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Fidd · 11-28-23, 07:18 AM

88. Speed of sound propagation in air/water used to determine when, at a given range, sounds are heard in relation to the event:

Speed of sound in air at surface: 340m per second
Speed of sound in water: 1481m per second

Example 1: At 1km range, a torpedo-hit will be seen as a flash/explosion at (say) time 15:00:00, with the sound heard inside the u-boat at a little over half a second later, but on the bridge, the report of the exploding torpedo would be heard at 15:00:03, or 3 seconds after the hit is seen.

Example 2: An escort drops DC's on another submarine 2km from your U-boat at 21:00:00. Inside the boat, the first you know of this is the sound of the exploding DC's 1.3 seconds later, but the sound of same from the bridge would be 6 seconds after they went off. If one allows a 2 second delay for the explosion to cause the plume of water to form, then were you in the Conning tower watching the escort, you'd see the DC plume 3.3 seconds after the charges detonate, and hear the detonation (at through water speed) 3.6 seconds before you saw the plume (0.67 seconds for distance through water + the 2 seconds before the plume forms)

Example: 3 You see a ship hit by a torpedo at 23:00:00 whilst you are 5km away. Inside the u-boat, the sound is heard 3.37 seconds later (at 23:00:03.7. If on the bridge, you'd hear the explosion 14.7 seconds after it occurred! (at 23:00:14.7)

Attenuation of sound with frequency in air https://physics.stackexchange.com/qu...uation-and-why
Attenuation of sound with frequency in water https://www.britannica.com/science/s...tic-properties

NB Decaf may have better sources/clearer explanations. The "take-home" is that sound attenuates quicker in air, and in both cases, the higher frequencies are lost first (if my reading of this is correct?)

11-28-23, 07:18 AM	#106
Fidd XO Join Date: Apr 2005 Location: Blighty! Posts: 437 Downloads: 10 Uploads: 0	88. Speed of sound propagation in air/water used to determine when, at a given range, sounds are heard in relation to the event: Speed of sound in air at surface: 340m per second Speed of sound in water: 1481m per second Example 1: At 1km range, a torpedo-hit will be seen as a flash/explosion at (say) time 15:00:00, with the sound heard inside the u-boat at a little over half a second later, but on the bridge, the report of the exploding torpedo would be heard at 15:00:03, or 3 seconds after the hit is seen. Example 2: An escort drops DC's on another submarine 2km from your U-boat at 21:00:00. Inside the boat, the first you know of this is the sound of the exploding DC's 1.3 seconds later, but the sound of same from the bridge would be 6 seconds after they went off. If one allows a 2 second delay for the explosion to cause the plume of water to form, then were you in the Conning tower watching the escort, you'd see the DC plume 3.3 seconds after the charges detonate, and hear the detonation (at through water speed) 3.6 seconds before you saw the plume (0.67 seconds for distance through water + the 2 seconds before the plume forms) Example: 3 You see a ship hit by a torpedo at 23:00:00 whilst you are 5km away. Inside the u-boat, the sound is heard 3.37 seconds later (at 23:00:03.7. If on the bridge, you'd hear the explosion 14.7 seconds after it occurred! (at 23:00:14.7) Attenuation of sound with frequency in air https://physics.stackexchange.com/qu...uation-and-why Attenuation of sound with frequency in water https://www.britannica.com/science/s...tic-properties NB Decaf may have better sources/clearer explanations. The "take-home" is that sound attenuates quicker in air, and in both cases, the higher frequencies are lost first (if my reading of this is correct?) Last edited by Fidd; 12-05-23 at 12:52 PM.