Surveillance Microphone Diffraction Cover Plate
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Solution Overview
Problem
Surveillance microphones in jail rooms face issues with poor acoustics due to sound reflection and echo, leading to distortion and loss of important frequencies, especially between 250 Hz and 8,000 Hz, and are prone to tampering in security environments.
Innovation Solution
A diffraction cover plate with a specific pattern of openings is used to improve sound wave detection by an omnidirectional microphone, enhancing its directional stability and reducing frequency loss between 3,000 to 6,000 Hz, while also providing protection for the microphone components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a standard omnidirectional microphone is used in a surveillance room, then it can capture sound from all directions, but it suffers from poor acoustics including sound reflection, echo, and frequency loss between 250 Hz and 8,000 Hz
Solution Approach 1:
A diffraction cover plate is introduced as an intermediary component between the sound source and the microphone. The plate contains a specific pattern of openings that diffract sound waves before they reach the microphone, improving frequency response and reducing acoustic distortions while maintaining omnidirectional capture capability
Solution Approach 2:
The diffraction cover plate modifies the physical parameters of sound wave propagation by creating controlled diffraction patterns. The specific geometry and distribution of openings in the plate change the acoustic field characteristics, enhancing frequency detection in the critical 250 Hz to 8,000 Hz range
2Ease of operation
If a microphone is placed in a security environment like a jail room, then it can monitor conversations, but it is vulnerable to tampering and destruction
Solution Approach 1:
The microphone is nested within a protective housing that is mounted to the diffraction cover plate. This nested structure provides physical protection for the microphone components while maintaining the surveillance functionality, effectively shielding the device from tampering and destruction in security environments
3Area of stationary object
If multiple conversations and ambient sounds are present in a monitored space, then comprehensive coverage is achieved, but sound quality deteriorates due to noise from different frequencies
Solution Approach 1:
The diffraction cover plate creates localized acoustic zones through its pattern of openings. Each opening diffracts sound waves in specific patterns, creating regions of enhanced sound quality that improve intelligibility of primary conversations while managing ambient noise from different frequencies across the coverage area
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 enhances the microphone's coverage pattern and intelligibility by maintaining sound detection across a wider range of frequencies and angular positions, and the secure design prevents tampering by integrating with tamper-proof structures.
Implementation Method 1
a sound diffraction pattern of different sized openings placed through the cover plate; the sound diffraction pattern located in alignment to the mounted microphone head
Data Source
AI summary
An acoustic microphone assembly for surveillance into a protected space includes a microphone including a transducer and a diagram adapted for picking up acoustic sound waves, electronic circuitry for processing input, a power source, and an audio output wire or trace for delivering processed digital sound to a sound system, a cover plate having at least two bolt openings for mounting to a base plate on a wall or structure the cover plate covering an opening there through into the protected space, the cover plate accepting an orthogonal mounting of the microphone, and a sound diffraction pattern of different sized openings placed through the cover plate, the sound diffraction pattern located in alignment to the mounted microphone head and having a foot print roughly equal to the circumference of the head of the microphone.