Mindblown: a blog about philosophy.
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Effects of Leaks and Flanking Transmission
Leaks in a wall frequently occur in practice and are very serious. Unless great care is taken in construction, leaks will occur and the theoretical TL of a wall will not be achieved. This effect is particularly noticeable at high frequency where the TL of a wall would be expected to be high. In this region, a leak can…
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Transmission Through Composite Walls
Often partitions are composed of several different elements, such as a brick wall having windows and doors. The average transmission loss TLav of this composite structure can be calculated as follows: suppose τ1 is the transmission coefficient of element of area S1, etc. and that a diffuse reverberant sound field of intensity εc/4 (where ε is the energy density in the incident field…
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Sound and Vibration Transmission and Structural Response Using Statistical Energy Analysis (SEA)
12.4.1 Introduction Statistical Energy Analysis is often abbreviated to SEA. SEA was first used in the early 1960s to predict the vibration response of aerospace structures to acoustical environments and to determine the transmission of acoustical and vibrational energy in such structures [21–26]. Ungar, Eichler, Lyon, Maidanik, Smith, Scharton and Manning were some of the…
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Sound Transmission for Double and Multiple Panels
In order to achieve high TL with a minimum of weight, multiple panels with air spaces between the panels are usually employed. They are used in applications such as aircraft cabin walls and high‐rise buildings where weight savings are important. Higher TL is possible with a multiple‐panel than with a single‐panel partition (of the same mass per unit area),…
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Sound Transmission Theory for Single Panels
12.2.1 Mass‐Law Transmission Loss We will consider the case of a plane sound wave incident on a partition. For simplicity, we shall assume that the partition is thin (in wavelengths) and infinite in extent. For convenience, we assume that the x‐ and y‐axes are in the plane of the paper (see Figure 12.1) and that the direction of…
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Introduction
Buildings are very complex mechanical structures and are subjected to many external and internal sources of noise and vibration. The requirements of lightweight construction in new buildings have made these buildings more susceptible to noise and vibration‐related problems. Thus, occupants frequently complain about the levels of noise and vibration they experience. Internal sources of noise…
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Noise Control of Industrial Production Machinery
Production machinery and equipment that generate intense noise include machines that operate with impacts such as forging hammers [100, 101], cold headers, stamping presses, riveters, jolting tables, some machine tools, and impact‐generating assembly stations. With the exception of forging plants, in which forging hammers are the dominant source of noise, noise sources in manufacturing plants can…
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Noise Due to Fluid Flow
Valve‐Induced Noise Control valves are used in industrial plants to control the rate of fluid flow by creating a pressure drop across the valve. The flow is first accelerated by this process and then the kinetic energy is converted into thermal energy or heat through turbulence and/or shock waves. In the process a small fraction…
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Pumps
Pumps are used to transport liquids and suspensions of solid particles in hydraulic systems. The noise generated in such systems is produced not only by the pump but also by the driving motor (usually an electric motor with its cooling fan). The noise and vibration created is carried throughout the hydraulic system as fluid‐borne noise…
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Compressors
Compressors can be considered to be pumps for gases. Although there are some differences in construction details between compressors and pumps, their principles of operation, however, are essentially the same (see Section 11.3.4). Since gases normally have much lower densities than liquids, it is possible to operate compressors at much higher speeds than pumps. However, gases…
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