Did German bombers make a different sound and why?

[pattle]

I often hear that German bombers made a different sound to British aircraft during the blitz, my mum and others tell me the German planes made a woo woo woo sound while the British aircraft made more of a roar. Going by the amount of accounts and witnesses there seems little doubt that German aircraft actually did make this sound and I have heard a number of explanations of why this happened which include the following.

1) That the sound was caused by a large number of aircraft in formation that had engines running at different rpm's.
2) That twin engine German aircraft had each engine set at a different rpm to either frighten civilians, confuse radar or because the engines were tired and could not be synchronised correctly.
3) That the pilots themselves de-synchronised the engines while in flight to confuse the anti aircraft defences.

I would have thought that de-synchronised engines would have been a bad thing for both crew and aircraft.

 

[pbehn]

I believe it is called the doppler effect on twin engines

 

[stona]

My grand mother would confirm the uneven sound of German aircraft engines.
She said that it sounded as if the bombers were asking..."where do you want it?......where do you want it?......where do you want it?"
Cheers
Steve

 

[FLYBOYJ]

I don't think early WW2 twin engine bombers had effective propeller synchrophasers.

Propeller synchronization - Wikipedia, the free encyclopedia

Here's a little chat on the same subject...

http://www.pprune.org/archive/index.php/t-135198.html

 

[GrauGeist]

Have you ever heard numerous engines of the same type operating in the same area?

And example would be riding in a B-17. You can hear the engines creating a low frequency "wow wow wow" sound. When you multiply these similiar engines, all set to comparable RPMs, (add distance or other accoustic adjustments) you'll get harmonic sounds like the ones being discussed here.

 

[stona]

In 1942 BBC engineers were attempting to record Nightingale song in a garden in Surrey when Bomber Command passed overhead. Consequently they started to record the sound of the bombers.

There is a link to the recording on this page (play recording). You can clearly here the aircraft as well as a beautiful Nightingale song, remarkable and from such a dowdy looking little bird

The British stream of four engine bombers makes a constant droning sound quite unlike described by people who also heard German aircraft pass overhead. My grand mother was quite sure she could tell "ours" from "theirs". Living in Kent she would certainly have heard "theirs" often enough.

Cheers

Steve

 

[silence]

If you play two guitar strings that are just slightly out of tune with each other, say at 300Hz and 303Hz, you'll get that beating sound.

To get a good demonstration, pick up a guitar and play a harmonic on the A-string at the fifth fret and a harmonic on the D-string at the 7the fret (using harmonics make the effect far easier to hear). If the two strings are properly in tune with each other, there will not be a "beating" sound. However, if they are just slightly out of tune with each other you'll hear that beating sound, and the more out of tune they are the faster the beating sound.

Its a very simple and quick way to get the strings on a guitar (or bass) in tune with each other.

 

[OldSkeptic]

There are 2 theories, one to confuse sound locators. The other by Stllpepper was that in their 109s they were constantly switching propeller pitch (which changed the revs) to gain boost at high altitudes.
They'd change to get more revs, hence more boost, then back to cruise setting.

 

[stona]

I reckon it has already been answered above by FLYBOYJ. It seems a lack of synchronisation between the two engines on Luftwaffe types is the most likely cause of "where do you want it?.....where do you want it?" as perceived by people on the ground.
Just my hunch
Cheers
Steve

 

[pattle]

The British stream of four engine bombers makes a constant droning sound quite unlike described by people who also heard German aircraft pass overhead. My grand mother was quite sure she could tell "ours" from "theirs". Living in Kent she would certainly have heard "theirs" often enough.

Cheers

Steve[/QUOTE]

Yes that is exactly what I have been told and the same goes for large American formations, my Dad lived in Derby and used to see the Americans practice flying in vast formations that seemed to take for ever to pass over, He tells me they were incredibly noisy but had a much more even sound than the Germans. From what I can gather it was possible for the Germans to synchronise a HE111's engines but it was not possible to synchronise one He111's engines to another He111, while I am led to believe that with the Lancaster and Halifaxfor example it was.
I think this will be one of those threads where lots of people confidently post opposite opinions leaving me none the wiser.

 

[gumbyk]

Synchronising engines between two different aircraft would be near impossible. How would one pilot be able to hear another aircraft's engines over the noise of his own aircraft?

With enough aircraft flying in close proximity, all of the various beat frequencies would virtually eliminate each other. (what would the possible resonant frequency of 100 engines, all at slightly different RPM's be?)
However, with aircraft a bit more spaced out, it may be that a beat frequency would be heard due to interference between aircraft.

This could be an explanation. Are there any reports of this from the other side of the Channel?

 

[GrauGeist]

The dynamics of the engine's operation creates a certain frequency. When you multiply that many times over, you have interaction of these frequencies. These harmonics will create a wide range of audible effects.

The best example I can think of, that most can relate to, would be a passing train. Especially if it's moving slowly and has several locomotives coupled. You can clearly hear (and feel, in this case) the low sound frequencies falling in and out of sync. Even if the engine RPMs are matched exactly, you'll hear the soundwaves hitting each other, creating a change in pitch, or a "warbling" as those frequencies try and cancel each other out.

