music – NOAA Teacher at Sea Blog

September 13, 2024November 9, 2024

Lisa Werner: How Does Communication with Popoki Work? September 11, 2024

NOAA Teacher at Sea

Lisa Werner

Aboard NOAA Ship Bell M. Shimada

August 29-September 13, 2024

Mission: EXPRESS Project

Geographic Area of Cruise: Pacific Coast, near Northern California

Date: September 11, 2024

Weather Data from the Bridge (Coquille Bank):

Latitude: 42º58.378’ N

Longitude: 124º50.146’W

Wind Speed: 23.78 knots

Air Temperature: 14.3ºC/57.74ºF

Conditions: Rain

Science Log

Let’s talk about how Popoki, the autonomous underwater vehicle (or AUV), ‘converses’ with the AUV pilot aboard the ship. The map and directions for the route Popoki will be mapping is programmed into her computers ahead of each dive. On this mission, Popoki has been deployed daily, so every evening, the scientists carefully plan out where she will go on each deployment. They also plan the path Popoki will go when on location – this cruise she has made a lot of sawtooth-shaped patterns to give the scientists the greatest survey of what is in the areas they want to study.

photo of a computer screen showing, at center, an image from a computer-generated model of the underwater bathymetry of an area. Overlaid on the image are topographic lines and depth numbers. overlaid on that is a zig-zagging white line showing Popoki's route. — *Of course, tomorrow’s dive pattern is not a sawtooth pattern. The pattern is drawn out in the white lines over the diagram of the ocean floor contour.*

Though this seems like it would be easy to set up Popoki and let her run her course, that is not quite the end of the story. During a dive, the ocean current is sometimes unknown in any given area, so the AUV pilot needs to be able to help Popoki adjust her positioning. It would not be a very big help to get pictures of an entirely different area than the scientists were aiming for because the ocean currents took Popoki to a different area of the sea floor. The scientists also need to be able to help Popoki if she gets stuck on fishing line, or if the conditions above the water change – such as weather changes or vessel traffic – that would require Popoki to surface ahead of her scheduled time.

To communicate with Popoki, an acoustic modem system is used. There is a modem aboard the ship that can send messages to Popoki through a series of chirping sounds. The pitches and lengths of the chirps are all part of the code that Popoki can understand. She has a device that ‘listens’ for these sounds and can then follow the coded instructions to alter her pre-programmed course. She also communicates regularly with the AUV pilot – sending the coordinates she believes she’s at, her depth, battery life, and how many pictures she has taken so far in the dive.

close-up view of a piece of electronic equipment inside a water-proof housing (with the lid removed to show the contents). There are knobs, dials, CAT-5 cables. — *The modem that communicates with Popoki*

Popoki’s communication device points upward, so when deployment is taking place, the scientists place a transducer into the water to use to communicate. Once Popoki is on her way to her programmed starting point, and farther away from the ship, the transducer is removed from the water.

crewmembers, wearing hard hats and life vests, lean over the rail of the ship and use hooked poles to guide a small yellow object suspended from what looks like a fishing pole safely down toward the water's surface. — *This is the transducer that is placed in the water for deployment*

Sometimes there are difficulties with this communication, and this is where the ship’ crew plays a very important role. The officers on the bridge work to position the ship in areas that allow for Popoki and the acoustic modem to speak to each other easily. The angle of the ship will change as Popoki goes through her programmed patterns, adjusting so that the chirps of the modem have a direct line to Popoki. Distance also plays an important part of the communication process – if the ship and Popoki are too far away from each other, there can be interference with the communication. Ocean current, wave heights and lengths, and other sounds coming from the ship can interfere with the communication, as well. The AUV pilot and the ship’s crew work very closely together throughout the entirety of the dive to help the Popoki and the pilot have clear communication.

photo over someone's shoulder of a computer screen displaying a gridded graph. on the graph is a simplified outline of the ship (like a rectangle with a triangle attached to one end) and some dots to the ship's port side — *AUV pilot Jeff Anderson’s screen showing the ship’s position and Popoki’s position (Denoted as dots)*

