Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Dave Malham 
Oh, and a couple of other tips for anyone wanting to use condoms for
protecting microphones - wipe as much of the lubricant off as you can
before use (it's a b***er  to remove from microphone) and use the
featherlite variety for maximum acoustic transparence.

 Dave

On 19 February 2013 21:46, Dave Malham  wrote:
> The trouble with the sort of materials used in condoms is that they
> are inherently stretchy. Under any sort of pressure (more than a quite
> small depth of water)  the material presses through any holes and
> either (a) rips or be (b) comes into contact with the diaphragm which
> is potentially almost as big a disaster. That's why the first DIY
> hydrophone I linked to uses an electret capsule immersed in oil in a
> canister. I have uses both condoms and cling film to waterproof
> microphones but only really for splash proofing.  For those situations
> you can measure the mic before wrapping and after so that compensation
> can be made for the inevitable resonances. Probably not possible for
> underwater systems without the the same problems of needing a
> calibrated source and a lot of underwater space which, given the fact
> that it probably won't be possible to use the assembly at any sort of
> depth, is not going to be easy.
>
>Dave
>
> PS The wackiest thing I ever sealed a microphone for (with cling film)
> was to listen to worms under the ground for a biologist who was trying
> to find a way to assess the number of worms in a given volume of soil
> without crushing them up with the soil and extracting the (now dead)
> biological material.
>
> On 19 February 2013 17:48, Martin Leese  
> wrote:
>> Fons Adriaensen wrote:
>>
>>> Don't know what Len will think of it, but putting a Tetramic
>>> (or any such mic) in a plastic bag isn't likely to produce
>>> anything usable. Basic problem is that the acoustic impedance
>>> of water is around 3400 times higher than that of air, so the
>>> water/air interface will reflect almost all energy. You need
>>> a transducer that is more or less matched to the acoustic
>>> impedance.
>>
>> I have read that the standard trick is to use a
>> condom.  However, I puzzle whether this would
>> work with a Tetramic.
>>
>> Regards,
>> Martin
>> --
>> Martin J Leese
>> E-mail: martin.leese  stanfordalumni.org
>> Web: http://members.tripod.com/martin_leese/
>> ___
>> Sursound mailing list
>> Sursound@music.vt.edu
>> https://mail.music.vt.edu/mailman/listinfo/sursound
>
>
>
> --
> As of 1st October 2012, I have retired from the University, so this
> disclaimer is redundant
>
>
> These are my own views and may or may not be shared by my employer
>
> Dave Malham
> Ex-Music Research Centre
> Department of Music
> The University of York
> Heslington
> York YO10 5DD
> UK
>
> 'Ambisonics - Component Imaging for Audio'



-- 
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant


These are my own views and may or may not be shared by my employer

Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Iain Mott 
the worm-mic reminds me of this installation in Brazil "Som da
terra" (sound of the earth) at the garden/gallery "Inhotim" - it's by
American artist Doug Aitken - where 5 mics are lowered 202m down into
the earth. Here's a video showing the installation and an EV re20
protected in a plastic water bottle. Someone describes the sound as
being violent and noisy sometimes and other times more peaceful. 

