Fiber Microphone for Directional Acoustic Sensing
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Solution Overview
Problem
Current miniature microphones face challenges in achieving directional sound sensing due to limitations in frequency response, noise, sensitivity matching, and size, particularly in hearing aids, where they rely on pressure detection and require bias voltage and external power, limiting their ability to provide directional output independent of frequency and requiring multiple spatial locations for sound sampling.
Innovation Solution
A fiber microphone that detects acoustic particle velocity rather than pressure, using a thin fiber subjected to viscous drag in a magnetic field to induce a voltage, allowing for directional output without frequency dependence and external power, and can be designed as a nano-scale, low-cost, passive sensor with flat frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional miniature microphones use pressure detection with bias voltage and external power, then they can achieve sound sensing, but they face limitations in frequency response, noise, sensitivity matching, and size, and require multiple spatial locations for directional output
Solution Approach 1:
The patent extracts the directional sensing capability from complex multi-microphone arrays and implements it in a single microphone element. The fiber optic sensor detects acoustic particle velocity directly, eliminating the need for multiple spatial sampling locations and complex signal processing required by conventional pressure-detection-based directional microphones
Solution Approach 2:
The patent replaces the conventional electrical pressure detection system with an optical detection system. Fiber optic sensors detect acoustic particle velocity through optical means, substituting electrical bias voltage and power requirements with optical interrogation, thereby reducing electrical complexity and improving frequency response
2Adaptability or versatility
If conventional microphones rely on pressure detection requiring bias voltage and external power, then they can operate, but they cannot provide directional output independent of frequency and require external power sources
Solution Approach 1:
The fiber optic microphone is self-service in terms of power requirements. The optical sensor detects acoustic particle velocity passively without requiring external bias voltage or power sources. The system uses the acoustic field itself to modulate the optical signal, enabling directional output independent of frequency without external power
Solution Approach 2:
The patent substitutes electrical power and bias voltage requirements with optical detection. The fiber optic sensor converts acoustic particle velocity directly into optical signal variations, eliminating the need for electrical power sources and enabling frequency-independent directional sensing
3Volume of moving object
If miniature microphones are reduced in size for hearing aids, then they can be miniaturized, but they face challenges in noise floor, sensitivity, and directional sensing capability
Solution Approach 1:
The patent replaces conventional electrical microphone transduction with optical detection using fiber optic sensors. This substitution eliminates electrical noise sources and enables miniaturization without compromising noise floor performance, as optical detection is inherently more resistant to electromagnetic interference and can be implemented at smaller scales
Solution Approach 2:
The patent changes the detection parameter from acoustic pressure to acoustic particle velocity. This parameter change enables superior noise performance and directional sensing in miniaturized configurations, as particle velocity detection is less susceptible to noise and can be effectively implemented in compact fiber optic sensor designs
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 fiber microphone provides a directional output that is independent of frequency, with a noise floor of 30 dBA and directivity index of 4.8 dB over the audible range, enabling improved speech intelligibility in noisy environments and overcoming limitations of existing directional hearing aids.
Implementation Method 1
The thin fiber is held on its two ends and subjected to oscillating flow in the direction normal to its long axis as a result of viscous drag of a fluid medium that itself responds to vibrations.
Implementation Method 2
employing a magnetic field to induce a voltage across the conductive element as a result of oscillations within the magnetic field
Data Source
AI summary
A metamaterial comprising, a plurality of acoustic vector field sensors, each configured to sense an acoustic vector field of a fluid within a fluid-filled space in response to fluid waves, and producing an electrical signal corresponding to the sensed acoustic vector field; a processor configured to perform a time and space transform on the electrical signal; and at least one phased array transducer, configured to emit fluid waves according to a produced acoustic vector field pattern dependent on a result of the time and space transform, a within a portion of the fluid.