Active/Passive noise control

[leka]

Active/Passive noise control

hi everyone,
I am currently working on a project to reduce noise in AC/Heating systems in airplanes. As reference am using some literature in Engineering Noise Control and some research papers on Active/Passive noise control. I am currently searching for some information on; if there are materials that are good reflectors of sound at low frequencies, between 500Hz and 1KHz. The current aplication that have in mind calls for a sort of a muffler(closed ends pipe, from outside). Geometry and other parameters are not defined yet.
If anyone has any sources or knows any information related to mechanisms for noise reduction or have any ideas feel free to elaborate.

cheers

 

[Artman]

In your research you have probably already come across this, but I'll mention it just the same. Phase cancellation is an active form of noise reduction. You may want to check into that.

 

[ravenprp]

Active and passive noise control are two commonly used techniques to reduce noise levels in various environments. Both methods have their own advantages and limitations, and the choice of which to use depends on the specific application and noise source.

Passive noise control involves using materials or structures to absorb, reflect, or block sound waves. This can be achieved by using sound-absorbing materials, such as foam or fiberglass, to reduce the transmission of sound. It can also involve adding barriers or enclosures to block the sound from reaching the receiver. Passive noise control is typically less expensive and easier to implement compared to active noise control.

Active noise control, on the other hand, involves using electronic devices to actively cancel out noise waves. This is achieved by using microphones to detect the noise and then generating a counteracting sound wave to cancel it out. Active noise control is more complex and expensive, but it can be more effective in reducing low-frequency noise levels.

In your project to reduce noise in AC/Heating systems in airplanes, both active and passive noise control techniques can be used. For low-frequency noise reduction, passive noise control may be more suitable as it can effectively absorb or reflect sound waves. However, if the noise source is primarily at a specific frequency, active noise control may be more effective in cancelling it out.

In terms of materials that are good reflectors of sound at low frequencies, some commonly used materials include concrete, steel, and heavy curtains. However, the effectiveness of these materials also depends on the specific application and noise source. It may be helpful to consult with experts in the field or conduct some experiments to determine the best material for your specific project.

Overall, both active and passive noise control techniques have their own advantages and can be used in combination for maximum noise reduction. I hope this information helps in your project and I wish you success in finding the best solution for reducing noise in AC/Heating systems in airplanes.