http://www.youtube.com/watch?v=ITr5NzDSqlw





Em Ter, 2013-02-19 às 21:46 +, Dave Malham escreveu:
> The trouble with the sort of materials used in condoms is that they
> are inherently stretchy. Under any sort of pressure (more than a quite
> small depth of water)  the material presses through any holes and
> either (a) rips or be (b) comes into contact with the diaphragm which
> is potentially almost as big a disaster. That's why the first DIY
> hydrophone I linked to uses an electret capsule immersed in oil in a
> canister. I have uses both condoms and cling film to waterproof
> microphones but only really for splash proofing.  For those situations
> you can measure the mic before wrapping and after so that compensation
> can be made for the inevitable resonances. Probably not possible for
> underwater systems without the the same problems of needing a
> calibrated source and a lot of underwater space which, given the fact
> that it probably won't be possible to use the assembly at any sort of
> depth, is not going to be easy.
> 
>Dave
> 
> PS The wackiest thing I ever sealed a microphone for (with cling film)
> was to listen to worms under the ground for a biologist who was trying
> to find a way to assess the number of worms in a given volume of soil
> without crushing them up with the soil and extracting the (now dead)
> biological material.
> 
> On 19 February 2013 17:48, Martin Leese  
> wrote:
> > Fons Adriaensen wrote:
> >
> >> Don't know what Len will think of it, but putting a Tetramic
> >> (or any such mic) in a plastic bag isn't likely to produce
> >> anything usable. Basic problem is that the acoustic impedance
> >> of water is around 3400 times higher than that of air, so the
> >> water/air interface will reflect almost all energy. You need
> >> a transducer that is more or less matched to the acoustic
> >> impedance.
> >
> > I have read that the standard trick is to use a
> > condom.  However, I puzzle whether this would
> > work with a Tetramic.
> >
> > Regards,
> > Martin
> > --
> > Martin J Leese
> > E-mail: martin.leese  stanfordalumni.org
> > Web: http://members.tripod.com/martin_leese/
> > ___
> > Sursound mailing list
> > Sursound@music.vt.edu
> > https://mail.music.vt.edu/mailman/listinfo/sursound
> 
> 
> 


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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Dave Malham 
The trouble with the sort of materials used in condoms is that they
are inherently stretchy. Under any sort of pressure (more than a quite
small depth of water)  the material presses through any holes and
either (a) rips or be (b) comes into contact with the diaphragm which
is potentially almost as big a disaster. That's why the first DIY
hydrophone I linked to uses an electret capsule immersed in oil in a
canister. I have uses both condoms and cling film to waterproof
microphones but only really for splash proofing.  For those situations
you can measure the mic before wrapping and after so that compensation
can be made for the inevitable resonances. Probably not possible for
underwater systems without the the same problems of needing a
calibrated source and a lot of underwater space which, given the fact
that it probably won't be possible to use the assembly at any sort of
depth, is not going to be easy.

   Dave

PS The wackiest thing I ever sealed a microphone for (with cling film)
was to listen to worms under the ground for a biologist who was trying
to find a way to assess the number of worms in a given volume of soil
without crushing them up with the soil and extracting the (now dead)
biological material.

On 19 February 2013 17:48, Martin Leese  wrote:
> Fons Adriaensen wrote:
>
>> Don't know what Len will think of it, but putting a Tetramic
>> (or any such mic) in a plastic bag isn't likely to produce
>> anything usable. Basic problem is that the acoustic impedance
>> of water is around 3400 times higher than that of air, so the
>> water/air interface will reflect almost all energy. You need
>> a transducer that is more or less matched to the acoustic
>> impedance.
>
> I have read that the standard trick is to use a
> condom.  However, I puzzle whether this would
> work with a Tetramic.
>
> Regards,
> Martin
> --
> Martin J Leese
> E-mail: martin.leese  stanfordalumni.org
> Web: http://members.tripod.com/martin_leese/
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound



-- 
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant


These are my own views and may or may not be shared by my employer

Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Dave Malham 
Absolutely!

 Dave

On 19 February 2013 12:49, Fons Adriaensen  wrote:
> On Tue, Feb 19, 2013 at 09:54:25AM +, Dave Malham wrote:
>
>> The trouble with Angelo's kit is that it's not really "hi-fi".
>> Works well for what it was designed for (noise pollution research) but
>> not really good enough for serious audio.
>
> It was primarily designed to find the direction of arrival of sounds,
> which is something entirely different from reproduction.
>
> Ciao,
>
> --
> FA
>
> A world of exhaustive, reliable metadata would be an utopia.
> It's also a pipe-dream, founded on self-delusion, nerd hubris
> and hysterically inflated market opportunities. (Cory Doctorow)
>
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound



-- 
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant


These are my own views and may or may not be shared by my employer

Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Martin Leese 
David Worrall wrote:
> Subject: [Sursound] Ambisonic hydrophone?

