Re: [PSUBS-MAILIST] Test #2 of collision avoidance sonar

[Jon Wallace <jonw@psubs.org>]

Good work!

There are a couple of variables that could influence determining (from 
sound alone) whether the unit has any directionality in this kind of 
field test.  First, the topside boat may have been going more in an 
ellipse than a circle, with perigee pointed at the front of the 
hydrophone.  As the distance of the surface boat increased around the 
ellipse, the sound would diminish due to distance not directionality.  
The other variable is any drift under water by Kyle's submarine would 
cause the same effect.  Whether the unit is truly directional can easily 
be tested from the surface where better visual clues and a more static 
environment would provide a better environment to determine the 
directional characteristics of the hydrophone.

My experience with surface testing, and I think evident on Kyle's 
sub-surface video, is that it is pretty easy to determine from sound 
alone (non-directional) whether something is moving toward or from you.  
The audio cues are pretty self-evident and easy to interpret with 
objects getting closer also getting louder, and the reverse for things 
moving away.  Additionally, with ear training over time, I think one 
could easily gain experience with estimating range.  Surface boat 
propellers have a rather distinctive sound that is easily identifiable.  
By just spending some time on the surface and listening/watching boat 
traffic, I think you could become accustomed enough to make reasonable 
estimations of "that one is too close" or "that one is definitely far 
enough away".  Of course, this in itself is variable depending upon 
depth since depth alone will increase the distance to the source and 
change the amount of sound energy intercepted.  So it would seem that 
for this type of surface collision avoidance that the sub, when using 
only audio clues, would have to stop at a certain depth each time so 
that the sounds the pilot was hearing, and was use to interpreting, were 
consistently from the same surface distance.  It doesn't matter what the 
distance is (15, 20 feet?) but the pilot would need to consistently stop 
at the chosen depth and perform a surface collision avoidance test.

Jon


David Bartsch wrote:
> To all:
>  
>   This to me is a very interesting clip. It shows his marker buoy as 
> it deploys and his boat submerges. This allows his partner to pinpoint 
> his location while maneuvering his surface craft sonar target. His 
> tests are conducted with a controlled surface contact and still he 
> picks up unknown contacts!
>   In all, a very fun submarine video! My thanks to Kyle for having 
> shared with us this footage.
>   It should be noted that the hydrophone used in these tests is a 
> special hybrid under investigation. It lacks an air resonance chamber 
> hence should be operable to great depths without the fear of imploding 
> or flooding. It is directional to some degree as his friend becomes 
> loudest as he positions himself to Kyles' forward facing. This 
> hydrophone is quite rugged in how it was constructed and could 
> withstand a considerable punishment before becoming disabled. Again, 
> this hydrophone is still under testing but the initial results look 
> promising.
>   Dean Ackman is also using this form of hybrid on his new submarines 
> underwater communications sonar. Its use as a communications 
> hydrophone should be known as soon as these tests are conducted.
>  
>   From Kyle...Enjoy the video!
>  
>                                                                                
> David Bartsch




************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003.  Your email address appears in our database
because either you, or someone you know, requested you receive messages
from our organization.

If you want to be removed from this mailing list simply click on the
link below or send a blank email message to:
	removeme-personal_submersibles@psubs.org

Removal of your email address from this mailing list occurs by an
automated process and should be complete within five minutes of
our server receiving your request.

PSUBS.ORG
PO Box 53
Weare, NH  03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************