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Topic: Sound intensity level

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	Decibel - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-13)
		The decibel is widely used in measurements of the loudness of sound.
		Commonly, sound intensities are specified as a sound pressure level (SPL) relative to 20 micropascals (20 µPa) in gases and 1 µPa in other media (standardized in ANSI S1.1-1994).
		The levels change with the distance from the source of the sound; in general, the level decreases as the distance from the source increases.
	en.wikipedia.org /wiki/Decibel (3563 words)

	Sound intensity - Wikipedia, the free encyclopedia
		Sound intensity is not the same physical quantity as sound pressure.
		Hearing is directly sensitive to sound pressure which is related to sound intensity.
		In stereo the level differences have been called "intensity" differences, but sound intensity is a specifically defined quantity and cannot be sensed by a simple microphone, nor would it be valuable in music recording if it could.
	en.wikipedia.org /wiki/Sound_intensity (214 words)

	Acoustics Monitoring Program
		The sound levels to which most mammals are sensitive extend over many orders of magnitude and, for this reason, it is convenient to use a logarithmic scale when measuring sound.
		Whenever "level" is added to the terms sound intensity or sound pressure, it usually implies that the measurement is in decibels.
		Typically the units of SIL are dB relative to the reference intensity at 1 meter (e.g., 20 dB re 1µPa @ 1m) - i.e.
	www.pmel.noaa.gov /vents/acoustics/tutorial/7-SPL-SIL.html (386 words)

	Sound Intensity
		To assess sound loudness, as distinct from an objective intensity measurement, the sensitivity of the ear must be factored in.
		Since audible sound consists of pressure waves, one of the ways to quantify the sound is to state the amount of pressure variation relative to atmospheric pressure caused by the sound.
		Sound level measurements in decibels are generally referenced to a standard threshold of hearing at 1000 Hz for the human ear which can be stated in terms of sound intensity:
	hyperphysics.phy-astr.gsu.edu /hbase/sound/intens.html (493 words)

	Sound Power and Intensity
		For a sound wave, the amount of energy transported is proportional to the square of the amplitude of the wave.
		Both sound pressure level and sound intensity level are purported to measure the same thing: the loudness of a sound that we hear.
		The next step to show the equality of sound pressure level and sound intensity level is to realize that the intensity in a sound wave is proportional to the square of the amplitude of the sound wave.
	hep.physics.indiana.edu /~rickv/Sound_intensity.html (912 words)

	Sound Pressure Level -- Recommendations and Resources (Site not responding. Last check: 2007-10-13)
		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.
		This is often misprinted.) 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 intensity level or acoustic intensity level is a logarithmic measure of the sound intensity in comparison to the reference level of 0 dB (decibels).
	www.becomingapediatrician.com /health/134/sound-pressure-level.html (927 words)

	Sound_Intensity (Site not responding. Last check: 2007-10-13)
		The sound energy transmitted per unit time through a unit area, thereby being a measure of the magnitude of a sound.
		for the conversion of intensity ratios to decibels.
		Sound intensity is proportional to the square of the
	www2.sfu.ca /sonic-studio/handbook/Sound_Intensity.html (95 words)

	Problem B: Audiophobia
		The loudness or intensity level of sound is usually measured in decibels and sound having intensity level 130 decibels or higher is considered painful.
		The intensity level of normal conversation is 6065 decibels and that of heavy traffic is 7080 decibels.
		The integer on each edge is the average intensity level of sound (in decibels) in the corresponding street.
	acm.uva.es /p/v100/10048.html (465 words)

	Sound Level (Site not responding. Last check: 2007-10-13)
		The rate at which the wave energy from a sound source is transferred from one location to another is expressed in terms of its intensity.
		Sound intensity is perceived by our ears as loudness, in the same fashion as a sound's frequency is perceived by our ears as its pitch.
		To compare relative intensity levels, we use a logarithmic scale and reference the threshold of sound as a standard for comparison.
	online.cctt.org /physicslab/content/Phy1HON/lessonnotes/decibels/soundlevel.asp (376 words)

	Sound pressure and loudness (Site not responding. Last check: 2007-10-13)
		Sound intensity level measures the level of sound at a given distance from a given source.
		The sound intensity from a single source depends on two things, the sound power, W, produced by the source and the distance from the source squared, R
		This formula is handy if we want to know how the sound intensity for a source with a given power depends on distance, or, how the sound intensity for a source at a given distance depends on power.
	carini.physics.indiana.edu /P105S98/Pressure-and-loudness.html (894 words)

