NPRB outreach presentations

OVERVIEW

As part of an outreach effort for NPRB 1218, I spent three days at Blatchely Middle School in Sitka, AK, (April 22-24) presenting the concepts of array beam forming to five periods of  Stacy Golden’s science class.   My motivation was to use NPRB 1218 as an opportunity to explain to students some fundamental physics and engineering concepts that extend way beyond underwater acoustics.

CLASSROOM PRESENTATION

One day was spent talking in the classroom and conducting a demonstration on how our ears localize sounds.    The presentation is included below, and I used class iPads and headphones to allow five classes of 20-30 students each to listen to the sounds in detail.  (The demo stereo sound played on the iPads is on slide 13).

Here is a link to the presentation.

HYDROPHONE DEPLOYMENT

On April 23 I deployed two hydrophones simultaneously in Sitka Harbor, separated by 5 feet, and demonstrated to classes how adjusting the separation between the phones influences one’s ability to determine the direction of various sounds.  Below are some sound snippets of various vessels detected and “tracked” in Thompson Harbor.  Both hydrophones were deployed at 1 m depth off the side of the floating dock, with “broadside” facing south and right “end fire” facing Sitka Channel.  The snippets feed the sound from one hydrophone (the one closer to the harbor parking lot) into the left ear , and the sound from the hydrophone closer to Sitka Channel into the right ear.  There is interference from a radio station that can be heard on some samples.  The samples have been decimated to 8 kHz, and channels normalized to equal “loudness”.

 

The Thompson harbor two-element array deployment.  The "left" hydrophone cable is visible to the left of the table.  The "right" hydrophone is behind the table.  Thus, vessels entering or exiting the channel are heard on the "right" audio channel.  Some directional hydrophone assemblies are also visible.
The Thompson harbor two-element array deployment. The “left” hydrophone cable is visible to the left of the table. The “right” hydrophone is behind the table. Thus, vessels entering or exiting the channel are heard on the “right” audio channel. Some directional hydrophone assemblies are also visible.

 

A close up of the (relatively antiquated) real-time monitoring and recording setup.
A close up of the (relatively antiquated) real-time monitoring and recording setup.

 

A group of us listening to a vessel go by.  The sounds from this vessel would appear to come from the "right" on the recordings.
A group of us listening to a vessel go by. The sounds from this vessel would appear to come from the “right” on the recordings.

 

(1): A seaplane takes off from Sitka Channel, passing from left to right across the array, eventually passing right “end fire”.  This sound contains a fine example of harmonics, and how the volume of the propellor increases when the plane passes to the side.  The sound attenuates once the plane lifts off the water:

 

Here is a spectrogram of the data:

Note the harmonics of the plane.  The engine rpm times the number of blades yields frequency of the lowest harmonic.
Note the harmonics of the plane. The engine rpm times the number of blades yields frequency of the lowest harmonic.

 

(2): An unknown vessel makes a U-turn while “end fire” to the right of the array and then accelerates when entering the Sitka Sound Channel.

 

(3):  The Thompson Harbor harbormaster passes “broadside” to the array from left to right, revving his outboard motor just as he reaches his closest point of approach:

Here is a spectrogram of the data:

Harmonics from the outboard can be seen, along with cavitation bubbles and interference fringes from the "Lloyd's Mirror Effect".
Harmonics from the outboard can be seen, along with cavitation bubbles and interference fringes from the “Lloyd’s Mirror Effect”.

(4):  A vessel passes to the right “end fire,” while Blatchley Middle School teacher Stacy Golden bangs a metal rod to the left “end fire” of the array:

Here is a spectrogram of the banging:

Banging a metal rod can actually produce ultrasonic sounds!
Banging a metal rod can actually produce ultrasonic sounds!

