Hot answers tagged

37 votes
Accepted

What does a Bode plot represent and what is a pole and zero of a Bode plot?

Bode plot Take a typical 2nd order low pass filter amplitude response bode plot: - 3-D picture introducing pole-zero diagram Here's the bigger picture of that response when combined with a pole ...
Andy aka's user avatar
  • 452k
23 votes

Is there any way to measure sound intensity in decibels without using a microphone?

If your customers aren't electrical engineers, how would they tell a small microphone on your main circuit board from say an oscillator, opamp, or voltage regulator? So any customer that only buys ...
Constantine A. B.'s user avatar
22 votes

What is the meaning of dBi?

For an antenna, a gain of 22 dBi means a gain of 22 dB with respect to a theoretical isotropic antenna. If an isotrpoic antenna radiates 1 watt, it would radiate that power uniformly over the 4π ...
Neil_UK's user avatar
  • 165k
12 votes
Accepted

The unit that is written between parentheses alongside the dB

dB is a measure of ratio, nothing more. As such, if an absolute measurement is expressed in dB, then we need to know what the denominator of that ratio is. For frequently used units, like dBm for ...
Neil_UK's user avatar
  • 165k
12 votes
Accepted

Is there any way to measure sound intensity in decibels without using a microphone?

You need to improve the definition of your problem. Privacy Does that mean any talking is unintelligible? The fact that some sounds can be heard, at a specific time, even if they are unintelligible as ...
Neil_UK's user avatar
  • 165k
11 votes
Accepted

Where does this decibel equation come from, why a factor of 20?

Sound power (\$P\$) is proportional to the sound intensity (\$I\$): $$ P = A\ I $$ where \$A\$ is the surface area. And sound intensity (\$I\$) is proportional to the square of sound pressure: $$ I = \...
Rohat Kılıç's user avatar
9 votes

Is there any way to measure sound intensity in decibels without using a microphone?

Any device or transducer that can convert sound to electrical signal is by definition a microphone. Even capacitors can exhibit microphonics and can ruin your signal by converting audio or mechanical ...
Justme's user avatar
  • 143k
8 votes

Why -3 dB in signal to noise ratio (SNR)

-3dB is the point of 50% power. The point when the tipping point changes from a majority of the power to a minority of the power gets through. The native form of the equation is: $$ SNR=10\log_{10}\...
DKNguyen's user avatar
  • 56.4k
7 votes
Accepted

Meaning of dB while dealing with amplifier(Op-Amp)

Here's some common dB values for voltage amplification: 20dB gain => \$10^{\left(\frac{20}{20}\right)}=10\$ 6dB gain => \$10^{\left(\frac{6}{20}\right)}≈2\$ 3dB gain => \$10^{\left(\frac{3}{20}\...
Harry Svensson's user avatar
7 votes
Accepted

What is the meaning of dBi?

Say you have a source of 0 dBm power. If you hook it up to an antenna with 22 dBi gain, then in the direction of the main lobe, your source appears to be 22 dB stronger than it would if it were ...
Joren Vaes's user avatar
  • 12.5k
6 votes

How to interpret this type of dBm?

How to interpret this type of dBm? The same way you would interpret dBm × Hz, since wavelength is proportional to 1/Hz: dBm/wavelength = dBm/(1/Hz) =dBm × Hz. It's not all that different compared to ...
Kuba hasn't forgotten Monica's user avatar
6 votes

How to interpret this type of dBm?

The other two answers have reassured you that integrating the power is the correct thing to do, and why it's expressed that way. Please bear in mind that 'integrating dBm' does not mean integrating ...
Neil_UK's user avatar
  • 165k
6 votes
Accepted

Convert dB to ohms

Presumably what you're measuring is return loss, or S11, in dB, of the load that you want the resistance of. Let's assume you're measuring a pure resistor at the reference plane, so S11 will have a ...
Neil_UK's user avatar
  • 165k
5 votes

Calculate linear phase when given in decibel

Taking as a clue that the phase lag at low frequency is about 90 'somethings', we can safely assume that the phase axis numbers are in degrees, and the dB is a typo.
Neil_UK's user avatar
  • 165k
5 votes
Accepted

A confusion with power ratio jargon used in antenna directivity (dBi/dBd)

An isotropic antenna would radiate equally well (or be equally sensitive) in all directions. A dipole antenna is directional, radiating little or no power off the ends of the element, instead ...
Peter Bennett's user avatar
5 votes

Valid or invalid logarithm operation?

