Anything related to the decibel (dB) and similar logarithmic units of measurements (dBm, dBW, etc.).
Anything related to the decibel (dB) and similar logarithmic units of measurements (dBm, dBW, etc.).
See also Wikipedia on decibel.
Questions tagged [decibel]
89 questions
32
votes
5 answers
What is the significance of -3 dB?
My oscilloscope has 100 MHz -3dB bandwidth. -3dB is 0.707 units (\$\sqrt{2} / 2\$). What does this mean, why 70.7% attenuation? Is there any particular reason for this attenuation level?
Thomas O
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4 answers
Why do 16 bit systems have a minimum dBFS of -96?
I'm working through the example on this page:
http://chimera.labs.oreilly.com/books/1234000001552/ch03.html
I totally understand why the maximum level of an audio system would be 0 because the log of 1 is 0.
However, I'm confused about the minimum.…
Aptary
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1 answer
The unit that is written between parentheses alongside the dB
What is the meaning of the unit that is written between parentheses alongside the dB unit? For example 2 dB (mW) or 2 dB (uW)? What exactly does this unit refer to? Does it refers to the unit of the reference value, the measured value (P2), or both?
John adams
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Why do we use dB to represent the difference between two voltages?
For example, the passband of a LC resonant circuit is the differences of frequency at +3db and -3db.
Why do we prefer dB?
Jichao
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mW or W when calculating decibels
In my instrumentation class we have been given the following formula to get the power in decibels:
\$10Log(Power(mW)/mW)\$
I'd like to know if taking the power in miliwatts is something widely done or has any importance?
PhoenixPerson
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If a microphone has an output voltage of 2.5mV @ 1Pa, what would its output voltage be when 98dB SPL is applied to the diaphragm?
Microphone spec sheets specify a microphone’s sensitivity by displaying the voltage at the output of the microphone when 1 Pa is applied to the diaphragm. If a microphone has an output voltage of 2.5mV @ 1Pa, …
Lamar Bryant
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vote
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What is the proper dB unit to use when expressing the amplitude of a sample in a digital audio recording?
I've seen 20*Log10(amplitude) as the proper way to calculate dB, where 0 < amplitude <= 1. (So, to get amplitude when signed integer data types are used to represent amplitudes, you use value/maxvalue for positive values and value/minvalue for…
trw
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How to solve decibels?
If a microphone has an output voltage of 1.45mV @ 1 Pa and a microphone preamplifier adds 50dB of gain, what would the voltage at the output of the mic pre be, assuming the pressure applied to the diaphragm…
Lamar Bryant
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The importance of Decibels
I have a question , why decibels are useful for electrical engineers ?? I still can't figure out why it is useful to use decibels in expressing power ratios , gain and other things ?
John adams
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Is the 3dB turnover and 45° correspondence only valid for low pass filter transfer function?
I have been reading at some systems that at 3dB point the phase shift becomes 45°. But is this fact only valid for low pass filters?
GNZ
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Decibel vs Decibel milliwatts
What are the differences between Decibel (dB) and Decibel milliwatts (dBm)? I'm most interested in dBm with cell phone signal strength. Please give a detailed explanation. I'm not familiar with the basics so I didn't understand what I was reading…
cokedude
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