Conference unifix::sailing

Gregg,

Call the NE Aquarium.  If that doesn't lead to anything, send me mail and
I'll put you in touch with one of their project directors. 

J.

    
    Or Woods Hole, or Scripps...
    
    I believe this is gonna run $$$$$ unless it can be borrowed...
    
    Sounds like fun, tho!
    
    Scott.

    I have a friend in Falmouth, MA who used to work at WHOI (as did I once
    upon a time...). Although he was a programmer in the Geophysics dept,
    he fanagled a crew position on a 50' motorsailor whose purpose was to
    go to Stellwagon to listen to whales! Beats writing siesmic plotting
    programs...     Send me mail and i'll give you his #.

    Also try Sipican Corp, in Marion. They do lotsa underwater stuff.

    Also try Benthos Corp, in Falmouth. They also do lotsa u/w stuff,
    including video and audio...
    

    paul

    Thanks!
    
    A book I read said that the cost for the mikes range from 30 to
    hundreds of dollars.
    
    Gregg

You'llhave to go back several year but they had an article in the
Amature Scientist that told how to make them from scratch. It wasn't
to hard.

    One source is Edmund Scientific.  They have the mic at a reasable price
    and an amplifier for a outragious price.
    
    From the current catalog  #12N1
    
    Hydrophone Microphone Head
    	Freq response: 10 to 60000 hz 64 db.  61 db 10 to 2000 hz
    	Impedance: Low will operate into bot high and low impedance inputs
    	Operating depth: 300 ft.  max depth without damage 360 ft.
    	Hydrophone Microphone head  A41,759   $23.95
    
    
    Underwater hydrophone
    	Kit includes underwater mic with 20ft of cable
    	Specs the same as above
    	Earphones
    	Amplifier
    		Input impedance 4.7megohms across 100pf
    		output power 0.5 w rms
    		freq response 52 db 100 hz -20 Khz
    		Battery 9v Alkaline type
    		Voltage gain input to headphone jack at full volume 70db.  
    		23db to tape out jack
    	Case plastic 1x2x3 inches  5 oz with battery
    
    	Hydrophone	A38,095	$250.00
    
    Edmund Scientific Company
    101 E. Gloucester pike
    Barrington, NJ. 08007-1380
    
    609-573-62500
    
    I have used the mic with a home made amp.  It works well.  The main
    limitation is you will hear power boats for miles around.  Also you
    must drift or anchore as the flow noise will hide the fish sounds.
    
    With mic they send you instruction on how to comnnect the cable to the
    mic.   If you want to use it a depths greater than I think 30 feet the
    mic must be put into a oil filled conatiner such as plastic ketchup
    bottle.
    
    Give me call If you need any other info.  237-6561 

    Oh the other bit of info.  Is the whales don't sing here.  Just off of
    South America.  That was what the guide on a whale watch boat told me.
    
    Ken C
    

    Ken,
    
    REALLY? Wow, they don't sing in the Northeast? Not even the humpbacks?
    
    I wonder why? Could be an irrascible audience - you know them New
    Englanders... :^)
    
    Gregg

re .9:

How 'bout heaving to? Hove to the sails don't luff (at least in a strong 
wind) and it isn't difficult either to heave to or get back under way.

Hmmm...any chance you could fabricate the audio equivalent of a 
glass-bottom boat?  I've heard whale and dolphin squeaks and squeals from
inside a fiberglass hull underway in calm conditions (no engine running,
of course).  Perhaps you could make a box to put over the side, with a
bottom of thin material, on which could be mounted a regular microphone.  
A slight loss in fidelity might be made up for by the amp and the >$200
savings. 

Just a thought....

John.

    Alan,
    
    Well what I had in mind was to slow down and do some scanning as I was
    sailing out there. I just want to:
    
    Slow down
    
    Listen (maybe record)
    
    Speed up.
    
     And it's simpler to just ease the sheets and sail inefficiently.
    
     Now, when I want to hang around, then your idea is better.
    
     BTW, I want to connect the hydrophone to, say, something as simple as
    a Walkman or portable cassette. That allows you to listen with the
    headphones as you record.
    
     is there a better idea?
    
    Gregg

    John,
    
     For that matter, I could try a regular mike encased in an inflated
    balloon (weighted of course). I figured I might try this, but one of
    the books I read sugested that the fidelity loss would be too high.
    