Think of it as ripples in a pond from two identical stones tossed in. The ripples will be identical until they hit each other. When they do collide, they alter themselves to a certain degree. Now toss hundreds of those same stones in the pool and you'll have a better idea of what was going on in the skies over England.

I'm sure that if the Allied bombers were operating at the same altitudes over Europe that the Germans were operating at, over England, people on the ground would have heard the same effect.

 

[Cave Tonitrum]

It's as simple as different engines sounding different. A Spitfire sounds different than a Bf-109. A P-47 sounds different than a P-40. Why would formations of British as opposed to German bombers be any different?

 

[stona]

It's as simple as different engines sounding different. A Spitfire sounds different than a Bf-109. A P-47 sounds different than a P-40. Why would formations of British as opposed to German bombers be any different?

It's not that simple.

A Spitfire does sound different to a Bf 109 but not in that way and the difference is actually quite subtle. Unless you are lucky enough to have heard both at the same (or similar) time they are virtually indistinguishable. If either aircraft flew alone past me, wearing a blindfold, I doubt I could be certain of which it was and I have heard both engines. I would be even more dubious of anyone claiming to be able to tell the difference between the sounds of formations of the two types.

The asynchronous drone or beat of formations of German twins is often commented on. I've heard such comments first hand from several "civilians" including my own grandmother. It is something quite different from a general difference in sound.

Cheers

Steve

 

[Cave Tonitrum]

I have heard both. (Spitfire and Bf-109) Seen both do flyby's but not together. They do sound different and I could easily distinguish the two.

I would expect a concentration of 100 BMW-801's to sound different from a concentration of 100 Rolls Royce Merlins (both featuring different propeller designs) irrespective of the synchronization issue. There were likely also other differences between concentrations of German and British bombers heard by good British folk that might have contributed to perceived differences in sound. Was the altitude and speed of German bombers, hot en route to and escaping from bombing runs the same as British bombers, over friendly territory, departing and returning home?

I'm interested in other thoughts on whether there would be a perceived difference merely on the basis of the different engines / propellers.

 

[stona]

I've heard both too and I did say they sound different. The argument is not about our ability to identify aircraft by engine noise when flown past a blindfolded listener on its own. I admire your confidence though

The Luftwaffe formations undoubtedly made a distinctive sound. This "woo....wooo....wooo" or "where do you want it" as described in contemporary accounts was quite different to British formations. I think that FLYBOYJ hit the nail on the head. His explanation matches others I have heard over the years, all referring to the unsynchronised engines on German twins.

My grandmother certainly couldn't distinguish single engine types. She told me that she and a friend, when fruit picking, once waved cheerily at two aircraft passing at low level moments before they strafed a train station (which one I'd have to check)

Cheers

Steve

 

[s1chris]

I agree that there would be a difference between Allied and German bombers based on engine type.
It has to be comparable to the difference between 100 Ferrari's and 100 jaguar XK's for example. Very distinguishable as an individual machine but amplified when en masse.

My grandma to this day remembers the distinctive sound of the German bombers compared to when large groups of allied aircraft were flying overhead in preparation for overlord. My Grandad said the same when he was alive.

Edit : I think more than one factor is responsible for the distinctive sound.

 

[pattle]

I'm almost certain that the distinctive woo woo woo sound applied to lone German twin engine bombers as well as those in groups. My confidence in saying this comes from what I have been told and read, common examples include accounts of lone German bombers being first heard and then sighted, a common theme in these accounts is that these bombers have for whatever reason become detached from the main body of aircraft and have gone off course whilst returning from a raid, in such accounts I have heard of these aircraft dropping their bombs on handy targets before returning home, another common theme in accounts describe low flying German bombers appearing and being followed by RAF fighters. It has occurred to me that these lone aircraft may have been damaged and certainly some were actually seen to be shot down.
In the case of night time accounts witnesses are confident of having heard a lone aircraft which was often being fired at by anti aircraft guns, of course it was difficult to see these aircraft in darkness. Night time attacks from what I understand would not have been conducted by formations of aircraft like in daytime but aircraft in a stream, accounts from RAF night fighter pilots generally describe lone aircraft not groups of aircraft.

 

[Cave Tonitrum]

Stona, I don't think we're having an argument but to the extent that you are characterizing it as such, it is you who argued that you (and by extension, others) would not be able to distinguish between a Spitfire and Bf-109 if blindfolded. I merely pointed out that I could. Your admiration is easily purchased but thank you nonetheless.

I'm certainly not saying that the lack of synchronization between engines wouldn't lend an additional character to the symphony of sound emitted. I'm just pointing out that formations of German bombers would likely sound different from formations of British bombers (as individual aircraft do) for simpler, more obvious reasons. Perhaps that could account for the woo, woo, woo. Perhaps not.


Edited to add: (as individual aircraft do)

 

[MikeGazdik]

Apples to Oranges, but..... When I was in the U.S. Army in Germany in the mid 80's, 2 friends and I were the very best at identifying the sound of the aircraft overhead without seeing the plane first. That was a time when A-10's, F4 Phantoms,, F-16's, F-15's, F-111's, Tornado's and F-18 Hornets (Canadian, with the false canopy painted on the belly), a few F104's, flew everyday and all day. We could tell them all by sound. The hardest to distinguish was the Eagle and the Falcon, because of the same engines, but the twins in the Eagle , to the careful listener, was identifiable.