Vibration Sensor Acoustic Low-Pass Filter Design
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Solution Overview
Problem
Existing vibration sensors have flat low-frequency response curves, leading to mechanical or electronic overload and signal distortion, and electronic filters introduce thermal noise and space constraints.
Innovation Solution
A vibration sensor with a predetermined low-frequency roll-off response curve achieved through acoustical impedance settings, using moveable masses, pressure transmitting arrangements, and pressure detection, without electronic means, to dampen low frequencies and prevent overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electronic filters are used to remove low frequencies, then low-frequency noise is reduced, but thermal noise increases and signal-to-noise ratio degrades
Solution Approach 1:
The patent replaces electronic filtering with an acoustic low-pass filter comprising a movable mass, pressure-transmitting arrangement, and pressure detection arrangement. This mechanical-acoustic system attenuates low frequencies before they reach the electronic signal processing stage, eliminating thermal noise from electronic filters while maintaining signal-to-noise ratio.
Solution Approach 2:
The patent introduces an acoustic low-pass filter as an intermediary between the vibration sensor and the electronic signal processing device. This intermediary attenuates low-frequency signals acoustically, preventing them from overloading the electronic system and eliminating the need for electronic filters that would otherwise degrade signal quality through thermal noise.
2Object-affected harmful factors
If electronic filters are used to remove low frequencies, then low-frequency noise is reduced, but valuable ASIC space is consumed
Solution Approach 1:
The patent replaces electronic filtering circuitry with a mechanical-acoustic low-pass filter system. By performing frequency attenuation in the acoustic domain rather than the electronic domain, the invention eliminates the need for additional electronic filter components on the ASIC, freeing up valuable chip space for other functional elements.
3Ease of operation
If low frequencies are not damped, then the sensor response is flat, but mechanical or electronic overload occurs
Solution Approach 1:
The patent applies frequency-dependent attenuation selectively to low frequencies while maintaining full sensitivity to higher frequencies. The acoustic low-pass filter is designed with specific geometric parameters (movable mass, pressure-transmitting arrangement dimensions) that create a cutoff frequency, allowing the sensor to have a flat response above this frequency while automatically attenuating lower frequencies to prevent overload.
4Strength
If low frequencies are removed electronically, then overload is prevented, but signal distortion occurs
Solution Approach 1:
The patent replaces electronic frequency removal with acoustic attenuation. The mechanical-acoustic low-pass filter naturally rolls off low frequencies through its physical design rather than abrupt electronic cutoff, avoiding phase distortion and signal degradation. This preserves signal integrity while preventing overload of the electronic system.
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 solution effectively damps low frequencies, avoiding electronic overload and thermal noise, while allowing signal amplification above predefined frequencies, enhancing signal-to-noise ratio and reducing mechanical resonance.
Implementation Method 1
a moveable mass being adapted to generate pressure variations in response to movements thereof
Implementation Method 2
a first acoustical opening defining a first acoustical impedance being acoustically connected to the pressure transmitting arrangement, the first acoustical impedance setting a predetermined low-frequency roll-off response of the vibration sensor
Data Source
Figure 1
Figure 2a~2d
Figure 3a~3b
AI summary
The present invention relates to a vibration sensor comprising a pressure detecting arrangement adapted to detect generated pressure variations, and provide an output signal in response to the detected pressure variations, and a pressure generating arrangement adapted to generate pressure variations in response to movements thereof wherein an intermediate volume exists between the pressure detecting arrangement and the pressure generating arrangement. In a preferred embodiment the pressure detecting arrangement comprises a stand-alone and self-contained MEMS microphone unit comprising a MEMS microphone cartridge and a signal processing unit.