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Topic: Sound energy density

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Sound pressure level

Acoustics

	Sound energy density - Wikipedia, the free encyclopedia
		The sound energy density or sound density (symbol E or w) is an adequate measure to describe the sound field at a given point as a sound energy value.
		In opposite to the sound intensity I, which gives the sound energy per area A, the sound energy density E (also: sound density) describes the time medium value of the sound energy per volume unit; it gives information obout the sound energy which is at a definded place of room.
		In speaking of average energy density in general, it is necessary to distinguish between the space average (at a given instant) and the time average (at a given point).
	en.wikipedia.org /wiki/Sound_energy_density (292 words)

	Sound Quality Terms and Definitions
		Arithmetic mean sound pressure level: Of several related sound pressure levels measured at different positions or sound pressure levels measured at different positions or different times, or both, in a specified frequency band, the sum of the sound pressure levels divided by the number of levels.
		Sound Energy, E: [ML ]; J-energy added to an elastic medium by the presence of sound, consisting of potential energy in the form of deviations from static pressure and of kinetic energy in the form of particle velocity.
		Sound transmission coefficient, r: [dimensionless]---of a partition, in a specified frequency band, the fraction of the airborne sound power incident on the partition that is transmitted by the partition and radiated on the other side.
	www.owenscorning.com /around/sound/definitions.html (6963 words)

	I. Sound-wave energy density in a gaseous ether.---[Return home]
		, the energy density (energy by cubic meter) in x(t) is:
		But to calculate the whole energy of an extended wave, it is more easy to use the average of this variable energy density than to use always this formula (a bit too complicated).
		, and the whole newtonian kinetic energy contained in a volume V of a constant sound-wave in amplitude and in frequency is: E= Da.V. This energy is the energy needed to produce the sound-wave, or the sound-wave energy.
	pages.sbcglobal.net /webster.kehr/DeWitte/sound.htm (325 words)

	Klipsch Audio Technologies
		Sound is produced by variations in air pressure around the average steady-state barometric pressure, caused by the physical movements of objects and the surface in the air.
		The alternating variations of pressure at a sound source cause sound waves to radiate out from the source in the same manner as waves are caused in water by a dropped stone.
		The sound pressure level of a sound, in decibels, 20 times the logarithm to the base 10 of the ratio of the measured effective sound pressure of this sound to a reference effective sound pressure.
	www.klipsch.com /thegarage/audiolingo.aspx (2072 words)

	Acoustics Monitoring Program
		This "channeling" of sound occurs because there is a minimum in the vertical sound speed profile in the ocean caused by changes in the density of the water column.
		This minimum sound speed at the channel axis is the result of higher temperatures toward the surface of the ocean and higher pressures toward the bottom of the ocean.
		Sound energy is refracted towards the axis of the sound channel away from the surface and the bottom of the ocean.
	www.pmel.noaa.gov /vents/acoustics/tutorial/11-sofar.html (490 words)

	Terminology
		Commonly referred to as the mean-square sound-pressure ratio, sound energy, or just plain energy, acoustic energy is the square of the ratio of the mean-square sound pressure (often referred to as frequency weighted), and the reference mean-square sound pressure of 20 µPa, the threshold of human hearing.
		A sound wave whose front has been changed in direction by an obstacle in the propagation medium, where the medium is air for the purposes of this document.
		The ratio of the sound energy, as a function of frequency, absorbed by a surface, and the sound energy incident upon that surface.
	www.fhwa.dot.gov /environment/noise/term.htm (3703 words)

	Sound Quality Glossary Terms
		Sound energy, E: [ML2T-2]; J-energy added to an elastic medium by the presence of sound, consisting of potential energy in the form of deviations from static pressure and of kinetic energy in the form of particle velocity.
		Sound energy density, D: [ML-1T-2]; J/m---the quotient obtained when the sound energy in a region is divided by the volume of the region.
		Sound intensity, I: [MT-3]; W/m2 the quotient obtained when the average rate of energy flow in a specified direction and sense is divided by the area, perpendicular to that direction, through or toward which it flows.
	www.owenscorning.com /around/sound/glossary.asp (7146 words)

	Theremin Vox - Sound pressure
		Sound pressure p (or acoustic pressure) is the measurement in pascals of the root mean square (RMS) pressure deviation (from atmospheric pressure) caused by a sound wave passing through a fixed point.
		The amplitude of sound pressure from a point source decreases in the free field (direct field) proportional to the inverse of the distance from that source.
		Sound pressure level is a decibel scale based on a reference sound pressure of 20 µPa (micropascals), calculated in dB as:
	www.thereminvox.com /article/articleview/162/1/37 (224 words)