But isn't dBm + dBm operation invalid? x dBm is a power. It's perfectly reasonable to add together two powers to get another power, powers add after all. However, if you took a signal of -45dBm and ...
Neil_UK's user avatar
  • 165k
4 votes
Accepted

Exact meaning of dB?

Typically the noise floor is the ratio of the noise with input shorted to the maximum output. If you have an amplifier capable of 1V RMS output and the noise floor is -120dB then the noise is 1uV ...
Spehro Pefhany's user avatar
4 votes

Valid or invalid logarithm operation?

You're missing the point of using decibel: multiplication in linear terms becomes addition in logarithmic terms. So, since the question was "what is the ratio of transmitted power to sensitivity&...
Marcus Müller's user avatar
3 votes
Accepted

Calculate linear phase when given in decibel

It looks like the data sheet has screwed up. The right hand vertical scale should not be "Phase (dB)" but "Phase (degrees)". This sort of thing happens now and then. How do I know? I know this ...
Andy aka's user avatar
  • 452k
3 votes
Accepted

Receiving power from antenna (Homework)

You are confusing dB with "linear" units. To convert from mW (a linear unit) to dBm (decibels with respect to 1mW), use the equation: Power_dBm = 10*log10(Power_mW) As a general rule of thumb, you ...
Selvek's user avatar
  • 1,957
3 votes

How to convert volts to dB SPL

Coming here many years later and I am still confused by the top answer, only because I am trying to solve this exact problem. As stated in the top answer, voltage gain is calculated as 20*log10(V1/...
Travis Babola's user avatar
3 votes

What is the significance of -3 dB?

Kellenjb's answer is excellent, I just wanted to add a webpage that gave me a "Ohhh" moment when I was reading about this -3db thing. Maybe it helps to visualize. I read a tutorial on Band Pass ...
dimsum88's user avatar
3 votes
Accepted

Understanding microphone sensitivity

For example, a microphone's sensitivity is -46dB(V)/Pa -46 dBV is about 5 mV RMS and bear in mind we are talking about pure sinewaves at 1kHz (mid band). It's 5 mV because \$10^{\frac{-46}{20}}\$ = 5 ...
Andy aka's user avatar
  • 452k
3 votes

How to convert dBm to V/m, A/m², and W/m²

If you assume all the power shown by the spectrum analyser is efficiently transferred from space to your antenna then that's a beginning. For this to be true, the antenna has to be matched to the 50 ...
Andy aka's user avatar
  • 452k
3 votes

How to interpret this type of dBm?

would the integral of that section give the average power in dBm Yes, it would give you the (total) power in dBm over the interval [2065nm ; 2075nm] what is the purpose of using dBm/nm and what does ...
Rahmany's user avatar
  • 474
3 votes

How does dB apply for non-linear components?

Think of dB as something like a comparison tool to compare one value to another (reference). One important point here is that the things to be compared should be of same type and unit. This can be ...
Rohat Kılıç's user avatar
3 votes

Is there any way to measure sound intensity in decibels without using a microphone?

Yes, in fact, it is a common ultrasound measuring technique to measure sound intensity by looking at the force exerted on a target (with a sensitive weighing apparatus). Ultrasonic power output ...
Whit3rd's user avatar
  • 7,558
2 votes

Electret microphone - How to reduce sensitivity

When you unsolder the microphone, you'll find the layout on the bottom somewhat like the following (here a Panasonic WM-52B): There are two solder pads that are almost split in the middle. In this ...
user107063's user avatar
  • 3,693
2 votes

Electret microphone - How to reduce sensitivity

The "Linkwitz mod" reduces the sensitivity of an electret mic and allows the mic to have very loud sounds (from a drum) with low distortion. You cut the pcb trace that connects the metal ...
Audioguru's user avatar
  • 4,308
2 votes
Accepted

How does doubling the voltage amplitude change the decibels?

If the voltage is increased by G then the signal has increased by: - \$20\cdot log_{10}(G)\$ decibels. This would also mean the same decibel increase in SPL. However, for "A" weighting you should ...
Andy aka's user avatar
  • 452k

Only top scored, non community-wiki answers of a minimum length are eligible