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Questions tagged [decibel]

Anything related to the decibel (dB) and similar logarithmic units of measurements (dBm, dBW, etc.).

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How can I get 110 dB from a 10 or 15 mm piezo?

I’m trying to get the loudest sound possible out of a 10 or 15 mm piezo. I got 120 dB from a 20 mm piezo with 12 V but hoping to get the same sound from a smaller size. Any suggestions?
Mary 's user avatar
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1 answer
102 views

Noise decibel meter - how to convert MAX4466 voltage output to unweighted dB(SPL)

Using this microcontroller with that electret microphone amplifier, I want to build an unweighted dB(SPL) meter as good as it can get - then compare it to this ready made breakout board, this NIOSH ...
Systembolaget's user avatar
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2 answers
45 views

KY038 sound sensor: Voltage to SPL

I'm writing code to measure frequencies with a KY038 microphone sound sensor. It uses an LM393 voltage comparator. How do I convert voltage to sound pressure level (SPL)?
HAMZA SAVAI's user avatar
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2 answers
94 views

Conversion of radio emissions to decibels and role of impedance ratio to power ratio

This question is about a web article about radio noise suppression by Ferrite beads. The above diagram plots of a family of four curves for the ferrite bead. Each curve depicts the relation of ...
Jacob Miller's user avatar
10 votes
6 answers
2k views

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

I am trying to measure sound intensity in decibels without using microphone in a home automation project. Due to privacy concerns, I don't want to use a microphone in the device. Is there any way I ...
Moaz Azam's user avatar
0 votes
3 answers
106 views

How does dB apply for non-linear components?

I understand that decibels are used to express power and we can use 20log(V1/V2) and 10log(P1/P2) to find the voltage and power ratios. But what are we meant to do when it comes to non-linear ...
zsky3333's user avatar
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1 answer
127 views

How to convert from datasheet dB value to pressure per volt?

I am trying to measure sound waves using a Raspberry Pi Pico ADC pin but am having trouble converting the sensitivity value on my data sheet into pressure units per volt. I have read a many articles ...
user10709800's user avatar
0 votes
1 answer
3k views

Convert dB to ohms

I did some impedance measurements in high frequencies using a VNA. I did not pay attention to the format of the measured values that were in dB so it is now to late for me to reperform measurements. I ...
Wallflower's user avatar
5 votes
3 answers
587 views

How to interpret this type of dBm?

I have encountered a spec of a laser diode given in dBm/nm instead of dBm: If I want to know the average power between 2065nm and 2075nm, would the integral of that section give the average power in ...
user1245's user avatar
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2 votes
3 answers
576 views

Valid or invalid logarithm operation?

Is the following operation valid or invalid? The question is to calculate receiver gain and this is one of the steps I got confused. The receiver sensitivity is given -45dBm and transmitted power is ...
eldenlord9394's user avatar
0 votes
2 answers
73 views

What happens when we reach the maximun atenuation in Optical Networks Terminals (Optical fiber )?

Let´s suppose We have the following Optical Network Terminal : According to datasheet, the receiver sensitivity is : -27 dBm Now Let´s suppose We have the following fiber optical network : As we ...
NIN's user avatar
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1 answer
497 views

Meaning of dB units in periodogram (FFT)

When I calculate spectrum of a voltage signal using FFT and then I calculate periodogram using $$S_k=10\cdot log_{10}(\frac{1}{N}|X_k|^2)$$ where \$X_k\$ if the result of FFT and \$N\$ is number of ...
Jiří Maier's user avatar
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1 vote
3 answers
1k views

Scale dB SPL based on mic sensitivity

I have a measurement performed using GRAS 46AE microphone calibrated at 410mVrms at 114dB (250Hz). I have a .wav file recorded and performed stft and obtained the magnitude. Now I would like to scale ...
Shan's user avatar
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2 votes
0 answers
706 views

Sound level meter using a microphone with ADC

I'm working with STM32F4, MAX4466 amplifier and a condenser microphone. In other words, Adafruit 1063. I want to get the sound level in dB unit. I know: Microphone sensitivity: 0.0063096 V/Pa ...
sabruri1's user avatar
3 votes
1 answer
2k views

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

For sound levels, it is said that decibels follow this equation: $$ dB = 20 \log(\frac{p_s}{p_0}) $$ Where \$p_s\$ is the pressure of the measured sound wave (in Pascals) and \$p_0\$ is some fixed ...
user525966's user avatar
0 votes
0 answers
31 views

How to solve decibels? [duplicate]

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, ...
Lamar Bryant's user avatar
0 votes
1 answer
163 views

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 ...
Lamar Bryant's user avatar
9 votes
2 answers
2k views

What is the meaning of dBi?

