Watts and Decibels
PolkThug
Posts: 7,532
Good read for how watts and decibels correspond.
"DECIBEL, or dB
- excerpt from Audio Dictionary by Glenn While
Literally, one tenth of a bel. The bel is named after Alexander Graham Bell, and the number of bels is defined as the common logarithm of the ratio of two powers. Thus, two powers, one of which is ten times the other, will differ by 1 bel; 10 WATTS are 1 bel higher in level than 1W. A 360-horsepower car is 1 bel more powerful than a 36-horsepower motorcycle. Any power ratio may be expressed in bels, and it is important to note that only power ratios are allowed. A bel is a pure number with no dimensions.
The bel had its origin in the Bell Telephone Labs, where workers needed a convenient way to express power losses in telephone lines as power ratios. Because the bel is a power ratio of 10, and this is a rather large ratio, it is convenient to divide it into tenths of bels, or decibels, abbr. dB. Ten dB is 1 bel; thus the DECIBEL is ten times the common log of the ratio of two powers. The DECIBEL was originally called the "transmission unit," or TU, by the Bell Labs people.
Because of the properties of logarithms, it is easy and convenient to form some "rules of thumb" about decibels. The common log of 2 is 0.301, so a power ratio of 2 is 3.01 dB, normally taken as 3 dB. Therefore, any two powers differing by a factor of 2 will be 3 dB apart, and this applies to any type of power whatever, so long as it is power. Two light bulbs of 100W and 50W differ by 3 dB, just as electric motors of 1 horsepower and 2 horsepower differ by 3 dB. So, any time a power is doubled, it is increased by 3 dB. An increase of 6 dB represents two doublings of power, or a power ratio of 4. If an orchestra increases its SOUND PRESSURE LEVEL by 3 dB, its acoustic power output will be doubled.
Another rule of thumb that is useful to remember is that 10 dB is a power ratio of 10. Any time a power is increased tenfold, it is increased by 10 dB; thus, a 200W power amplifier will put out 10 dB more electrical power than a 20W amplifier, and its sound power output will also increase by 10 dB.
Another way to think of decibels is to think in terms of percentages. We all know what 10 percent means, and nobody thinks of percentages as being quantities of anything. A DECIBEL is nothing more than a power change of 27 percent, 3 dB is a power change of 100 percent, and 10 dB is a power change of 1,000 percent. "
"DECIBEL, or dB
- excerpt from Audio Dictionary by Glenn While
Literally, one tenth of a bel. The bel is named after Alexander Graham Bell, and the number of bels is defined as the common logarithm of the ratio of two powers. Thus, two powers, one of which is ten times the other, will differ by 1 bel; 10 WATTS are 1 bel higher in level than 1W. A 360-horsepower car is 1 bel more powerful than a 36-horsepower motorcycle. Any power ratio may be expressed in bels, and it is important to note that only power ratios are allowed. A bel is a pure number with no dimensions.
The bel had its origin in the Bell Telephone Labs, where workers needed a convenient way to express power losses in telephone lines as power ratios. Because the bel is a power ratio of 10, and this is a rather large ratio, it is convenient to divide it into tenths of bels, or decibels, abbr. dB. Ten dB is 1 bel; thus the DECIBEL is ten times the common log of the ratio of two powers. The DECIBEL was originally called the "transmission unit," or TU, by the Bell Labs people.
Because of the properties of logarithms, it is easy and convenient to form some "rules of thumb" about decibels. The common log of 2 is 0.301, so a power ratio of 2 is 3.01 dB, normally taken as 3 dB. Therefore, any two powers differing by a factor of 2 will be 3 dB apart, and this applies to any type of power whatever, so long as it is power. Two light bulbs of 100W and 50W differ by 3 dB, just as electric motors of 1 horsepower and 2 horsepower differ by 3 dB. So, any time a power is doubled, it is increased by 3 dB. An increase of 6 dB represents two doublings of power, or a power ratio of 4. If an orchestra increases its SOUND PRESSURE LEVEL by 3 dB, its acoustic power output will be doubled.
Another rule of thumb that is useful to remember is that 10 dB is a power ratio of 10. Any time a power is increased tenfold, it is increased by 10 dB; thus, a 200W power amplifier will put out 10 dB more electrical power than a 20W amplifier, and its sound power output will also increase by 10 dB.
Another way to think of decibels is to think in terms of percentages. We all know what 10 percent means, and nobody thinks of percentages as being quantities of anything. A DECIBEL is nothing more than a power change of 27 percent, 3 dB is a power change of 100 percent, and 10 dB is a power change of 1,000 percent. "
Post edited by RyanC_Masimo on
Comments
-
Now that we've cleared that up....Originally posted by PolkThug
Two light bulbs of 100W and 50W differ by 3 dB...
Will you turned down the friggin' light bulb???More later,
Tour...
Vox Copuli
Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb
"Death doesn't come with a Uhaul." - Dennis Gardner
"It's easy to get lost in price vs performance vs ego vs illusion." - doro
"There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD -
That's why my wife gets mad when I leave all the lights on, its too friggin loud!
-
I find overhead lights to be too "bright"..
I prefer lamps...Cary SLP-98L F1 DC Pre Amp (Jag Blue)
Parasound HCA-3500
Cary Audio V12 amp (Jag Red)
Polk Audio Xm Reciever (Autographed by THE MAN Himself) :cool:
Magnum Dynalab MD-102 Analog Tuna
Jolida JD-100 CDP
Polk Audio LSi9 Speaks (ebony)
SVS PC-Ultra Sub
AQ Bedrock Speaker Cables (Bi-Wired)
MIT Shotgun S1 I/C`s
AQ Black Thunder Sub Cables
PS Audio Plus Power Cords
Magnum Dynalab ST-2 FM Antenna
Sanus Cherry wood Speak Stands
Adona AV45CS3 / 3 Tier Rack (Black /Gold)
:cool: -
Its all coming together now. I like track lighting arrays.
