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Topic: Noise weighting

	Noise weighting -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-07)
		(Sound of any kind (especially unintelligible or dissonant sound)) Noise weighting measurements are made in lines terminated either by the measuring set or the class of instrument.
		The most widely used noise weightings were established by agencies concerned with public telephone service, and are based on characteristics of specific commercial telephone instruments, representing successive stages of technological development.
		The same weighting nomenclature and units are used in military versions of commercial noise measuring sets.
	www.absoluteastronomy.com /encyclopedia/n/no/noise_weighting.htm (101 words)

	Development of a Muffler for Small Arms Range Noise Mitigation
		In environmental noise, the sound pressure level is usually measured using one of the frequency networks of the sound level meter.
		The A-weighting frequency network of the sound level meter deemphasizes the lower frequency portion of the noise spectrum to approximate the human ear's response to the noise.
		Thus, the A-weighting of the frequency content of the noise signal has been found to have an excellent correlation with the human subjective judgment of annoyance of the noise.
	www.cecer.army.mil /techreports/pate_muffler/pate_muffler.post-12.htm (1588 words)

	NPC Library: Noise Control Terms Made Somewhat Easier
		This dictionary of terms related to noise and noise control is a useful tool for those who are investigating how to reduce the amount of noise pollution in their environment.
		Loss of hearing caused by noise exposures that are part of the social environment, exclusive of occupational-noise exposure, physiological changes with age, and disease.
		The weighted sound pressure level obtained by the use of a sound level meter and frequency weighting network, such as A, B, or C as specified in ANSI specifications for sound level meters (ANSI Sl.4-1971, or the latest approved revision).
	www.nonoise.org /library/diction/soundict.htm (3820 words)

	Flat weighting - Wikipedia, the free encyclopedia
		Flat weighting: In a noise-measuring set, a noise weighting based on an amplitude-frequency characteristic that is flat over a frequency range that must be stated.
		Note 1: Flat noise power is expressed in dBrn (f
		Note 2: "3 kHz flat weighting" and "15 kHz flat weighting" are based on amplitude-frequency characteristics that are flat between 30 Hz and the frequency indicated.
	en.wikipedia.org /wiki/Flat_weighting (95 words)

	[No title] (Site not responding. Last check: 2007-11-07)
		The goal of the noise reduction is to reduce the noise level without distorting the speech, thus reduce the stress on the listener and - ideally - increase intelligibility.
		Spectral weighting basically means that different spectral regions of the mixed signal of speech and noise are attenuated with different factors.
		A new weighting rule has been developed at IND with the aim of preserving the characteristics of the background noise while minimizing the speech distortion [Gustafsson, Jax, Vary-98], [Gustafsson, Jax-98].
	www.ind.rwth-aachen.de /research/noise_reduction.html (3079 words)

	[No title]
		As a consequence, the relationship between measurements made with the North American noise meter and the CCITT psophometer is dependent on the frequency spectrum of the noise being measured.
		To determine the contribution of this noise, an additional measurement is made using a 2\(hytone signal consisting of the high pair or low pair of tones at the same power level as the 4\(hytone signal.
		Also, because quantizing noise can cause a significant phase jitter reading, care must be exercised in the choice of the carrier frequency and in the filtering to suppress the effect of noise on the measurement.
	www.nmedia.net /docs/ccitt/1988/4_4/4_4_04.troff (13237 words)

	Health Standards for Occupational Noise Exposure in Coal, Metal, and Nonmetal Mines; Proposed Rule; 30 CFR Parts 56, ...
		Weighting networks were designed to approximate the response of the human ear to tones of equal loudness.
		A-weighted sound level measurement was adopted by the U.S. Department of Labor as part of the Occupational Safety and Health Standards and by the British Occupational Hygiene Society in its Hygiene Standards for Wide-Band Noise.
		The workers in the highest noise areas were required to wear hearing protectors and most of the workers in the moderate noise areas chose to wear hearing protectors.
	www.msha.gov /REGS/FEDREG/PROPOSED/1996PROP/NOISE2.HTM (19072 words)

	NPC Resources: Environmental Noise Booklet from Bruer & Kjaer
		Noise of this kind is typical for large diesel engines in trains, ships, and power plants and, since the noise is hard to muffle and spreads easily in all directions, it can be heard for miles.
		The annoyance due to a given noise source is perceived very differently from person to person, and is also dependent upon many non-acoustic factors such as the prominence of the source, its importance to the listener’s economy and his or her personal opinion of the source.
		Outdoor noise levels usually decrease with increasing distance from the source because of geometrical spreading of the noise energy over a bigger surface and absorption of the noise by the atmosphere and by the ground.
	www.nonoise.org /library/envnoise (10684 words)

	Signal presence determination method for use in a contaminated medium - Patent 4358738 (Site not responding. Last check: 2007-11-07)
		In the present invention a multiplicity of weighting means are used to sense the presence of noise and each weighting means is used to operate circuitry to indicate the presence of noise.
		However, even if very weak noise waves have unexpected spectral characteristics and thus none of the weighting adjustments were pre-adjusted for the noise, the level of the noise wave would not allow the circuit to indicate a mismatch and thus the overall circuit will correctly indicate signal absence.
		These weighting adjustments should be set for a specific type of noise and should be adjusted so that when that type of noise is present the adjustment equalizes the level fed to separate detectors 110 and 130.
	www.freepatentsonline.com /4358738.html (4703 words)

