Air raid - how far hearable?

[CZ_RAF]

Hi all,

I would like to ask for hypothetical help as I have not my own experience.

If anybody stated he heard the explosions of bombs how far they were hearable from the drop point? I know that there are a lot of facts which must be taken into account but I am interested if it means 1-5 km or 5-10 km or more??

The same question I have for the AA fire - how far the fire was hearable?

TIA

Pavel

[Dick]

Hi Pavel
I would suspect that your bigger figure could apply. If you look into the literature of WW1 it is common to find references to the fact that the artillery bombardment that preceded the attacks on the Somme in various years could be heard from Southern England as a distant rumble.The volume of fire was enormous and a Bombing raid would not come close to it but up to 15Kms might be a good estimate. On a smaller scale,I live north of the area known as Salisbury Plain which has been an Army training ground for centuries and contains several firing ranges. It is not unknown to be able to hear Artillery or Tank fire from the plain up to about 20 Kms away although the volume of fire is very much lower. The difficulty might be identifying it as a bombing raid or gunfire
Regards
Dick

[alclark]

I've heard the sound of bombing from the range at Tain from nearly 15km away on a hill above Brora and those are individual bombs being dropped at fairly well spaced intervals.

[Argus]

My parents told me, that they could hear, feel and see the fire in the sky, when the allied bombed the North German Coastal cities.

I live in Denmark on the southside of Isle of Funen, so the distance must be a little more than mentioned, but across water, the Baltic Sea.

Just to illustrate with a map:

http://www.bfn.de/habitatmare/en/images/kies-und-sandgewinnung/karte-kies-und-sandgewinnung-ostsee.gif

Regards

Finn Buch

[northeagle]

It depends on the wind and weather I would think. I can hear the guns on Otterburn ranges and they are about twenty miles away. Fire reflecting in a sky can be seen further away than that, I used to often see the furnaces in the next County, about thirty miles away.

Best Wishes.
Robert.

[jonny]

Pavel,

As above, the whole issue depends on atmospherics, the environment, weather conditions and wind and the size of the explosive being used. As someone who has been around military explosions for most of his working life, I can tell you that there are no hard and fast rules to this issue.

Rgds

Jonny

[Resmoroh]

Sound is transmitted through the atmosphere. Sometimes, depending on changes of temperature/humidity/wind-direction with height the sound energy may well be dispersed. On the other hand, on some occasions it may be concentrated some considerable distances away.
The Met Office did a great deal of work on this topic many years ago. It was (then) mainly concerned with the loud "bangs" made at Shoeburyness/Foulness, and how they would be heard in Essex/Kent. There was also the problem of the Liberty Ship SS Richard Montgomery which broke her back whilst anchored just off Sheerness. She had (has?) enough HE as cargo that if it went off it would make glaziers in Essex/Kent a fortune in replacing windows!
The same formula can be looked at from the other end of the telescope. If you can find out who could hear a 'bang', and where, then you could work out how much HE had been used. Clever stuff!!
HTH
Peter Davies

[Lyffe]

Taking Peter's post a little further the noise of explosions does not decay at a constant rate in every direction from the source. In other words on any one occasion the furthest distance from the source a sound is heard in one direction might only be half at which it is heard in another direction. Also, if listening posts placed at, say, 10, 15, 20, 25 km in a straight line from the source, then the noise, in decibels, might be greater than at 10 or 20 km.

The concentration of sound (focussing) to which Peter refer's in his first sentence is an extreme example of my last sentence above. Anyone living on the edge of Salisbury Plain will know there are occasions when the noise of the artillery is exceptionally loud, so loud that buildings shudder and, on occasion, suffer damage; on any one occasion that doesn't occur all round the Plain but in a very small area - the focus.

It's some years ago now but I can remember one particular incident in Devizes, about 25 km to the northwest of the Larkhill artillery ranges. The noise of the guns was phenomenal and our house shuddered, windows shook and tiles rattled with every explosion. The odd thing was that the wind was a 10 knot northwesterly so one would imagine the noise would have been loudest to the southeast of Larkhill. However, when I subsequently interviewed people within the whole area, it quickly became clear that the area most affected was in the immediate vicinity of Devizes - upwind, not downwind, from the source.

A simple question Pavel but, as Jonny says, no simple answer.

Brian

[G3XOI]

I can help with the visibility of fires.

If you ignore the "loom" or reflection on clouds, one's horizon can be calculated, so distance to see fires on the ground is calculable.

If you take the square root of your eye above the surface of the sea in freet, then this gives the figure for the horizon in nautical miles. Do the same for the height of the seat of the fire and add the two figures.

example: Your eye is 100 feet so horizon is 10 nm. The base of the fire is at 16 ft, so it's horizon is 4nm so you will see the seat of the fire 14nm away.

[CZ_RAF]

Hi all,

many thanks for your posts and ideas.
I know it is very difficult to answer my question but as I have not my own experience it help me to get some kind of idea that it may be herable easily 15-25 km - I was supposing much less originally!

So thank you once more to put me into the right dimensions

Pavel