Outdoor Loudspeaker Grille Geometry for AVAS Sound and Water Protection
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Solution Overview
Problem
Existing outdoor loudspeakers for Acoustic Vehicle Alerting Systems (AVAS) face issues with grille designs that negatively impact sound pressure level (SPL) response, particularly in the frequency ranges important for AVAS loudspeakers, due to the grille's structure obstructing sound transmission and providing inadequate protection against water and solid object impacts.
Innovation Solution
A loudspeaker assembly design with a grille that maintains a low V1/V2 ratio, where V1 is the volume between the loudspeaker's front face and grille's rear face, and V2 is the volume between the grille's rear face and a perpendicular plane, along with specific ratios of A1/A2 and A1/A3, to enhance sound transmission and protect against water ingress, while using a contoured rear grille face to match the loudspeaker's contours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a stiff material grille with labyrinthine structure is used to protect the loudspeaker diaphragm from water jet or solid object impact, then the protection against environmental hazards is improved, but the sound pressure level response is worsened due to obstruction of sound transmission
Solution Approach 1:
The grille is designed with a porous structure comprising a substrate with pores and a coating layer with pores, allowing sound waves to pass through while providing protection against water and solid objects. The porous structure enables acoustic transmission without compromising protective function.
Solution Approach 2:
The grille combines a substrate material with a coating layer to form a composite structure. The substrate provides mechanical strength and structural support, while the coating layer enhances protection against environmental hazards and maintains acoustic transmission properties.
2Object-affected harmful factors
If a grille with labyrinthine structure is used to prevent direct line of sight onto the loudspeaker diaphragm, then the protection is improved, but the sound transmission is attenuated particularly in critical frequency ranges
Solution Approach 1:
The porous grille structure allows sound waves to pass through the pores while providing protection. The pore size and distribution are optimized to maintain sound transmission in critical frequency ranges (1.8 kHz - 3.6 kHz) while preventing direct impact paths for water and solid objects.
Solution Approach 2:
The grille parameters including pore size, porosity, and thickness are optimized to balance protection and sound transmission. The V1/V2 ratio is controlled within 0.05-0.5 to minimize acoustic interference while maintaining protective function.
3Reliability
If the grille is positioned closer to the loudspeaker diaphragm to reduce the enclosed volume V1, then the sound pressure level in critical frequency ranges is improved, but the protection against water ingress may be compromised
Solution Approach 1:
The porous grille structure enables close positioning to the diaphragm while maintaining water ingress protection. The pores are sized to allow acoustic transmission while preventing water penetration, enabling optimal acoustic performance without compromising protection.
Solution Approach 2:
The composite structure of substrate and coating layer provides both mechanical protection and acoustic transmission. This allows the grille to be positioned closer to the diaphragm for improved sound pressure level while the coating layer maintains protection against environmental hazards.
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 boosts sound pressure level in critical frequency ranges for AVAS loudspeakers, providing enhanced sound quality and protection against environmental hazards without significant attenuation, ensuring effective operation in outdoor conditions.
Implementation Method 1
The grille has a porous structure comprising a substrate with pores and a coating layer with pores
Data Source
AI summary
A loudspeaker assembly for use outdoors. The loudspeaker assembly includes: a loudspeaker, including a drive unit and a diaphragm, wherein the drive unit is configured to move the diaphragm along a movement axis, a grille, positioned in front of a front face of the loudspeaker, the grille being configured to permit sound produced by the front face of the diaphragm to pass through the grille, and to inhibit the ingress of water incident on the front face of the grille from entering into a space enclosed between a rear face of the grille and the front face of the loudspeaker.