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Aniruddha Natekar
Sales Application Engineering Commercial Gensets - America
Cummins Power Generation
(800) 888-6626
Ani began working at Cummins Power Generation in 2007. His role in the sales application engineering department entails providing technical recommendations on installations amongst other mechanical considerations, providing application engineering support...more»»
Muffler noise
Posted by Michael from San Diego, CA, US on December 1, 2009
If I have a muffler with a higher level of sound attenuation, my system noise should be lower, right?
Not necessarily. Exhaust is just one of the main sub systems which account for total noise levels. Radiator fan and the mechanical noise from the engine follow suit. With a higher grade muffler, the exhaust noise will be reduced but unless the other sources of noise are addressed, the total sound levels may not change. The goal for any system designer should be to reduce the sound level for the entire system and not just a particular component.
Definition of decibels
Posted by Marlyn from Chicago, IL, US on December 1, 2009
Is there more than one definition for decibels?
There are two dB scales: A and L. • The dB(L) unit is a linear scale that treats all audible frequencies as having equal value. However, the human ear does not experience all sound frequencies as equally loud. The ear is particularly sensitive to frequencies in the range of 1,000 to 4,000 Hertz (cycles per second), and not as sensitive to sounds in the lower or higher frequencies. • Therefore, the “A-weighting filter,” which is an approximation of loudness, is used to correct the sound pressure levels to more accurately reflect what the human ear perceives. This frequency-weighting results in the dB(A) scale, which was adopted by OSHA in 1972 as the official regulated sound level descriptor.
Noise
Posted by Gary from Albany, NY, US on December 1, 2009
What exactly is noise?
Sound is what the human ear hears; noise is simply unwanted sound. Sound is produced by vibrating objects and reaches the listener’s ear as pressure waves in the air or other media. Sound is technically a variation in pressure in the region adjacent to the ear. When the amount of sound becomes uncomfortable or annoying, it means that the variations in air pressure near the ear have reached too high an amplitude. The human ear has such a wide dynamic range that the decibel (dB) scale was devised to express sound levels. The dB scale is logarithmic because the ratio between the softest sound the ear can detect and the loudest sound it can experience without damage is roughly a million to one or 1:106. By using a base-10 logarithmic scale, the whole range of human hearing can be described by a more convenient number that ranges from 0 dB (threshold of normal hearing) to 140 dB (the threshold of pain).