At this point, you may be wondering WHY do we use Popoki. I’m sure that you can see her benefits in exploring areas we have not yet seen, but the why actually goes much deeper than that (no pun intended). One of the first things Popoki is doing is looking at areas that are being considered for future offshore wind farm sites. There is a great interest in putting wind turbines over the ocean to create renewable energy for our country. Having been on the Pacific Ocean for 2 weeks now, I can definitely attest to the fact that the wind is very strong in these areas, so there is plenty of energy to harvest. Popoki is identifying the deep sea habitats and geological features on the seafloor that would need to be considered when anchoring any wind turbines.

Popoki is also looking at the changes to the habitats as a result of different regulations that have taken place in fishing areas in this region. Some of the locations we have visited were mapped out by Popoki in the past, and scientists are looking to see whether fishing regulations have helped the populations of ocean life return. Finally, Popoki has been looking for evidence of seeps in the ocean floor. These geological areas are spots where cracks in the ocean floor have occurred due to plate tectonics.

underwater image of the seafloor. it's mostly muddy, with only a little relief, but through the center is a dark crack in the floor, with what appears to be steam (maybe hotter water) rising out of it. we can also make out what might be corals, and a fish. — *Picture of an ocean seep (Photo credit: Popoki)*

Personal Log

The ship’s crew spends a lot of time preparing for safety. Just like we have fire, tornado, and lockdown drills in our school, the ship has drills to practice for emergencies as well. They need to be ready for any emergency, and everyone has a role to play. We have practiced the drills each week.

Throughout my time on NOAA Ship Bell M. Shimada, I have gotten to experience some pretty amazing things. However, my absolute favorite moment was getting “Helm time.” That’s right – I got to drive the ship! With Ops Officer Lieutenant Jaime Hendrix and Ensign Megan Sixt guiding me, I got to turn the ship to hard rudder, causing her to drive in a circle. I also got to get her back to her appropriate heading for the transit we were making, and then practice keeping her on course. It was really interesting to see how the ship reacts to the controls and to see what she does! I am so grateful to CO Laura Gibson for this opportunity, and really appreciate the help LT Hendrix and ENS Sixt gave me!

photo of Lisa wearing a bright red survival suit - all we can see of her is her eyes (with glasses) and a portion of her Teacher at Sea beanie hat. she stands on deck on a clear day and stretches her arms out for the photo — *Me wearing the Immersion (or “Gumby”) suit (Photo credit: Curt Whitmire)*

We practice where to gather, or ‘muster,’ in the event of a fire or abandoning ship. At the very beginning of the cruise, we get right to work with a tour of where to find the lifeboats, how to deploy them, and then we get to the drills.

Recently, I had the opportunity to learn to use the flares and the line thrower. The line thrower is used for ship to ship transfers or for rescuing someone who’s fallen overboard. Although it is really fun to get the experience to use these devices, it is definitely something that you hope only gets used in training. However, knowing they are there and that everyone knows how to use them makes you feel a bit better if an emergency does happen.

Lisa, wearing very large, thick gloves, poses near the ship's railing and smiles at the camera. in her left hand, over the railing, she holds a lit flare. it's a mostly clear day, and the sky is blue with a few clouds, and the ocean has a few whitecaps. — *I now know how to use the flares! (Photo credit: Alice Kojima-Clarke*)

Trying out the line thrower

We are not on autopilot!!! ENS Sixt and LT Hendrix helping me learn to drive a ship! (Photo credit: Randy Scott)

Music Connections

Communicating with Popoki has a lot to do with acoustics. Listening to her pilot talk about how important the angles between Popoki and the ship are reminded me a lot of preparing for a recital when I was a music education student at UW-Whitewater. As an undergraduate, we had several performance requirements per semester. For solo performances, the more experienced music majors would always pass on a very important piece of acoustic information to the new undergrads – always aim the trombone bell at the 3rd exit sign along the stage right wall. Hitting this sweet spot would cause the recital hall to ring, the trombone sound to be dark and full, and the experience to be the best for all who were listening. New trombone majors learned very quickly that this was not a piece of urban legend, but by bouncing the brass sound off of the wall at this angle, it was much more pleasant for the audience than to play directly at their faces.

