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resistors: the braking resistors of electric trains, used to dissipate electrical power when the catenary is not receptive during braking, can make electromagnetically induced acoustic noise; coils: in magnetic resonance imaging, "coil noise" is that part of total system noise attributed to the receiving coil, due to its non-zero temperature.
Mains hum, electric hum, cycle hum, or power line hum is a sound associated with alternating current which is twice the frequency of the mains electricity. The fundamental frequency of this sound is usually double that of fundamental 50/60 Hz , i.e., 100/120 Hz, depending on the local power-line frequency .
One local couple sued the power company for the disruption the hum was causing them. [27] The hum was louder inside their house than out, in part, they believed, because their house vibrated in resonance to the 60 Hz hum. In the lawsuit they claimed that the volume of the hum was measured at up to 64.1 dB in the couple's home. [28]
Schematic of a vacuum sewer system A vacuum toilet at Lau Fau Shan Roundabout in Hong Kong A portable vacuum sewer system on the underside of a train carriage, serving the vacuum toilet and sink inside the train. A vacuum sewer or pneumatic sewer system is a method of transporting sewage from its source to a sewage treatment plant.
An acoustic cleaning horn on material handling equipment. Acoustic cleaning is a maintenance method used in material-handling and storage systems that handle bulk granular or particulate materials, such as grain elevators, to remove the buildup of material on surfaces.
The result is a wide-bandwidth high-power source. Conventional diodes can be used in breakdown. The avalanche breakdown also has multistate noise. The noise output power randomly switches among several output levels. Multistate noise looks somewhat like flicker ( ) noise. The effect is process dependent, but it can be minimized.
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Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, [1] [3] which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.