> Does anone know of such a beast?
> (I thought of putting the TetraMic in a plastic bag, but I'm not sure Len
> would approve :-)
>
> Or how one might go about building one...
> Failing which, does anyone have a recommendation on a cost-effective
> single-channel unit?

About a year ago, the following real-time
sound installation was mentioned on the list:
http://www.dezeen.com/2011/09/14/sonic-seascape-terrace-by-decoster-taivalkoski-haaslahti-and-montes-de-oca/

Not many technical details are given, except
that signals from hydrophones are processed
into a four-channel Ambisonic soundscape.

Perhaps you could contact the artists for more
information.

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Michael Chapman 
> Fons Adriaensen wrote:
>
>> Don't know what Len will think of it, but putting a Tetramic
>> (or any such mic) in a plastic bag isn't likely to produce
>> anything usable. Basic problem is that the acoustic impedance
>> of water is around 3400 times higher than that of air, so the
>> water/air interface will reflect almost all energy. You need
>> a transducer that is more or less matched to the acoustic
>> impedance.
>
> I have read that the standard trick is to use a
> condom.  However, I puzzle whether this would
> work with a Tetramic.
>

Apparently there is a special size for precocious youth in Switzerland.
Might be your solution ... ?

Michael
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Martin Leese 
Fons Adriaensen wrote:

> Don't know what Len will think of it, but putting a Tetramic
> (or any such mic) in a plastic bag isn't likely to produce
> anything usable. Basic problem is that the acoustic impedance
> of water is around 3400 times higher than that of air, so the
> water/air interface will reflect almost all energy. You need
> a transducer that is more or less matched to the acoustic
> impedance.

I have read that the standard trick is to use a
condom.  However, I puzzle whether this would
work with a Tetramic.

Regards,
Martin
-- 
Martin J Leese
E-mail: martin.leese  stanfordalumni.org
Web: http://members.tripod.com/martin_leese/
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Fons Adriaensen 
On Tue, Feb 19, 2013 at 09:54:25AM +, Dave Malham wrote:

> The trouble with Angelo's kit is that it's not really "hi-fi".
> Works well for what it was designed for (noise pollution research) but
> not really good enough for serious audio.

It was primarily designed to find the direction of arrival of sounds,
which is something entirely different from reproduction.

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Dave Malham 
Angelo's paper relating to this is at
http://www.angelofarina.it/Public/UAM-2011/

 Dave

On 19 February 2013 04:03, Marc Lavallée  wrote:
> umashankar manthravadi  a écrit :
>> angelo farina has exactly the beast you are looking for. he had a
>> power point presentation describing its use here is the link
>> http://www.angelofarina.it/Public/Presentations/UAM2011_Underwater_Ambisonics_files/frame.htmumashankar
>
> Fons Adriaensen  a écrit :
>> Most hydrophones (and certainly any low-cost ones) will be
>> omnis, so the A/B processing will be very different from
>> what is required for a normal tetra mic using directional
>> capsules.
>
> Hydrophones are omnidirectional, and the underwater probe for the
> Brahma is tetrahedral... Are omnidirectional "sensors" appropriate to
> build tetrahedral ambisonic microphones?
>
> --
> Marc
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound



-- 
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant


These are my own views and may or may not be shared by my employer

Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Ambisonic hydrophone?

