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