If you zoom in on this picture of the USS Iowa firing pretty much every gun they’ve got, you’ll see that there are in fact a number of sailors standing on deck to observe the event (look below and left of the central tower).
How loud would it have been where they are standing? Is there a potential for barotrauma?
It’s loud, but most of the sound pressure energy is directed away from the ship. Notice how the barrels actually go past the ships deck area. Ships personnel would have been issued hearing protection.
I’ve always been impressed that you can dent the ocean.
Your hearing will be an issue, but if you’re wandering around carefree on the deck of a battleship, the muzzle blast can rip you to bits:
I’m not sure of the answer, Machine Elf, but I think you’d find helpful this 1989 paper from the Naval Surface Warfare Center, 16 inch Gunblast Experiments. It discusses modelling the blast wave from the muzzle of the 16 inch gun of the Iowa class battleships. This was done to figure out, among other things, what structures could be placed on the deck or near the guns during the overhaul of the battleships in the 1970s.
A common bandied-about stat on the Internet is that a 9-gun broadside has a sound level of 215 dB at 1m. No idea if that’s true or not, and I don’t know if that’s helpful in figuring out the sound level on the bridge wings where some of the observers in those photos are, but it’s an impressive number all the same.
I would think it would be loud. I know from experience a 5’ gun is loud. I was sight check on mount 52 on a destroyer doing target practice. I was standing leaning my back against the gun mount. Mount 51 fired. It was like someone had slammed the side of the gun mount with a sledge hammer real hard. I learned in an instant not to lean on anything in a gun mount while the gun next to you was firing. I also figured the Chief’s had a good laugh on me in the Chief’s mess that night.
So I would think without protection it could cost you your hearing.
I’ve seen several references that 194 db is the loudest possible.
Here’s an explanation though I can’t vouch for it’s accuracy.
It seems to make sense to my uneducated mind.
By the 80s the Navy was pretty sensitive to loud noises and hearing loss. While on the USS Ranger I watched the New Jersey fire. It was quite loud at probably about 3000’
If it was dangerous to to be on deck where the sailors were, they would have at least had on the heavy duty “mickey mouse ears” noise protectors. The type you would use when using needle guns or deck grinders and any other tool that could cause hearing loss. I believe the Marines had to wear them when doing the 30cal machine gun firing procedures and that the jet shop mechanics wore them when testing the jet engines. From the picture linked I see no sign of visible hearing protection. So from that I conclude the noise level was probably no worse than a loud vacuum.
I’ll ditto What Exit. I served in engineering on the carrier Kitty Hawk 88-92. We had to get an annual hearing test to track us. I was issued rubber ribbed sized earplugs. (Insert joke here)
I know the guys on the flight deck were supposed to wear double protection. First expandable foam earplugs then the big headphone cans.
Not a reliable source but the movie Under Siege had Tommy Lee Jones reelling after being on deck when the big guns fired.
PDF link:
www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA210220
Figure 28, page 33 (reported as page 38 by my version of Adobe) is a poor quality picture of a graph of decibels for the 16" mk7. (Up near 200 by the muzzle, it seems to me.)
I have a good friend, now 90 years old, who served on a destroyer in the Pacific during WWII. He was a loader on the 20 and 40mm antiaircraft guns, and they did a LOT of shooting at Japanese Kamikazes. And back then nobody used ear protection, except for maybe a small wad of cotton, and most didn’t even do that.
For years my friend has been deaf in one ear, and has only 20% hearing in the other, and that’s if his hearing aids are working. He’s deaf as a post without them.
It looks to me like the sailors in the pic mostly have their hands over their ears based on their arm positions. I’m not sure they are wearing any protection.
Also, moving a battleship sideways is pretty damn impressive; look at the bow wave at the front of the pic.
That’s part of the pressure wave from the muzzle blast. I saw somewhere that it’s been calculated that it moves the ship a fraction of an inch.
ETA:Even less.
My dad’s not around to ask questions to anymore, but he served 2.5 years in turret #2 of the USS Maryland starting in 1943 and participated in 6 major navel bombardments. He never had hearing problems other than his love of Hank Williams Sr. 
He told me the most active bombardment happened the day the Japanese signed the treaty. The US Navy that was stationed at Okinawa on that night was ordered to fire at will all guns all night out toward the open the sea from the harbour.
Oh, and he told me that the ship would move about a yard back sideways whenever they fired all guns. I cannot imagine doing that job, but he told me it was the best time of his getting to life fire off big guns when you are 18 years old.
