This means that the two sound intensity levels differ by 3.01 dB, or about 3 dB, as advertised. Another example is that if one sound is 10 7 10 7 as intense as another, it is 70 dB higher. 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 10 3 times) as intense. One more observation readily verified by examining Table 17.2 or using I = ( Δ p ) 2 ρv w 2 I = ( Δ p ) 2 ρv w 2 is that each factor of 10 in intensity corresponds to 10 dB. Power is the rate at which energy is transferred by the wave. Intensity is defined to be the power per unit area carried by a wave.

The relevant physical quantity is sound intensity, a concept that is valid for all sounds whether or not they are in the audible range. High noise exposure is hazardous to hearing, and it is common for musicians to have hearing losses that are sufficiently severe that they interfere with the musicians’ abilities to perform. In cartoons depicting a screaming person (or an animal making a loud noise), the cartoonist often shows an open mouth with a vibrating uvula, the hanging tissue at the back of the mouth, to suggest a loud sound coming from the throat Figure 17.12. We are all very familiar with the loudness of sounds and aware that they are related to how energetically the source is vibrating. But when a passing motorist has his stereo turned up, you cannot even hear what the person next to you in your car is saying. After settling into bed, you may hear your blood pulsing through your ears. In a quiet forest, you can sometimes hear a single leaf fall to the ground. Figure 17.11 Noise on crowded roadways like this one in Delhi makes it hard to hear others unless they shout.

The decibel scale mastering physics