On average, human ears are sensitive to a sound of intensity 10−12 watt per meter squared at a frequency of 1000 hertz and can perceive a range of sound up to 1 watt per meter squared. However, a sound of this intensity can cause severe pain. To incorporate the massive range in SI units, the logarithmic scale is used to define the intensity level. On this scale, the intensity of 10−12 watt per meter squared is 0 decibels. For instance, the rustle of leaves in the forest has an intensity level of about 10 decibels, an average home is about 40 decibels, noisy traffic is 70 decibels, whereas the threshold of pain is 120 decibels.