Acoustically Absorptive Air Duct Structure for Muffler-Free HVAC

Solution Overview

Problem

Existing air ducts in vehicular environmental control systems, such as those in aircraft, generate noise that contributes to passenger discomfort, and noise attenuating mufflers add weight, volume, and cost to these systems.

Innovation Solution

An acoustically absorptive air duct comprising an air impervious inner layer, a structural middle layer with through openings, and an acoustically absorptive outer layer, which together form a multi-layer construction that absorbs and redirects noise without the need for additional mufflers, reducing weight, volume, and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If noise attenuating mufflers are used to reduce noise generated by moving air within an environmental control system, then noise attenuation performance is improved, but weight increases

Engineering Contradiction:

Improvenoise attenuation performanceVSAvoidweight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent combines the air duct and noise attenuation functions into a single integrated structure. The multi-layer construction (inner air-impermeable layer, middle structural layer with through-openings, and outer acoustically absorptive layer) simultaneously serves as both the air conduit and the noise attenuating component, eliminating the need for separate mufflers and thereby reducing weight.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The air duct employs a composite multi-layer structure where each layer has specific properties: the inner layer is air-impermeable for sealing, the middle layer provides structural integrity with controlled porosity (30-50% through-opening area), and the outer layer provides acoustic absorption. This composite construction achieves noise attenuation without requiring additional heavy muffling components.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If noise attenuating mufflers are used to reduce noise generated by moving air within an environmental control system, then noise attenuation performance is improved, but volume increases

Engineering Contradiction:

Improvenoise attenuation performanceVSAvoidvolume

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The air duct and noise attenuation system are merged into one integrated component. The multi-layer wall structure of the air duct itself provides noise attenuation functionality, eliminating the need for separate voluminous mufflers and thereby reducing the overall system volume.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The noise attenuation is achieved through localized modifications to the air duct wall structure rather than adding separate voluminous components. The middle layer's through-openings (occupying 30-50% of surface area) and the outer absorptive layer provide targeted acoustic treatment at the duct wall level, maintaining compact dimensions.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If noise attenuating mufflers are used to reduce noise generated by moving air within an environmental control system, then noise attenuation performance is improved, but cost increases

Engineering Contradiction:

Improvenoise attenuation performanceVSAvoidcost

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The air duct and noise attenuation system are merged into one integrated component. The multi-layer wall structure of the air duct itself provides noise attenuation functionality, eliminating the need for separate voluminous mufflers and thereby reducing the overall system volume.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The noise attenuation is achieved through localized modifications to the air duct wall structure rather than adding separate voluminous components. The middle layer's through-openings (occupying 30-50% of surface area) and the outer absorptive layer provide targeted acoustic treatment at the duct wall level, maintaining compact dimensions.

Inventive Principle:

Principle #3Local quality

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 acoustically absorptive air duct achieves noise attenuation performance comparable to mufflers while significantly reducing weight, volume, and cost, enhancing the efficiency and robustness of environmental control systems.

Implementation Method 1

a structural middle layer comprising a structural component, said structural middle layer comprising a structural middle layer first side and a structural middle layer second side, with the structural middle layer first side positioned adjacent the air impervious inner layer second side, with the structural middle layer comprising a plurality of through openings

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Implementation Method 2

an acoustically absorptive outer layer positioned adjacent the structural middle layer second side

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentUS12358627B2Acoustic air duct for environmental control system in vehicle

Publication Date: 2025.07.15 THE BOEING CO

AI summary

Apparatuses, systems, and methods comprising acoustically absorptive air ducts comprising an internally positioned structure component as an endoskeleton and an air impervious inner layer, and an acoustically absorptive foam outer layer, environmental control systems comprising such air ducts, and vehicles incorporating such environmental control systems are disclosed with methods for manufacture and installations are disclosed.