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Orion
| | Posted on Tuesday, May 27, 2003 - 1:09 am: | 
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What does the "-20db", "-38db" and "-44db" indicate in the three examples of popular mics listed below. I guess a good way to answer it would be by saying "the -20db is _____ compared to the -44db".
Output Level: -20 dB below 1 volt per microbar at 1 kHz into 1 megohm load
Output Level: -38 dB below 1 volt per microbar at 1 kHz into 1 megohm load
Output Level: -44 dB below 1 volt per microbar at 1 kHz into 1 megohm load |
2600
| | Posted on Monday, June 02, 2003 - 2:17 am: |
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The "dB" is a ratio between two power levels. A two-to-one power ratio is very nearly 3 dB. A calculator will say that it is 3.0103 dB. A ten-to-one power ratio is 10 dB. A hundred-to-one power ratio is 20 dB. A thousand-to-one is 30 dB, and a ten thousand-to-one power ratio is 40 dB. Since power increases (or decreases) as the square of voltage, 10 dB is a voltage ratio of 3.16 to one.
Using their "1 Volt" reference point, -20 dB would be one-tenth of a Volt.
-38 dB should be around .012 Volts.
-44dB should be half that, more conveniently described as around 6 milliVolts, or .006 Volts.
The way microphone output levels are described, the lower the "dB" number, the higher the actual mike output level. The higher the number, the wimpier it is.
73 |
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