Saturn V was loud but didn't melt concrete

The Saturn V carried man to the moon and remains the most powerful rocket to successfully launch to orbit. It captures the imagination—but sometimes, it might capture a bit too much imagination. Abundant internet claims ...

The science of stadium sound

Football fans attending BYU home games the last two seasons may have noticed a few students roving through the crowd, giving their full attention to hand-held scientific instruments instead of the game.

Eastern US to be overrun by billions of cicadas (Update)

Any day now, billions of cicadas with bulging red eyes will crawl out of the earth after 17 years underground and overrun the East Coast. The insects will arrive in such numbers that people in the southern state of North ...

The Bloodhound SSC: Faster than a speeding bullet

Twenty-nine years ago today, Richard Noble in Thrust2 broke the land speed record for Britain at 633.468 mph in October 1983. That day saw the start of my love affair with the land speed record. Again in September 1997 Richard ...

How hummingbirds produce fluttering sounds during courtship

Though famous for their mid-air hovering during hunting, tiny hummingbirds have another trait that is literally telltale: males of some hummingbird species generate loud sounds with their tail feathers while courting females. ...

Tiny water boatman is a champion singer

(PhysOrg.com) -- Researchers studying the lesser water boatman have discovered that adjusting for size, M. scholtzi, a tiny freshwater bug, is the apparent world champion at producing the loudest noise. At only 2.3mm (about ...

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Decibel

The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. A decibel is one tenth of a bel, a seldom-used unit.

The decibel is used for a wide variety of measurements in science and engineering, most prominently in acoustics, electronics, and control theory. In electronics, the gains of amplifiers, attenuation of signals, and signal-to-noise ratios are often expressed in decibels. The decibel confers a number of advantages, such as the ability to conveniently represent very large or small numbers, and the ability to carry out multiplication of ratios by simple addition and subtraction.

The decibel symbol is often qualified with a suffix, that indicates which reference quantity or frequency weighting function has been used. For example, dBm indicates a reference level of one milliwatt, while dBu is referenced to 0.775 volts RMS.

The definitions of the decibel and bel use base 10 logarithms. The neper, an alternative logarithmic ratio unit sometimes used, uses the natural logarithm (base e).

A change in power ratio by a factor of 10 is a 10 dB change. A change in power ratio by a factor of two is approximately a 3 dB change.

This text uses material from Wikipedia, licensed under CC BY-SA