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HomeMy WebLinkAboutSDP201800067 Other 2019-03-183/18/2019 Frequency Weightings - A -Weighted, C-Weighted or Z-Weighted Home Contact Applications Products Rental Calibration [dews Resources Help Search + Car* Tel. 888-206-4377 info@nolsemeters.com Home > Help > FAQ > Frequency Weighting Frequency Weightings - A -Weighted, C-Weighted or Z Weighted? The human ear responds more to frequencies between 500 Hz and 8 kHz and is less sensitive to very low -pitch or high - pitch noises. The frequency weightings used in sound level meters are often related to the response of the human ear, to ensure that the meter is measuring pretty much what you actually hear. It is extremely important that sound level measurements are made using the correct frequency weighting - usually A - weighting. For example, measuring a tonal noise of around 31 Hz could result in a 40 dB error if using C-weighting instead of A -weighting. A Weighting The most common weighting that is used in noise measurement is A -Weighting. Like the human ear, this effectively cuts off the lower and higher frequencies that the average person cannot hear. Defined in the sound level meter standards (IEC 60651, IEC 60804, IEC 61672, ANSI S1.4), a graph of the frequency response can be seen to the right. A -weighted measurements are expressed as dBA or dB(A). C Weighting The response of the human ear varies with the sound level. At higher levels, 100 dB and above, the ear's response is flatter, as shown in the C-Weighted Response to the right. Although the A -Weighted response is used for most applications, C-Weighting is also available on many sound level meters. C Weighting is usually used for Peak measurements and also in some entertainment noise measurement, where the transmission of bass noise can be a problem. C-weighted measurements are expressed as dBC or dB(C). C-Weighted Frequency Response 10 mPO _6o 16 31.5 63 125 250 500 1000 2000 4000 8000 16000 Fregreecj [Hs] 0 •10 ,2a https:llwwuv.noisemeters.comlhelpffaglfrequency-weighting.asp 1/2 Z Weighting Z-weighting is a flat frequency response of 101-lz to 20kHz t1.5dB. This response replaces the older "Linear" or "Unweighted" responses as these did not define the frequency range over which the meter would be linear. Z-weighted measurements are expressed as dBZ or dB(Z). (Frequently Asked Questions Home - Contact - Applications - Products - Rental - News - Resources - Search - Help Telephone 888-206-4877 Sound Level Meters - Dosimeters - Noise Signs - Microphones & Calibrators info@noisemeters.com https://www.noisemeters.00mthelp/faglfTequency-weighting.asp 212 3/18/2019 Maximum, Minimum and Peak Sound Level `Home Contact Applications Products Rental Calibration News Resources Help Search F -.-; 11 Tel. 888-206-4377 Info@nolsemeters.com Home > Help > FAQ > Min, Max, Peak Maximum, Minimum and Peak Sound Level Which Meter? _Yj The maximum and minimum sound levels are simply the highest and lowest time -weighted sound level measured. Be careful with the Peak, as the terms "Peak" and "Maximum" mean very different things in the world of sound level meters. Maximum and Minimum - Lmax and Lmin The Lmax and Lmin parameters are quite easy to understand. They are simply the highest and lowest values measured by the sound level meter over a given period of time. They are based on the time -weighted sound level in dB, using either the Fast or Slow time constant. The Lmax and Lmin term used should indicate the frequency weighting and time constant used: LAFinax The maximum level with A -weighted frequency response and Fast time constant. LAFmin The minimum level with A -weighted frequency response and Fast time constant. LASmax The maximum level with A -weighted frequency response and Slow time constant. LASmin The minimum level with A -weighted frequency response and Slow time constant. Other frequency weightings, such as C-Weighting or Z-Weighting can be used but are rarefy needed in any noise measurement application. Peak Sound Pressure The Peak is not the same as the Maximum Sound Level. The Peak, referred to as the Lpeak or sometimes Lpk, is the maximum value reached by the sound pressure. There is no time -constant applied and the signal has not passed through an RMS circuit or calculator. This is the true Peak of the sound pressure wave. For a pure tone, the Peak will be 3 dB above the Maximum Sound Level. For varying signals there can be a huge difference and there is no way to calculate the Peak from the Max or any other measurement. Unlike the Sound Level and the Leq, the Peak measurement is usually C-Weighted rather than A -Weighted. Some older meters used Linear, but C-weighting has replaced that in most standards, including the European Noise at Work regulations. The C-weighted Peak measurement is usually expressed as LCpeak in