view of an empty performance hall — *The beautiful Light Recital Hall at the University of Wisconsin-Whitewater – a great place to perform and explore acoustics! (Photo credit: Dr. Glenn Hayes*)

Communicating with Popoki is similar in a way – rather than bouncing her communications off of corners and walls, however, she responds better to the sound waves coming directly at her. She has a sweet spot, too, but it is more about decreasing the angles. This is a much more efficient method of communication for her, because she does not care about the timbre of her chirps!

Another great moment I really enjoyed during our time together was helping our Chief Scientist Dr. Clarke learn ukulele! I always believe that music is everywhere, and Dr. Clarke proved that theory again for me by bringing her ukulele along on this cruise when she heard the Teacher at Sea was a music teacher! Hopefully she had as much fun as I did!

In the computer lab, Lisa and Dr. Clarke sit in chairs facing one another. Lisa, smiling, leans forward to hold up an open laptop where Dr. Clarke can see it easily. Dr. Clarke watches the screen as she picks at her ukulele. — *Dr. Elizabeth Clarke showing off her virtuoso skills with a little “Hot Cross Buns” (Photo credit: Alice Kojima-Clarke*)

Sounds from the ship today will feature the sound of the ship’s engine outside from the very top deck of the ship.

This is the sound of the engine humming from the Fly Deck. You can also hear the waves, as we are in transit to our next station!

Student Questions

St. Bruno students are fascinated by sea creatures, and they have sent me on a quest to learn about the octopus. I think they will be very excited to see this picture and learn about the deep sea octopus!

underwater image of the seafood showing many brittle stars and some corals. in the lower right, there is a sponge, which since it is viewed from above appears as a white ring. inside the sponge, an octopus is curled up - we can see one eye and several tentacles — *Look at the octopus curled up in a sponge in the bottom right corner. You can see the octopus’s eye sticking out! (Photo credit: Popoki*)

Final Notes

The NOAA Teacher at Sea Program is an incredible opportunity for any teacher. As you can see, you do not need to be a science teacher in order to apply. There are so many connections to be made with the ocean, and students get really excited about learning through their teacher’s experience. Applications for the program will open soon. You can find more information here. Thank you so much to the crew of NOAA Ship Bell M. Shimada, the EXPRESS Scientists, and the NOAA Teacher at Sea program for this opportunity. What an incredible experience!

September 2, 2024September 2, 2024

Lisa Werner: Popoki Goes to Sea, August 30, 2024

NOAA Teacher at Sea

Lisa Werner

Aboard NOAA Ship Bell M. Shimada

August 29-September 13, 2024

Mission: EXPRESS Project

Geographic Area of Cruise: Pacific Coast, near Oregon

Date: August 30, 2024

Weather Data from the Bridge (Daisy Bank)

Latitude: 44.37 º N

Longitude: 124.44º W

Wind Speed: NW at 3.17 knots

Air Temperature: 15.7° Celsius (60.26° F)

Conditions: Foggy

Science and Technology Log

Today was the first deployment of the autonomous underwater vehicle (or AUV) for this sailing. The AUV’s name is Popoki ‘Eiwa (which is Hawaiian for ‘Cat Nine,’ and refers to Popoki’s catlike stealth, and the fact that this is the ninth one of this class of AUVs). There was a lot of prep work done yesterday to make sure Popoki was ready for her first outing for this trip (though she has had close to 300 deployments, according to Chief Scientist Dr. Elizabeth Clarke).

