US Navy sonar & divers

[citykid]

The new sonar that the US Navy developed, but isn't allowed to use because it supposedly is killing whales and other life, . Anyone know if it poses any danger to us while we are in the water

 

[Gary D.]

No danger at all if you have the big red “S” on your chest. If it kills marine mammals it will kill humans. The stuff they had 40+ years ago could kill marine mammals and divers and that was mild stuff in comparison. That is one of many reasons the divers secure a harbor prior to making any dives in the area.

Another thing to remember is that there are a lot more tree huggers today that are watching out for the environment and making people accountable for their actions. 40 years ago there were too few to make a difference.

Gary D.

 

[dschonbrun]

can you please provide the name of this "new Navy sonar"?

 

[Mr.X]

I remember one summer where I was instructing scuba off a beach in Ca. There was a military(?) contractor that pulled in to do some type of "stealthy" work off Catalina Island. What was interesting was they they were actively pinging in the area to the point where it was quite disruptive underwater. Not so loud to bother the heck out of you, but enough to distract even while wearing a hood.

Luckily they left after a few days. I might add that the Navy seems to conduct all these military exercises from time to time there...including bringing in some black-looking hovercraft.

X

 

[Gary D.]

I don't know if it has it's own name. Each generation just gets more powerful. The early stuff was mild compaired to todays.

Gary D.

 

[Scubakevdm]

The new sonar that the US Navy developed, but isn't allowed to use because it supposedly is killing whales and other life, . Anyone know if it poses any danger to us while we are in the water

Subs have to go very far offshore before they dive, and typically don't drive around with their active sonar on. They save it for special occasions like determining exact range just prior to firing a torpedo. Some things that you can do to minimize your risk of being pinged are, don't go diving in the middle of the ocean around Navy warships, because submarines often are training with them. Don't dive on submarine piers, because sometimes the sonar techs actually do work, and every once in a while this work involves testing the active sonar system. And lastly, don't dive with foriegn submarine sound signatures cranked up on your underwater Ipod.

 

[Gene_Hobbs]

The new sonar that the US Navy developed, but isn't allowed to use because it supposedly is killing whales and other life, . Anyone know if it poses any danger to us while we are in the water

This is a good paper on the testing.

Fothergill, Sims, and Curley. Recreational scuba divers' aversion to low-frequency underwater sound. Undersea Hyperb Med. 2001 Spring;28(1):9-18. RRR ID: 2368

There are a few more in the Repository but I don't have time to add the refs today. Check here

 

[AzAtty]

You're probably thinking of SURTASS LFA. It has received a lot of bad press in the past several years. It's a combination of a "passive towed array" (a miles-long string of hydrophones that emits no sound waves) and an "active" low frequency sonar emitter (sends out sound waves in the 100 Hz to 500 Hz range that reflect off submerged objects).

The U.S. Navy claims that its studies show that sound levels below 160 dB will not cause physiological harm to human divers. The Navy restricts the use of LFA sonar to sound levels of 145 dB in areas known to be frequented by divers.

On the other hand, environmentalists claim that marine mammals have suffered physiological damage or aversion responses as far as 300 miles from an active low frequency sonar source.

Regardless, I would not want to be anywhere near an active emitter while underwater.

 

[covediver]

Noise in the sea affects divers in many different ways. Anyone too close to the noise could be affected. The Navy has done research on this and has a practice of not ensonifying areas where divers are likely to be present. Sonar is not the only noise to have this affect. When research involves seismic surveys to look at the sea floor and deeper, safety considerations for divers are also taken into consideration. For example, the National Science Foundation did an environmental analysis of its worldwide seismic survey program a few years ago and used a very conservative threshold for exposure to divers. Divers working on dams for the Bureau of Reclamation have protocols for noise exposure. The information is out there and is relatively straight forward.

A word of caution in interpreting the results. Underwater, noise is referenced to transmission in water, such as 140 db. People see this number and think the sound approximates the that of a jet engine. Now, this level of noise is not the equivalent of exposure in air, which would roughly be about 70 to 75 db, well within human tolerance, signal characteristics aside.

 

[Scubakevdm]

With LFA, the main concern as far as recreational divers are concerned, is not physiological damage resulting directly from the active transmissions, but rather being scared by the sound and possibly vibration, and panicing. Also, the physiological damage that occured during the navy testing at 160 db included temporary shifts in hearing levels, headaches and increased sensitivity to loud noises and irritablity.