Robb and other hydrophonists,
I went out yesterday to record from kayak, got some good stuff, but more im=
provements in technique needed. Though we were drifting only about one-to-t=
wo knots, the phones were streaming behind almost flat, so I get a lot of s=
urface noise of wind and wave, and also less stereo image. I'm considering =
attaching lead weights to the cables just above the phones, maybe hydrodyna=
mic lead fishing weights, to keep them more vertical. Might this help?
David
--- In "Kawika" <> wrote:
>
> Thanks Robb, this is very helpful. I'm headed out in the morning to drift=
downwind 3-4 miles in the same area, Mahaulepu to Kikiaoala. Hoping to get=
closer to the singers and drop the snapping shrimp more into the backgroun=
d 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 w=
hen the hydrophone is towed. Were you drifting substantially on the wind?"
>
> -----------That's what I figured, cable strum; my friend the experienced =
sea-kayaker noted we were drifting offshore at .5 Knots. I said thanks for =
noticing, as we had to then plow up-wind to get back to port, and suspend r=
ecording as it would be wet.
>
> --------------since I don't know the freq range of the Humpbacks, I'm lea=
ry 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 <Robb@> 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 holdin=
g
> > 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, yo=
u
> > 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 luck=
y.
> > >
> > > Aloha, David
> > >
> > >
> > Aloha, Robb
> >
>
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