dB(C). The LCpeak is used for occupational noise measurement where loud bangs are present. The Peak is not usually used for environmental noise measurement and is useless when any wind is present. A gust of wind will easily give very high LCPeak readings. Frequently Asked Questions Home - Contact - Applications - Products - Rental - News - Resources - Search - Help Telephone 888-2064377 Sound Level Meters - Dosimeters - Noise Signs - Microphones & Calibrators info@nolsemeters.com https*llwww.noisemeters.00m/help/faq/min-max-peak.asp 111 3/18/2019 Sound Level or Leq / Lavg for Noise Measurements Home Colntact Applications Products Rental Calibration News Resources Search Help Tel. 888-206-4377 info@noisemeters.com Home > Help > FAQ > Leq, Lavg, Sound Level Sound Level or Leq? which Meter? v The decision to use either the Sound Level (Fast or Slow) or the Leq I Lavg is usually determined by any measurement regulations that are being followed or by the nature of the noise being measured. Many occupational noise regulations state that the Leq or Lavg should be used but the guidelines for many motor vehicle measurements state that the Sound Level can be used. Check the measurement standards for any references to Leq, Lavg or Integrating Sound Level Meter. If these terms are used then you must measure the Leq or Lavg. If not, you should be fine with a standard non -integrating sound level meter, which certainly costs less. If in doubt, please email NoiseMeters, putting in as much information about your application as you can. Sound Level This is the basic measurement of any Sound Level Meter. A Frequency Weighting and Time Weighting will be applied to the sound signal that is picked up by the microphone. The sound level is expressed in decibels, or dB. The Sound Level is the basic measurement used for many applications. However, you should check any regulations that you are following to ensure that the Sound Level alone is adequate. Parameters such as Max (Lmax), Min (Lmin) and Ln (percentiles) are all based on the Sound Level. Leq, Lavg - Average Sound Level The Leq or Lavg is best described as the Average Sound Level over the period of the measurement. Usually measured A weighted, the Leq has no time constant applied, but the Lavg is usually Slow time weighted. As it is an average, it will settle to a steady value, making it much easier to read accurately than with a simple instantaneous Sound Level. Being an average, it is also showing the total energy of the noise being measured, so it is a better indicator of potential hearing damage or the likelihood that the noise will generate complaints. A sound level meter that measures the Leq or Lavg will be referred to as an Integrating Sound Level Meter and it should meet the standards IEC60804, IEC 61672 or ANSI S1.4. < Frequently Asked Questions Home - Contact -Applications - Products - Rental - News - Resources - Search - Help Sound Level Meters - Dosimeters - Noise Signs - Microphones & Calibrators Telephone 888-206-4377 info@noisemeters.com https:/twww.noisemeters.com/help/fagAavg-leq.asp 1 /1 3/18/2019 Sound Level Meter Time weightings - Fast, Slow or Impulse? Home Contact I Applications Products Rental Calibration flews Resources Help Search I Carl Home > Help > FAQ > Time Weighting Time Weightings - Fast, Slow or Impulse? • Tel. 888 206-4377 info@nofsemeters.com Which Meter? Sound level measurements using any grade of sound level meter can be Fast, Slow, or Impulse time weighted. These weightings date back to the time when sound level meters had analogue meters and defined the speed at which the meter moved. Under Fast the needle would move fast to show quickly varying noise and under Slow the needle would be damped to smooth the noise out to be easier to read. The Impulse time weighting is about four times faster than Fast, with a short rising time constant but a slow falling one. It is little used in most countries these days and so can usually be ignored. Fast corresponds to a 125 ms time constant. Slow corresponds to a 1 second time constant. Impulse has a time constant of 35 ms. As these time constants were set in standards, they have continued in digital meters, now being calculated or simulated before being displayed, stored or used to calculate other acoustic parameters that need the time weighting. The following terms are used to express the sound level, clearly indicating the time weighting as well as the frequency weighting: LAS Slow, A -weighted Sound Level LAF Fast, A -weighted Sound Level LCS Slow, C-weighted Sound Level LCF Fast, C-weighted Sound Level What About Leq? The Leq is the "Equivalent Continuous Sound Level" - it is the average sound level. For this reason there is no time constant applied to the Leq. More about Leq. What About Peak? The Peak is the maximum value reached by the sound pressure. It therefore has no