A quick question: If you have a large scale warbird, runned with an electrical motor setup, is it possible to add some sort of speaker setup to play off the sound of the full scale plane?

Or is this just a weird idea that entered my head?

I've thought about the same kind of thing. Not just engine sounds. Doesn't a WWI plane during a low pass across the field just cry out for the "taka-taka-taka" of a vintage machine gun?

I saw a "Spirit of St. Louis" at the Rhinebeck R/C weekend last year and it had a speaker deal in it. When it flew past the flight line you could hear Jimmy Stewart shouting down, "Which way to Ireland?" Very cool. Only trouble was that the plane had to idle down and the crowd had to be pretty quiet to hear it well. Don't know how it was done though.

If you get a scale sound, make sure you get the correct sound for the airplane you are building. The reason is that airplanes sound different. For example if I was standing at an airport and a T-28, P-51, AT-6 and F4U took off and I could not see the airplane in question I could identify the airplane just by the sound. The AT-6 has very loud prop noise that is does not sound like a F4U or the T-28.

And then how to you prove the sound is correct?

Do you get a typical radial engine sound and under what power setting, cruise, full power for takeoff or idle.

another question, if the airplane is 200 feet up how big of speaker would you need to create the effect of the engine sound from that distance? it is easy to get a scale factor for speed, distance and areas (although scale speed is another can of worms), but I have never heard a good explanation on how scale sound. but most engineering explanations for sound are based upon distance squared.

Good luck

I have a Tamiya Sherman Tank that has a sound sythisizer in it so the technology is out there. The engine idles at rest and changes sound on acceleration. It also has the turret motor noise not to mention the machine gun and cannon. They made recordings of a real Sherman to get the sounds. I'm sure its doable for an electric airplane if you could find the right hardware. There are several tapes and CDs of different airplanes out there for the sounds. Don

If you want scale sound, well, that's a not too easy to do.
I've seen a large scale BF109 in germany with engine sound delivered through a speaker at the bottom of the fuselage. One of the problems is the models own engine disturbing the sound coming out of the speaker. Of course there are CD's out there with the correct sound for your type of model, if you're lucky it exists for different RPM-settings.
I'm an engineer in the "digital audio effects" field and from my view, almost everything is possible, you only need knowledge, time and (of course) some money.
One of the biggest and most audible problems is the so called Doppler-effect: This effect raises and lowers the pitch of a sound according to the relative speed of the sound source and the listener. (policecar siren approaching you seems to be of higher freq. than a siren moving away from you).
Our models are moving with much lower speeds than the real-ones, the effect with a rc-model is therefore much less, this makes your "engine" sound flat and a bit boring...
Conclusions:[ul][*] it can be done[*] it can be done very well, but you can't change the laws of physics (Doppler)[*] not shure whether the result is worth the effort (just my view)
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hope this helps

Flo

Thanks for the feedback! I guess I have to think what I want to do and how to do it. On the issue of doppler effect, wouldnt that work based on the fact that when the sound from the speaker moves towards you it will have a higher pitch than the sound when it goes away from you? Sound is sound and it travels at the speed of sound...? Its quite some time since i did physics at highschool

Ill do some more research on the subject and post it here when i have something to tell...

In Scale comps there are marks awarded for "Authentic Sound" and I am always baffled as to how the judges can be asked to award marks in this category.

None of the models I see at comps come anywhere near to the sound of a full size, and in most cases the judges will never have heard one anyway, so I don't see the point in awarding a score (especially since I fly electric scale and usually score next to zero !!)

What you described is the Doppler effect. The point he was making is that the actual speed of the model may not be sufficient to give you enough of the effect.

A real P51 with the Merlin wide open passing in-front of you at 400+mph will create that wonderful sound. (God, I love that sound!) A model of a P51 traveling at 100+ may not be fast enough to give you the shift in the pre-recorded sound.

That is all true but I think the real problem would be to get it loud enough. It would be difficult to get the recored sound up to around 90db in a small space, low weight and within practical power limits. Remember, your recorded sound has to compete with the sound that your motor makes.

One possibility would be to use an mechanical amplifier instead of a traditional permanent magnet speaker system. A small transducer through a wave guide or resonator might produce better results. (Similar in approach to an old style phonograph and that Bose "Wave" radio.) This approach would be lightweight, low power but take up some room. (I thought about using this idea to add realistic machine gun sounds to WWI vintage planes.)

This is out of my field of engineering. Any acoustic engineers out there?

Petter ..
You are not the only one that have sound in mind for electric planes.
my only problem seems to be a suiteble laudspeeker that can give enough sound pressure.... might be possible that it can be done with a pieso speaker.. but I am not sure.
But really I think it be worth it....
Claus

The only thing that sounds like a Merlin is a Merlin unfortunatly.
Trying to emulate the sound of a simple Cessna light aeroplane is difficult enough if not impossible with a model.... our engines rev to high and the prop (the biggest contributor to full sized sound) are so small in comparision.

We experimented with a 3rd scale Tiger Moth/G38 with a Tony Clark reduction drive and super mufler togerther with a 36" wooden prop (max revs about 2200rpm idle 500rpm). Without doubt the most convincing combo I've ever witnessed. I have also seen two different aeroplanes powered by the wonderful Moki (RCS in the USA) 215cc radial. Both were seriously large models swinging big wood... now I'm quite sure a real FW. 190 would sound distinctly different but once again, boy this was an impressive sounding RC aeroplane... Once you get this many cc's poppin' and coughin' and again a seriously large prop beating the air, things start happening. You get the Doppler effect, you get the prop sound... it's not "scale" but it's starting to sound like an aeroplane and not a model.

Unfortunatley, you just can't "fake it".

Lots of interesting points here. What about a switch on your remote to simulate doppler effect, so when the plane is about to pass you (and the crowd around you), you hit the switch to go from a higher to lower pitch of the sound... ? I dont know... just mumbeling on here...

If you are using a 30+ cells motor setup, it should be possible to borrow some juice from that so you need a audio-simulator/amplifier box with a super efficient speaker of some sort connected...

Well, true sound is available for some models and it isn't done with speakers. My T-33 sounds almost exactly like the real thing. There are true turboprop engines available for models as well. Unfortunately, this is probably about the only way you will ever be successfull creating a truly authentic sound for a model airplane.

I have often had thoughts of building a 1/72 scale aircraft carrier where the propellers would spin on the planes and play back the sound of many engines starting up. Actually did build a carrier but gave up the idea of the engine sounds out of pure frustration at even finding anything at all to accomplish it.

Randy Linderman's B-25 "Lady Luck" has a good setup in here is a link if it will work

http://flyinglindy.homestead.com/b25...finishing.html


Check out the whole thing. He has some Great idea's

Thanks for your explanation help Chevelle
I'm a bit limited in doing good explanations in English. But now the Doppler thing should be clear.
petter: good idea with the switch, the only thing is that you have to alter the pitch constantly an your approach, to make it realistic... I think it would sound better without it.
Another thing mentioned is the power required to produce enough sound pressure. Remember that you have to cope with an engine sound which is at around 85dB (or more). The high frequency components of your "target"-engine are easy to produce, the low ones are not, you just don't have enough power and a suitable speaker...
..have you ever withnessed a Skyraider taxiing by 30ft away from you? You'd know what I mean... Earthquake...[&:]
Flo