequency
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a construction element comprising a panel (11) made of a rigid material and at least one non-linear dynamic absorber (9) comprising: a leaf (1) with two end portions (2a) and an intermediate portion (2b) with a non-linear spring function; a mass (3) attached to the intermediate portion (2b) with a non-linear spring function of the leaf; an attachment means (4) making it possible to attach the two end portions (2a) of the leaf (1) to a solid mounting such that the intermediate portion (2b) with a non-linear spring function can oscillate around the position or positions of equilibrium thereof, the non-linear dynamic absorber (9) being rigidly attached to the panel (11) via the attachment means (4). The invention also relates to a partition containing such a construction element as well as to the use of such an absorber or construction element in order to reduce the acoustic transparency of a wall.