Hello Hans, Hans Fugal schrieb am 17.07.2007 17:22: > I haven't been following the doppler and directional sound stuff, so I > apologize if the following is known about and under construction. > > I'm running the PLIB branch CVS (last updated last night). > > Start up with the Bravo or the 787 (and probably others) and switch to > an outside view. Move the view to the front of the plane and note the > pitch of the engines, then move to the back of the plane and note the > pitch. Yes, I think I hear the same. Thanks for reporting. > The pitch is higher in front than in back. This seems like it > might be caused by doppler, but I suppose there may be another > explanation. I don't think that this is the Doppler effect (at least it should not be the Doppler effect ;-) ) > I don't notice it with the Cessna. Yes, that's strange. I do not notice this with all airplanes, too. > If it _is_ a doppler > effect, it's wrong. Absolutely! What is interesting, that not all aircrafts have this effect. Maybe this is only with aircrafts with more than one sound source and what we hear is just the position dependence of the sound mixing? While moving the external-view camera we get real Doppler effects; realistic, but maybe confusing. This could confuse our ears, too. I think, that after moving the external camera I sometimes hear "wrong" pitch. Switching then between external views, the "wrong" pitch is constant. But moving to cockpit view and back to external view "resets" the pitch to normal. Strange. Could this be the phase shift between the two engine sounds? Switching to cockpit view switches the external sounds off and switching form cockpit view to external view switches them on without phase shift. Moving the external camera causes some Doppler Effects (resulting in a phase shift of the two identical jet sounds played with identical pitch). I think 787 and Bravo uses the jet.wav sound. I tried to play this sound twice with some phase shift and I think I get the same. > There would be no doppler effect if neither the > source nor the ear is moving relative to eachother (as is of course > the case when sitting on the runway). > > The second observation is in flyby mode, and has to do with > directional sound. I notice that when the plane is flying almost > directly toward the observation point, the sound still comes full from > one side, and when the plane passes and heads almost directly away > >from the observer the sound comes full from the other side. I have > even observed the plane coming at a significant angle with the sound > coming from the opposite side from what it should. It seems like the > stereo effect is being applied in a simplistic way, rather than based > on the angle between straight-ahead and where the plane is. > No, that should be correct/realistic, but maybe there is a bug. But I was not able, to reproduce this bug here. Which aircraft you are using? This could be the cause, if the aircraft is using a stereo sound file. Which operating system you are running? There are some OS-dependencies in the sound, but the stereo calculation is always done by OpenAL itself. Can you check, if you have this effect with the A6M2, too?
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