Humans are equipped with sensitive ears capable of detecting sound waves of extremely low intensity, as faint as 1 x 10-12 W/m2. This is known as the threshold of hearing (TOH). The most intense sound which the ear can safely detect without suffering any physical damage is more than one billion times more intense. Physicists therefore often use a logarithmic scale (based on powers of ten) for intensity: the decibel scale. The TOH is assigned a sound level of 0 dB. A sound (e.g. the sound of rustling leaves) which is 10 times more intense (1 x 10-11 W/m2) is assigned a sound level of 10 dB. A sound (e.g. a whisper) which is 10\times 10 or 100 times more intense (1 x 10-10 W/m2) is assigned a sound level of 20 db. Etc. In general, if one sound is 10x times more intense than another sound, then it has a sound level which is 10x more decibels than the less intense sound. Practice Question 2 (a) How many times louder is a 100 dB sound than a 50 dB sound? A. 2 B. 4 C. 50 D. 100000 (b) If the intensity of sound produced by a rock band is 120 dB at 1.0 m, what is the intensity of the sound at 100.0 m?