Noise Reduction in a Cylindrical Shell

1966 ◽  
Vol 39 (6) ◽  
pp. 1254-1255 ◽  
Author(s):  
Jerome E. Manning
2011 ◽  
Vol 338 ◽  
pp. 406-410
Author(s):  
Fu Zhen Pang ◽  
Fu Bin Pang ◽  
Xu Chao Yin ◽  
Shuai Lv

This paper studies the influence of acoustic coating to the underwater sound radiation characteristic of a double hull cylindrical shell by the Statistical Energy Analysis (SEA) method. Influence of covering density and laying location of acoustic coating to the underwater sound radiation characteristic of the double hull cylindrical shell structure are discussed. Study shows that low covering density of acoustic coating will cause “sound leaking” phenomena, sound will leak out from the uncovered area of the double hull cylindrical hull structure and radiate into the surrounding water, which harms the underwater noise reduction performance of the acoustic coating; however, the noise reduction capacity of the acoustic coating improves gradually as the covering density increases. Besides, laying location of acoustic coating also impact the underwater sound radiation performance of the double hull cylindrical shell structure; inner hull covered with acoustic coating is better than the outer hull covered from the noise treatment point of view


2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Menghui Qi ◽  
Bin Li ◽  
Shilin Yan ◽  
Qinghua Yan ◽  
Qiyu He

To solve the problem of the harsh midlow frequency noise of rocket fairing, the cylindrical section of the protective precision instrument fairing is simplified as cylindrical shells, and different lining strategies of melamine foam (MF) are studied experimentally and numerically. Based on Virtual.Lab Acoustic software, a finite element model of the cylindrical cavity is established, and the correctness is verified by comparison with the measured data. On that basis, the influences of the lining position of different thickness MF on the noise reduction of cylindrical shells are investigated. It is shown that the thickness and location of the laying material have a significant effect on the noise reduction at the same specific gravity.


1993 ◽  
Vol 2 (1) ◽  
pp. 51-53 ◽  
Author(s):  
Ruth A. Bentler
Keyword(s):  

Author(s):  
О. Д. Донець ◽  
В. П. Іщук

The basic results of calculation and research works carried out in the process of creation of power unit of regional passenger airplanes’ family are given. The design features of the propulsion engines and engine of the auxiliary power plant are described. The aforementioned propulsion system includes propulsion engines D-436-148 and engine AI-450-MS of auxiliary power plant. In order to comply with the requirements of Section 4 of the ICAO standard (noise reduction of the aircraft in site), in part of ensuring the noise reduction of engines, when creating the power plant of the An-148/An-158 aircraft family, a single- and double-layer acoustic filler was used in the structure of the engine nacelle and air intake. The use of electronic system for automatic control of propulsion engines such as FADEC and its integration into the digital airborne aircraft complex ensured the operation of engines, included in the power plant provided with high specific fuel consumption, as well as increased the level of automation of the power plant control and monitoring, and ensured aircraft automation landing in ICAO category 3A. In addition, the use of the aforementioned electronic system, allowed to operate the power plant of the aircraft in accordance with technical status. The use of the AI-450-MS auxiliary power plant with an electronic control system such as FADEC, and the drive of the service compressor from a free turbine, eliminated the effect of changes in power and air takeoff, on the deviation of the engine from optimal mode, which also minimized the fuel consumption. The use of fuel metering system TIS-158, allowed to ensure control of its condition and assemblies, without the use of auxiliary devices, built-in control means. In the fire protection system, the use of the electronic control and monitor unit, as well as the use of digital serial code for the exchange of information between the elements of the system and the aircraft systems, has reduced the number of connections, which increased the reliability of the system and reduced its weight characteristics.


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