Bangs In The Night!

[stona]

A supersonic shock wave bang is a single sharp event.

It is for one observer in one position but it is a continuous event, as long as the aircraft remains at supersonic speed. Two observers a distance apart but both on the so called 'boom carpet' will hear a sonic boom at slightly different times, depending how far apart they are and how fast the aircraft is travelling.

Not all booms are equal being a function of the physical properties of the aircraft producing the effect as well as its altitude etc.

Cheers

Steve

[Guest]

I've always heard them as a double bang ie b-bang, as there is a shockwave from the nose and also at the tail. It's known as a N wave, one boom is caused by the nose as the pressure rises and the other at the tail when the pressure drops back to normal.

[stona]

The two shockwaves merge into one supersonic wave travelling behind the aircraft (space ship or flying saucer for those of an imaginative disposition) according to my old physics teacher. Mr Snell (he must have been good because I can remember his name 45 years later) was quite keen on practical examples to interest young boys, luckily for me. This would have been around the time Concorde first flew.

The double boom is caused by another effect. A boom accompanies any rapid change in pressure, hence an observer hears one as the high pressure wave arrives and another as pressure returns to normal.

Cheers

Steve

[stona]

The two shockwaves merge into one supersonic wave travelling behind the aircraft (space ship or flying saucer for those of an imaginative disposition) according to my old physics teacher. Mr Snell (he must have been good because I can remember his name 45 years later) was quite keen on practical examples to interest young boys, luckily for me. This would have been around the time Concorde first flew.

The double boom is caused by another effect. A boom accompanies any rapid change in pressure, hence an observer hears one as the high pressure wave arrives and another as pressure returns to normal, as you quite rightly said.

Cheers

Steve

[Guest]

I mentioned we some times used to in Jersey received two bangs apart, Could be quite a time.from the Concorde. Can any one say if that is due to direction change (of the aircraft that is not the Island ).

Laurie

[flyjoe180]

Yes Laurie, it's possible that the aircraft you heard went supersonic twice. The speed of sound is not consistent, it varies with density, temperature and altitude. That's why land speed record seekers head to the salt Lakes, it's hot, low air density and high density altitude, where the speed of sound is actually lower in True Air Speed than it is at sea level.