While many people are aware of what the term decibel means, not many can accurately say what the various acronyms associated with it are meant for – this article will help provide an explanation. Decibels were named to honor Alexander Graham Bell, the inventor of the telephone – the term refers to the intensity of a sound and is often referred to as dB for short. From +40 to -20 is a 60 dB difference.If you require a quiet actuator for your application where noise pollution is a concern, the best way is to check out the noise rating along with verifying this value with a decibel chart. 2 times 10 is -20, so now my damaged power source is producing 20 dB less than a milliwatt, or -20 dBm. Running the numbers now gives a very different result. Instead of producing 10 watts, it now produces one-hundredth of a milliwatt. So, lightning hit my power source, and now it's very weak. 4 times 10 is 40, so that means that my power source is producing 40 dB more power than a milliwatt, or +40 dBm. The log of 10,000, according to my convenient HP calculator, is 4. Plugging that into our handy-dandy dB formula, we get: Let's run the numbers to show how it works…Ī milliwatt is 1/1000 of a watt. Let's say, for example, that I am measuring a power source, and the power meter shows that it is producing 10 watts. P1 is the measured power that I am trying to compare to the milliwatt. Let me unpack that with an example: If I want an absolute measurement of power, such as dBm (power referenced to a milliwatt, as mentioned above), then P2 is one milliwatt. Allow me to explain… If you have a power source that is so many decibels above or below the power you are comparing it to, that is P1 in the equation above, while P2 is the power you are using to compare it to. P1 is the power in question, while P2 is the reference power. However, with modern calculators, you don't need to. It's not simple if you cannot handle logarithms. The formula for calculating decibels is relatively simple. More power equals a positive number less power equals a negative number. For example, the one-watt transmitter mentioned above is -10 dB compared to the 10-watt transmitter. Wait, what? Yes, decibels can be negative. For example, 10 dBm is 10 dB above one milliwatt or 10 milliwatts. Once decibels are referenced to a certain standard, they become a measurement with an absolute meaning. dBm means decibels related to a milliwatt of power, dBW is decibels related to one watt, dBV is decibels related to one volt. These terms represent decibels related to some standard of measurement. If decibels are a relative measurement, then what are all these terms like dBm, dBW, dBV, and so on? There is a relative relationship between the two things. For example, a 10-watt transmitter is 10 dB more powerful than a 1-watt transmitter. 10 decibels with respect to what? That's like saying "ten times." Ten times what? So, decibels represent a ratio of two levels. Decibels express a ratio between two levels of power (or, in some cases, voltage), meaning that a figure of "10 decibels" is meaningless. Keep your trusty calculator at the ready, and you'll be all set! Let's get started… Decibels are a relative measurement. Yes, I will share a few formulas, but I promise you won't have to work out anything by hand. My goal is to help you understand how decibels work and why they are important without drowning you in a sea of math. Cheat sheets, such as our handy decibel chart, can make it easier to employ this helpful tool, but even with such aids, folks without a basic understanding of the concept can still get lost. Decibels (dB) are a mysterious, mathematically complex concept for many people.īecause the math behind decibels is slightly more advanced than the basic stuff, many folks unfortunately shy away from using decibels to their disadvantage.
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