Holographic Meta-Surface Audio for Frequency-Steered Directional Sound
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Solution Overview
Problem
Existing directional audio devices face challenges in emitting sound waves in specific directions without increasing volume, requiring additional components and complex structures, and suffer from frequency scanning phenomena when adjusting emission angles by changing frequencies.
Innovation Solution
A holographic-based directional audio device with a holographic meta-surface on a flat plate, featuring grooves designed by surface admittance based on cosine or sine functions, allows for adjusting emission angles through frequency changes without frequency scanning, and includes anti-interference walls to prevent wave interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a blocking plate, horn, or additional sound wave generators are installed to achieve directional sound emission, then directionality is improved, but device volume and structural complexity increase
Solution Approach 1:
The patent combines the sound wave generation function and the directional control function into a single integrated device. The sound wave generator is positioned at the center of a flat plate with holographic meta-surface, eliminating the need for separate blocking plates, horns, or additional generators. This integration achieves directional sound emission while minimizing device volume.
Solution Approach 2:
The patent replaces traditional mechanical directional control mechanisms (blocking plates, horns, physical arrays of generators) with a holographic meta-surface that uses surface admittance modulation. This substitution eliminates complex mechanical structures while achieving precise directional control through acoustic field manipulation.
2Ease of operation
If a flat plate with grooves is used to emit sound waves in a specific direction, then directionality is improved, but the device cannot emit sound waves in multiple directions and requires additional fixing members
Solution Approach 1:
The holographic meta-surface on the flat plate provides multi-directional sound emission capability while maintaining a single integrated structure. By adjusting the surface admittance distribution, the device can emit sound waves in multiple directions without requiring additional fixing members or structural modifications, achieving both directionality and versatility.
3Adaptability or versatility
If the holographic meta-surface includes both forward and backward dominant regions to emit sound waves in multiple directions, then emission versatility is improved, but frequency scanning phenomenon causes beam splitting and loss of directionality
Solution Approach 1:
The patent applies local quality by creating different surface admittance regions (forward dominant and backward dominant) at specific locations on the holographic meta-surface. Each region is optimized for its specific emission direction, allowing the device to achieve multi-directional emission while maintaining stable directionality in each beam without frequency scanning-induced beam splitting.
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 device achieves precise sound wave emission in specific directions with adjustable angles and prevents beam splitting, enabling multi-beam emission types without increasing volume or complexity.
Implementation Method 1
a depth of the grooves constituting the holographic meta-surface is determined by surface admittance calculated on the basis of a cosine function or a sine function of a sum of a first value that is a product of a frequency of the sound wave, a refractive index according to a surface of the unit cell, and a radial distance from a center of the flat plate to the unit cell and a second value that is a product of the frequency of the sound wave, a position value of the unit cell, and an emission angle of the sound wave
Implementation Method 2
a frequency scanning phenomenon in which a sound wave is emitted in a beam splitting type rather than a beam type while being distributed in a forward direction and a backward direction in another specific frequency domain is caused
Implementation Method 3
a holographic-based directional audio device 10 that has a holographic meta-surface 11 formed on the surface of a flat plate 10 and can emit a sound wave at a predetermined angle has been developed
Data Source
AI summary
Proposed is a holographic-based directional audio device capable of sound wave scanning to adjust an emission angle of a sound wave through a frequency change of the sound wave. The holographic-based directional audio device includes a sound wave generator configured to generate the sound wave, a flat plate positioned at a side of the sound wave generator, and a holographic meta-surface composed of a plurality of unit cells, each of which comprises a plurality of grooves formed on a surface of the flat plate and which is continuously arrayed, and configured to emit the sound wave.