Crewmembers on the deck of the ship surrounded a large piece of scientific equipment suspended above the deck's surface by a cable. It is made of two yellow cylinders, each tapered on one end, mounted one above the other by metal beams. There is propeller mounted vertically midway across the front metal beam. There is another propeller mounted horizontally atop the lower cylinder. We can also see instrumentation, a red flag sticking up out of the bag, the NOAA symbol and the name Popoki. Crewmembers wear hard hats and float vests or life vests. — *Preparing to deploy Popoki*

An autonomous underwater vehicle (AUV) is unique because it is not tethered to NOAA Ship Bell M. Shimada in any way. The AUV must be programmed to do what the scientists want. The advantage of Popoki over other submersibles is that Popoki hovers a few meters over the ocean floor, so it can handle rocky terrains better. While underwater, Popoki takes pictures of the ocean floor every few seconds, allowing scientists to see fish, coral, and the marine habitat of the location.

Images from Popoki

underwater image of what must be corals - a few small fish swim nearby — Small fish swim among the deep-sea corals

underwater image of a skate swimming across sandy bottom — A skate swims along the ocean bottom

underwater view of an orange sea star with as many as 22 arms, on sandy bottom — An orange sunflower sea star

underwater view of a striking orange and pink fish, probably a rockfish of some sort, above ocean floor with some rocks and corals — A rockfish

underwater view of a mottled brown fish resting on a rocky bottom, near a white coral — Fish spotted near the ocean bottom

The first thing necessary for Popoki’s deployment today was to have a Green-Amber-Red (GAR) Daily Risk Assessment Meeting. This took place on the bridge, and Chief Scientist Dr. Clarke and her science team met with Commanding Officer Gibson and her ship crew. Both parties looked at current conditions and the necessary actions of the deployment, mission, and recovery of the AUV. They assessed categories such as resources, weather, and mission complexity to determine whether conditions were acceptable for a deployment today. Everyone communicated questions and concerns about the mission objectives. In the end, it was decided the mission was an Amber level – meaning to use extra caution. This is normal for the first deployment of a sailing, as there are new crew involved who have never dealt with Popoki before. Also, during the dive, the ship needs to be able to stay in a position to communicate with the AUV. The risk assessment served as a reminder to everyone to pay very close attention to everything that was going on and to communicate effectively and efficiently to get the job done.

After some deck testing, it was time to get Popoki to sea. She was hoisted off of the deck using the ship’s winch and side a-frame, and then gently lowered to the water. It takes many crew members to make sure that the 600-lb. Popoki does not get hurt or that she does not rub along the side of the ship.

Popoki was deployed a little before 10 am, and recovery started around 2:30 pm. She has a very busy work day (the subsequent dives for our trip will be around 7 hours), and Jeff Anderson, AUV pilot and scientist, will have a busy evening of analyzing the pictures she is bringing back. The recovery process is fascinating to watch, as it is an intricate dance of ship control by the highly skilled bridge of the ship, and the scientists and deck crew with impressive skill trying to wrangle the AUV with lines, hooks, and the winch. No easy feat for sure, though they certainly made it look less difficult than it was! Popoki will be deployed every day of this sailing, weather permitting.

view over the ship's railing of the autonomous underwater vehicle in the water on its return. from the surface, we can only see one of the two yellow cylinders that make up the instrument's body. We also see the red flag mounted on the back. Crewmembers farther down the deck extend hooks on poles, connected to winch cables, toward the swimming AUV. The ocean is fairly calm, and gray, reflecting a foggy gray sky. — *Hooking the Popoki to bring her back*

view down the ship's railing as crewmembers wearing hard hats and life vests use hooks on poles, and cables, to hoist the autonomous underwater vehicle out of the water; in this view it is suspended just above the ocean surface, dripping water. The ocean is calm and gray, reflecting a gray foggy sky. — *Hoisting Popoki back onboard to the ship*

Popoki does not just bring back pictures – she has a sophisticated collection of sensors that will graph the salinity, dissolved oxygen, and temperature, along with graphs that monitor the use of her propellors, battery usage, buoyancy, etc. It is really impressive to see all that she has encountered during the entirety of her dive.

