When an engine runs, hig pressure exhaust gas is released. This causes a pressure wave in the air causing and explosion very fast to form a steady noise. These are two group low frequency from 50 HZ to 500 HZ. To reduce the noise, the engine exhaust is connect to exhaust pipe to the silencer it is also called as muffler in automobile vehicles. In the muffler the gases or the polluted air are allowed to expand gradually and to cool.
There are various type of mufflers they are explained as below. Baffle Type Muffler: In this type of muffler there will be number of plates that are arranged alternatively to reduce the speed and temperature of the gases which pass through it. Wave Cancellation Muffler In this type there will be two and more path for the exhaust gases to pass through0the muffler. As the lenght of the path increases the temperature and speed decreases and reduces the noise. Resonance Type Muffler: In this type of muffler it consists many number of helmholtz resonators in series, through which a pipe containing access ports passes. Richard clayderman piano music. These resonators reduces the noises when the gases pass through. Absorber Type Muffler: This type of muffler contains sound absorbing particles like fiber glass and other fine particles which are placed in the case around the perforated tube through which the exhaush gases pass.
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These particles absorbs the sounds and temperature by the increse in size of the air passing through pipe. These are the basic explaination for the muffler working and these are the types of mufflers. By technology these types of mufflers are designed in advanced way now a days. There will two mufflers in heavy vehicles named as pre-silencer and post-silencer all silencer work under basic principle of reducing sound and temperature by increasing the flow of gases or by particles which absorbs the sound and temperature. I have attached an image which is drawn roughly open it and zoom to view the types. Regards, Stephen Raj.
Each cylinder in automobile emits waste gases in form of pulsating waves and sets up pressure waves in the exhaust system-exhaust port. The manifold is having average pressure levels higher than the atmospheric which depends on the engine speed and load. On extreme speeds and loads, the exhaust manifold attains pressures above atmospheric pressure.
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These pressure waves travel at speed of the sound and relative to the moving exhaust gas, which in turn exits with a high velocity creating an objectionable exhaust boom or noise. Exhaust silencer or muffler can be designed suitably and is accomplished the muffling of this exhaust noise. The basic principle is based on a few principles of physics. The velocity of sound is directly proportional to the square root of the product of the pressure and the ratio of the specific heats and inversely to the square root of the density of the gas. When the temperature is varied, the velocity also changes directly as the temperature by thermal expansion of the gas and the temperature. The noise can be reduced considerably by providing resonance chambers.