The decibel system represents the intensity of a sound. The decibel system has a logarithmic scale, which means that decibels increase exponentially. Every 10 decibel increase represents a tenfold increase in energy. So a sound at 30 decibels has 10 times the energy of a sound at 20 decibels and 100 times the energy of a sound at 10 decibels.
Normal speech between two people typically has a range of 50 to 60 decibels. When two people are speaking in a public place with background noise, normal speech is louder, around five extra decibels. However, due to differing speech patterns among people, the range of normal speech could reach 65 decibels for some people who naturally talk louder than average. Conversely, some people who naturally speak softer may have an average level of 47 decibels during normal speech.
Shouting levels can vary, especially between men and women. Women typically have a lower effective level of loudness than men and may only be able to shout at around 75 decibels. Some men, on the other hand, can shout at over 100 decibels. Approximately 15 percent of women cannot raise their voices above 75 decibels while 15 percent of men can shout over 96 decibels.
The general lower limit for speech is around 30 decibels. Some people may be able to whisper quieter than this, but listeners may have trouble understanding speech below 30 decibels. This is the lower limit and some people may whisper at as much as 40 decibels.
Because decibels are a relative measurement rather than an absolute measurement, the lower limit for the ear is 0 decibels. Anyone exposed to extended periods of sound above normal speech, 85 decibels or more, risks damaging their hearing by disrupting the sensitive structures of the human ear. At 120 decibels, people experience pain. This sound would be equivalent to a nearby jackhammer.