Hi Ricardo,
peak frequencies in both recordings seem about the same. The "PC directly.wav" file shows more echoes, which influences BatExplorer's measures. Measures offered by BatExplorer often have to be manually adjusted. - About the sampling rate etc: As a dilettante in matters electronics or physics, I have just relied on the advice given by Al Milano in his review (
http://batdetecting.blogspot.de/2014/06/review-micro-trio-from-ciel-new-x05.html ) of the micro trio:
As for your recorder, one of the lower quality settings (i.e. 16-bit/44.1kHz) is all that is needed. And, will provide even better results in some cases than higher quality settings. This is also true, when using lower-quality (inexpensive) digital voice recorders. However, you should feel free to experiment.
Therefore, I chose the following settings for the MP330:
- source: line-in
- quality: medium (of three options; resulting in ~500 KB files; the highest produces > 1MB files)
- volume: I chose the 2nd lowest of the eight options. More about that below: (*)
Feeded with *.wav based on these settings, Audacity produces sound files in 16-bit/44.1kHz quality. The 16-bit seems a bit of a waste, as the micro trio gives us only 8-bit sound. Anyway, I was happy to follow Milano's hint. According to its manual, the micro trio is using a sample rate of 120 kHz (8 bit) in time-expansion mode. Does it improve our results to put the MP330's recording quality on "high" instead of "medium"? I have tried, but wasn't impressed - so I just kept preferring "medium".
There is a power-point explanation online, how to set up the H2n for unattended recording with a Pettersson D240X:
http://www.sonobat.com/SamsonZoomAutorecording.html . Even here, with top-notch equipment, they recommend "16-bit/44.1kHz quality". And there is the hint:
"Turn on to lowest volume setting."
(*) But trying the lowest volume level was a disaster. On the other side, The "loudest" level (8) produced results similar to your files, with the kHz axis in BatExplorer going up to 160 kHz, where no bat calls can be expected. So I decided to put the volume on "two". Any idea/explanation why level 3 might be better is welcome, of course. So far I haven't tried it.
Stefan