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SEL and measuring loudness of a call
Hi,
I am currently working on measuring some frog calls using Raven Pro v1.5, and I have some questions which hopefully someone can provide some insight on 1) What does the new measurement "SEL" stand for and what does it measure? 2) If I wish to measure on average how "loud" a frog call is, which measurement should I be using? Is it the average/rms amplitude or average power? 3) If the measurement for question 2 is the average/rms amplitude, how can I convert the unitless measurement to the units dB SPL? I apologize if the questions sound ignorant as I am still not very familiar with the field of bioacoustics. Thank you for the help! 
#2




Re: SEL and measuring loudness of a call
Quote:
If Raven is not calibrated, Raven's dB power and amplitude measurements are relative to an arbitrary reference, meaning that you can make relative comparisons of dB within a recording but *not* absolute dB measurements. To calibrate Raven Pro 1.5 beta, you first will need to characterize your recording equipment to determine the scaling relationship between sound pressure and sample values in your digital recording. Which acoustical measurement you choose should be related to the research question you are addressing. Here are descriptions of a handful of related measurements in Raven: Average Power is the average power spectral density (PSD) to within a factor of the sample period. It's unfortunate that Raven was released using the incorrect terminology, but we're sort of stuck with it now. The average power is the sum of the square magnitudes of the Fourier coefficients across time and frequency, divided by the the product of the number of Fourier bins in the selection and the number of spectrogram frames in the selection. Another way to think of it is the sum of the square magnitude across time and frequency, divided by the product of the selection duration and the selection delta frequency (bandwidth). Conceptually, this really is the 2D average of the square magnitudes. Of course, we express the resulting average in dB. Inband power is average inband power, not PSD. Numerically, it's the sum of the square magnitudes of the Fourier coefficients in the selection divided by the product of the DFT size and the number of spectrogram frames in the selection. Conceptually, it's the time average of the sum of the actual PSD, including the factor of the sample period, times the Fourier bin size. Leq is calculated on the time domain signal. It's the sum of the squared sample values divided by the number of samples. Again, it is expressed in dB. If you use a rectangular window function, the inband power from 0 to the Nyquist frequency should equal the Leq. There may be a slight discrepancy if you use another window function, but for the rectangular window the math is easy. SEL is "Sound Exposure Level". You can find it defined in Wikipedia and many other sources. I can recommend Principles of Animal Communication by Bradbury and Vehrencamp. Perhaps others on the list will step up to recommend other texts. You may also be interested in attending one of our Sound Analysis Workshops. Mike 
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