When we say, for example, an antenna has spec of 22 dBi; Does it mean that its power is 22 dB stronger for any point at fixed direction than if it were to emit spherically?
Noob_Guy's user avatar
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5 answers
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dB scale in LTspice

I have a question about the dB scale in Ltspice. As far as I know it uses 1 of the unit (so 1V in case of Voltage) as a reference and then plots the dB value, which is defined by 20*log(V/Vref). (So ...
Sandra's user avatar
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0 votes
1 answer
1k views

How to scale audio signal from PCM data to a dB SPL value?

0 I've got a set with MEMS microphones that measure audio signals at ultrasonic frequencies. The MEMS microphones have a PDM output which is then converted into PCM (this is necessary to allow for a ...
dg1271's user avatar
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3 votes
3 answers
8k views

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

Currently I am using a spectrum analyser (SA) Keysight N9020, with an antenna to get readings off the air. The reading on the SA gives a reading of a unit, dBm. However, I need to convert dBm to V/m, ...
arthur yeo's user avatar
10 votes
1 answer
4k views

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

I studied Bode plots and the author of my book is somehow relating zeros of transfer functions to Bode plots. What is the relation between zeros or poles of a Bode plot and transfer function? We ...
Ali Aqdas's user avatar
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-2 votes
1 answer
3k views

dBA conversion into dB or dB SPL

I saw many websites that how to convert dBA sound to Db and dB SPL conversion. but I did not find any such relationship to convert dBA into dB or dBSPL. Is there any such formula or relationship that ...
Hariom Saini's user avatar
0 votes
2 answers
963 views

3dB frequency of inverting amplifier

There is already a similar question in this website, but I still can't solve this. I have the following information: An inverting opamp with nominal gain -20V/V, DC gain 10^4 and unit gain 10^6Hz. I ...
João Silva's user avatar
0 votes
2 answers
78 views

What does that statement exactly mean? ( about dB )

When you separate the collected signals, each car’s channel must attenuate the other cars’ signals at least by 20 dB. A speaker will be able to generate a sound which contains 3 different frequency ...
muyustan's user avatar
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1 vote
3 answers
5k views

What's the reference dB level in a spectrum analyser?

I am using a spectrum analyser to measure the 248kHz buck switching frequency and its harmonics in my board. I have set the frequency range from 200kHz and 1MHz and I am using a near field H-probe. ...
user avatar
3 votes
2 answers
2k views

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

I'm reading about a signal to noise ratio (SNR), I'm quite new to this kind of stuff. $$SNR=10\log_{10}\left(\frac{P_{SIGNAL}}{P_{NOISE}}\right)=20\log_{10}\left(\frac{A_{SIGNAL}}{A_{NOISE}}\right)$$ ...
Stefano Barone's user avatar
1 vote
2 answers
220 views

Why is the microphone output level not proportional to the sound level?

I set up a system to measure the sound pressure level in a location. This consists of a Knowles SPU0410LR5H-QB microphone connected to the codec SGTL5000, which is connected to the micro-controller ...
chamod's user avatar
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1 vote
1 answer
2k views

Understanding function generator output when units are in dBm

I am using a function generator with output in units of dBm. It has an output impedance of 50 ohms. I am measuring this output on an oscilloscope, and am failing to understand the waveform's amplitude....
teddyv's user avatar
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0 votes
0 answers
31 views

Finding the gain difference for a ultrasonic assembly

I am tuning an ultrasonic assembly for a welding application and tuned the system to operate at 41kHz according to the oscilloscope. The transducer operates at 40kHz, when calculating the gain with ...
Neamus's user avatar
  • 281
0 votes
3 answers
866 views

Convert -dB to equivalent +dB

I asked this question on stackoverflow and stackexchange mathematics, but on both sites my question was closed and suggested to ask here as mentioned in the comments to this question on mathematics. ...
Rouzbeh Zarandi's user avatar
8 votes
1 answer
821 views

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 ...
John adams's user avatar
0 votes
2 answers
166 views

The importance of Decibels [duplicate]

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's user avatar
1 vote
2 answers
263 views

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/...
trw's user avatar
  • 111
0 votes
1 answer
270 views

