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	Sound pressure level - Wikipedia, the free encyclopedia
		Since the human ear does not have a flat spectral response, sound pressure levels are often frequency weighted so that the measured level will match perceived sound level.
		The most common means is measuring the sound pressure level from the speaker with the measuring device placed directly in front of and one meter away from the source.
		Then a particular sound (usually white noise or pink noise) is played through the source at a particular intensity so that the source is consuming one watt of power.
	en.wikipedia.org /wiki/Sound_pressure_level (470 words)

	Sound
		Sound is defined as a mechanical compression and rarefaction or a longitudinal displacement wave that propagates through a medium (solid, liquid or gas).
		Sounds that are sine waves with a single pair of frequency and amplitude components are generally perceived as a pure tone.
		While the sound may still be referred to in general use as a single frequency (for example, a piano striking the A above middle C is said to be playing a note at 440 Hz) the sound you perceive will be colored by all of the frequency components and their relative amplitudes (see timbre.)
	www.brainyencyclopedia.com /encyclopedia/s/so/sound.html (639 words)

	Intensity and the Decibel Scale
		The greater the amplitude of vibrations of the particles of the medium, the greater the rate at which energy is transported through it, and the more intense that the sound wave is. Intensity is the energy/time/area; and since the energy/time ratio is equivalent to the quantity power, intensity is simply the power/area.
		As a sound wave carries its energy through a two-dimensional or three-dimensional medium, the intensity of the sound wave decreases with increasing distance from the source.
		The threshold of hearing is assigned a sound level of 0 decibels (abbreviated 0 dB); this sound corresponds to an intensity of 1*10
	www.glenbrook.k12.il.us /gbssci/phys/Class/sound/u11l2b.html (1211 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 intensity level - Wikipedia, the free encyclopedia
		It has been suggested that this article or section be merged with Sound intensity.
		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).
		The measure of a ratio of two sound intensities is
	en.wikipedia.org /wiki/Sound_intensity_level (133 words)

	Essential Accessories: The Radio Shack Sound Pressure Level Meter
		The perceived loudness of the sound we hear is proportional to the pressure of the sound wave.
		Having the ability to measure the pressure level of a sound wave in a listening room is extremely useful when attempting to optimize the room's loudspeaker and listener positions.
		The Radio Shack sound pressure level meter is a small hand-held device for measuring the pressure level of a sound wave in an acoustic environment such as your listening room.
	www.audiophilia.com /hardware/spl.htm (1682 words)

	Moulton Labs -- About the Loudness of Sounds and the Risk of Hearing Damage
		Sound Pressure Level is an expression of the magnitude of sound waves at some particular point in space.
		It is the sound level I use for mixing (which is to say that I set the monitor levels so that 0 VU on the console output meters yields a Sound Pressure Level of 90 decibels -- more about this later).
		It is the sound level of a circular saw cutting through hardwood, or a chain saw at full bore, as heard by the user.
	www.moultonlabs.com /articles/93aboutloud.htm (3234 words)

	What is a decibel? (Site not responding. Last check: 2007-10-15)
		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 (2886 words)

	Setting Sound System Level Controls
		Level controls for equalizers: the need to provide make-up gain in the case where significant cutting of the signal makes it too small, or the opposite case, where a lot of boosting makes the overall signal too large, requiring attenuation.
		First, a sound source is connected to the mixing console (or separate mic preamp) to provide the maximum system signal output, then this signal is used to set the outboard units.
		If there is only one level control, regardless of its location, set it to give you the maximum output level either by observing the OL light, or the transducer, or the oscilloscope, or by setting an output level of +20 dBu as shown on your AC voltmeter.
	www.rane.com /note135.html (3321 words)

	Physics Demonstrations - Sound
		Sound appears to be a topic distinct from motion and heat.
		The monitoring of sound levels requires an A-scale sound level meter with a frequency response matched to the response of the ear or one capable of displaying the sound level for all of the various frequency ranges[3].
		A dramatic illustration of the variation of the speed of sound with the density of a gas is performed by breathing a low density and a high density gas and talking as the gas is expelled from the lungs.
	sprott.physics.wisc.edu /demobook/chapter3.htm (7341 words)

	Physics 128 Lecture: Standing Waves
		The power of a sound wave is proportional to the amplitude of the wave squared,and the frequency of the wave squared.
		The intensity of a periodic sound wave is proportional to the square of the amplitude and the square of the frequency of the wave.
		The new sound level is 80 + 20 = 100 dB.
	www.cord.edu /dept/physics/p128/lecture99_35.html (994 words)

