How Sensitive is the Human Ear?
The ear is most sensitive to sounds of frequency about 3,500 Hz (cycles per second) which is near the highest note a piccolo can produce, and for this frequency the threshold intensity (or the lower limit of intensity below which a sound is inaudible) is 0.0000000000000000155 of a watt, the pressure amplitude is about 0.00011 dyne per cm² and the displacement amplitude is about 0.000000000125 cm. Putting these figures into more understandable common references gives the following: The threshold intensity represents the intensity of the light and heat received from a 50-watt electric light bulb at a distance of 4,800 kms (3,000 miles) in empty space (i.e., if none were being absorbed by the atmosphere). That’s more than the distance from one side of Australia to the other!!! To understand the pressure amplitude figure, we need to know that the area of the human eardrum is about 1 cm² and the weight of a mosquito is of the order of 1 dyne. If, therefore, an insect of weight about one ten