photo of a computer screen displaying a graph labeled "Depth vs Time," with Mission Time as the x-axis and Depth as the y-axis. There is a dark purple line and a green line displaying the data. — Data showing Popoki’s different depths over the time of her dive – notice how many peaks and valleys occur – that’s a lot of shifts for ocean floor terrain, telling us it is very rocky and a lot of terrain changes below Popoki

Personal Log

I really enjoyed being a part of the risk assessment meeting and noticing how important it was that every person involved in the deployment, operation, and return of Popoki had all of the information of the day’s agenda. Every aspect of the day’s goal was planned, with every person aware of which portion he/she was responsible for. Although I don’t necessarily need to assess the risks involved with holding a music concert, the coordination of communication reminded me a lot of how big music events run at our school. Every person in our school – teachers, students, custodians, parent volunteers – all have a very important role to play in the success of the concert. The risk assessment for Popoki gave me a new perspective on how to best address all of the moving pieces necessary to communicate the needs for the concert, and the involvement of everyone in the success of the event!

Additionally, the pictures that came back from Popoki were so impressive to see, even while unedited (the computer runs a color-correction program). It is truly remarkable how the majority of people can be floating above 300 meters of water and never know what is directly below us! It was like looking at pictures from an oceanography documentary, except knowing that I was right above what was being shown on the screen. Seeing something that so few people get to see while being in the location the pictures were taken is an incredible experience! I am just in awe!

view over a man's shoulder of the laptop that he is working on. The laptop displays a black-and-white image of coral. The man sits at a metal desk or bench and uses an attached computer mouse with his right hand. In front of him is a cloudy window through which we can see an exterior ship railing. — *AUV Pilot and Scientist Jeff Anderson looking at initial images from the AUV.*

Music Connection

I did not talk about this up above, because I really wanted to discuss this here in the Music Connection: How do you think scientists on NOAA Ship Bell M. Shimada communicate with Popoki?

If you guessed through the use of sound, you are correct! The technology is similar to that of a fax machine – a computer translates the programming from the scientist into a series of audio tones that are sent to Popoki. Popoki communicates back with a set of digital signals. It is a complicated oscillation of pitches in a variety of rhythms from the scientist doing the programming, a handoff period (because you do not want both the ship and Popoki transmitting at the same time), and then tones of different durations from Popoki responding with what actions she is doing (confirming the commands being followed, documenting images being recorded, recording position, etc.).

This is a sample of the audio coming from Popoki during her testing on the deck of the ship before deployment.

Student Questions

The students I teach made up a list of questions for me to get answers for them, which I called “Homework for your Teacher.” One of the questions they asked was if there were any jellyfish in the area I was going to be. After my visit to the aquarium, I learned that Moon Jellyfish were in the area. Today, while I was on the bridge, Ops Officer Lt. Jaime Hendrix showed me a jellyfish that we could see in the water, as it was near the surface. It was incredible to see a jellyfish outside of an aquarium, and I was impressed I could see the Moon Jellyfish all the way up on the bridge!

August 31, 2024August 31, 2024

Lisa Werner: Introduction to OREGON (Not Alaska!) – August 29, 2024

NOAA Teacher at Sea

Lisa Werner

Aboard NOAA Ship Bell M. Shimada

August 29 – September 13, 2024

Mission: Expanding Pacific Research and Exploration of Submerged Systems (EXPRESS) Project

Geographic Area of Cruise: Pacific Coast, near Southern Oregon and Northern California

Date: August 29, 2024

Weather Data (Newport, OR)

Date: 08/29/2024
Time: 0730
Latitude: 44.6°N
Longitude: 124.05°W

Science and Technology Log

Originally I was scheduled to be a part of NOAA Ship Fairweather‘s hydrography mission, but ship repairs have changed my assignment. I am now going to be on NOAA Ship Bell M. Shimada, working on the EXPRESS mission. EXPRESS stands for Expanding Pacific Research and Exploitation of Submerged Systems.