	NPC Library: An Introduction to Sound Basics
		Figure 2.2 is a graph used to estimate the amount of background noise influencing a measurement, and the corresponding decibel level to be subtracted from the total measurement to determine the decibel level of the noise source being monitored.
		C-weighting is used during the calibration of sound level meters to insure that the sound level displayed on the meter is invariant of the frequency of the calibrator.
		Sound level measurements made for assessing sound attenuation as specified in part 7030.0050, subpart 3, item B, C, or D, shall be made according to the requirements of this part.
	www.nonoise.org /library/sndbasic/sndbasic.htm (4415 words)

	Campanella Associates (Acoustics Consultants) - Acoustics FAQ
		Sound is often represented diagrammatically as a sine wave, but physically sound (in air) is a longitudinal wave where the wave motion is in the direction of the movement of energy.
		The speed of sound in air at a temperature of 0 degrees C and 50% relative humidity is 331.6 m/s.
		If one approaches a sound source by moving toward it with a velocity, v, the frequency of the sound heard is F=Fo(c+v)/c, where Fo is the emitted sound frequency, c is the speed of sound in still air and v is the speed of the observer or the moving source.
	www.campanellaacoustics.com /faq.htm (9635 words)

	Sound Level Meter
		In the SLOW position, the meter is damped and indicates an average-value sound level.
		When the sound is coming mainly from one direction, the level reading might be significantly affected by reflections from your body.
		Sound is vibration and in a room these vibrations will tend to gather against, and move along the large, uninterrupted flat surfaces such as the walls and ceilings.
	www.fredsoundofmusic.com /soundmeter.html (1234 words)

	Anderson Hardwood Floors : Installation & Care : Noise Reduction
		While the ability of a surface to absorb airborne sound is important, there is another type of sound to be considered.
		That is, sound transmission between the floor in a bedroom, for instance, and the living space below.
		Sound masking systems produce a background sound (sometimes called âwhite noiseâ) that masks or covers conversational distractions and unwanted noise.
	www.andersonfloors.com /instcare/instpro/noisereduction.aspx (541 words)

	Sound Level Meters (Site not responding. Last check: 2007-10-15)
		The model QC-10 is a general purpose calibrator that generates a constant sound pressure level of 114 dB at a fixed frequency of 1,000 Hz.
		Enforcement of local noise ordinances requires field testing of noise levels and documentation of measurement results, particularly in the event a citation is issued.
		Both meters are rugged, high-quality devices meeting all the applicable accuracy and performance requirements for sound level meters as defined by ANSI S1.4 and S1.43, IEC 61672, 651 and 804.
	www.emsys.ie /sound_level_meters (877 words)

	Soundproofing by Soundprooffoam.com - Free Soundproofing Advice
		Reduces the sound of fluids flowing through pipes, especially PVC; for soundproofing noisy pipes in homes, condos, apartments, offices, schools, anywhere public spaces may be adjacent to restrooms, lavatories, laundry facilities, or kitchens.
		Blocking sound is achieved by using a solid, mass loaded vinyl barrier material that blocks the sound waves.
		Sound absorption is achieved by using an acoustical material to absorb the reflection of sound within a room (echo, reverberation, standing sound waves).
	www.soundprooffoam.com (970 words)

	Sound Advice: Take your time when building a sound system (Site not responding. Last check: 2007-10-15)
		Moreover, the tiny speakers in some systems, with or without a subwoofer, produce inferior sound compared with that produced by high-quality conventional two-channel stereo speakers (with a woofer, midrange and tweeter).
		You can enjoy great stereo sound with movies and music, while saving up for the rest of your system.
		For the most accurate possible adjustment, use a sound pressure level meter.
	www.startribune.com /stories/789/5568964.html (522 words)

	Encyclopedia article on Sound pressure level [EncycloZine] (Site not responding. Last check: 2007-10-15)
		This measurement can also be represented as a strict efficiency ratio of audio output(sound power) to electrical input(electrical power), but this is far less common.
		This method of rating speakers using SPL is often deceiving because most speakers produce very different SPLs at different frequencies of sound, often varying as much as +- 10 dB throughout the speaker's usable frequency range(it generally varies less in higher quality speakers).
		Conversion of sound pressure level to sound pressure (http://www.sengpielaudio.com/calculator-soundlevel.htm)
	encyclozine.com /Sound_pressure_level (326 words)