	Physics 230 Lectures, Fall 2002
		Kinetic and potential energy densities for a clamped string oscillating in its second harmonic.
		The kinetic and potential energy densities are the same for a progressive wave.
		Estimates of magnitude of particle displacements in a sound wave.
	dept.physics.upenn.edu /~mele/archives/webpage230/phys230.f02/log.html (763 words)

	Sound energy flux - Wikipedia, the free encyclopedia
		The sound energy flux is the average rate of flow of sound energy for one period through any specified area.
		In a medium of density ρ for a plane or spherical free wave having a velocity of propagation v, the sound energy flux through the area A corresponding to an effective sound pressure p is
		where θ = the angle between the direction of propagation of the sound and the normal to the area A.
	en.wikipedia.org /wiki/Sound_energy_flux (117 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		] The ratio of sound energy absorbed to that arriving at a surface or medium.
		] Diminution of the intensity of sound energy propagating in a medium; caused by absorption, spreading, and scattering.
		] A method of studying propagation, reflection, and refraction of sound waves, in which a sound wave is generated by a spark and is illuminated a fraction of a second later by a second spark, causing the wave to cast a shadow on a photographic plate.
	www.accessscience.com /Dictionary/S/S39/DictS39.html (2889 words)

	SIGHTINGS:
		Scientists have long known that sound is composed of pulsing waves of energy, but it was considered useless as a power source because at high levels sound waves distort into shock waves.
		Sound waves, patterns of compression and expansion in a gas such as air, are often created and studied in closed or semi-closed containers called cavities.
		In the past, attempts to make such sound waves louder (by adding more sound energy into the cavity) would fail beyond a certain point because additional energy would merely lead to the formation of a shock wave which would quickly dissipate the energy as heat.
	www.rense.com /earthchanges/sound.htm (575 words)

	Dictionary of Technical Terms for Aerospace Use - R
		irradiance (radiant flux density) produced by radiation from the source upon a unit surface area oriented normal to the line between source and receiver, divided by the solid angle subtended by the source at the receiving surface.
		The process by which energy is propagated through any medium by virtue of the wave motion of that medium, as in the propagation of sound wave through the atmosphere, or ocean waves along the water surface.
		sound energy density, initially in a steady state, to decrease, after the source is stopped, to one-millionth of its initial value.
	roland.grc.nasa.gov /~dglover/dictionary/r.html (10660 words)

	Dictionary of Technical Terms for Aerospace Use - S
		radio energy may be detected only at various distance intervals from the energy source as the result of the presence of an energy reflecting or refracting layer in the atmosphere.
		sound energy contained in a given infinitesimal part of the medium divided by the volume of that part of the medium.
		sound energy transmitted in the specified direction through a unit area normal to this direction at the point considered.
	roland.grc.nasa.gov /~dglover/dictionary/s.html (10691 words)

	NIOSH/Criteria for a Recommended Standard--Occupational Noise Exposure, 1998 (Site not responding. Last check: 2007-11-06)
		Sound intensity: Average rate of sound energy transmitted in a specified direction at a point through a unit area normal to this direction at the point considered.
		Sound pressure level: (1) Ten times the logarithm to the base ten of the ratio of the time-mean-square pressure of a sound, in a stated frequency band, to the square of the reference sound pressure in gases of 20 micropascals (µPa).
		Sound pressure level (SPL), expressed in decibels, is a measure of the amplitude of the pressure change that produces sound.
	www.nonoise.org /hearing/criteria/criteria.htm (15661 words)

	Energy Density of Aviation Fuel
		Although these fuels differ in things such as volatility and freezing points, their energy density, or heat content, is just about the same.
		Energy density is defined as the amount of energy per mass or it is the heat released when a known amount of fuel is burned under very specific conditions.
		In International Metric Units (SI), energy density is measured in MJ/kg (or MJ/L) The energy density of aviation fuel is generally between 43 and 48 MJ/kg.
	hypertextbook.com /facts/2003/EvelynGofman.shtml (275 words)

	Chapter 2: Terminology - Measurement of Highway-Related Noise
		DYNAMIC RANGE: The difference between the highest input sound pressure level achievable without exceeding a specified non-linearity or distortion of the output signal, for a specified frequency range, and the lowest input sound pressure level for which the level linearity is within specified tolerances.
		SOUND ABSORPTION COEFFICIENT (α): (See also Sabine Absorption Coefficient) The ratio of the sound energy, as a function of frequency, absorbed by a surface, to the sound energy incident upon that surface.
		SOUND PRESSURE LEVEL (SPL): Ten times the logarithm to the base 10 of the ratio of the time-mean-squared pressure of a sound, in a stated frequency band, to the square of the reference sound pressure of 20 µPa, the threshold of human hearing.
	www.fhwa.dot.gov /environment/noise/measure/chap2.htm (1843 words)

