To keep your operators safe and reduce NIHL, it is important to measure the total sound level. The total sound level is now in accordance with OSHA regulations for the operator to work all 8 hours at the machine without hearing protection.Ī commonly used acronym in hearing safety is NIHL, or Noise Induced Hearing Loss. By replacing all four copper tubes with Super Air Nozzles, Equation 2 becomes: The noise level for each nozzle is 74 dBA. In this same example, we replaced the copper tubes with an EXAIR Super Air Nozzle, model 1110SS. In looking at the OSHA chart, the operator would only be allowed to operate the machine only a little over one hour without hearing protection. The total amount of sound that the operator was exposed to was determined by Equation 2 with four values. The decibel level for a copper tube was measured at 98 dBA. Where L1, L2… represents the sound pressure level in dBA for each sound source.Īs an example, a manufacturing plant had an operator using a machine that had four copper tubes to blow off a cutting operation (reference photo below). To determine the total sound level, we can add all the sound pressure levels together by Equation 2: To use the OSHA chart accurately, the total noise level in dBA should be calculated. OSHA created a chart in the 29CFR-1910.95(a) standard that shows the noise levels over exposure times for an operator. Sound measurements for safety are measured in the A-weighted scale. For higher and lower frequencies, the change in the sound value is much greater than the mid-level frequencies that are within our hearing range. The A-weighting is the most commonly used value as the sound pressure levels are adjusted by the frequency level. The C-weighting is for very loud noises with high peaks or sharp impacts like gunfire. This adjustment is done in two different ways A-weighting and C-weighting. L = 20 * Log 10 (0.1Pa/0.00002Pa) = 74 dBīecause human ears are sensitive to different frequencies, the sound pressure levels can be modified, or weighted, to indicate an effective loudness level for humans. With Equation 1, we can get the following decibel level: Pref – reference sound pressure, 0.00002 PaĪs an example, the sound pressure from a passenger car as heard from the roadside is 0.1 Pa. This correlation between sound pressures and sound pressure levels are calculated by Equation 1: From sound pressures, we can arrive to a sound pressure level which is measured in decibel, dB. The lowest pressure perceived by human hearing is 0.00002 Pa, and we can use this value as a reference point. In looking at a single source of sound, sound pressure is created by the loudness of a noise. This is very important when it comes to minimizing hearing loss. Sounds can be added together to determine the overall sound level that your hear. Today I will be discussing what happens when you have more than one sound source, as often heard within manufacturing plants. I discussed the logarithmic equations around sound. I recently wrote a blog about “Sound Power and Sound Pressure”.
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