Microperforated HVAC Air Distribution Pipe for Low-Frequency Noise Attenuation
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Solution Overview
Problem
HVAC air distribution pipes in vehicles fail to effectively attenuate noise from the fan and compressor, particularly at low frequencies, leading to discomfort for passengers.
Innovation Solution
A single-layer tubular air distribution pipe made from a cellular, elastically deformable material with microperforations on its internal and/or external surfaces, extending radially across the pipe's thickness, which enhances acoustic attenuation by absorbing noise across a broader frequency range, including low frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer tubular wall made from cellular and elastically deformable material is used, then the pipe structure is simple and easy to manufacture, but the acoustic attenuation performance is insufficient, particularly at low frequencies
Solution Approach 1:
The patent applies porous materials by incorporating microperforations into the single-layer tubular wall. These microperforations create a porous structure that enables acoustic attenuation through friction and viscous effects as sound waves pass through the perforated walls, thereby reducing noise transmission while maintaining the simplicity of the single-layer structure
Solution Approach 2:
The patent applies parameter changes by modifying the physical parameters of the tubular wall through microperforations. The microperforations alter the acoustic impedance and damping characteristics of the wall material, enabling effective low-frequency noise attenuation without changing the fundamental single-layer structure or material composition
2Object-affected harmful factors
If microperforations are added to the pipe wall, then acoustic attenuation at low frequencies is improved, but the pipe structure becomes more complex
Solution Approach 1:
The microperforations create a porous structure in the tubular wall that provides acoustic attenuation functionality. This porous configuration allows the pipe to absorb and dissipate sound energy, particularly at low frequencies, while maintaining a relatively simple single-layer construction without requiring multiple layers or complex assemblies
3Device complexity
If conventional HVAC pipes are used, then the system is simple, but noise from fan and compressor is transmitted to the passenger compartment
Solution Approach 1:
The patent applies parameter changes by introducing microperforations into the conventional single-layer tubular wall. This modification changes the acoustic parameters of the pipe wall, enabling it to attenuate noise from fan and compressor while maintaining the overall simplicity of the HVAC air distribution system
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 microperforated design significantly improves acoustic attenuation, particularly at frequencies between 50 and 800 Hz, reducing noise transmission and enhancing passenger comfort by increasing the pipe's ability to absorb and dissipate acoustic energy.
Implementation Method 1
the wall comprises microperforations for acoustic attenuation, these microperforations extending from at least one of the internal and external surfaces of the wall in the direction of the other of these surfaces
Implementation Method 2
the microperforations being configured to give the pipe an acoustic attenuation of around 10dB at frequencies below 1000Hz, and in particular between 50 and 800 Hz
Data Source
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AI summary
Air distribution pipe (34) for an HVAC circuit of a vehicle, this pipe (34) comprising a single single-layer tubular wall (36) made from a cellular and elastically deformable material, said wall (36) comprising acoustic attenuation micro-perforations, these micro-perforations extending from at least one of the internal and external surfaces of the wall (36) towards the other of these surfaces, or even to the other of these surfaces.