Audio Frequency Response Offset in dB

Say I have some audio device with the following absolute frequency response: I want to shift the curve up, so that the 1kHz point is the 0dB point, and everything else is relative to this point. Am I ...
User7251's user avatar
  • 365
0 votes
2 answers
170 views

Calculate linear phase when given in decibel

The datasheet of the LT6230 shows the op amp's phase lag in decibels (page 14). The datasheet does not give a formula to recalculate the angle in degrees, so can I just assume the following being the ...
einball's user avatar
  • 300
1 vote
2 answers
550 views

Receiving power from antenna (Homework)

The question: "At a carrier frequency of 2 GHz, assuming a transmit antenna gain of 3 dBi and a receive antenna gain of 0 dBi, calculate the line-of-sight received power at a distance of 100 m from ...
Scavenger23's user avatar
0 votes
2 answers
886 views

Conversion from dBm to dB\$\mu\$V?

I am trying to derive the conversion from dBm to dB\$\mu\$V. So, please correct me If I am wrong. \begin{align} \textrm{dBm} &= 10 \log_{10} \left( \frac{P}{1\textrm{mW}} \right) = 10 \log(P) + ...
learning's user avatar
  • 233
0 votes
0 answers
46 views

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's user avatar
  • 1,791
0 votes
1 answer
147 views

Are these equations correct? (transfer function)

I have a given transfer function \$ |H| = \frac{R_2}{\sqrt{R_1^2+\frac{1}{(\omega c)^2}}} \$ where \$ c = 1\mathrm{\mu F} \$ and \$ R_1,R_2 \$ are unknown. I know that \$ |H(j\omega_c)| = 50.1 \$ ...
arnoldschwarzenegger's user avatar
0 votes
1 answer
1k views

Convert dB to resistance

I am new to this, but I wanted to ask how it would be possible to convert a dB value into resistance. I've been looking at an isolated analog switch from http://www.ti.com/lit/ds/symlink/ts5a3359.pdf ...
Alex Feng's user avatar
0 votes
4 answers
7k views

Units for fourier transform of measured voltage

I have a measured voltage signal that I want to present in the frequency domain. My current process is to take the FFT of the signal, then use \$20 \text{log}_{10}|X|\$ where \$|X|\$ is the magnitude ...
loudnoises's user avatar
  • 1,856
0 votes
2 answers
1k views

Converting arbitrary mic input number to dB SPL

I'm trying to convert an arbitrary input number from a laptop microphone into SPL. The microphone specs are available on https://docs-emea.rs-online.com/webdocs/105f/0900766b8105f0e3.pdf. From what I'...
Alfie Mitchell's user avatar
2 votes
1 answer
240 views

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

Below is an excerpt from a book: Two common terms you'll hear in specifying the gain of an antenna are dBi and dBd. These terms are defined as dB of gain referenced to an Isotrope (dBi) and dB of ...
user1245's user avatar
  • 4,333
0 votes
0 answers
48 views

The Output of High/Low Pass filters and the DB changes that occur

I recently just learned what a dB is (decibel) and am trying to figure out why in high/low pass filters these drops occur. Also how they're affected. Say I have a high pass filter with a cutoff ...
Capn Jack's user avatar
  • 777
3 votes
2 answers
3k views

How does doubling the voltage amplitude change the decibels?

Suppose I listen to some music on my headphones. Now change the amplitude (in volts, as measured e.g. with an oscilloscope) of the audio signal by a constant factor G. Assuming that the amplifier in ...
Fritz's user avatar
  • 768
0 votes
2 answers
661 views

How to calculate PWM duty cycle to compensate for different piezo sounder response at different frequencies?

How to calculate PWM duty cycle to compensate for different piezo sounder response at different frequencies? I have a piezo sounder, and the datasheet informs me that I will get the following ...
Tantalum's user avatar
1 vote
3 answers
3k views

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

I have found a question in MIT open-course material.The question is to Design an amplifier(Op-Amp) with a gain of 20dB While searching about ...
Utshaw's user avatar
  • 187
-1 votes
2 answers
2k views

SNR and attenuation question

I have the question above from random material and I tried to solve it. Here, I assume signal power to be S1(dB) and noise power to be N1(dB) at input, and S2(dB) and N2(dB) at output. So below is ...
LUKA's user avatar
  • 25
2 votes
3 answers
2k views

Electret microphone - How to reduce sensitivity

I am doing a classic LED - sound reactive project. The only thing that is bothering me is that my electret microphone (MAX4466 from Adafruit) is clipping, and it is because the maximum gain of this ...
Lalous's user avatar
  • 39