	Physics Tutorials: Sound - Decibel Levels
		The range of energy from the lowest sound that can be heard to a sound so loud that is produces pain rather than the sensation of hearing is so large that an exponential scale is used.
		Intensity of sound is measured in Watts per square meter.
		To express the intensity level in dB (deciBels) multiply the logarithm of the ratio by 10.
	www.internet4classrooms.com /sound_decibel.htm (288 words)

	Harmonics
		Intensity level relates to an idealized response of the ear without any frequency effects.
		Intensity relates to the actual power produced by the sound source and the distance of the ear from it.
		Hence the intensity is a physical quantity accounting for both the power radiated by the source and the distance of the receiver to the source.
	www.colorado.edu /physics/phys1240/phys1240_fa04/Intensity.htm (600 words)

	Sound level SPL in dB - pressure level L sound pressure p sound intensity I - dB conversion of sound units calculating ... (Site not responding. Last check: 2007-10-13)
		Sound level SPL in dB - pressure level L sound pressure p sound intensity I - dB conversion of sound units calculating spl sound level calculation air - sengpielaudio
		Differentiate: Sound pressure p is a "sound field value" - sound intensity I is a "sound energy value".
		To speak of the intensity of a sound pressure is nonsense.
	www.sengpielaudio.com /calculator-soundlevel.htm (334 words)

	A journey of a thousand miles begins with one step. (Site not responding. Last check: 2007-10-13)
		The decibel (dB) is a measure of logarithmic ratio of intensity level.
		B is a decibel measure of the intensity level of the sound, I, with respect to a reference intensity level of sound, I0.
		Assuming a minimum voltage level corresponding to Formula 3-1 with a radius to the recording device of 1 cm and a recording resistance of 1 ohm, the minimum magnitude of voltage is 3.545 *10^-8 volts.
	www.owlnet.rice.edu /~elec301/Projects99/adda/dlr.html (613 words)

	00.05.10: Discovering the Mathematics of Sound
		Sound is the form of energy which most of us seem to take for granted.
		In the case of sound waves, the disturbance is in the form of a change in pressure and density which is sometimes described as a vibration in the medium.
		If a sound source 100 feet away has an intensity of 90 dB and you were to move to a distance 200 feet from the source, the intensity of the sound would drop by 6 dB (if the distance from the source is doubled, there is a drop of 6 dB).
	www.yale.edu /ynhti/curriculum/units/2000/5/00.05.10.x.html (3579 words)

	What is a decibel? (Site not responding. Last check: 2007-10-13)
		Sound is usually measured with microphones and they respond (approximately) proportionally to the sound pressure, p.
		i.e., it is the sound level corresponding to 0.02 mPa.
		The most widely used sound level filter is the A scale, which roughly corresponds to the inverse of the 40 dB (at 1 kHz) equal-loudness curve.
	www.phys.unsw.edu.au /~jw/dB.html (3313 words)

	SLI \| Basic Science \| Analysis of Sound Waves (Site not responding. Last check: 2007-10-13)
		Another reason for using this scale is that the ear itself 'hears' logarithmically and humans judge the relative loudness of two sounds by the ratio of their intensities, a logarithmic behaviour.
		When sound intensity is expressed as a decibel it is referred to as sound intensity level and is given the symbol L
		Using equation 2.4, calculate the sound pressure level of a sound with a sound pressure of 2 Pa.
	www.safetyline.wa.gov.au /institute/level2/course18/lecture54/l54_02.asp (363 words)

	Arch 215 Homework 1
		What intensity level would be observed at a distance of 80 feet with four firetruck sirens of the same power going at the same time?
		The inverse square law usually gives a good approximation of the decrease in sound intensity with distance from the source in outdoor situations.
		Sound also carries better and more rapidly in warmer air, curving the sound path if the air is warmer near the ground or vice versa.
	www.usc.edu /dept/architecture/mbs/315/315hw5.html (306 words)

	[No title]
		As the condensations and rarefactions of the sound wave move away from the disturbance, the individual air molecules are not carried with the wave.
		However, since the intensity level is defined in terms of logarithms, the intensity level at that point is (from Equation 16.10) 68 dB.
		The sound intensity level generated by N people is given by Equation 16.10 as EMBED Equation where I0 is the threshold of hearing.
	www.fiu.edu /~tgarcia/teaching/phy2053/ch16.doc (1682 words)

	Pitch
		Sound intensities are scaled by factors of ten using what is called a logarithmic scale.
		This scale is referred to as the sound intensity level and the reference point for beginning this scale is the threshold of hearing.
		Because each interval on this scale represents such a large increase in sound intensity, a finer scale in which bels are divided into decibels (dB) is often the most convenient.
	chemgeo.colstate.edu /pcs/topic42.htm (407 words)

