MEMS Microphone Back Volume Apertures for Frequency Response Shaping
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Solution Overview
Problem
MEMS microphones exhibit non-uniform sensitivity across various frequencies, failing to meet performance specifications due to inconsistent frequency response.
Innovation Solution
The acoustic sensor assembly incorporates a housing with a back volume divided into two portions, acoustically coupled by one or more apertures that shape the frequency response by varying acoustic impedance, allowing for increased or decreased sensitivity at specific frequencies through aperture configuration and placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional MEMS microphone structure is used, then the device achieves low cost and small size, but the frequency response is non-uniform and sensitivity varies across frequencies
Solution Approach 1:
The back volume of the housing is divided into two separate portions (first back volume portion and second back volume portion) that are acoustically coupled through apertures. This segmentation allows independent acoustic treatment of each portion, enabling frequency response shaping while maintaining a relatively simple overall housing structure.
Solution Approach 2:
Apertures are strategically positioned and sized in specific locations within the housing to create localized acoustic impedance variations. These apertures are configured to provide different acoustic properties at different frequencies, allowing sensitivity adjustment at specific frequency ranges without affecting the entire frequency spectrum uniformly.
2Manufacturing precision
If the back volume is increased to improve low-frequency response, then sensitivity at low frequencies improves, but the overall device size increases
Solution Approach 1:
The second back volume portion is positioned adjacent to and acoustically coupled with the first back volume portion through apertures in the housing walls. This nested arrangement allows the acoustic benefits of a larger total back volume to be achieved while keeping the physical footprint compact, as the two portions are efficiently packed within the housing boundaries.
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
This configuration enhances the frequency response of MEMS microphones, improving sensitivity at desired frequencies, thereby meeting performance specifications and providing more desirable acoustic performance.
Implementation Method 1
One or more apertures acoustically couple the first and second portions of the back volume and are structured to shape a frequency response of the acoustic sensor assembly
Data Source
AI summary
An acoustic sensor assembly includes a housing having an external-device interface and a sound port to an interior of the housing. An electro-acoustic transducer and an electrical circuit are disposed within the housing. The electro-acoustic transducer separates the interior into a front volume and a back volume, where the sound port acoustically couples the front volume to an exterior of the housing. The back volume includes a first portion and a second portion. The electrical circuit is electrically coupled to the electro-acoustic transducer and to the external-device interface. One or more apertures acoustically couple the first and second portions of the back volume and are structured to shape a frequency response of the acoustic sensor assembly.