     Also, it said you have to get the mike (whatever it is) down about 10
    feet. They wrote that somehow that cuts out a lot of surface noise.
    
    Gregg

    The flow noise is mostly due to the simple microphone enclosures and
    the cable.  The plastic bottles have ridges which generate turbulance.
    The other source of noise is the cable itself.  The common vinyl
    covered microphone cable is a great conductor of sound.  I guess a
    rubber covered cable would be better.  The other source of flow noise
    is the rolling of the boat.
    
    The one I have has a short (about 30 ft cable made out of vinyl) so
    it is not long enough to get below the thermocline layer.  One of the
    winter projects is to replace the cable with a rubber covered one.
    
    The main problem with just putting a mic in a bag inthe water is the
    hydostatic pressure.  A typical mic has a small hole in the back to 
    equalize the air pressure.  If put into water with out any way 
    for the prussure to equalize the mis will be destroyed.  The pressure 
    is about 0.43 lb per in squared per foot of depth  
    
    There where three articles in Scienfic American over the last 20 years
    on how to build hydrophones.  I have copies if any one in intrested.
    
    One other use for a hydrophone is the find krill.  Bait fish
    eat these and the Bluefish eat the bait fish.  
    
    

    If the mike was in an inflated bag, the pressure would equalize to the
    bag pressure, would it not?
    
    Gregg

    I would suggest feeding your audio through an inexpensive automotive
    (12V) equalizer, at least 5 band. This would allow you to discriminate
    and boost the spectrum your looking for, effectively enhancing what
    is probably a marginal S/N ratio. Considering the probable lack of
    linearity in such an inexpensive microphone and probable high back-
    ground noise level you'll need all the help you can get...

    Hmmm, doesn't the range of sounds (at least from a humpback) span both
    ends of the human hearing spectrum? I thought they made low frequency
    noises as well as way up past the sonic range.
    
    Gregg

    They may very well but the more bands you have the better able you are
    to contour the response of the system. Chances are the white noise is
    fairly wide band while the target emissions may be relatively narrow
    band. You could boost the narrow band filter and hopefully keep the 
    majority of the white noise suppressed. For more serious filtering
    you would have to record the emissions and digitally filter. Very
    expensive equipment needed here. Another thought for technologically
    manageable filtering is noise-cancelling mike system is a significant
    amount of noise is generated at the surface or elsewhere away from
    the deep mike. You would need two mikes, a mixer (simple diode is fine)
    and an inverting amplifier. The mikes should be impedence matched BTW.
    The deep mike would drive one of the mixer inputs and the shallow
    mike (say right under the boat) would feed through a unity gain
    inverting amplifier (about 5-8 parts and $10 at Radio/Shack) to
    the other mixer input. Hum! scatch what I said about a simple
    diode mixer, you might need to adjust the gain ratio. A mixer
    with input gain control is needed. Lots of white noise will
    get into the shallow mike from the boat waves etc, but it will
    be inverted (180 d phase shifted) so it will cancel any of the
    same noise getting down to the deep mike in real time. By adjusting
    the gain of one of the channels you would optimize the noise
    canceling effect. The more I think about this the niftier it
    sounds, if you'll excuse the pun....

    I wonder if one of those radio mikes (mike with fm transmitter) in a
    balloon would work.  There would be no cable noise.  Tie a string to
    the balloon, weight the balloon and let it sink to the required depth.

    
    Unfortunately, nope.
    
    And towing just about anything is gonna be noisy- I like the listen-
    and-stop idea...
    
    	Scott

    REF .-2
    
    The salt water makes an effective shield for rf.  The only frequencies
    that can pentrate are in the low Khz range.  The Navy runs a a large 
    megawatt xmitter in Maine to contact deep running submarines.
    
    I will let you know how the rubber cable works.  
    
    Ken C
    

Whales migrate to the Northeast in the spring time ( you can see them regularly
off Stellwagon Bank ~ April ). The humpbacks, finbacks and minkes are here to
EAT :-). They cruise back down to the sterile, warm Carribean waters, and farther
south to find a mate and calve their babies around October.

Singing is primarily an activity associated with mating, so I doubt you will
pick up much in the whale melody department around here I am afraid.

Good Luck though,

	JoAnne (former NE Aquarium whalewatch volunteer)