Acoustic Wavefront Shaping Device for Siren Noise Direction
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Solution Overview
Problem
Emergency vehicle sirens emit loud sounds that spread in all directions, causing noise pollution and disturbing residents and businesses, leading to property value decreases and health issues, while existing phased array sound systems are impractical for mounting on vehicles due to size and complexity constraints.
Innovation Solution
A sound wavefront shaping device using macroscopic metamaterial structures and channels with varying wavelet transit times and temperature controls to direct acoustic energy primarily towards the ground, inspired by the porpoise's melon structure, reducing sound propagation into buildings and maintaining loudness for roadside warning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional sirens emit sound in all directions, then warning coverage is maximized, but noise pollution and health impacts on nearby buildings increase
Solution Approach 1:
The patent segments the sound emission by using multiple acoustic wavefront modifiers positioned at different locations on the vehicle. Each modifier processes sound waves in specific directions, allowing the system to direct warning sounds toward the road while redirecting sounds away from nearby buildings, thus reducing noise pollution while maintaining warning effectiveness.
Solution Approach 2:
The patent applies local quality by making different parts of the sound emission system have different functions. Acoustic wavefront modifiers are strategically positioned to create direction-specific sound patterns: enhancing warning coverage in directions where road users are located while suppressing sound propagation toward residential or commercial buildings.
2Ease of operation
If phased array sound systems are used to direct sound, then sound directionality is improved, but device complexity and size increase making vehicle mounting impractical
Solution Approach 1:
The patent uses acoustic wavefront modifiers that replicate and redirect sound waves rather than generating entirely new directed sound fields. These modifiers act as passive or semi-passive elements that copy the siren's sound output and reshape its propagation pattern, achieving directionality without requiring complex active electronic control systems.
Solution Approach 2:
The patent employs relatively simple acoustic wavefront modifier structures that can be manufactured and installed on emergency vehicles without requiring expensive, complex phased array electronics. The modifiers are designed as straightforward acoustic components rather than sophisticated electronic systems, reducing overall device complexity and cost.
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
Effectively directs siren sounds towards the ground, reducing noise pollution for nearby buildings while ensuring adequate warning for roadside vehicles and pedestrians, thus protecting property values and public health.
Implementation Method 1
A sound wavefront shaping device using macroscopic metamaterial structures and channels with varying wavelet transit times and temperature controls to direct acoustic energy primarily towards the ground
Implementation Method 2
channels with varying wavelet transit times and temperature controls to direct acoustic energy primarily towards the ground
Data Source
AI summary
An acoustic wavefront shaping device for altering the propagation of emergency siren sounds is provided. The device includes an enclosed framework containing sound channels mounted before a siren horn. The sound channels are positioned to partition the spherical wavefronts emitted by the siren and transmit each wavelet from the channel's entrance to exit into free space. The interior space of the sound channels contain acoustic macroscopic metamaterial structures that direct wavelet acoustic energy on meandering paths, which extend the transmission duration. Channels higher up in the framework, and away from the center, have straighter paths that transmit acoustic energy more quickly than other channels. The wavelets exit the channels at different times and reconfigure to form a wavefront that is squat and narrow, compared to spherical wavefronts. This wavefront expands into free space staying closer to the ground and closer to the center of the road than spherical wavefront expansion. The sound channels may be further configured with forced air currents to eliminate backscattering and eddies of acoustic energy flow, and the transmission duration of wavelets may be modified using temperature modification. Flexible macroscopic metamaterial structures can change shape in response to changing sound frequency to maintain wavefront shaping.