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1. toxie87
   

   Member
   Joined: Nov '12
   Posts: 2

   I`m doing some simulations using this toolbox and i must say i love it.
   Also i have a question. I`m generating some signals in simulink (Amplitude=1). Have 2 sources and 1 sensor. Currently only 'p' is recorded. The resulting value at the sensor_data.p is from -0.2 to 0.2 . How do i convert those into dB ? I need to get simulation results, and then compare it with microphone recordings, to see if they "match" .

   Posted 12 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi toxie87,

   Assuming you are doing linear simulations, the magnitude of your output scales linearly with the magnitude of your input (so in your case, if your input amplitude was 2 instead of 1, your output values would range from -0.4 to 0.4).

   If you know the actual pressure of your source in Pascals, you can use this to calculate the magnitude of your output in Pascals. You can then convert Pascals to a sound pressure level in dB using the formula 20*log10(p_output/p_ref), where p_ref = 20e-6;

   If you want a relative drop in dB, you can calculate this directly using by setting p_ref equal to your input magnitude (the scaling of the input and output doesn't matter, as long as they are the same).

   Hope that helps!

   Brad.

   Posted 12 years ago #

3. toxie87
   

   Member
   Joined: Nov '12
   Posts: 2

   Thanks for the reply Brad. I`m already using the formula u gave me, but due to the negative values, as a result i have complex numbers. Also the readings are pretty strange to me. 0.2246 is the maximum at the sensor and after the formula, the max is -Inf, the second largest is 186.72dB ?!?? It should be 81dB by my calculations. Am i wrong ?

   Posted 12 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi toxie87,

   Sorry, I should have mentioned, the value for p_output should be the RMS (root mean squared) value of your output signal (in steady state if you are using a continuous wave input). This will be a single positive number.

   Brad.

   Posted 12 years ago #

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