	George Mason University \|\| Physics and Astronomy (Site not responding. Last check: 2007-10-13)
		Sound intensity levels, I have measured in these classes, are close to that of a jackhammer, definitely unsafe.
		ACE’s certification guidelines for aerobics instructors and their teaching facilities state that sound levels for aerobics classes should be in the range of 70-80 db, a level, which insures the use of EPA standards in exercise classrooms.
		Sound ordinances in Fairfax County, Virginia, restrict the sound level in public settings to 90 dB and in residential settings to 55 dB.
	www.physics.gmu.edu /faculty_staff/exercise.html (2253 words)

	Theremin Vox - Sound pressure (Site not responding. Last check: 2007-10-13)
		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:
		"Sound intensity" is sound power per unit area, while "pressure" is a measure of force per unit area.
	www.thereminvox.com /article/articleview/162/1/37 (224 words)

	Norsonic — innovative sound instrumentation
		Sound intensity is the rate of flow of acoustic energy per unit area in a given direction.
		= the sound intensity level in decibels (re: 1pW/m
		Intensity in the direction from the source is regarded as positive intensity and towards the source as negative.
	www.norsonic.com /ProductsAndUses.php?menu=uses&subMenu=1499&nivaa=2 (1744 words)

	Inverse Square Law for Sound
		The sound intensity from a point source of sound will obey the inverse square law if there are no reflections or reverberation.
		A plot of the drop of sound intensity according to the inverse square law emphasizes the rapid loss associated with the inverse square law.
		It's intensity in decibels can be calculated by comparing the intensity to the threshold of hearing.
	hyperphysics.phy-astr.gsu.edu /hbase/acoustic/invsqs.html (132 words)

	Decibel Scales: Sound Pressure Level and Sound Intensity Level (Site not responding. Last check: 2007-10-13)
		The average size of the pressure variation away from the constant background level is the Pressure Amplitude of the sound wave.
		The relation between amplitude of the sine wave (measured from the background level to one extreme) to the pressure amplitude (average pressure excursion from the background) is shown in the figure below.
		Finally, because the intensity is related to the square of the pressure amplitude we replace the pressure amplitude ratio squared with the intensity ratio.
	physics.mtsu.edu /~wmr/log_3.htm (1841 words)

	Measurement of Sound Intensity - Measurement Encyclopedia - National Instruments
		In neither case is it acceptable for sound absorbing material to be present within the measurement surface because the resulting measurement will equal the sound power of the sound source minus the sound power lost in the sound absorber.
		The sound intensity probe is oriented perpendicular to the measurement surface such that sound intensity values for sounds passing from inside to outside of the measurement surface carry a positive sign.
		Be careful when recording negative intensity readings: there is a big difference between a sound intensity level of 85 dB in the negative direction, and a sound intensity level of –85 dB.
	zone.ni.com /devzone/nidzgloss.nsf/345429a29b12a2fc86256879000c059b/527e1cb2f5ce0231862568c600600adc?OpenDocument (890 words)

	Underwater Acoustics - Navy Ships
		Sound pressure is sound force per unit area, and is usually cited in micropascals (µPa), where 1 Pa is the pressure resulting from a force of one Newton exerted over an area of one square meter.
		Sound levels extend over many orders of magnitude and, for this reason, it is convenient to use a logarithmic scale when measuring sound.
		In practice, one can rarely measure source level at the standard 1m reference, so that source levels are usually estimated by measuring SPL at some known range from the source (assumed to be a single point), and the attenuation effects predicted and subtracted from the measured value to estimate the level at the reference range.
	www.fas.org /man/dod-101/sys/ship/acoustics.htm (2101 words)

	Appendix A: Intensity and Loudness Measures of Sound
		Intensity is proportional to the square of the distance to the sound source assuming anechoic conditions.
		The relationship between L and the intensity or average pressure variation of a single sound source is approximated as in Eq.
		When a sound source produces components at different frequencies or when more than one sound source exists, the calculation of L is more complicated and takes on one of three forms [12].
	www.music.miami.edu /programs/mue/research/jwest/App_A_Loudness/App_A_Loudness.html (559 words)

	Engineering Page > Noise > Sound Levels Explained
		In an open field sound is stronger near the source and weaker further away as the energy of the source is distributed over a larger area.
		Both the sound intensity level and associated sound pressure level will be lower further away.
		The intensity of sound is by definition the average power that is transmitted in the direction of progression, so intensity is a vector: it possesses magnitude and direction.
	www.engineeringpage.com /technology/noise/levels.html (682 words)

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