This project has three main goals:

To guide wise use of living and non-living marine resources,
To inform potential offshore energy decisions, and
To improve offshore earthquake, landslide, tsunami, and nautical hazard assessments.

One of the main aspects of this larger project that I will be experiencing will be the use of an autonomous underwater vehicle (AUV) named Popoki. I am incredibly excited to see the variety of experiments being done for this project!

Before we get going on the project, I had the great fortune of getting a tour of the NOAA Fisheries Lab (part of the Northwest Fisheries Science Center) and the Hatfield Marine Science Center with Alicia Billings, a Fishery Research Biologist. Alicia showed me where her office and work spaces are, taught me about how fish ages are figured out by counting the growth bands of the otoliths (“Ear stones”), and taught me a lot about the nets used for her studies on Pacific Hake. She had just gotten back from being at sea aboard NOAA Ship Bell M. Shimada, so she had a lot of insights as to how the time at sea works and how much the scientists look forward to being able to work in the ocean environment.

close-up photo of a printed poster or bookpage. This section is titled Pacific Hake: Maximum age: 25 years. There is a photo of a hake resting on the seafloor, and two magnified images of otolith crossections. — Pacific Hake otolith example – note the rings to count!

I also had the opportunity to visit the Oregon Coast Aquarium, which had some incredible touch tanks and viewing tunnels showing the marine life of Oregon. I was able to find answers to many of the homework questions the students I teach gave me before I left (mainly about the octopus, crab, and jellyfish populations!)

view of a Pacific Giant Octopus hanging out near the window of an aquarium tank — Pacific Giant Octopus

a zookeeper wearing latex gloves kneels to offer a piece of squid to a sea otter floating on its back near the edge of the water of its enclosure — Pacific Giant Octopus

Oregon Coast Aquarium images:
(1) The students I teach really wanted to see how an octopus moves, so they will love the videos I took of this very large octopus! (2) I arrived at the aquarium just in time to see the sea otters being fed. (3) One of the 3 tunnels that immerses visitors in the sea life of Oregon.

We leave port later today, and I cannot wait to see the incredible work being done!

Personal Log

I am very excited to be sailing aboard NOAA Ship Bell M. Shimada. I am so grateful to Emily Susko for arranging this quick change (while on her week off of work) so that I could still be a part of the Teacher at Sea program, despite the delays with NOAA Ship Fairweather.

Lisa, wearing her Teacher at Sea hat and t-shirt, poses for a photo by pointing excitedly at her nameplate on a wooden door. There are three other nameplates on this door, as well as smaller papers with muster station assignments — My name is on my stateroom door!

The EXPRESS program will be an excellent example of interdepartmental work, as it will feature scientists from NOAA, University of Alaska, and the Bureau of Ocean Energy Management. Combined with the beautiful partnership between the NOAA Officer Corps (the people who run the ships) and the NOAA science team (the people working on the specific project that sails aboard the ships), it will be great to see how all of these groups of people contribute to the greater project – definitely some great lessons and examples to bring back to the students in our school!

Music Connection

Since it is my belief that music connects to everything, the last section of each blog post will feature connections to music. While I was getting a tour of the beautiful Gladys Valley Marine Studies Building from Alicia, I saw an exhibit on a musical instrument that has been made from hollow bull kelp. There was a listening station where you could hear a hollowed bull kelp being played. The beauty of this instrument is that it is environmentally responsible – the bull kelp wash ashore regularly, so they do not need to be harvested. Kelp decays quickly, so the horn must be played within a week of it washing ashore. The projects displayed were showing the collaboration between music and ecology.

photo of a printed photo and caption displayed on a wall. the image shows a single piece of bull kelp lying in the sand. Mounted beneath, the caption reads: "Bull kelp, Nereocystis leutkeana, meaning "mermaid's bladder" is an annual macroalgae. It has a lovely natural history that weaves the story of our narrative. By providing structure to the rocky subtidal, it gives life to many organisms, past and present, small and large. From tiny juvenile rockfish to massive grey whales, extinct sea cows to urchin divers, many call kelp forests home." — Picture of bull kelp. Alicia Billings mentioned that sea lions and seals sometimes hold onto the kelp while feeding.

