On Mon, 2010-05-10 at 00:54 +0000, Steve Pelikan wrote:
>
> Richard: Since I don't know what it is _supposed_ to sound like I
> can't really offer any specific suggestions
It is supposed to sound more or less like it does. My recollection of
what I heard at the time is a much "clearer" sound than the recording,
but I guess that is just the limitations of the recording process and
the not best-available recording equipment.
My concerns about the result are around the self-noise starting to
become audible due to the amplification in post-processing, which I am
starting to think should have been avoided by simply using a
pre-amplifier when making the recording. With the benefit of hindsight
I will not attempt another trip like this without having some means of
getting reasonable recording levels from low level sound sources, though
I am still unclear on what would be good practical way to achieve this.
> 1) When the sounds of interest are moderately loud the process of
> filtering and amplifying can sometime make things worse. Would you be
> better off with a straight recording and if not, why not?
The original recording is very quiet, the filtering and amplification in
post (or some other method to achieve the same thing) was needed to get
the sounds up to normal listening levels.
> 1.5) The mic noise (or what I take it to be) is noticeable in the
> recoding you posted but there's enough going on that it isn't horrible
> or anything like that.
That's useful feedback; I have probably been listening to it too much,
and now focus on the hiss rather than the sound of the bats wings. :-(
> My guess is you can get significantly closer to what you want
> without investing in lots more expensive equipment.
Since the bats occasionally made contact with the microphone, I don't
think I could have got it any closer to them. :-)
> 2) There's periodic signals from 5.6 kHz increasing to 6.0 kHz. Do you
> know what they are, are they important?
That is a cicada, outside the cave. I was very surprised, and pleased,
to hear it at the time.
> 3) Others will know much more but my first reaction is that your mics
> aren't suffering from the humidity --- it basically sounds oaky and
> the question is just how to emphasize what you want.
Thanks. Before the trip I had read about possible problems with mics and
humidity, had sought advice from the group (but did not follow it very
carefully, as I was not hearing anything untoward either in monitoring
or later review) but on more careful listening was starting to get
worried that the humidity induced noise might be a much more subtle
effect than I was expecting.
Maybe someone could share a recording of humidity induced microphone
noise, so that I know what I am listening for in the future?
> 4) Are their possibly high Hz sounds that are lost? Some North
> American bats make "social" sounds in the 10-18 kHz range (not
> ultrasonic echolocation sounds) that might not turn up on a recording
> with regular mic but not need ultrasonic techniques and equipment to
> be audible.
I could not hear any other sound types at the time, but my high-end
hearing is showing some age-normal degradation.
> Anybody who get wet & dirty making a recording gets lots of credit!
I don't mind the wet and dirty part, but did find the high temperature
and humidity challenging (one reason for the trip was to find out
whether or not I could cope with those conditions).
Thanks for the feedback, it is all really helpful.
Richard
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