Condenser Microphone Aeration Hole Sound-Absorbing Filter
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Solution Overview
Problem
Conventional condenser microphones struggle to detect faint Korotkoff sounds with high sensitivity under fluctuating pressure conditions, such as those found in blood pressure cuff measurements, due to noise pickup from the conduit wall and difficulty in maintaining airtightness and pressure equivalence.
Innovation Solution
A condenser microphone design featuring a diaphragm and backplate with an aeration hole in the housing and a sound-absorbing filter on one surface, which absorbs unwanted frequency bands, allowing only targeted sound waves to reach the diaphragm, and a microphone unit with a sealant and configurational markings for easy assembly and terminal identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the microphone is disposed at the end opening of the conduit to detect Korotkoff sounds, then the detection sensitivity is improved, but the airtightness of the conduit cannot be maintained and pressure fluctuation cannot be applied to the microphone
Solution Approach 1:
The end wall of the conduit is segmented into multiple holes, allowing the microphone to be positioned at the end opening while maintaining airtightness. The holes provide acoustic access while the surrounding wall structure maintains the seal.
Solution Approach 2:
A microphone holder is introduced as an intermediary component that positions the microphone at the end opening while maintaining the airtight seal. The holder acts as a mediator between the acoustic detection requirement and the airtightness requirement.
2Reliability
If the microphone is disposed to contact the end wall of the conduit, then the airtightness is maintained, but noise is picked up via the conduit wall and faint Korotkoff sounds cannot be identified
Solution Approach 1:
The microphone is extracted from direct contact with the conduit wall and positioned at the end opening instead. This removes the noise pickup path through the wall while maintaining acoustic access to Korotkoff sounds.
Solution Approach 2:
The microphone positioning is changed from a two-dimensional contact with the end wall surface to a three-dimensional position at the end opening, allowing acoustic access without wall contact and reducing noise pickup.
3Measurement precision
If a sound-absorbing filter is disposed to cover the opening or aeration hole, then unwanted frequency bands are absorbed and targeted sound waves are enhanced, but the device complexity increases
Solution Approach 1:
A sound-absorbing filter made of porous material is used to cover the opening or aeration hole. The porous structure naturally absorbs unwanted frequency bands while allowing targeted sound waves to pass, providing frequency selectivity without complex mechanical structures.
Solution Approach 2:
The sound-absorbing filter is integrated as a composite component that combines acoustic filtering functionality with the housing structure, reducing overall device complexity while achieving frequency selectivity.
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 enables high-sensitivity detection of Korotkoff sounds by canceling out low-frequency pressure fluctuations and allowing high-frequency sounds to be detected accurately, while maintaining an airtight state and simplifying assembly and terminal identification.
Implementation Method 1
a sound-absorbing filter having sound absorption characteristics with respect to a frequency band targeted for detection is disposed so as to cover the opening or aeration hole
Implementation Method 2
a condenser microphone that detects Korotkoff sounds by means of diaphragm vibration
Data Source
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AI summary
The present invention provides a condenser microphone capable of detecting small sounds (e.g., Korotkoff sounds) with high sensitivity even in environments with variations in pressure, such as cuff pressure. A condenser microphone (10) is disposed as an acoustic sensor for detecting Korotkoff sounds in a communication space reachable by the internal pressure of the cuff of a blood pressure gauge. In the condenser microphone, a diaphragm (13) and a backplate 14) are disposed in the interior of a housing (11), an aeration hole (30) is formed in a wall (11B) that blocks off the housing back surface, and a sound-absorbing element (20) having sound absorption characteristics with respect to a frequency band targeted for detection is disposed on the front surface of a housing (11).