Decibel levels

FPSchazly · 05-11-23, 05:33 AM

Decibel are measured differently in air vs water. To convert a water dB to air dB, you subtract approximately 62 dB. Different reference pressures are used when measuring in air vs. water. So, the 115 dB in water is approximately 53 dB in air. I think that 115 dB number is also for the submarine at "all stop" because Dot Mod reports a higher dB on the tactical map when you're cruising around at a higher speed than 'all stop'. Hope this helps.

Thanks to PineMartenEmily and tychosis for these insights.

shake307 · 05-14-23, 02:12 AM

Well, shoot. I did not know dB levels were measured differently underwater. You taught me something, thanks.

FPSchazly · 05-15-23, 08:05 AM

Quote:

Originally Posted by shake307

Well, shoot. I did not know dB levels were measured differently underwater. You taught me something, thanks.

Glad to hear it

Chaussettes · 07-05-23, 01:14 PM

Subs are really that loud and get louder the faster you are moving, typically +1dB per knot, so a Los Angeles moving at 10 knots will be about 125dB. This is loud on it's own but a big consideration is ambient noise. You can view the current ambient noise level of the mission area on the conditions panel at the top in game. Ambient noise typically fluctuates anywhere from the mid 70s to over 120dB, and plays a big factor in being able to detect other vessels as well as the detectability of your own. For example:

A Los Angeles is moving at 10 knots and is generating ~125dB of noise. The ambient noise level is 110dB. You can get a general estimate of your real audible noise level by just subtracting the ambient noise level from your sub's noise level. So your real noise level in this scenario would be ~15dB. This would be very difficult to detect at any significant distance.

So yeah, your sub is generating over a hundred decibels of noise, but it's not really the audible noise that other vessels are able to hear, as most of it is drowned out by the ambient background noise.

A good easy to remember rule of thumb for ambient noise I use is:
70-90dB - It's very quiet, you can be heard easily.
90-110dB - It's somewhat noisy.
110-130dB - Someone is blowing into a microphone outside, it is next to impossible to hear anything or detect someone unless they are ontop of you.

SpeedyPC · 07-15-23, 10:57 PM

Quote:

Originally Posted by Chaussettes

A good easy to remember rule of thumb for ambient noise I use is:
70-90dB - It's very quiet, you can be heard easily.
90-110dB - It's somewhat noisy.
110-130dB - Someone is blowing into a microphone outside, it is next to impossible to hear anything or detect someone unless they are ontop of you.

Thanks for this method as a reminder

Oubaas · 07-06-23, 07:44 AM

I often wear a fishing trawler as a hat, if I can find one headed in the right direction.

Fire a decoy to draw them, then pull right up under that noisy trawler, match its speed, and sling torpedoes with near impunity, LOL!

Aktungbby · 07-06-23, 10:37 AM

Sugardust!

on the surface affter a 3 year 'silent run'!

Aktungbby · 07-06-23, 10:40 AM

Chausettes!

nice first post!

Kralizec · 07-24-23, 01:26 PM

Quote:

Originally Posted by FPSchazly

Decibel are measured differently in air vs water. To convert a water dB to air dB, you subtract approximately 62 dB. Different reference pressures are used when measuring in air vs. water. So, the 115 dB in water is approximately 53 dB in air. I think that 115 dB number is also for the submarine at "all stop" because Dot Mod reports a higher dB on the tactical map when you're cruising around at a higher speed than 'all stop'. Hope this helps.

Thanks to PineMartenEmily and tychosis for these insights.

