Grommet Soundproof Wall Design for Vehicle Noise Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing grommets with enhanced soundproof performance either increase in size and weight or require high-density materials, leading to higher costs, which is undesirable for achieving quiet cabin environments in vehicles.

Innovation Solution

A method for manufacturing grommets with a soundproof wall designed using the expression TL=20 log(ρ×f)−42.5, where TL is the transmission loss, ρ is the surface density, and f is the frequency, to achieve a transmission loss of at least 20 dB in the 1,000 Hz to 4,000 Hz frequency band, and incorporating soundproof walls to suppress sound pressure levels by at least 3 dB in the same frequency range, along with a panel engagement mechanism to reduce vibration and sound transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If thickness of peripheral wall forming air layer is increased or grommet is formed out of high density material to enhance soundproof performance, then soundproof performance is improved, but size and weight increase and costs increase

Engineering Contradiction:

Improvesound transmissionVSAvoidgrommet weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The grommet is divided into multiple functional sections: a peripheral wall forming an air layer, and a separate soundproof wall with specific thickness (5-15mm) and surface density (0.5-2.0kg/m²). This segmentation allows the soundproof wall to handle acoustic isolation while the peripheral wall maintains structural support, optimizing both soundproof performance and weight.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grommet combines different materials with complementary properties: the peripheral wall uses elastic material (natural rubber, synthetic rubber, or elastomer) for flexibility and sealing, while the soundproof wall uses materials with specific acoustic properties (foam, fabric, leather, or resin). This composite structure achieves superior soundproof performance without excessive weight.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

Engineering Contradiction:

Improvesound transmissionVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The soundproof wall is designed as a separate component with optimized thickness (5-15mm) and surface density parameters, allowing it to be manufactured independently or as part of the grommet. This segmentation enables cost-effective production by using moderate-thickness materials rather than requiring excessively thick peripheral walls.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention specifies optimal parameter ranges for the soundproof wall: thickness of 5-15mm and surface density of 0.5-2.0kg/m². These parameter optimizations ensure adequate soundproof performance (transmission loss ≥20dB in 1,000-4,000Hz band) while controlling material costs and manufacturing complexity.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

Engineering Contradiction:

Improvesound transmissionVSAvoidgrommet size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The grommet structure separates the air layer function (peripheral wall) from the soundproofing function (soundproof wall). The soundproof wall provides acoustic isolation with controlled thickness (5-15mm), preventing the need for excessively thick peripheral walls that would increase overall grommet size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The soundproof wall is strategically positioned to provide acoustic isolation where needed, with optimized local thickness (5-15mm) and surface density properties. This localized soundproofing approach achieves effective sound transmission loss without requiring uniform thickening of the entire grommet structure.

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 method effectively enhances soundproof performance in the 1,000 Hz to 4,000 Hz frequency range while maintaining a compact size and low weight, reducing sound transmission into vehicle cabins without increasing costs or material density, thus providing a comfortable indoor space.

Implementation Method 1

a soundproof wall that is formed in the sound shield space so as to cross a longitudinal direction of the wire harness

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentUS10449914B2Method for manufacturing grommet, and grommet

Publication Date: 2019.10.22 YAZAKI CORP

AI summary

A method for manufacturing a grommet, which is fixed to a wire harness W inserted into an opening portion of a panel P and which is fitted and attached to the opening portion to thereby support the wire harness W on the panel P. The grommet includes peripheral walls that surrounds the wire harness W to form a sound shield space S around the wire harness W, and a soundproof wall that is formed in the sound shield space S so as to cross a longitudinal direction of the wire harness W. The soundproof wall is designed by use of an expression of TL=20 log(ρ×f)−42.5 where TL designates transmission loss of the soundproof wall, ρ designates surface density of the soundproof wall, and f designates a frequency.