Loudspeaker Self-Supporting Porous Shell Directional Sound
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Solution Overview
Problem
Conventional loudspeakers face challenges in achieving high acoustic contrast and directional sound delivery when mounted in car seats, leading to listening fatigue and decreased sound quality due to their traditional design and mounting limitations, particularly in close proximity to the listener's ears.
Innovation Solution
A loudspeaker design featuring a self-supporting porous shell with specific airflow resistance, allowing sound to exit through the porous material, which enhances directional sound delivery and reduces blowing noises, while simplifying manufacturing and avoiding the need for complex joints or overmolding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the loudspeaker is mounted in a closed box, then the sound produced by the first radiating surface is separated from interfering sound produced by the second radiating surface, but the cavity acts as an additional spring which increases the loudspeaker resonance frequency and causes lower radiated SPL at substantially below resonance frequency
Solution Approach 1:
The patent applies porous materials (acoustic foam, porous plastic, or porous fabric) to cover the backward-facing radiating surface of the diaphragm. This allows the closed-box configuration to maintain its interference-rejection function while the porous material permits acoustic energy transmission, thereby recovering SPL that would otherwise be lost in a completely sealed enclosure. The porous material acts as an acoustic filter that blocks harmful sound paths while transmitting useful acoustic energy.
Solution Approach 2:
The patent combines the closed-box structure with porous acoustic materials to create a composite enclosure system. The closed box provides structural integrity and sound isolation, while the porous material layers provide acoustic transmission and damping. This composite approach resolves the contradiction by integrating the benefits of both sealed enclosure (interference rejection) and porous transmission (SPL recovery).
2Object-generated harmful factors
If the loudspeaker is mounted without cabinet, then two distinct lobes are produced front and back leading to figure of eight radiation pattern, but the acoustic path length between first and second radiating surfaces is very short causing low overall efficiency due to acoustic short circuit
Solution Approach 1:
The patent introduces porous acoustic materials within the enclosure to increase the effective acoustic path length between the front and back radiating surfaces. The porous structure creates tortuous sound paths that extend the acoustic travel distance, reducing the acoustic short circuit effect and improving electro-acoustical conversion efficiency while maintaining the directional radiation pattern.
Solution Approach 2:
The patent uses porous acoustic materials as intermediary elements between the diaphragm and the external environment. These materials mediate the acoustic energy transmission, allowing controlled sound leakage that increases path length and reduces the acoustic short circuit, thereby improving efficiency without requiring a large enclosed volume.
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 design achieves highly directional sound in the mid-high frequency range with improved acoustic performance and reduced noise interference, suitable for close proximity listening positions like car seats, while being easier and cheaper to manufacture.
Implementation Method 1
a self-supporting porous shell which encloses a volume configured to receive sound produced by the second radiating surface, wherein at least part of the self-supporting porous shell is provided by at least one self-supporting portion of porous material having a specific airflow resistance
Implementation Method 2
porous material having a specific airflow resistance in the range 500-10000 Pa·s/m so as to allow sound produced by the second radiating surface to exit the volume enclosed by the shell
Data Source
AI summary
A loudspeaker including: a diaphragm having a first radiating surface and a second radiating surface, wherein the first radiating surface and the second radiating surface are located on opposite faces of the diaphragm; a drive unit configured to move the diaphragm based on an electrical signal; a loudspeaker support structure, wherein the diaphragm is suspended from the loudspeaker support structure via one or more loudspeaker suspension elements. The loudspeaker support structure comprises a self-supporting porous shell which encloses a volume configured to receive sound produced by the second radiating surface, wherein at least part of the self-supporting porous shell is provided by at least one self-supporting portion of porous material having a specific airflow resistance in the range 500-10000 Pa·s/m so as to allow sound produced by the second radiating surface to exit the volume enclosed by the shell.