2013-02-19 Thread Dave Malham 
Hi,
The trouble with Angelo's kit is that it's not really "hi-fi".
Works well for what it was designed for (noise pollution research) but
not really good enough for serious audio. Because it's based on
differencing omni's to generate directional responses it has a
relatively limited bandwidth and because of the difficulty of
calibrating it it is not necessarily very accurate. As Fons says, the
cost of a good, flat frequency response, underwater speaker is
prohibitive (not to say humungous!)  but, even worse, underwater
anechoic chambers are not exactly common so you'd need to do the
calibration in deep water, well away from the shore, sea bottom etc.
Don't forget that the speed of sound in water is 5 times that in air
so everything has to be 5 times bigger (hence the large size of his
hydrophone). You CAN get figure 8 hydrophones but only if you have
military sized budgets - they have been used in aoustic torpedoes and
DIFAR buoys (google them) but it looks like using Blumlein
differencing techniques, with two different separations to cover low
and high frequencies separately might be the best approach for audio
purposes. Good hydrophones are several hundred (or more) Euros each
(for instance the Reson ones from
http://www.ambient.de/en/products/ambient-recording/underwater.html),
so this can get expensive and if you want to work in anything other
than the top waters, the cost of connectors and cable is frightening.
There are cheaper alternatives like the Dolphinear ones
(http://www.dolphinear.com/) which are pretty good or the JrF ones
(http://hydrophones.blogspot.co.uk/) or you can even make your own
(http://www.dosits.org/resources/all/classroom/buildhydrophone/ or
http://leafcutterjohn.com/?p=915).

As you can tell, I have been looking at this a lot, in the context of
the TBA-21 Academy project (http://tba21academy.org/), though since my
retirement I am no longer directly connected to them (at present)

   Dave



 
http://www.dezeen.com/2011/09/14/sonic-seascape-terrace-by-decoster-taivalkoski-haaslahti-and-montes-de-oca/

On 19 February 2013 04:03, Marc Lavallée  wrote:
> umashankar manthravadi  a écrit :
>> angelo farina has exactly the beast you are looking for. he had a
>> power point presentation describing its use here is the link
>> http://www.angelofarina.it/Public/Presentations/UAM2011_Underwater_Ambisonics_files/frame.htmumashankar
>
> Fons Adriaensen  a écrit :
>> Most hydrophones (and certainly any low-cost ones) will be
>> omnis, so the A/B processing will be very different from
>> what is required for a normal tetra mic using directional
>> capsules.
>
> Hydrophones are omnidirectional, and the underwater probe for the
> Brahma is tetrahedral... Are omnidirectional "sensors" appropriate to
> build tetrahedral ambisonic microphones?
>
> --
> Marc
> ___
> Sursound mailing list
> Sursound@music.vt.edu
> https://mail.music.vt.edu/mailman/listinfo/sursound



-- 
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant


These are my own views and may or may not be shared by my employer

Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK

'Ambisonics - Component Imaging for Audio'
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Re: [Sursound] Ambisonic hydrophone?

2013-02-18 Thread Marc Lavallée 
umashankar manthravadi  a écrit :
> angelo farina has exactly the beast you are looking for. he had a
> power point presentation describing its use here is the link
> http://www.angelofarina.it/Public/Presentations/UAM2011_Underwater_Ambisonics_files/frame.htmumashankar

Fons Adriaensen  a écrit :
> Most hydrophones (and certainly any low-cost ones) will be 
> omnis, so the A/B processing will be very different from
> what is required for a normal tetra mic using directional
> capsules.

Hydrophones are omnidirectional, and the underwater probe for the
Brahma is tetrahedral... Are omnidirectional "sensors" appropriate to
build tetrahedral ambisonic microphones?

--
Marc
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Re: [Sursound] Ambisonic hydrophone?

2013-02-18 Thread umashankar manthravadi 
angelo farina has exactly the beast you are looking for. he had a power point 
presentation describing its use here is the link 
http://www.angelofarina.it/Public/Presentations/UAM2011_Underwater_Ambisonics_files/frame.htmumashankar

i have published my poems. read (or buy) at http://stores.lulu.com/umashankar
 > From: worr...@avatar.com.au
> Date: Tue, 19 Feb 2013 05:49:37 +1100
> To: sursound@music.vt.edu
> Subject: [Sursound] Ambisonic hydrophone?
> 
> Now you've gotten me into a comms mode ... :-) 
> 
> Does anone know of such a beast?
> (I thought of putting the TetraMic in a plastic bag, but I'm not sure Len 
> would approve :-)
> 
> Or how one might go about building one...
> Failing which, does anyone have a recommendation on a cost-effective 
> single-channel unit?
> 
> 
> David
> _
> Dr David Worrall
> Experimental Composer, Polymedia
> Adjunct Research Fellow, Australian National University
> david.worr...@anu.edu.au
> Board Member, International Community for Auditory Display
> Regional Editor, Organised Sound (CUP) 
> IT Projects, Music Council of Australia 
> worrall.avatar.com.au sonification.com.au
> 
> 
> 
> 
> 
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Re: [Sursound] Ambisonic hydrophone?

