Thanks Robb, this is very helpful. I'm headed out in the morning to drift d=
ownwind 3-4 miles in the same area, Mahaulepu to Kikiaoala. Hoping to get c=
loser to the singers and drop the snapping shrimp more into the background =
noise.
Robb said
>"The edited version is certainly an
> improvement.
----------hey thanks!
Robb said--
" I'll speculate that all of that low-frequency rumble is
from vibrations in the hydrophone induced by cable strum. This happens whe=
n the hydrophone is towed. Were you drifting substantially on the wind?"
-----------That's what I figured, cable strum; my friend the experienced se=
a-kayaker noted we were drifting offshore at .5 Knots. I said thanks for no=
ticing, as we had to then plow up-wind to get back to port, and suspend rec=
ording as it would be wet.
--------------since I don't know the freq range of the Humpbacks, I'm leary=
of using the low-cut and missing something. More to learn here.
"I wonder if you clicked on the wrong flash player. The environmental
noise is pretty significant."
--------indeed I did--the correct one sounds more like home.
Aloha,
David
--- In Robb Nichols <> wrote:
>
> Thanks again, David. I'll reply in-line:
>
> On 3/11/2010 6:12 PM, Kawika wrote:
> >
> >
> > Hi Robb, I uploaded to files a brief mp3 comparison between raw and
> > mangl.. er, processed recordings, titled "Hump for nr"
> > http://tinyurl.com/y9kja2m <http://tinyurl.com/y9kja2m>
> >
> The comparison is enlightening. The edited version is certainly an
> improvement. I'll speculate that all of that low-frequency rumble is
> from vibrations in the hydrophone induced by cable strum. This happens
> when the hydrophone is towed. Were you drifting substantially on the
> wind? If so, maybe more of the noise that I attributed to invertebrate
> critters is surface noise from small wind waves. Bobbing up and down
> and drifting with the ocean swell can do this as well. Low-cut filters
> are a blessing at these times.
> >
> >
> > I listened to your "recording that I made last year while sitting in
> > a kayak just a few meters over a reef in Hawaii"--astounding! For me
> > the question is begged, Where are the snapping shrimp?
> >
> I wonder if you clicked on the wrong flash player. The environmental
> noise is pretty significant. It is the second one under the heading
> Robb Nichols, Aquarian Audio - Miscellaneous. The direct link is here:
>
> http://www.aqaud.com/Cust_files/audio/AqAud_humpbacks_reef0209.mp3
>
> >
> > if you were only a few meters over a reef. Or were the Humps so loud
> > that the shrimp receded into the background? My reason for going out
> > in the kayak of course is to escape the shrimp.
>
> I'm not the naturalist that I wish I were, so I don't really know what
> is making these noises. If anybody does, I'd love to hear. But I don't
> think it is shrimp. Around here, you can get similar sounds from
> colonies of barnacles. I'm sure that there are lots of species that
> make similar noise by direct percussive technique or by making or
> manipulating gas bubbles.
>
> I have 10 meter
> > cables with my H2a's, do you think I would benefit having longer
> > cables, to better avoid surface noise?
>
> If you're working our of a kayak, a longer cable might be cumbersome.
> It can certainly distance the hydrophone from boat and surface noise.
> And if I am correct about the cable strum while being adrift (or holding
> your position in a current), the longer cable will lower that frequency,
> which will be filtered more effectively by both the natural cutoff of
> the hydrophone, preamp, recorder and by any rumble filter that you
> engage. I think that, just as with other forms of nature recording, you
> count on luck to present you with the right conditions and pick up
> tricks with experience to help manage the times when you're not so lucky.
> >
> > Aloha, David
> >
> >
> Aloha, Robb
>
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
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