Active Muffler Duct for Server Chassis Noise Reduction
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Solution Overview
Problem
Conventional passive noise control methods are ineffective and costly for reducing low-frequency noise in blade chassis, particularly from cooling fans, which can exceed safety standards and pose health risks.
Innovation Solution
A server chassis system incorporating an active muffler that combines passive noise reduction using barrier and absorbing materials with active noise control (ANC) technology, where an ANC system senses noise, generates an anti-noise signal, and adjusts fan/blower speeds to minimize noise levels, effectively reducing noise across various frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive noise control methods (absorptive materials, partitions, enclosures) are used to reduce low-frequency noise, then noise attenuation is achieved, but the solution becomes bulky, expensive, and ineffective
Solution Approach 1:
The patent replaces passive mechanical noise control systems (absorptive materials, partitions, enclosures) with an active electronic control system. The active noise control system uses microphones to sense noise, electronic controllers to process signals, and loudspeakers to generate antinoise, substituting the bulky passive mechanical approach with a more compact electronic system that is particularly effective at low frequencies.
Solution Approach 2:
The patent changes the fundamental approach from passive static noise control to active dynamic control. By using electronic controllers that can adaptively adjust the antinoise signal parameters (amplitude, phase, frequency) in real-time based on sensed noise characteristics, the system achieves effective low-frequency noise reduction without the bulk and cost of traditional passive methods.
2Object-affected harmful factors
If active noise control is used to reduce low-frequency noise, then noise reduction efficiency improves and cost decreases, but system complexity increases
Solution Approach 1:
The patent introduces an electronic controller as an intermediary between the noise sensing (microphone) and noise cancellation (loudspeaker). This intermediary processes the noise signal, generates the appropriate antinoise signal, and drives the loudspeaker, thereby managing the system complexity through a dedicated control unit rather than requiring complex integration of all components.
Solution Approach 2:
The patent implements a feedback mechanism where an error microphone senses the residual noise and feeds this information back to the electronic controller. The controller uses this feedback to continuously adjust and optimize the antinoise signal, improving noise reduction effectiveness while managing system complexity through adaptive control rather than requiring overly complex predetermined systems.
3Temperature
If fan speed is increased to maintain heat dissipation, then cooling performance improves, but noise level increases
Solution Approach 1:
The patent converts the harmful noise generated by the fan into a useful signal for control. The microphone senses the fan noise, the electronic controller processes it to generate antinoise, and the loudspeaker emits this antinoise to cancel the fan noise. This allows the fan to operate at higher speeds for better heat dissipation while the generated noise is simultaneously used as the target for active cancellation.
Solution Approach 2:
The patent applies preliminary anti-action by generating the antinoise signal in advance to counteract the fan noise. The electronic controller continuously generates the antinoise signal that is phase-opposite to the expected fan noise, preventing the noise from propagating rather than merely reacting to it after generation. This allows the fan to operate efficiently without the noise penalty.
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 system achieves up to 10 dBA reduction in separated tones and 5 dBA in frequency noise, providing a more efficient and cost-effective solution compared to traditional passive methods while maintaining heat dissipation capabilities.
Implementation Method 1
It is based on the principle of superposition of sound waves. Generally, sound is a wave is travelling in space. If another, second sound wave having the same amplitude but opposite phase to the first sound wave can be created, the first wave can be totally cancelled.
Implementation Method 2
an acoustic sensor (typically a microphone) to sense the noise energy and/or wave amplitude of a noise pattern produced by a noise source
Implementation Method 3
Passive noise control technology, which usually involves using absorptive materials or noise partitions, enclosures, barriers and silencers
Data Source
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AI summary
An Active Muffler in the form of a duct having two open ends for conveying air from a within a cabinet to outside the cabinet. A fan or blower is incorporated in the duct. An Automatic Noise Control (ANC) unit is associated with the duct, and at least one microphone and at least one speaker are incorporated in to the duct for noise-reduction. An outer portion of the duct may be sound-absorbing material. the ANC unit may cause noise to be shifted to a frequency that can be absorbed by the sound-absorbing material.