(5): The F/V Venus passes “broadside” from left to right, while a Bay boat passes “broadside” from right to left:

 

Here is a spectrogram:

soundsamp_B12h30m16s23apr2014y_VenusAndBayBoat_clean_20140423T212100_1

(6):  The F/V Venus starts up its GenSet (generators) to the left “end fire” of the two-element hydrophone array.

How to charge a dead battery for the decoy device

When not used for long periods, the batteries should be disconnected inside the decoy to prevent full discharging, because if  the battery pack voltage falls below 1.5 V, the charger IC board will not permit charging.  However, here are some steps to “resuscitate” a dead battery pack.    Warning: you will need a 12 V power supply with alligator clips and a screwdriver.

Ideally you should have a power supply like this, set to 12 V output and current limited to 0.5 A.

Ideally you should have a power supply like this, set to 12 V output and current limited to 0.5 A.

Remove the lid of the decoy.  Make sure you keep track of the six screws and six plastic sleeves for the screws, which tend to fall out when the lid is upside down.  Find a box so that the lid can be flipped upside down while remaining connected to the charging board.

Remove the lid of the decoy. Make sure you keep track of the six screws and six plastic sleeves for the screws, which tend to fall out when the lid is upside down. Find a box so that the lid can be flipped upside down while remaining connected to the charging board.  Check that all connectors are connected–perhaps that is your problem!  In particular, the flat 8-wire connector needs to be together for the charger to work.

Make sure this connector is attached--this may be why charger is not working!
Make sure this connector is attached–this may be why charger is not working!

 

When storing for long periods, disconnect the two connectors next to the screwdriver (white and black/red connector.

When storing for long periods, disconnect the two connectors next to the screwdriver (both white and black/red connectors).

 

The white connectors have two exposed wires.  You will attach the black alligator clip (ground) to the wire on the left side of this photo--the wire that travels a longer distance.
The white connectors have two exposed wires. You will attach the black alligator clip (ground) to the wire on the left side of this photo–the wire that travels a longer distance.

 

An example of where to clip the black wire.  Note that I am showing a connector from the opposite side.
An example of where to clip the black wire. Note that I am showing a connector from the opposite side.

 

Now, with the conventional charger plugged in and on, and with the black alligator clip attached to any connector ground, choose one of the battery packs (one of the white connectors), clip the red alligator clip to a small screwdriver (with insulated handle), and touch the connector on the side of a small diode next the the white connector, as seen here.  Hold in place for a minute, then release and see if LED light comes on.  If light comes on while connecting, you're good to go.  Move on to the next connector and repeat.  Note that you do not need to move the black alligator clip.  When all is charging, let is charger fully, then unplug the conventional charger, then seal up the decoy.  Make sure that the speaker connector and 8-pin connector are connected before reattaching lid.
Now, with the conventional charger plugged in and on, and with the black alligator clip attached to any connector ground, choose one of the battery packs (one of the white connectors), clip the red alligator clip to a small screwdriver (with insulated handle), and touch the connector on the side of a small diode next the the white connector, as seen here. Hold in place for a minute, then release and see if LED light comes on.  If this happens (or light comes on while you are connected), you’re good to go!   Move on to the next connector and repeat. Note that you do not need to move the black alligator clip-all the ground wires on the white connectors are electrically connected. When all is charging, let it charger fully, then unplug the conventional charger, then seal up the decoy. Make sure that the speaker connector and 8-pin connector are connected before reattaching lid.

 

 

 

Some photos of TadPro assembly

Close up off bracket attachment with snap on gear
Close up off bracket attachment with snap on gear

 

14 complete TadPros, plus one dissembled for further acoustic research.
14 complete TadPros, plus one dissembled for further acoustic research.

 

Lauren Wild (Sitka Sound Science Center) displaying how a TadPro and light are attached to a demersal longline.
Lauren Wild (Sitka Sound Science Center) displaying how a TadPro and light are attached to a demersal longline.

 

photo
Assembled underwater light and Camera housing, on snap-on gear.

photo photo

scripps oceanography uc san diego