• Well, it's hard to compare against zero; you get infinity. So let's say between 10db and 50db. Each 10db is a power of 10. So a 40db sound difference is 10^4 or 10,000 times louder.
• A decibel is a very misunderstood measurement of sound volume. It is logarithmic, and for every 10dB a doubling of volume occurs. Also, 0 dB does not mean absolute silence, but is actually the designation for the quietest sound which can be heard. 10dB louder would be twice as loud, 20dB louder would be four times as loud, 30dB louder would be eight times as loud, 40dB louder would be sixteen times as loud Here's an article and chart for you - http://www.gcaudio.com/resources/howtos/voltageloudness.html Here's a page with quite a bit of info on relative volumes in terms of decibels - http://www.gcaudio.com/resources/howtos/loudness.html "Ultimate" Decibel chart - http://www.makeitlouder.com/Decibel%20Level%20Chart.txt http://community.discovery.com/eve/forums/a/tpc/f/7501919888/m/9511927169 Explanation of the Bel and Decibel - The human ear is capable of identifying a wide range of sounds. The level of sound the ear first begins to recognize (threshold of hearing) has been determined to be .0002 microbars. A microbar is a measurement of sound pressure similar to the inch being a measurement of length. The small amount of pressure causes the ear membrane to move less than the diameter of a single atom! A sound loud enough to begin to create a sensation of pain (threshold of pain) represents a sound pressure that is 3,162,300 times more than the threshold of hearing! These are the limits in our range of hearing. Of course, if we used the microbar to describe sounds, the numbers would be very cumbersome. In addition, it would be difficult to comprehend any comparisons. Early acousticians came up with a simple method of comparing two sounds. A sound that was perceived to be twice as loud as another was said to be one Bel greater in sound level. The Bel was used as a unit of comparison. It is not a unit of measure. Its namesake, Alexander Grahm Bell, was a pioneer in the science of audiology (the study of human hearing). It soon became apparent this unit of comparison was not very useful in describing the difference between similar sounds. A small unit of comparison, the decibel, was established. One decibel (1 dB) is one-tenth of a Bel. Since a decibel is one-tenth of a Bel, then 10 decibels (10 dB) would equal one Bel. In other words, a sound that is twice as loud as another sound could be described as being 10 decibels (10 dB) louder. By definition, one decibel (1 dB) represents the smallest change in volume a human ear can perceive. The threshold of hearing is defined as 0 dB SPL. However, sound still exists at 0 dB. Remember the dB (decibel) is a unit of comparison, not a unit of measure. For example, leaves rustling is given an average value of 10 dB SPL. That means the sound of leaves rustling is 10 dB louder than the threshold of hearing (0 dB SPL), or twice as loud. Commercial background music is approximately 60 dB SPL and a very quiet radio at home is 40 dB SPL. A sound that is 50 dB SPL would be twice as loud as 40 dB SPL and 60 dB SPL would be twice as loud as 50 dB SPL. http://www.soundinstitute.com/article_detail.cfm/ID/95
• I'm faily certain sound actually doubles every 3dB.
• To give examples, 0dB is considered the lowest sound normally heard by humans; 20dB might be the level of rustling leaves in a small breeze; 40dB the noise in a (relatively) quiet library, 60dB the level of a normal conversation indoors. In terms of audio, a 100dB range would be a wide range for loud and soft music.