| Author: | Shen, Yunlu |
| Title: | An investigation of low frequency noise and airflow effects due to wind past a duct |
| Degree: | M.Sc. |
| Year: | 2012 |
| Subject: | Air ducts -- Noise. Fluid dynamics. Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Structural Engineering |
| Pages: | xiv, 81 leaves : ill. (some col.) ; 30 cm. |
| Language: | English |
| Abstract: | Low frequency sound or infrasound is the sound below 20 Hz, which is often inaudible by human; somehow, it may be annoying and causing discomfort to exposed persons depending on the duration. In general, for sound pressure levels that present in our everyday life, the low-frequency effects are not shown to be significant in terms of causing long-term physiological damage. However, the sound pressure level over 120 dB will cause discomfort, mainly nausea due to periodic movement of the stomach and other organs of the body. In the progress of the study, I have started to work on measuring the noise levels for different types of ducts and further discussed the effects of ventilation for each duct as well. The cavity resonance is the most important factor that generates the low frequency noise, and its frequency is dependent on the length of duct and opening area of that. I attempt to alleviate the noise generation and increase the wind velocity inside and outside of chamber by reducing the resistance of wind flowing to the duct near the opening area. During the experiment, the airflow path is been proved as the key to deal with the problem of wind resistance. Inspired by Dr. Ng, I have designed a new shape of duct to guide the wind flow into the room in a smooth way, and the air flow path is expected to be streamlined with less resistance force. Based on the experiment data, it indicates that the sound press levels of new duct are slightly lower than that of current duct at low frequency range, and the wind velocity of inside room is increased as well. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b25515044.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 4.19 MB | Adobe PDF | View/Open |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/6855