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Noise Pollution
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
Section 50-204.10 of the Act establishes acceptable noise levels and exposures for safe working conditions and gives various means of actions that must be taken if these levels are exceeded. A 90 dB level of exposure to sound energy absorbed is taken as the limit of exposure that will not cause any type of hearing loss in more than 20% of those exposed. Workers in any industry must not be exposed to sound levels greater than 115 dB for any amount of time. Noise levels must be measured on the A scale of a standard sound level meter at slow response. The sound level meter is a measuring device that indicates sound intensity. “Slow response” is a particular setting on the meter, and when the meter is at this setting it will average out high-level noise of short-lived duration. For impact noise, a higher level of 140 dB is acceptable because the noise impulse due to impacts is over before the human ear has time to fully react to it.
Uncertainty in Measuring and Estimating Workplace Noise Exposure
Published in Robert Peters, Uncertainty in Acoustics, 2020
When considering the measurements you will be making, some thought needs to be given to how long your sampling period should be. Should you measure over three or four complete cycles of an operation? What we are measuring is an A-weighted Leq value, and modern sound level meters have a precision of 0.1 dB. Consequently, a useful way to confirm that your sampling period is long enough is to watch the value of the sound level displayed on your sound level meter and ensure that it is stable to a precision of 0.1 dB. Logically, if this is the case, then the uncertainty in your sampling will be reduced to the lowest level practical.
Noise and OSHA’s Hearing Conservation Program
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
There are several types of instruments that can be used to measure an employee’s sound-level exposure. The Type 1 sound-level meter is used for precision measurements in the field and has an accuracy of ±1 dB, while the Type 2 sound-level meter is used for general purposes in the field and has an accuracy of ±2 dB. The Type 2 sound-level meter is the minimum measuring device allowed for determining an employee’s noise-level exposure under the OSHA hearing conservation standard. Sound-level meters can be used to spot-check employee exposures, identify potential noise sources needing further evaluation, and assist in the feasibility of engineering controls.
Design modification of three-blade horizontal-axis wind turbine for noise reduction
Published in International Journal of Ambient Energy, 2022
D. Rajesh, P. Anand, Nishant Kumar Nath
Wind turbines majorly produce noise due to the effect of mechanical parts and aerodynamic effects of wind on blades. Sound reduction became an important factor in maintaining wind farms. In sound propagation, there will be the formation of sound pressure levels around the wind turbine. Sound pressure levels are measured using sound level meters that consist of a microphone that converts pressure variations into a voltage time series output that is calibrated in decibels. Testing is done in the anechoic room to calibrate the sound levels as shown in Figure 4. The sound is sensed by the micro phone, which is directly connected to the sound level meter and the computing system (Manwell, McGowan, and Rogers 2009). Whenever the sound is generated by the wind turbine, due to pressure variations in atmosphere, the sound pressure will be calibrated by the CLIO software with the help of the electro-acoustic integrated system, and the values of the micrometre parameters are listed in Table 4.