Microphone Sound Channel Geometry for Wider Frequency Detection
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Solution Overview
Problem
Existing acoustic devices using Helmholtz resonators narrow the frequency band of sound detection due to the formation of an acoustic low-pass filter, limiting the range of sounds that can be detected by the microphone.
Innovation Solution
The acoustic device features a sound collecting space with a uniform cross-sectional shape and area in front of the microphone, eliminating the formation of a Helmholtz resonator and utilizing a 1/4 wavelength resonator pipe to expand the detectable frequency band, while ensuring easy assembly and protection against dust and moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a Helmholtz resonator is formed with a small sound-collecting hole and a space in front of the microphone, then the acoustic device can be compact, but the frequency band of sound detection is narrowed due to acoustic low-pass filter effect
Solution Approach 1:
The invention extracts the harmful Helmholtz resonator structure from the acoustic device. By making the sound collecting space extend to the front end of the housing and eliminating the small sound-collecting hole configuration, the Helmholtz resonator is removed, thereby eliminating the acoustic low-pass filter effect that narrows the frequency band while maintaining compact device size
Solution Approach 2:
Instead of creating a Helmholtz resonator with a small sound-collecting hole and enclosed space, the invention inverts the approach by making the sound collecting space open to the front end of the housing. This inversion transforms the acoustic characteristics from low-pass filter behavior to a structure that preserves wide frequency band detection capability
2Ease of manufacture
If a non-uniform cross section sound collecting space is used, then assembly may be simpler, but the acoustic characteristics are compromised and frequency band is narrowed
Solution Approach 1:
The invention applies local quality by ensuring the sound collecting space has a uniform cross-sectional area along its length. This uniform cross-section is a specific local characteristic that prevents Helmholtz resonator formation and maintains wide frequency band detection, while the overall simple structure keeps manufacturing and assembly easy
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 device achieves a wider frequency band of sound detection, maintains compact size, and facilitates simple assembly with precise positioning of the microphone and sound collecting space, while preventing dust and moisture ingress.
Implementation Method 1
utilizing a 1/4 wavelength resonator pipe to expand the detectable frequency band
Implementation Method 2
a thin film having a thickness sufficient for use in an electro-acoustic transducer is formed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An acoustic device that includes: a support; and a microphone. The microphone is supported by the support. A sound collecting space is formed in front of the microphone. A front end of the sound collecting space is a sound collecting hole communicating with an external space. A shape of a cross section of the sound collecting space taken in a direction perpendicular to a center line extending in a longitudinal direction is uniform.