1507 Experimental study of various silencers applicable to natural ventilation holes (Evaluations by transmission loss and insertion loss)

2012 ◽  
Vol 2012.49 (0) ◽  
pp. 150701-150702
Author(s):  
Toru MIYAIRI ◽  
Shuichi SAKAMOTO ◽  
Seiya TATSUZA ◽  
Kensaku YANAGIMOTO ◽  
Seiji WATANABE
Keyword(s):  
Experimental Study ◽  
Insertion Loss ◽  
Natural Ventilation ◽  
Transmission Loss

Acoustic Performance of Louvred Facades for Brisbane Domestic Airport: An Integrated Approach

2012 ◽  
Author(s):  
Frank Butera ◽  
Keith Hewett
Keyword(s):  
Natural Ventilation ◽  
Transmission Loss ◽  
Internal Noise ◽  
Building Design ◽  
Integrated Approach ◽  
External Noise ◽  
Climatic Conditions ◽  
Sustainable Building ◽  
Heating And Cooling ◽  
Airport Terminals

Maximising cross ventilation is a low energy method of naturally ventilating and providing heating and cooling to deep plan spaces. Significant reduction in the emission of greenhouse gases can be achieved through minimising the use of mechanical systems in regions with climatic conditions that support the use of natural ventilation. Arup has provided input into the design of a louvered facade for the control of external noise for Brisbane Domestic Airport. A full scale prototype facade was constructed and noise transmission loss measurements were undertaken. The results indicate that significant noise reduction can be achieved to enable compliance with the internal noise limits for airport terminals, whilst using natural ventilation. The findings from this research will directly benefit building designers and innovators in the pursuit of achieving sustainable building design.

Assessing the Effects of Impedance Modifications Using the Moebius Transformation

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Y. Zhang ◽  
D. W. Herrin
Keyword(s):  
Insertion Loss ◽  
Transmission Loss ◽  
Mechanical Systems ◽  
Mechanical Impedance ◽  
Harmonic Excitation ◽  
Complex Domain ◽  
Moebius Transformation ◽  
Straight Lines

The Moebius transformation maps straight lines or circles in one complex domain into straight lines or circles in another. It has been observed that the equations relating acoustic or mechanical impedance modifications to responses under harmonic excitation are in the form of the Moebius transformation. Using the properties of the Moebius transformation, the impedance modification that will minimize the response at a particular frequency can be predicted provided that the modification is between two positions. To prove the utility of this method for acoustic and mechanical systems, it is demonstrated that the equations for calculation of transmission and insertion loss of mufflers, insertion loss of enclosures, and insertion loss of mounts are in the form of the Moebius transformation for impedance modifications. The method is demonstrated for enclosure insertion loss by adding a short duct in a partition introduced to an enclosure. In a similar manner, it is shown that the length or area of a bypass duct in a muffler can be tuned to maximize the transmission loss. In the final example, the insertion loss of an isolator system is improved at a particular frequency by adding mass to one side of the isolator.

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