There are 8 messages in this issue.
Topics in this digest:
1a. Re: underwater stereo recordings and phase
From: madl74
1b. Re: underwater stereo recordings and phase
From: Jim Wells
1c. Re: underwater stereo recordings and phase
From: Dan Dugan
1d. Re: underwater stereo recordings and phase
From: madl74
1e. Re: underwater stereo recordings and phase
From: madl74
2a. New study shows traffic noise is disruptive to wildlife
From: J. Charles Holt
2b. Re: New study shows traffic noise is disruptive to wildlife
From:
2c. Re: New study shows traffic noise is disruptive to wildlife
From: Bernie Krause
Messages
________________________________________________________________________
1a. Re: underwater stereo recordings and phase
Posted by: madl74
Date: Tue Sep 1, 2015 5:26 am ((PDT))
> I still don't see why whether the reflected wave, either from the surface >
> or from a solid reflector, should have any more effect than the same in
> an air environment.
Russell,
A reflection takes place at a boundary where the speed of sound (or light)
changes. For a reflection from slow to fast, most of the energy is bounced
back in phase. from fast to slow, the surface can't return the energy which
is reflected back in antiphase as energy has to be conserved.
See:
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reflec.html
An illustration of this effect is with organ pipes which are either closed
or open. A closed (stopped) pipe produces a sound one octave lower than an
open pipe.
David Brinicombe
Messages in this topic (12)
________________________________________________________________________
1b. Re: underwater stereo recordings and phase
Posted by: "Jim Wells" whitby333
Date: Tue Sep 1, 2015 8:57 am ((PDT))
Hey all,
Everything David is saying is impeccably correct. Pretty sure:).
I 'think' what Russell is asking is what practical difference does it make. Or
maybe he's asking what the difference is between air and water.
To the latter I'd say while similar (both are sound), sound acts differently in
different media.
But to the former, the more you know about the physics of the medium you're
recording:
a. The more you understand about what you're hearing
b. The better you might choose mics, and placement... for example.
Theory is dry, and science, and all, but when you get into it it's also filled
with beauty. Recording (anywhere!) is both art and science... when done well:).
I guess 'the difference' is in the ear of the beholder:).
For the record, I'm new here. While I've never had the opportunity to record
under water, it's fascinating to read the parallels between air and water, and
I enjoy the level of technical expertise I've seen so far.
Best,
Jim, CA
Have fun!
www.fantasonics.com
> On Sep 1, 2015, at 5:26 AM, [naturerecordists]
> <> wrote:
>
> > I still don't see why whether the reflected wave, either from the surface >
> > or from a solid reflector, should have any more effect than the same in
> > an air environment.
>
> Russell,
>
> A reflection takes place at a boundary where the speed of sound (or light)
> changes. For a reflection from slow to fast, most of the energy is bounced
> back in phase. from fast to slow, the surface can't return the energy which
> is reflected back in antiphase as energy has to be conserved.
>
> See:
> http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reflec.html
>
> An illustration of this effect is with organ pipes which are either closed
> or open. A closed (stopped) pipe produces a sound one octave lower than an
> open pipe.
>
> David Brinicombe
>
>
>
Messages in this topic (12)
________________________________________________________________________
1c. Re: underwater stereo recordings and phase
Posted by: "Dan Dugan" dandugan_1999
Date: Tue Sep 1, 2015 11:12 am ((PDT))
> A reflection takes place at a boundary where the speed of sound (or light)
> changes. For a reflection from slow to fast, most of the energy is bounced
> back in phase. from fast to slow, the surface can't return the energy which
> is reflected back in antiphase as energy has to be conserved.
>
> See:
> http://hyperphysics.phy-astr.gsu.edu/hbase/sound/reflec.html
>
> An illustration of this effect is with organ pipes which are either closed
> or open. A closed (stopped) pipe produces a sound one octave lower than an
> open pipe.
Thanks for this, David, very helpful.
