Bomb pitch

Why do bombs’ pitch change as they approach their target? You know that sound you always hear in the movies of bombs falling? Why the change in pitch as it drops?

drama and Doppler effect.

WAG: The bomb is slowing down as it gets lower and enters thicker atmosphere.

Edit: Hence the doppler effect.

Read up on doppler effect here:

The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler who proposed it in 1842, is the change in frequency of a wave for an observer moving relative to the source of the wave (or vice versa). It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium


So is that sound the one heard by the bomber or the bombed? Would the other person hear an opposite sound?

I dunno. I wouldn’t put too much faith in movies’ accuracy here.

Remember, these are the same folks that show people getting blown across the room with a shotgun blast, too.

Just a guess, but I am going to speculate anyway: Hollywood has trained us Americans to expect certain things in movies (cars can make long jumps and roar off without the undercarriage collapsing).

Bomb whistles (and the siren in Stukas) have been historically attached to frighten the enemy, but I assume that by and large, approaching bombs in movies make the sound they do because they height tension and drama, and the audience has been trained to expect those noises.

One of the things I recall in Vietnam documentaries was that high flying B52’s (who are so high you can’t hear them) were devasting because in one moment, there you are, marveling the butterflies, and the next moment, hell erupts all around you.

Some bombs have whistled. Most never did. This question was asked of some WWII vets on other boards and there was a consensus that some bombs whistled on the way down. At least one was equipped with a cardboard tube for the effect. They were all German-made.

It is mostly dramatic effect from Hollywood, but we have an answer to the OP.

The answer is still relevant if we concede the whistling/sound/siren was on bombers equipped with noise makers (often called sirens, and often the Stuka dive bomber is the plane).

Whether the plane screams in and out during its dive and ascent or the bomb does on its dive, it’'s the Doppler Effect that needs to be appreciated.

Bit too wild I think. More likely you hear a descending shriek from one that’s missing you. The further away it gets as it drops, the more its velocity away from you increases, and hence the greater the Doppler down-shift. Whereas the one that gets you has a steadily increasing velocity towards you, and screams on a rising note. I half-remember this being explained (minus the physics) in All Quiet on the Western Front, but I may be wrong.

Sorry. You are correct.

Doppler effect and psy-ops. Some bombs were puposely-made to whistle.
That’s why the Arc-Light missions were silent.
Ancient people shot whistling-flaming-arrows, according to R. Lee Ermy on the show on TV.
Fear is part of war.

Doppler works with bullets too…muhahaa.

There wouldn’t be any bombs accelerating away from you which is what would be required for the down shift.

Doesn’t the sound also drop in pitch as Wile E. Coyote plummets to the ground? Is that the same phenomenon?

The Stuka’s siren designed by WWI ace and Luftwaffe development chief Ernst Udet, was specifically called the “Jericho Trumpet”.

I have read that the dive flaps on the Douglas SBD Dauntless dive bomber using by the US Navy in WWII were basically large flaps with air holes cut in them. One of the side-effects of this design was that if a squadron of Dauntlesses were descending upon you, the banshee-like wail would likely cause you to void your bowels. Also, it could distract a ship’s defenders from the far more vulnerable (and destructive) Torpedo bombers which would be attacking at the same time against a bigger target.

Remember: Bombs make holes in the tops of ships to let the air in. Torpedos make holes in the bottom of ships to let the water in.

I never did find out if this was an intentional design quality of the Dauntless, or just another fun feature that came about by chance.

Oh, and fun fact: some “Smart” bombs (I think the older ones mostly) were known to make a “clicking” noise, due to the guidance fins snapping back and forth to guide the bomb in. More modern bombs had more finessed fins that did not need to snap all the way to the pegs in either direction to guide the bomb.

Suppose something passes overhead at a high speed. For simplicity’s sake, consider its movement as strictly horizontal. As it’s directly overhead, its velocity vector is normal to the line from you to it. Velocity away from you: nil. A few moments later, it’s a hundred yards downrange. Velocity away from you: considerable, and has been increasing since it passed overhead. There’s your acceleration away and your descending note.

That would give it a brief descending note initially then the note would stabilise particularly as it accelerates toward the earth and it’s horizontal movement slows. That doesn’t fit with the classic noise which is a descending note until impact. Either bombs didn’t really sound like that, or if they did, that’s not a satisfactory explanation.

Well, accelerating towards the earth doesn’t take anything away from horizontal movement, as I’m sure you know, but I’m sure as shooting not going to start number crunching at this point. Either bombs didn’t really sound like that, or if they did, it was a little gremlin playing a swannee whistle. Good enough for me.

No but air friction certainly slowed them down horizontally.

The holes in the dive brakes were to prevent buffeting of the tail planes. The holes smoothed out the air flow but still allowed for a braking effect.