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Sound Power Level
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time. It is defined as "through a surface, the product of the sound pressure, and the component of the particle velocity, at a point on the surface in the direction normal to the surface, integrated over that surface." The SI unit of sound power is the watt (W). It relates to the power of the sound force on a surface enclosing a sound source, in air. For a sound source, unlike sound pressure, sound power is neither room-dependent nor distance-dependent. Sound pressure is a property of the field at a point in space, while sound power is a property of a sound source, equal to the total power emitted by that source in all directions. Sound power passing through an area is sometimes called ''sound flux'' or ''acoustic flux'' through that area. Sound power level ''L''WA Regulations often specify a method for measurement that integrates sound pressure over a su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Energy
In physics, sound energy is a form of energy that can be heard by living things. Only those waves that have a frequency of 20 Hz to 20 kHz are audible to humans. However, this range is an average and will slightly change from individual to individual. Sound waves that have frequencies below 20 Hz are called infrasonic and those above 20 kHz are called ultrasonic. Sound is a longitudinal mechanical wave and as such consists physically in oscillatory elastic compression and in oscillatory displacement of a fluid. Therefore, the medium acts as storage for both potential and kinetic energy. Consequently, the sound energy in a volume of interest is defined as the sum of the potential and kinetic energy densities integrated over that volume: :W = W_\mathrm + W_\mathrm = \int_V \frac\, \mathrmV + \int_V \frac\, \mathrmV, where *''V'' is the volume of interest; *''p'' is the sound pressure; *''v'' is the particle velocity; *''ρ''0 is the density of the medium wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbofan
A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust. The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Engines that use more Propel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alarm Clock
An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or short naps; they can sometimes be used for other reminders as well. Most alarm clocks make sounds; some make light or vibration. Some have sensors to identify when a person is in a light stage of sleep, in order to avoid waking someone who is deeply asleep, which causes tiredness, even if the person has had adequate sleep. To turn off the sound or light, a button or handle on the clock is pressed; most clocks automatically turn off the alarm if left unattended long enough. A classic analog alarm clock has an extra Clock face, hand or inset dial that is used to show the time at which the alarm will ring. Alarm clock functions are also used in mobile phones, watches, and computers. Many alarm clocks have radio receivers that can be set to start playing at specified times, and are know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diesel Engine
The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compression (physics), compression; thus, the diesel engine is called a compression-ignition engine (CI engine). This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine (gasoline engine) or a gas engine (using a gaseous fuel like natural gas or liquefied petroleum gas). Introduction Diesel engines work by compressing only air, or air combined with residual combustion gases from the exhaust (known as exhaust gas recirculation, "EGR"). Air is inducted into the chamber during the intake stroke, and compressed during the compression stroke. This increases air temperature inside the Cylinder (engine), cylinder so that atomised diesel fuel injected into the combustion chamber ignites. The torque a dies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapid Transit
Rapid transit or mass rapid transit (MRT) or heavy rail, commonly referred to as metro, is a type of high-capacity public transport that is generally built in urban areas. A grade separation, grade separated rapid transit line below ground surface through a tunnel can be regionally called a subway, tube, metro or underground. They are sometimes grade-separated on elevated railways, in which case some are referred to as el trains – short for "elevated" – or skytrains. Rapid transit systems are usually electric railway, electric railways, that unlike buses or trams operate on an exclusive right-of-way (transportation), right-of-way, which cannot be accessed by pedestrians or other vehicles. Modern services on rapid transit systems are provided on designated lines between metro station, stations typically using electric multiple units on railway tracks. Some systems use rubber-tyred metro, guided rubber tires, magnetic levitation (''maglev''), or monorail. The stations typica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lawn Mower
A lawn mower (also known as a grass cutter or simply mower, also often spelled lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a lawn, grass surface to an even height. The height of the cut grass may be fixed by the mower's design but generally is adjustable by the operator, typically by a single master lever or by a mechanism on each of the machine's wheels. The blades may be powered by manual force, with wheels mechanically connected to the cutting blades so that the blades spin when the mower is pushed forward, or the machine may have a Battery (electricity), battery-powered or AC power plugs and sockets, plug-in electric motor. The most common self-contained power source for lawn mowers is a small four-stroke engine, 4-stroke (typically Single-cylinder engine, one-cylinder) internal combustion engine. Smaller mowers often lack any form of self-propulsion, requiring human power to move over a surface; "walk-behind" mowers are self-propelled, re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorcycle
A motorcycle (motorbike, bike; uni (if one-wheeled); trike (if three-wheeled); quad (if four-wheeled)) is a lightweight private 1-to-2 passenger personal motor vehicle Steering, steered by a Motorcycle handlebar, handlebar from a saddle-style seat. Motorcycle designs vary greatly to suit a range of different purposes: Long-distance motorcycle riding, long-distance travel, Motorcycle commuting, commuting, cruising (driving), cruising, Motorcycle sport, sport (including Motorcycle racing, racing), and Off-roading, off-road riding. Motorcycling is riding a motorcycle and being involved in other related social activities such as joining a motorcycle club and attending motorcycle rally, motorcycle rallies. The 1885 Daimler Reitwagen made by Gottlieb Daimler and Wilhelm Maybach in Germany was the first internal combustion, petroleum-fueled motorcycle. In 1894, Hildebrand & Wolfmüller became the first series production motorcycle. Globally, motorcycles are comparable numerically t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chain Saw
A chainsaw (or chain saw) is a portable handheld power saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. Modern chainsaws are typically gasoline or electric and are used in activities such as tree felling, limbing, bucking, pruning, cutting firebreaks in wildland fire suppression, harvesting of firewood, for use in chainsaw art and chainsaw mills, for cutting concrete, and cutting ice. Precursors to modern chainsaws were first used in surgery, with patents for wood chainsaws beginning in the late 19th century. A chainsaw comprises an engine, a drive mechanism, a guide bar, a cutting chain, a tensioning mechanism, and safety features. Various safety practices and working techniques are used with chainsaws. History In surgery A "flexible saw", consisting of a fine serrated link chain held between two wooden handles, was pioneered in the late 18th century (–1785) by two Scottish doctors, John Aitken and James Jeffray, for symp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rock Concert
A rock concert is a performance of rock music. During the 1950s, several American musical groups experimented with new musical forms that fused country music, blues, and swing genre to produce the earliest examples of "rock and roll." The coining of the phrase, "rock and roll," is often attributed to American, Alan Freed, a disk jockey and concert promoter who organized many of the first major rock concerts. Since then, the rock concert has become a staple of entertainment not only in the United States, but around the world. Bill Graham is widely credited with setting the format and standards for modern rock concerts. He introduced advance ticketing (and later computerized, online tickets), introduced modern security measures (a reaction to the deaths at the Altamont concert) and had clean toilets and safe conditions in large venues. Rock concerts are often associated with certain kinds of behavior. Dancing, shouting, singing along with the band, and ostentatious displays b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonic Boom
A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to the human ear. The crack of a supersonic bullet passing overhead or the crack of a bullwhip are examples of a small sonic boom. Sonic booms due to large supersonic aircraft can be particularly loud and startling, tend to awaken people, and may cause minor damage to some structures. This led to the prohibition of routine supersonic flight overland. Although sonic booms cannot be completely prevented, research suggests that with careful shaping of the vehicle, the nuisance due to sonic booms may be reduced to the point that overland supersonic flight may become a feasible option. A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from the supersonic objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thunder
Thunder is the sound caused by lightning. Depending upon the distance from and nature of the lightning, it can range from a long, low rumble to a sudden, loud crack. The sudden increase in temperature and hence pressure caused by the lightning produces rapid Thermal expansion, expansion of the air in the path of a Lightning strike, lightning bolt. In turn, this expansion of air creates a Shock wave, sonic shock wave, often referred to as a "thunderclap" or "peal of thunder". The scientific study of thunder is known as ''brontology'' and the irrational fear (phobia) of thunder is called ''brontophobia''. Etymology The ''d'' in Modern English ''thunder'' (from earlier Old English ''þunor'') is epenthetic, and is now found as well in Modern Dutch ''donder'' (cf. Middle Dutch ''donre''; also Old Norse ''þorr'', Old Frisian ''þuner'', Old High German ''donar'', all ultimately descended from Proto-Germanic *''þunraz''). In Latin the term was ''tonare'' "to thunder". The name of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symphony Orchestra
An orchestra (; ) is a large instrumental ensemble typical of classical music, which combines instruments from different families. There are typically four main sections of instruments: * String instruments, such as the violin, viola, cello, and double bass * Woodwinds, such as the flute, oboe, clarinet, bassoon, and occasional saxophone * Brass instruments, such as the French horn (commonly known as the "horn"), trumpet, trombone, cornet, and tuba, and sometimes euphonium * Percussion instruments, such as the timpani, snare drum, bass drum, cymbals, triangle, tambourine, tam-tam and mallet percussion instruments Other instruments such as the piano, harpsichord, pipe organ, and celesta may sometimes appear in a fifth keyboard section or may stand alone as soloist instruments, as may the concert harp and, for performances of some modern compositions, electronic instruments, and guitars. A full-size Western orchestra may sometimes be called a or philhar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