Hey Chaz!
It's not 62dB but 26dB, so 115dB becomes 89dB when changing SPL units from water (usually 1 micropascal is 0dB) to air (usually 20 micropascal is 0dB)

There is another factor: due to the difference in acoustic impedance, most of the sound will reflect off the surface of the water, and only about -60dB makes it through.
So if you are standing 1m above a 100dB(re 1μPa) underwater sound source, due to the boundary the sound you hear will only be 40dB(re 1μPa) loud. But since in air we prefer to use 20μPa as a reference, I'll subtract 26dB -> the sound pressure is therefore 14dB

05-11-23, 05:33 AM	#1
FPSchazly Good Hunting! Join Date: Apr 2014 Location: Maryland Posts: 771 Downloads: 15 Uploads: 1	Decibel are measured differently in air vs water. To convert a water dB to air dB, you subtract approximately 62 dB. Different reference pressures are used when measuring in air vs. water. So, the 115 dB in water is approximately 53 dB in air. I think that 115 dB number is also for the submarine at "all stop" because Dot Mod reports a higher dB on the tactical map when you're cruising around at a higher speed than 'all stop'. Hope this helps. Thanks to PineMartenEmily and tychosis for these insights. __________________ Your friendly neighborhood modern submarine YouTuber. My videos: Exclusive Look at Modern Naval Warfare! Dangerous Waters Liu Doctrine (LwAmi Learn to play Dangerous Waters

07-05-23, 01:14 PM	#4
Chaussettes Swabbie Join Date: Jul 2023 Posts: 13 Downloads: 10 Uploads: 0	Subs are really that loud and get louder the faster you are moving, typically +1dB per knot, so a Los Angeles moving at 10 knots will be about 125dB. This is loud on it's own but a big consideration is ambient noise. You can view the current ambient noise level of the mission area on the conditions panel at the top in game. Ambient noise typically fluctuates anywhere from the mid 70s to over 120dB, and plays a big factor in being able to detect other vessels as well as the detectability of your own. For example: A Los Angeles is moving at 10 knots and is generating ~125dB of noise. The ambient noise level is 110dB. You can get a general estimate of your real audible noise level by just subtracting the ambient noise level from your sub's noise level. So your real noise level in this scenario would be ~15dB. This would be very difficult to detect at any significant distance. So yeah, your sub is generating over a hundred decibels of noise, but it's not really the audible noise that other vessels are able to hear, as most of it is drowned out by the ambient background noise. A good easy to remember rule of thumb for ambient noise I use is: 70-90dB - It's very quiet, you can be heard easily. 90-110dB - It's somewhat noisy. 110-130dB - Someone is blowing into a microphone outside, it is next to impossible to hear anything or detect someone unless they are ontop of you. Last edited by Chaussettes; 07-06-23 at 02:21 PM.

07-06-23, 10:37 AM	#7
Aktungbby Gefallen Engel U-666 Join Date: Jul 2013 Location: On a tilted, overheated, overpopulated spinning mudball on Collision course with Andromeda Galaxy Posts: 28,014 Downloads: 22 Uploads: 0	Welcome back! Sugardust! on the surface affter a 3 year 'silent run'! __________________ "Only two things are infinite; The Universe and human squirrelyness; and I'm not too sure about the Universe"

07-06-23, 10:40 AM	#8
Aktungbby Gefallen Engel U-666 Join Date: Jul 2013 Location: On a tilted, overheated, overpopulated spinning mudball on Collision course with Andromeda Galaxy Posts: 28,014 Downloads: 22 Uploads: 0	Welcome aboard! Chausettes! nice first post! __________________ "Only two things are infinite; The Universe and human squirrelyness; and I'm not too sure about the Universe"

05-14-23, 02:12 AM	#2
shake307 Watch Join Date: Nov 2013 Location: The Cowboy State, Wyo Posts: 18 Downloads: 32 Uploads: 0	Well, shoot. I did not know dB levels were measured differently underwater. You taught me something, thanks.

07-06-23, 07:44 AM	#6
Oubaas Weps Join Date: Oct 2011 Location: Arkansas, USA Posts: 358 Downloads: 65 Uploads: 0	I often wear a fishing trawler as a hat, if I can find one headed in the right direction. Fire a decoy to draw them, then pull right up under that noisy trawler, match its speed, and sling torpedoes with near impunity, LOL!