Mode of learning : Fulltime Class Room
Domain / Subject : Engineering & Technology
Function : General
Trainer name : Prof. Dhanesh N. Manik
Starts on : 17th Sep 2014
Duration : 3 Days
Difficulty : Advanced
Concerted efforts to reduce noise in machines started in the 1950s. Preventing noise induced hearing loss of factory workers was the main concern of these efforts. Due to the pioneering efforts of Paul Sabine in quantifying the acoustic absorption properties of materials used in auditoria during the beginning of 20th century, acoustic materials were extensively used to reduce noise in machinery. It resulted in band-aid measures like providing enclosures. Although enclosures were effective in reducing noise in machines, they presented difficulties in heat dissipation and maintenance, thus limiting their application to only certain machines. In addition, the enclosures were expensive and sometimes more expensive than the machines themselves.
The first launching of the manmade satellite, Sputnik, in 1957, sparked competition between many countries to build satellite launch vehicle structures. The electronics of the guidance systems used in these launch vehicles failed many times due to the acoustic noise and boundary layer noise generated at the time of launching. The traditional structural design techniques based on normal modes using natural frequencies and the corresponding modeshapes of structures was not useful in designing such space structures. Thus began extensive research into vibro- acoustics and random vibration that explained many phenomena of noise generation and its reduction at the source.
Now vibro-acoustics is extensively used to reduce noise in aerospace vehicles, ships, submarines, automobiles and machinery to reduce noise at the source, which is very effective in reducing noise at a nominal cost. Customer demands for quiet machines and stiff competition among manufacturers to produce such machines at a lesser cost have made vibro-acoustics an important body of knowledge that engineers need to be aware of.
The course begins with the fundamentals of vibration and noise. The concept of wave propagation is introduced that is a very important viewpoint in vibro-acoustics. This is followed by extensive discussion on random vibration, which is not only required for understanding the basics of vibration and noise measurement techniques but has applications in statistical energy analyis (SEA). Since most noise in machines is produced due to vibration by continuous systems, they are discussed next; important continuous systems discussed are: beams, plates and shells. Important noise sources like monopoles and dipoles are discussed, followed by room acoustics that relates sound pressure levels generated by machines within an enclosed space. Although noise can be produced by vibration, all vibration will not produce noise. This is a key element in preventing noise in machines by understanding the conditions under which vibration results in noise; this is discussed in the session on sound-structure interaction. Statistical energy analysis (SEA), which is an important vibro-acoustic technique in the high frequency range, is discussed in detail. Many practical examples are provided in the final sessions.
This is a Level 2 course that is meant for scientists and engineers who already have some knowledge of vibration and noise and have some exposure to its basics and, are already working on reducing vibration and noise. Those participants who attend the course must have a graduate degree in engineering with basic knowledge of mechanics, circuit theory, fluid mechanics and mathematics. This course is mainly useful to those who are interested in mathematical modeling of machines to reduce noise at the design stage.
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