Hearing Protector Loudspeaker Capsule Acoustic Venting

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Solution Overview

Problem

Conventional hearing protectors with integrated loudspeakers suffer from inadequate frequency response in the low-frequency range (20-300 Hz) due to the small volume of the loudspeaker capsule, which affects sound reproduction, especially in music listening scenarios.

Innovation Solution

The design incorporates a loudspeaker with an integrated capsule that includes a peripheral wall with a circumferential groove and a tubular collar, allowing for controlled airflow between the capsule's enclosed air volume and the ambient surroundings through strategically placed holes or ducts, optimizing the frequency response by maintaining low damping and enhancing low-frequency sound reproduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the loudspeaker capsule volume is kept small to avoid acoustic shorting, then the loudspeaker element is protected from acoustic shorting, but the frequency path in the base range (20-300 Hz) is negatively affected

Engineering Contradiction:

Improveacoustic shorting preventionVSAvoidfrequency path quality

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The capsule is divided into two separate volumes: a first volume (V1) enclosed by the capsule walls and a second volume (V2) formed by the enclosure. These two volumes are separated by a partition wall with an acoustic shorting prevention opening, allowing each volume to function independently for acoustic shorting prevention while the connection between them improves low-frequency response.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A tube or duct connects the first volume and second volume, acting as an intermediary channel for acoustic pressure equalization. This connection improves the frequency path in the base range while the partition wall with opening prevents direct acoustic shorting between the loudspeaker element and external environment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If passive noise absorbent is added to the muff to improve noise protection, then noise protection is improved, but the frequency path and sound pressure curve are negatively affected

Engineering Contradiction:

Improvenoise protectionVSAvoidfrequency path quality

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The noise absorbent is selectively placed only in the portion of the muff excluding the enclosed space, rather than filling the entire muff. This localized placement allows noise protection in the outer region while preserving the frequency path quality in the inner enclosed space where sound reproduction occurs.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the capsule volume is increased to improve base range frequency response, then the frequency path in the base range is improved, but the loudspeaker element becomes susceptible to acoustic shorting

Engineering Contradiction:

Improvefrequency path qualityVSAvoidacoustic shorting prevention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

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

This approach significantly improves the low-frequency sound pressure curve, providing a noticeable base lift in the 20-300 Hz range without substantial deterioration in damping, as demonstrated by measurements and listening tests, with optimal results achieved within specific hole area limits.

Implementation Method 1

a drive unit for driving the loudspeaker

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a first volume V1 enclosed by capsule walls and a second volume V2 formed by the enclosure, said volumes being separated by a partition wall having an opening for preventing acoustic shorting

Methodology Applied

Scientific EffectAcoustic compliance: Acoustic Absorption

Implementation Method 3

said volumes being separated by a partition wall having an opening for preventing acoustic shorting

Methodology Applied

Scientific EffectPressure equalization: Pressure Gradient

Data Source

PatentEP2301257B1Hearing protector

Publication Date: 2022.06.01 3M INNOVATIVE PROPERTIES CO

Figure 1
Figure 2

AI summary

A hearing protector has two closed muffs (2) which sealingly abut against the wearer's head, so that there is formed a closed space in each muff (2) and about the user's ear. A loudspeaker (4) is disposed interiorly in the muff and has a membrane (5) whose one side is turned to face towards the user's ear, and whose opposing side is turned to face towards a closed volume which is defined by the membrane and an enclosure. In order to improve the base reproduction in listening to music, the interior of the enclosure is, via at least one hole or one duct, in communication with the ambient surroundings outside the closed space of the muff (2). In one preferred embodiment, the enclosure comprises a capsule (7) which is integrated part of the loudspeaker (4).