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JAP

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- How could I find the SNR of an acoustic signal knowing its sound level (db ref uPa @1m)

Hi, I'm trying to model the transmission loss and SNR of an acoustic signal underwater. I'm using this expression to modelize the transmitted signal:

The only data I have to find P is the sound level (

where I is the intensity from the source in W/m^2 and Iref is the reference intensity of sound in water which value is 6.667*10^-19 W/m^2. Knowing the

where

Putting these two equations together, I can find P that should be :

With regard to the SNR, I use the passive sonar equation, however I find very optimist results (i.e. more than 20 dB for a range of 800m...) so I'm not really sure my calculations are right. If there's any pro in the underwater acoustics field that could give me a hand to resolve this, I will be very grateful.

Thanks!

JAP

y = sqrt(P)*exp(1i*2*fr*pi*t)'

where P is the transmission power in watts, fr is the transmission frequency and t is the acquisition time.The only data I have to find P is the sound level (

*SL*) of my source that is supposed to be 142 dB ref 1uPa at 1 meter from the source. According to the Matlab documentation site (https://fr.mathworks.com/help/phased/ug/sonar-equation.html) sound level can be defined as:*SL*= 10log10(I/Iref)

*SL*value, I can isolate*I*to find the acoustic pressure*p_rms*and then the power*P*because*I*can be defined as follows:*I=p_rms^2/ρc*and

*I = P/4*pi*r^2*

*p_rms:*signal acoustic pressure in Pascal,*ρ:*water density (1000kg/m^3),*c:*sound speed in water (1500 m/s)Putting these two equations together, I can find P that should be :

P =

However, when I use the value of my source (142 dB), I get a power of 1.33 mW! I believe it doesn't make sense 'cause the signal source should be detected at the receiver at least at 500 m from the source.*p_rms^2**(4*pi*r^2)/(*ρc)*With regard to the SNR, I use the passive sonar equation, however I find very optimist results (i.e. more than 20 dB for a range of 800m...) so I'm not really sure my calculations are right. If there's any pro in the underwater acoustics field that could give me a hand to resolve this, I will be very grateful.

Thanks!

JAP