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morbo!
12-07-2006, 02:54 AM
hiya`s
Today I was asked what a db was?

I suppose i read way too much
Becase i was talking to a relitivy smart person
It threw me for a second.
my reply was
It`s the linear measurment of the exponental event of sound:applaud:

I dont know if that was the right answer

But i got a firm nod and a i understand

Kinda left me wondering if i really did?

how close was i guy`s?

clmrt
12-07-2006, 04:33 AM
The decibel (dB) is a measure of the ratio (http://en.wikipedia.org/wiki/Ratio) between two quantities, and is used in a wide variety of measurements in acoustics (http://en.wikipedia.org/wiki/Acoustics), physics (http://en.wikipedia.org/wiki/Physics) and electronics (http://en.wikipedia.org/wiki/Electronics). While originally only used for power (http://en.wikipedia.org/wiki/Power_%28physics%29) and intensity (http://en.wikipedia.org/wiki/Intensity_%28physics%29) ratios, it has come to be used more generally in engineering (http://en.wikipedia.org/wiki/Engineering). The decibel is widely used in measurements of the loudness (http://en.wikipedia.org/wiki/Loudness) of sound (http://en.wikipedia.org/wiki/Sound). It is a "dimensionless unit (http://en.wikipedia.org/wiki/Dimensionless_unit)" like percent (http://en.wikipedia.org/wiki/Percent). Decibels are useful because they allow even very large or small ratios to be represented with a conveniently small number (similar to scientific notation (http://en.wikipedia.org/wiki/Scientific_notation)). This is achieved by using a logarithm (http://en.wikipedia.org/wiki/Logarithm).

[edit (http://en.wikipedia.org/w/index.php?title=Decibel&action=edit&section=14)] Relation to Loudspeakers

Speaker sensitivity is usually given in dBSPL @ 1 Watt (http://en.wikipedia.org/wiki/Watt) @ 1 meter (http://en.wikipedia.org/wiki/Meter).
The equation for dBSPL is :http://upload.wikimedia.org/math/0/c/e/0cebf8abae5f07a048cc247a351cb8af.png.
This means that a doubling in sound pressure output from a speaker relates to a 6 dBSPL increase.

[edit (http://en.wikipedia.org/w/index.php?title=Decibel&action=edit&section=15)] A practical example

A fictional 2 way speaker (http://en.wikipedia.org/w/index.php?title=2_way_speaker&action=edit) (A box with separate driver for high("Treble") and low("Bass") ) has the following specs:
High driver: 92 dBSPL @ 1W @ 1m. A Low driver: 86 dBSPL @ 1W @ 1m. B
Now if we want to match the output of the two speakers so the sound is "equally loud" we need to do the following:
Get the difference between the two by subtracting the sensitivity:
Difference in sensitivity = A-B
= 92 dBSPL - 86 dBSPL
= 6 dBSPL
As we concluded earlier this 6dB difference requires that we double the power delivered to the low driver. Since a doubling in [power] relates to 3 dB, we need to adjust the cross-over unit in this system so that the [gain] of the Low signal is 3dB more than the Highs. If there is no crossover you can always adjust the Amplifier's output to be 3dB more

******

dB(SPL)
dB(Sound Pressure Level) — relative to 20 micropascals (μPa) = 2×10−5 Pa, the quietest sound a human can hear.[1] (http://en.wikipedia.org/wiki/Decibel#_note-SPL) This is roughly the sound of a mosquito flying 3 metres away. This is often abbreviated to just "dB", which gives some the erroneous notion that "dB" is an absolute unit by itself.

morbo!
12-07-2006, 04:46 AM
Thanks
Thats gonna take awhile to sink in.
But it appears my answer was`t too bad in terms of referance.

Wonder how i pulled that out my ass.

Just not wanting too appear stupid?:blink:

I was no where near the net or i prolly woulda googled it.