a man wearing long orange gloves holds a stalk of bull kelp, with his right hand grasping one end as if it were a garden hose, and his left hand holding the other end of the kelp to his lips. His cheeks are puffed out from blowing into the horn. He stands on a beach with muted colors. — Picture of bull kelp. Alicia Billings mentioned that sea lions and seals sometimes hold onto the kelp while feeding.

July 26, 2018July 26, 2018

David Tourtellot: A Musical Perspective of Sonar, July 24, 2018

NOAA Teacher at Sea

David Tourtellot

Aboard NOAA Ship Thomas Jefferson

July 9-26, 2018

Mission: Hydrographic Survey – Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 24^th, 2018

Weather Data from the Bridge

Latitude: 29°09.1270’N

Longitude: 093°46.5544’W

Visibility: 5 Nautical Miles

Sky Condition: 8/8

Wind: Direction: 70.1°, Speed: 13.3 knots

Temperature:

Seawater: 29.24°C

Air: Dry bulb:26.9°C Wet bulb: 24.7°C

Science and Technology Log

Coming to NOAA Ship Thomas Jefferson, I was eager to learn all I could about sonar. I am amazed that we have the ability to explore the ocean floor using sound.

An uncharted wreck discovered by NOAA Ship Thomas Jefferson

Over the course of my previous blog entries, I have described the tools and processes used to survey using sonar. This time, I am going to try to frame the sounds that the sonars are using in a musical context, in the hope that doing so will help students (and myself) better understand the underlying concepts.

Note – many aspects of music are not standardized. For the purpose of this blog post, all musical tuning will be in equal temperament, at A=440. When I reference the range of a piano, I will be referencing a standard 88-key instrument. Many of the sonar frequencies do not correspond exactly to an in-tune pitch, so they have been written to the nearest pitch, with a comment regarding if the true frequency is higher or lower than the one written.

In sonar and in music, when considering soundwaves it is important to know their frequency, a measure of how many waves occur over the course of a set period of time. Frequency is measured in a unit called Hertz (abbreviated as Hz), which measures how many soundwaves occur in one second. One Hertz is equal to one soundwave per second. For example, if you heard a sound with a frequency of 100Hz, your ears would be detecting 100 soundwaves every second. Musicians also are concerned with frequency, but will use another name for it: pitch. These words are synonymous – sounds that are higher in pitch are higher in frequency, and sounds that are lower in pitch are lower in frequency.

Below are the eight octaves of the note A that are found on a piano, each labeled with their frequency. The notes’ frequencies have an exponential relationship – as you move from low to high by octave, each note has a frequency that is double that of its predecessor.

Piano As with frequencies — The frequency of each A on a piano

The highest note on a piano, C, has a frequency of 4186.01Hz

Average, healthy young humans hear sounds ranging from 20Hz to 20,000Hz. All sounds outside of that range are inaudible to people, but otherwise no different from sounds that fall within the human range of hearing. The highest note we would be able to hear would be an E♭, at a frequency of 19,912.16Hz (a frequency of exactly 20,000Hz would fall in between E♭ and E♮, though would be closer to E♭). If put on a musical staff, it would look like this:

High Eb 19kHz — The frequency of the highest note in the human range of hearing

The hull of NOAA Ship Thomas Jefferson is equipped with several sonar transmitters and receivers, which can operate at a wide variety of frequencies.