	Table chart sound pressure levels level sound pressure and sound intensity ratio calculation comparison - sengpielaudio (Site not responding. Last check: 2007-11-06)
		The sound pressure level decreases in the free field with 6dB per distance doubling.
		The sound pressure in a free field is inversely proportional to the distance from the mic to the source.
		The sound pressure is the force F in newtons N of a sound on a surface area A in m
	www.sengpielaudio.com /TableOfSoundPressureLevels.htm (264 words)

	CARA - Results 2D - Frequency Dependence of Reverberation Times;; Transient Room Response, Reverberation Diagram (Site not responding. Last check: 2007-11-06)
		To examine the temporal behaviour of the sound field in a room, you consider the sequentially arriving pulses being created by a single Dirac-Pulse that is sent out from the loudspeaker and is many times reflected at the room walls.
		This 'Total Energy Density' is identical to the energy density at the listening place of the steady state sound field being permanently excited by a white noise signal.
		The time dependence of the 'Total Energy Density' is calculated by integrating the 'Reverberation Diagram' from time T=t to T=end.
	www.cara.de /ENU/CARA/res2d3.html (205 words)

	Physics 4830 Course Notes
		Let's say we play a steady tone for a long time in our room the sound energy will build up and we will call the energy density: e.
		C is the fraction of energy lost each time the sound wave reflects off the surface.
		Another common practice is to make a scale model of the concert hall and test the model with higher frequency sound sources so that the wavelengths are in proportion to the size of the model.
	www.colorado.edu /physics/phys4830/phys4830_fa01/lab/n0920.htm (767 words)

	Theremin Vox - Particle displacement
		Particle displacement or particle amplitude ξ is a distance measurement in m (metre) of the movement of a particle(real or imagined) in a medium as it transmits a wave.
		In most cases this is a longitudinal wave of pressure as with sound, but it can also be a transverse wave as with the vibration of a taut string.
		When applied to a sound wave through a medium of air, particle displacement would be the physical movement back and forth of a molecule of air in the direction the sound wave is travelling as it passes.
	www.thereminvox.com /article/articleprint/163/-1/37 (132 words)

	Sound Wave Intensity
		The energy density of sound waves is given by:
		Just how much energy an object receives therefore depends on how much area it intersects in the incoming sound wave, not just on the energy density of the sound wave itself.
		For this reason the energy carried by sound waves is best measured by intensity: the energy per unit time per unit area perpendicular to the direction of wave propagation.
	www.phy.duke.edu /~rgb/Class/phy51/phy51/node41.html (281 words)

	Sonoluminescence: an Introduction (Site not responding. Last check: 2007-11-06)
		The mystery of how a low-energy-density sound wave can concentrate enough energy in a small enough volume to cause the emission of light is still unsolved.
		Shorter wavelength light has higher energy, and the observed spectrum of emitted light seems to indicate a temperature in the bubble of at least 10,000 degrees Celsius, and possibly a temperature in excess of one million degrees Celsius.
		For unknown reasons, the addition of a small amount of noble gas (such as helium, argon, or xenon) to the gas in the bubble increases the intensity of the emitted light dramatically.
	www-phys.llnl.gov /N_Div/sonolum (424 words)

	Gravity Theory -- Introducing Energy-Density Component
		Currently, many hundreds of millions of dollars have been spent, and hundreds of millions are now being sought, by an international university and investigative consortium in order to continue their research into gravity waves and to unravel the mysteries of gravity.
		First, two bodies of some energy density to interact with each other, and second, connecting diallel lines which provide not only particle flow between the bodies, but also the flow of photon and gravitational information as well.
		In summary then, the conditions needed for the gravitational field are two objects with some energy density (not just mass) and with diallel lines running between these two energy-density objects, which diallel lines are conducting particles, i.e.
	www.allanstime.com /UnifiedFieldTheory/gravity.htm (1715 words)

	INTRODUCTION. (Site not responding. Last check: 2007-11-06)
		High level university courses on relativity explained classically for secondary school students.
		Properties of the sound-wave energy contained in a simple resonator in motion.
		Optics law for a sound-wave in a medium where the speed is variable.
	pages.sbcglobal.net /webster.kehr/DeWitte/introduc.htm (50 words)

	The Phenomenon of Sound: Waves--Physical Science lesson plan (grades K-5)--DiscoverySchool.com (Site not responding. Last check: 2007-11-06)
		Prior to this activity, students should understand that sound is a form of energy that travels in invisible waves.
		Explain that sound needs a medium, but space is a vacuum with no solids, liquids, or gases for sound waves to travel through or vibrate in.
		Knows that vibrations (e.g., sounds, and earthquakes) move at different speeds in different materials, have different wavelengths, and set up wavelike disturbances that spread away from the source.
	school.discovery.com /lessonplans/programs/soundwaves (2341 words)

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