	General MIDI Level 1 Sound Set
		Though this can obviously result in wide variations in performance from the same song data on different GM sound sources, the authors of General MIDI felt it important to allow each manufacturer to have their own ideas and express their personal aesthetics when it comes to picking the exact timbres for each sound.
		These sounds are the same for all MIDI Channels except Channel 10, which has only percussion sounds and some sound "effects".
		The General MIDI Level 1 instrument sounds are grouped by families.
	www.midi.org /about-midi/gm/gm1sound.shtml (365 words)

	Nokia 5100 Interactive Tutorial
		The sound meter is a fun and useful feature that allows you to measure the estimated noise level of your surroundings (dB representation).
		There is also a numerical presentation of the sound level.
		It is not possible to measure the estimated noise level of a call in progress.
	www.nokia.com /support/tutorials/5100/english/sound_level_master.html (183 words)

	Welcome to Audio - Design and manufacture broadcast quality radio microphone systems.
		Audio design their location sound systems to be flexible.
		This location sound however was of less use against cancellations which had occurred far away in the ionospheric radio microphone, uhf systems disturbances of the signals.
		Careful monitoring of RF level over a huge dynamic range audio ltd, wireless microphone which is individually tracked on each unit means that the receiver can never switch to a worse signal.
	www.audioltd.com (1034 words)

	Glencoe Online Science Quiz Chapter
		The sound from a trumpet results from __________.
		The lowest frequency in a sound wave is called the __________.
		Two or more pitches played together that sound pleasant are __________.
	www.glencoe.com /qe/science.php?qi=2239 (41 words)

	Sound Card Performance Test Techtalk Jitter or FM Distortion
		Ear damage results when the ear is subjected to too loud of a sound, at the wrong frequency, for too long of a time, on too many occasions.
		One general trend is that ear damage occurs at the lowest sound levels at 3 kHz, but the ear is less susceptable to damage from the same noise of the same intensity, at higher and lower frequencies.
		Another general trend is that reducing the noise level by about 10 dB, approximately doubles the length of time it can be tolerated without ear damage.
	www.pcavtech.com /soundcards/techtalk/Ear_Damage (297 words)

	Sound Level Meters in the UK
		The Sound Level Meter Specialists in the UK Our whole business is the supply of sound level meters.
		As a result we have an excellent knowledge of this complex equipment and we are more than happy to offer free advice on which sound level meter most suits your application.
		This range of sound level meters includes instruments designed for noise at work and others for environmental noise measurement.
	www.slmshop.co.uk (213 words)

	Sound Pressure Level Meter by RadioShack
		Enter the RadioShack digital Sound Pressure Level (SPL, for short) Meter: a handy, portable, lightweight, easy to use and affordable (at 60 bucks) measuring instrument that can help you debunking many of the myths you may have heard by your friends.
		It measures the level of the sound pressure generated by a musical instrument, a stereo system or an angry mother-in-law, by means of a built-in microphone
		Anyway, RadioShack offers more sophisticated Sound Level Meters (follow this link to see the various models) but these are more expensive.
	www.tnt-audio.com /clinica/spl-meter_e.html (1102 words)

	Interfax: Target Media proposes standard limiting LCD specialty advertisingdevices to sound level of 55 dB
		The 55dB sound level will likely be sufficient for office building environments, but might possibly be insufficient for louder places, such as airports and hypermarkets, Kong said.
		Meanwhile, this new sound level proposal is also the second time Target Media has raised suggestions for an industrial standard in the past two months.
		"The sound suggestion is complementary to those we have raised in the past," Kong said.
	www.interfax.com /4/85983/news.aspx (409 words)

	Sound Level Meters: Eckel Instrument Division
		For your added security we are a world leader in noise control technology, giving you peace of mind that when you talk to us, you will be assisted by a Member of the Institute of Acoustics who will be able to advise you which meter is required for your particular application.
		We only supply high grade digital sound level meters.
		Use the sound meters that we utilise when testing sound levels in avionic and automotive wind tunnel applications.
	www.soundlevelmeters.co.uk (121 words)

	sound, sounds, sounding, soundest, sounder, sounded- WordWeb dictionary definition
		(phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some language
		"a sound approach to the problem"; "sound advice"; "no sound explanation for his decision"
		"a sound timber"; "the wall is sound"; "a sound foundation"
	wordwebonline.com /en/SOUND (219 words)

	Sound Level Meters
		Monarch 321 IEC 651 Type II Sound Level Meter
		Maintain Sound Level Meters and Dosimeters accuracy in the field.
		Sound pressure output at 114dB and 94dB at 1KHz
	www.monarchinstrument.com /Sound.htm (463 words)

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