I’ve only thrown my mics into vernal pools and ditches, so they just fall on
the bottom and become boundary mics, I suppose, though one could ask what the
impedance transition is between water and wet mud.
I wonder if in still water putting the hydrophone just below the surface would
give a boundary mic effect—or since the transition is the opposite direction,
what would be the inverse of the effect? A suck-out rather than a build-up of
pressure?
Someone a few days ago remarked that with the static sounds common in ponds
they didn’t hear any stereo effect, just L and R independent. I wonder if that
was because the high-frequencies are short-range and there simply weren’t any
low or mid frequencies present to make any imaging.
-Dan
Messages in this topic (12)
________________________________________________________________________
1d. Re: underwater stereo recordings and phase
Posted by: madl74
Date: Tue Sep 1, 2015 6:28 pm ((PDT))
> I 'think' what Russell is asking is what practical difference does it make.
Jim,
I covered that in n earlier email. Underwater, with or without a mic, the
surface antiphase reflection partially cancels out the direct sound in the
water, according to the wavelength of that sound which is 4.4 times the
wavelength we are used to in air. Next time you dive and resurface, listen
out for the frequency shift of the underwater noises as you approach the
surface. Either that or dunk a hydrophone and let someone else do the
diving. :-)
The thread was about underwater stereo and the problems arising from
multiple reflections underwater with a 1kHz wavelength being 1.5Metres
instead of 340cms.
David Brinicombe
Messages in this topic (12)
________________________________________________________________________
1e. Re: underwater stereo recordings and phase
Posted by: madl74
Date: Tue Sep 1, 2015 6:58 pm ((PDT))
> I wonder if in still water putting the hydrophone just below the surface
> would give a boundary mic effect—or since the transition is the opposite
> direction, what would be the inverse of the effect? A suck-out rather than a
> build-up of pressure?
Dan,
Try it and report back. The theory says that when close the negative
reflection would counter the direct signal. My experience (some time ago)
was that it sounded better deeper. Must check my own theory out though. :-)
> Someone a few days ago remarked that with the static sounds common in ponds
> they didn’t hear any stereo effect, just L and R independent.
I'm going to buy a pair of JrF hydrophones and check them out as a fig-8
pair and as a spaced binaural pair at 750cms. The problem I have is that my
local river is a bit shallow.
Note; Jez is currently recovering from a car crash so there will be a delay
on dispatching JrF mics. I'm sending him a get well soon message.
David Brinicombe
Messages in this topic (12)
________________________________________________________________________
________________________________________________________________________
2a. New study shows traffic noise is disruptive to wildlife
Posted by: "J. Charles Holt"
Date: Tue Sep 1, 2015 9:26 am ((PDT))
http://m.pnas.org/content/early/2015/08/27/1504710112
"Decades of research demonstrate that roads impact wildlife and suggest traffic
noise as a primary cause of population declines near roads. We created a
“phantom road” using an array of speakers to apply traffic noise to a roadless
landscape, directly testing the effect of noise alone on an entire songbird
community during autumn migration. Thirty-one percent of the bird community
avoided the phantom road. For individuals that stayed despite the noise,
overall body condition decreased by a full SD and some species showed a change
in ability to gain body condition when exposed to traffic noise during
migratory stopover. We conducted complementary laboratory experiments that
implicate foraging-vigilance behavior as one mechanism driving this pattern.
Our results suggest that noise degrades habitat that is otherwise suitable, and
that the presence of a species does not indicate the absence of an impact."
- Charles
Messages in this topic (3)
________________________________________________________________________
2b. Re: New study shows traffic noise is disruptive to wildlife
Posted by:
Date: Tue Sep 1, 2015 6:02 pm ((PDT))
Charles,
Obviously traffic noise interferes with communication among birds, creating
problems for defense of territory and self, as well as for mating potential. I
think I remember reading that this has led to birds, exposed to this noise,
changing or modifying their songs, as a result. Another aspect of noise
pollution. We know how it affects us as nature recordists.