	Noise Measurement Briefing from Product Technology Partners (Site not responding. Last check: 2007-11-07)
		The A-weighted sound level has been shown to correlate with subjective responses and two sounds judged to be of similar loudness would produce similar dB(A) values, although their unweighted dB values would vary considerably.
		For impact noise, the OSHA requires measurements to be made using a sound level meter with a linear frequency response, a peak detection circuit and a response time which is approximately 1000 times faster than the 'Impulse' response.
		One factor that may substantially affect the accuracy of environmental measurements is the level of background noise in relation to the noise being measured.
	www.ptpart.co.uk /noise.htm (1022 words)

	Rane Professional Audio Reference (W) (Site not responding. Last check: 2007-11-07)
		A-weighting (not official but commonly written as dBA) The A-curve is a wide bandpass filter centered at 2.5 kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB attenuation at 20 kHz, therefore it tends to heavily roll-off the low end, with a more modest effect on high frequencies.
		It is the inverse of the 30-phon (or 30 dB-SPL) equal-loudness curve of Fletcher-Munson.
		From an energy standpoint white noise has constant power per hertz (also referred to as unit bandwidth), i.e., at every frequency there is the same amount of power (while pink noise, for instance, has constant power per octave band of frequency).
	www.rane.com /par-w.html (2680 words)

	Equivalent Sound Level and Its Relationship to Other Noise Measures (Part 2) (Site not responding. Last check: 2007-11-07)
		Weightings of 5 dB are applied to the evening period and 10 dB to the night period.
		The constant (-12) is an arbitrary constant, and the factor 16.7 is used to weight the nighttime exposure in the 9-hour night period on a 10 to 1 basis with the daytime exposure in the 15-hour daytime period.
		The interim HUD standards for outdoor noise are specified for all noise sources, other than aircraft, in terms of A-weighted sound level not to be exceeded more than a certain fraction of the day.
	www.netvista.net /~hpb/epa1974/epa1974b.html (2379 words)

	MS Excel: dBA, dBB, dBC, dBD, dBG, dBU, dBAU Weighting Tables (Site not responding. Last check: 2007-11-07)
		It is rather clear that the dB(A) weighting is a poor representation of subjective loudness at higher levels, when there is a significant low-frequent content in the measured noise.
		During the late 1960s, hearing Damage Risk Criteria were proposed for noise exposures involving very high frequencies (10-20 kilohertz) and extending into the ultrasonic frequency range (greater than 20 kHz, usually thought to be the upper frequency limit of young normal hearing).
		A pink noise is a random logarithmic flat noise, meaning the energetic content per frequency band is equal.
	www.acoustics-noise.com /dBA-B-C-D-U-G-U-AU-tables.shtml (2004 words)

	IDL Help (Site not responding. Last check: 2007-11-07)
		Default=0 ; weighting - Selects weighting scheme in final image ; combination: ; 0 (default) - Poissonian weighting - co-add ; detected DN from non-CR pixels.
		RSH ; 20 Jun. 1997 - Fixed error in using input noise cube.
		Intermediate as well as final ; mean is exptime weighted.
	www.astro.washington.edu /deutsch-bin/getpro/library01.html?CR_REJECT (2165 words)

	Applied Dynamic Measurements - Acoustic Weighting Networks
		The AWN-3 is designed for use in OEM applications where a plug-in acoustic weighting network is required.
		The device offers simultaneous A, B and C weighted outputs with a ± 2.5V signal range that is suitable for most modern instrumentation.
		Typical A weighting noise spectral density 70 nV/Hz Typical B weighting noise spectral density 60 nV/Hz Typical C weighting noise spectral density 50 nV/Hz (All noise measurements at 1 kHz with battery supply and terminated input)
	www.admnetworks.com /weighting.htm (391 words)

	Definition: ha1-receiver weighting (Site not responding. Last check: 2007-11-07)
		HA1-receiver weighting: A noise weighting used in a noise measuring set to measure noise across the HA1-receiver of a 302-type or similar instrument.
		Note 1: The meter scale readings of an HA1 test set are in dBa (HA1).
		Note 2: HA1 noise weighting is obsolete for new DOD applications.
	www.atis.org /tg2k/_ha1-receiver_weighting.html (86 words)

	Audio Scientific - Auto Calculators & Various References Links
		Signal to Noise Ratio Autocalculator - using Excel SNR_Autocalculator
		Equal Loudness Curves - A, B, C Weighting Networks http://www.sfu.ca/sonic-studio/Equal_Loudness_Contours.html
		Noise Spectrum Types, Noise Color - White, Pink, Red, Orange, Green, Blue, Purple, Grey, Brown, Black http://www.ptpart.co.uk/colors.htm ftp://svr-ftp.eng.cam.ac.uk/pub/comp.speech/info/Colors_of_noise_pseudo_FAQ.txt
	www.audioscientific.com /Auto%20Calculators%20&%20References%20Links.htm (715 words)

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