TJ Sonar — The hull of NOAA Ship Thomas Jefferson, with several sonars. Note that the projectors that transmit lower frequencies are larger than the ones that transmit higher frequencies. This is similar to musical instruments – instruments that make lower sounds, like the tuba or the double bass, are larger than instruments that make higher sounds, like the trumpet or the violin

Higher frequencies provide higher resolution returns for the sonar, but they dissipate more quickly as they travel through water than lower frequencies do. Surveyors assess the depth of the water they are surveying, and choose the frequency that will give them the best return based on their conditions. Most of the sonar frequencies are too high for humans to hear. The ship’s multi-beam echo sounder has a variable frequency range of 200,000Hz-400,000Hz, though as I’ve been on board they’ve been scanning with it at 300,000Hz. Likewise, the multi-beam sonars on the launches have also been running at 300,000Hz. The ship has a sub-bottom profiler, which is a sonar used for surveying beneath the seafloor. It operates at a frequency of 12,000Hz, and has the distinction of being the only sonar on the ship that is audible to humans, however, we have not had a need to use it during my time aboard the Thomas Jefferson.

The ship’s side scan towfish (which I described in my previous blog entry) operates at 455,000Hz.

Here, we can see what those frequencies would look like if they were to be put on a musical staff.

Assorted Sonars and reference pitches — The frequencies of sonar, with reference pitches

Altering the frequency isn’t the only way to affect the quality of the reading which the sonar is getting. Surveyors can also change the pulse of the sonar. The pulse is the duration of the ping. To think about it in musical terms, changing the pulse would be akin to switching from playing quarter notes to playing half notes, while keeping the tempo and pitch the same. Different sonar pulses yield different readings. Shorter pulses provide higher resolution, but like higher frequency pings, dissipate faster in water, whereas longer pulses provide lower resolution, but can reach greater depths.

Personal Log

Mariners have a reputation for being a rather superstitious bunch, so I decided to ask around to see if that held true for the crew of the Thomas Jefferson. Overall, I found that most didn’t strictly adhere to any, but they were happy to share some of their favorites.

Everyone I spoke to told me that it is considered bad luck to leave port on a Friday, though the Commanding Officer, CDR Chris van Westendorp, assured me that you could counteract that bad luck by making three 360° turns to the left as soon as the ship is able. Many on the crew are also avid fishermen, and told me that bringing bananas aboard would lead to a bad catch, and one went so far as to be mistrustful of yellow lighters as well.

Certain tattoos are said to bring good luck – I was told that sailors often have a chicken and a pig tattooed on their feet. According to custom, those animals were often stored in wooden crates that would float if a ship went down, and having them tattooed onto you would afford you the same benefit. When asked if he was superstitious one of our helmsmen Jim proudly showed me a tattoo he has of a dolphin. He explained that having a sea creature tattooed on your body would prevent drowning. “It works!” he said with a grin, “I’ve never drowned!”

Several maritime superstitions deal with foul weather. Umbrellas are said to cause bad weather, as is split pea soup. Whistling while on the bridge is said to “whistle in the winds.” While not a superstition per se, many crew members told me variations of the same meteorological mantra: Red sky at night, sailor’s delight. Red sky in the morning, sailors take warning.

One of the NOAA Corps Officers aboard, ENS Garrison Grant, knew several old superstitions related to shipbuilding. When laying the keel (the first piece of the ship to be put into place), shipbuilders would scatter evergreen boughs and tie red ribbons around it to ward off witches. Historically, having women aboard was considered bad luck, though, conversely it was said that if they showed their bare breasts to a storm, it would subside. This is why several ancient ships had topless women carved into the masthead. Legend has it that in order to assure that a ship would float, when it was ready to be launched for the first time, virgins would be tied to the rails that guided the ship from the ship yard into the water. The weight of the ship would crush them, and their blood would act as a lubricant, allowing the ship to slide into the water for the first time. Yikes! Thankfully, as society became more civilized, this practice evolved into the custom of breaking a bottle of champagne against a ship’s bow!

Did you know? Musical instruments play an important role in ship safety! In accordance with maritime law, ships will use auditory cues to make other vessels aware of their presence in heavy fog. For large ships, this includes the ringing of a gong at regular intervals.

Latest Highlight: During this week’s fire drill, I got to try the fire hose. It was very powerful and a lot of fun!