Hello Ken,
I found easily how to filter with obspy (Butterworth too). Here is a sample:
st[0].filter(type="bandpass", freqmin=1.0, freqmax=2.0)
Not that easy to find a slice of my signal that should not be influenced by harmonics. But I think I managed to get a small ‘noise’ slice.
Here are my results:
- Noise : 45 dB SPL
- Raie around 1.5 Hz : 60 dB SPL
That would make a 15 dB SNR
I’m not sure what conclusion I can get from this, except it is a meaningfull signal…
(About your case, I don’t understand why you do this calculation : sig = sqrt(1000^2 - 250^2). As I understand, but I might miss something, dB signal - dB noise is enough, no ? Nethertheless, as you mentionned, it does not make a hudge difference at the end)