time constant applied. More about Peak. a Frequently Asked Questions Home -Contact -Applications -Products -Rental -News -Resources -Search Help Sound Level Meters - Dosimeters - Noise Signs - Microphones & Calibrators Telephone 888-206-4377 info@noisemeters.com https:/Avww.noisemeters.00m/help/fag/time-weighting.asp 1/1 3/1812019 OSHA Occupational Noise Regulations 1910.95 - Protecting Workers Hearing Home Contact I Applications - Products Rental Calibration News Resources Help Search Cali Tel. 888-206-4377 info@noisemeters.com Home > Help > FAQ > OSHA Regulations OSHA Occupational Noise Regulations-1910.95 Which Meter? v The OSHA noise exposure standards define two action levels at which worker protection must be provided and used. These actions are based on the 8-hour Time Weighted Average (TWA) of the noise levels that the worker is exposed to throughout the working day: TWA Dose Action Details 85 dBA 50% + Hearing Conservation Provide hearing protection for workers to wear if they choose to. + Program Give training on the risks of high noise exposure. Monitor the levels regularly in case they increase. Provide audiometric testing. 90 dBA 100% Noise Control Program Provide hearing protection, which must be worn. + + Provide training on the risks of high levels and the wearing of protection. Provide audiometric testing. The measurements for Hearing Conservation (HC) should be made using a noise dosimeter or sound level meter with its threshold set to 80dB. The measurements for Noise Control (NC) or permissible exposure level (PEL) should be made with a threshold of 90dB. Modern dosimeters such as the dBadge can measure both at the same time. When noise levels are particularly high (say > 95 dBA) you should also check that the hearing protection that you are providing is adequate. A number of methods are available and the most accurate requires the use of a meter with Octave Band Filters. Time Weighted Average - TWA - Noise Levels These noise exposure limits are not based on instantaneous sound levels. They are based on the TWA TWA Calculator (time weighted average) or Dose %, which indicates the average noise levels that the worker is exposed to throughout a working day. The two most common ways to find out a workers TWA are: 1. Sound Level Meter - Manual Measurements • Measure the sound levels at the different times of day and different locations that the worker usually visits. • Find out how long the worker spends at each location. • Calculate the TWA. See TWA Calculator. If a worker stays at just one or two locations with constant noise levels then this is a relatively easy task. https:/Avww.noisemeters.com/help/osha/ 1/3 2. Use a Noise Dosimeter • Fit the Noise Dosimeter to the worker at the start of the working day. • Remove the dosimeter at the end of the day and read off the TWA or Dose % figure. t The dosimeter approach is much easier when a worker moves between different locations or the noise levels are changing all the time. When to Monitor the Noise Levels The noise levels in a work place should be carefully monitored using the correct grade of equipment if there is any possibility that a worker will be exposed and an 8 hour time weighted average noise level of 85 dB(A) or above. This monitoring should be repeated periodically (e.g. every year or every two years) or whenever there is change to machinery, production levels or processes that may impact on the noise levels. Which Sound Level Meter or Noise Dosimeter? To be sure of getting accurate and repeatable noise measurements that can be used for protecting workers' hearing and protecting your company from legal claims, you should use the correct grade of sound level meter.. The OSHA regulations recommend the use of a Type 2 sound level meter (you can also use Type 1 as it is more accurate) with "Slow" time weighting. You should also use a Sound Level. Calibrator to check that the meter is operating correctly before making important measurements. Here are some suggestions: k CEL240 Type 2 Sound Level Meter Ideal for quick measurements, from which you can calculate a worker's TWA. Recommended: CEL240-K Noise Measurement Kit (includes the meter and a Calibrator) - $895.00 CEL620 Integrating Sound Level Meter Includes all the measurements for an occupational noise survey. Data logging included Recommended: CEL260A2-K Sound Level Meter and Calibrator: $2033.00 CEL632 Advanced Integrating Sound Level Meter More detailed data logging and removable preamplifier. Options for octave and 1/3 octave band filters. Recommended: CEL632A2-K (includes meter and a Calibrator) - $2570.00 dBadge Logging Noise Dosimeter Mounts on the worker's shoulder and monitors the noise levels throughout the day. Recommended: CEL35OKS Noise Dosimeter Kit (includes 5 dosimeters, Calibrator and accessories) - https://www.noisem6ters.comthelp/0shal 2/3