![]() The sound intensity in the car is 57.8 dB. Therefore, by putting on both layers of ear protection, the worker reduces the sound intensity by a factor of 3162. The ratio of the full sound intensity to the reduced sound intensity the worker hears is approximately 3162. For example, a 90 dB sound compared with a 60 dB sound is 30 dB greater, or three factors of 10 (that is, 10 3 times) as intense. Each factor of 10 in intensity corresponds to 10 dB. That is, the threshold of human hearing is 0 decibels. The ratio of the full sound intensity to the reduced sound intensity, expressed as Watts per meter squared is. (c) The eight-hour time-weighted average sound level (TWA), in decibels, may be computed from the dose, in percent, by means of the formula: TWA 16.61. The decibel level of a sound having an intensity of 10 12 W/m 2 is 0 dB, because log 10 1 0. To identify which sound is which, they can be labeled with the index values 1 and 2: Using this mathematical formula for logarithms, the decibel formula can be rearranged to solve for I: The mathematical formula for logarithms needed is: Here dB stands for decibels, log stands for logarithm and II0 expresses sound intensity or reference intensity. To convert a power ratio to either bels or decibels, use one of these equations: When using the unit of the bel or decibel to express a voltage or current ratio, it must be cast in terms of an equivalent power ratio. If V and R are voltage and resistance, then power is given by Equation 8.9. The bel is fundamentally a unit for expressing power gain or loss. decibel (dB) relates to the volume factor, while A represents a weighting. This equation can be represented by: The intensity of sound in decibels is 10 dB × log (II0). A decibel is literally a deci-bel: one-tenth of a bel. This problem can be solved by finding I for decibel values of 120 dB and 85.0 dB, and then dividing the full intensity by the reduced intensity. First, decibels are always about power ratios, so don’t think there is a voltage dB and a current dB that is different from a power dB. Here the unit scale is termed as a decibel or dB. What is the ratio of the full sound intensity to the reduced sound intensity the worker hears?Īnswer: The decibel scale is logarithmic, and so a small drop in the decibel intensity means a much larger drop in the intensity expressed as. This reduces the intensity of the sound he hears from 120 dB to 85.0 dB. The sound intensity in the car is approximately 57.8 dB.Ģ) A worker uses double ear protection, both earplugs and earmuffs, to reduce the intensity of the sound of a jackhammer. The intensity of the sound in decibels can now be found using the decibel formula: "Micro" means, and so the sound intensity in the car is: What is this sound intensity in decibels?Īnswer: The sound intensity in the car is expressed in micro-Watts per meter squared.
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