2013-02-18 Thread Jörn Nettingsmeier 

On 02/18/2013 10:23 PM, Fons Adriaensen wrote:

On Tue, Feb 19, 2013 at 05:49:37AM +1100, David Worrall wrote:


Does anone know of such a beast?
(I thought of putting the TetraMic in a plastic bag, but I'm not sure Len would 
approve :-)


Don't know what Len will think of it, but putting a Tetramic
(or any such mic) in a plastic bag isn't likely to produce
anything usable. Basic problem is that the acoustic impedance
of water is around 3400 times higher than that of air, so the
water/air interface will reflect almost all energy. You need
a transducer that is more or less matched to the acoustic
impedance.


Or how one might go about building one...
Failing which, does anyone have a recommendation on a cost-effective 
single-channel unit?


Have a look at 
Prices start at around $130.

I know of one experimental underwater AMB mic using these -
but can't tell much more.

Most hydrophones (and certainly any low-cost ones) will be
omnis, so the A/B processing will be very different from
what is required for a normal tetra mic using directional
capsules. If they are not omnis then calibration becomes
a real practical problem, it requires underwater impulse
response measurements which in turn require a calibrated
underwater source - an expensive item.


like fons says, your usual hydrophone will be an omni.

the speed of sound is quite high under water, so you cannot easily 
design an acoustic delay element to obtain a useful directional response.


if you don't want to use spaced omnis, check out he sonar surround stuff:
http://www.ambient.de/en/products/ambient-recording/underwater/directivity-sphere.html
not ambisonic, but at least you get some surround information, which is 
quite an engineering feat. the guy who makes them is really kind of 
cool, i've talked to him at tonmeistertagung 2010 in leipzig...


--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT

http://stackingdwarves.net

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Re: [Sursound] Ambisonic hydrophone?

2013-02-18 Thread Fons Adriaensen 
On Tue, Feb 19, 2013 at 05:49:37AM +1100, David Worrall wrote:

> Does anone know of such a beast?
> (I thought of putting the TetraMic in a plastic bag, but I'm not sure Len 
> would approve :-)

Don't know what Len will think of it, but putting a Tetramic
(or any such mic) in a plastic bag isn't likely to produce 
anything usable. Basic problem is that the acoustic impedance
of water is around 3400 times higher than that of air, so the
water/air interface will reflect almost all energy. You need
a transducer that is more or less matched to the acoustic
impedance.

> Or how one might go about building one...
> Failing which, does anyone have a recommendation on a cost-effective 
> single-channel unit?

Have a look at 
Prices start at around $130.

I know of one experimental underwater AMB mic using these -
but can't tell much more.

Most hydrophones (and certainly any low-cost ones) will be 
omnis, so the A/B processing will be very different from
what is required for a normal tetra mic using directional
capsules. If they are not omnis then calibration becomes
a real practical problem, it requires underwater impulse
response measurements which in turn require a calibrated
underwater source - an expensive item.

Ciao,

-- 
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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[Sursound] Ambisonic hydrophone?

2013-02-18 Thread David Worrall 
Now you've gotten me into a comms mode ... :-) 

Does anone know of such a beast?
(I thought of putting the TetraMic in a plastic bag, but I'm not sure Len would 
approve :-)

Or how one might go about building one...
Failing which, does anyone have a recommendation on a cost-effective 
single-channel unit?


David
_
Dr David Worrall
Experimental Composer, Polymedia
Adjunct Research Fellow, Australian National University
david.worr...@anu.edu.au
Board Member, International Community for Auditory Display
Regional Editor, Organised Sound (CUP) 
IT Projects, Music Council of Australia 
worrall.avatar.com.au   sonification.com.au





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