0
$\begingroup$

I wonder how I can convert dBA (A weighted) to dB and vice versa. can anybody provide any kind of table or online conversion app? thanks

following formula comes from https://en.wikipedia.org/wiki/A-weighting :\begin{align} R_A(f) &= {12194^2 f^4 \over \left(f^2 + 20.6^2\right)\ \sqrt{\left(f^2 + 107.7^2\right)\left(f^2 + 737.9^2\right)}\ \left(f^2 + 12194^2\right)}\ ,\\[3pt] A(f) &= 20\log_{10}\left(R_A(f)\right) - 20\log_{10}\left(R_A(1000)\right) \\ &\approx 20\log_{10}\left(R_A(f)\right) + 2.00 \end{align} how can I inverse this formula? I also must mention that I have a specific frequency and I just want to convert this specific frequency SPL

Improve this question
$\endgroup$
7
  • 1
    $\begingroup$ this has nothing to do with filter-design,kalman-filters, digital, and only kind of something with filters. $\endgroup$
    – Marcus Müller
    Feb 22, 2021 at 13:47
  • $\begingroup$ Do you have a single SPL value, or SPl values for the whole spectrum? $\endgroup$
    – Justme
    Feb 22, 2021 at 18:37
  • $\begingroup$ @Justme. just single value $\endgroup$
    – SeAlGhz
    Feb 27, 2021 at 19:48
  • $\begingroup$ @ali if you have a single value, and no information about the frequencies present in the signal, it cannot be known how it is converted between unweighted and A-weighted values, as it depends on the frequencies present in the signal. $\endgroup$
    – Justme
    Feb 27, 2021 at 20:04
  • 1
    $\begingroup$ @ali Why did you not say earlier then, that detail is important and should be edited in the question. The formula gives you the weight at any frequency. So if you have a single frequency, you can calculate the weight at that single frequency. And since you know the weighted value and how much the value was weighted, you can also know what was the unweighted value. $\endgroup$
    – Justme
    Feb 27, 2021 at 20:21

1 Answer 1

Reset to default
0
$\begingroup$

You can't convert these directly. You need to start with either a calibrated pressure time domain pressure wave form or a calibrated power spectrum. To create calculate unweighted dBSPL yo simply sum the total energy. To calculate dBA, you need to apply an A-weighting filter to either one of those first.

Improve this answer
$\endgroup$
2
  • $\begingroup$ how can I calibrate ADMP401 precisely do you know have any idea? $\endgroup$
    – SeAlGhz
    Feb 22, 2021 at 15:26
  • $\begingroup$ With a good measurement microphone and a matching calibrator. You use the calibrator to calibrate the measurement mic and then the measurement mic to calibrate the ADMP401. It also depends on what exactly you mean by "precisely". +1dB is very different from +- 0.1dB $\endgroup$
    – Hilmar
    Feb 22, 2021 at 16:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.