Solar Energy
As energy costs rise, more and more consumers seek alternative means to meet their heating...
A thermometer measures temperature in degrees Fahrenheit and Celcius, and a ruler measures length in inches and centimeters. When it comes to the measurement of sound volume, the unit that is used is the decibel. Really, the sound unit is the bel, which is named after Alexander Graham Bell, the inventor of the telephone. But for common sounds, the bel was too large so the decibel, which is one-tenth of a bel, was created. The decibel scale is set to the human capacity for hearing. A sound that the human ear can just barely hear, such as the buzz of a mosquito, is 0 decibels. Someone's whisper in your ear is 20 decibels, and a vacuum cleaner is 80 decibels. At 130 decibels, the human pain threshold is reached; this means that any sounds louder than 130 decibels, such as a jet engine or bomb explosion, can hurt the listener. This is why sirens are set at 130 decibels.
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