All the best,
Ernie Jardine
Pickering Ontario
www.birdsongidentification.com
-----Original Message-----
From: 'J. Charles Holt' [naturerecordists]
<>
To: naturerecordists <>
Sent: Tue, Sep 1, 2015 12:27 pm
Subject: [Nature Recordists] New study shows traffic noise is disruptive to
wildlife
http://m.pnas.org/content/early/2015/08/27/1504710112
"Decades of research demonstrate that roads impact wildlife and suggest
traffic noise as a primary cause of population declines near roads. We created
a “phantom road” using an array of speakers to apply traffic noise to a
roadless landscape, directly testing the effect of noise alone on an entire
songbird community during autumn migration. Thirty-one percent of the bird
community avoided the phantom road. For individuals that stayed despite the
noise, overall body condition decreased by a full SD and some species showed a
change in ability to gain body condition when exposed to traffic noise during
migratory stopover. We conducted complementary laboratory experiments that
implicate foraging-vigilance behavior as one mechanism driving this pattern.
Our results suggest that noise degrades habitat that is otherwise suitable, and
that the presence of a species does not indicate the absence of an impact."
- Charles
Messages in this topic (3)
________________________________________________________________________
2c. Re: New study shows traffic noise is disruptive to wildlife
Posted by: "Bernie Krause" bigchirp1
Date: Tue Sep 1, 2015 6:21 pm ((PDT))
In Sonoma, California�s Valley of the Moon, there was no birdsong this spring
or summer. None. A combo of global warming (the spring season occurs on average
14 days earlier than 20 years ago), bird populations have shifted, and altho
there have been some calls and other vocal interchange, there has been absolute
silence as far as song is concerned. I am currently drafting a paper to show
the effects that have caused it and the consequences.
Bernie Krause
On Sep 1, 2015, at 6:02 PM, [naturerecordists]
<> wrote:
>
>
> Charles,
>
> Obviously traffic noise interferes with communication among birds, creating
> problems for defense of territory and self, as well as for mating potential.
> I think I remember reading that this has led to birds, exposed to this noise,
> changing or modifying their songs, as a result. Another aspect of noise
> pollution. We know how it affects us as nature recordists.
>
> All the best,
> Ernie Jardine
> Pickering Ontario
>
>
> www.birdsongidentification.com
>
>
> -----Original Message-----
> From: 'J. Charles Holt' [naturerecordists]
> <>
> To: naturerecordists <>
> Sent: Tue, Sep 1, 2015 12:27 pm
> Subject: [Nature Recordists] New study shows traffic noise is disruptive to
> wildlife
>
> http://m.pnas.org/content/early/2015/08/27/1504710112
>
> "Decades of research demonstrate that roads impact wildlife and suggest
> traffic noise as a primary cause of population declines near roads. We
> created a �phantom road� using an array of speakers to apply traffic noise to
> a roadless landscape, directly testing the effect of noise alone on an entire
> songbird community during autumn migration. Thirty-one percent of the bird
> community avoided the phantom road. For individuals that stayed despite the
> noise, overall body condition decreased by a full SD and some species showed
> a change in ability to gain body condition when exposed to traffic noise
> during migratory stopover. We conducted complementary laboratory experiments
> that implicate foraging-vigilance behavior as one mechanism driving this
> pattern. Our results suggest that noise degrades habitat that is otherwise
> suitable, and that the presence of a species does not indicate the absence of
> an impact."
>
> - Charles
>
>
>
Wild Sanctuary
POB 536
Glen Ellen, CA 95442
707-996-6677
http://www.wildsanctuary.com
SKYPE: biophony
FaceBook: http://www.facebook.com/BernieKrauseAuthor
TED Global talk:
http://www.ted.com/talks/bernie_krause_the_voice_of_the_natural_world.html
Messages in this topic (3)
"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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