Microphone Module with Shared Middle Sound Inlet
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microphone modules for hearing aids face challenges in maintaining directional hearing due to microphone mismatch and drift, particularly at low frequencies, and require complex manual matching and space-consuming designs.
Innovation Solution
A microphone module comprising a first directional microphone with a cardioid polar pattern and a second directional microphone with an anti-cardioid polar pattern, both sharing a middle sound inlet arrangement with acoustical resistance, which ensures robust directionality regardless of microphone mismatch and simplifies mechanical construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If matched pair of two omni-directional microphones are used to achieve directional hearing, then directional output can be generated, but the directivity degrades heavily due to mismatch and drift especially at low frequencies
Solution Approach 1:
The patent merges a cardioid microphone and an anti-cardioid microphone into a single module with shared acoustic volumes (front volume, rear volume, and middle volume). This integration ensures that both microphones experience identical acoustic environments and drift conditions, making their responses inherently matched regardless of manufacturing variations or environmental changes.
Solution Approach 2:
The patent introduces a middle sound inlet arrangement with acoustical resistance means that serves both the cardioid and anti-cardioid microphones. This shared middle volume acts as an intermediary that equalizes the acoustic pressure experienced by both microphones, compensating for any mismatches in their individual responses.
2Reliability
If manual matching and amplitude/phase correction are performed to achieve directional hearing, then directivity can be improved, but the production process becomes time consuming
Solution Approach 1:
The shared acoustic volume design makes the system self-matching. Both microphones automatically experience the same acoustic conditions and drift, eliminating the need for external matching procedures. The system self-corrects for environmental changes without requiring manual intervention during production or operation.
3Reliability
If Blumlein pair design with two directional microphones oriented at 90 degree angle is used, then directional hearing can be achieved, but the design becomes bulky and requires significant space
Solution Approach 1:
The patent combines two directional microphones (cardioid and anti-cardioid) that would traditionally be oriented at 90 degrees into a compact module where they share common acoustic volumes. This merging allows the microphones to be positioned much closer together, dramatically reducing the overall module size while maintaining directional hearing capability.
Solution Approach 2:
The patent implements a nested volume structure where the front volume, rear volume, and middle volume are acoustically coupled. The cardioid and anti-cardioid microphones are embedded within this nested acoustic architecture, allowing them to share acoustic pathways and reducing the physical space required compared to separate microphone placements.
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 module provides stable directional hearing unaffected by microphone mismatch and drift, especially at low frequencies, and achieves a compact design by sharing a common housing, enhancing the robustness and efficiency of directional signal output.
Implementation Method 1
a middle sound inlet arrangement being acoustically connected to the front and rear membranes, said middle sound inlet arrangement comprising acoustical resistance means arranged at least partly therein
Data Source
AI summary
The present invention relates to a microphone module comprising a first directional microphone comprising a front sound inlet and a front membrane, a second directional microphone comprising a rear sound inlet and a rear membrane, and a middle sound inlet arrangement being acoustically connected to the front and rear membranes, said middle sound inlet arrangement comprising acoustical resistance means arranged at least partly therein. The microphone module aims at generating a cardioid and an anti-cardioid response, or alternatively any other back-to-back polar patterns.