Tomaso, where did you get this myth from? Do you know how a trumpet works? The sound that we hear is a standing wave in the horn. The AC component of our blow (sound) is more or less static. In fact, I glued a headphone driver to a mouthpiece and got a very acceptable trumpet sound and could measure the impedance of the horn too. The only air that moves is the DC component (our exhale). It needs to be carefully dosed so that we have enough air to play phrases, but not back up so much that we suffocate. Bernoulli is of absolutely no significance to the trumpet player except for how the spit key works, and that is more capillary action which is related. This myth about venturi keeps coming up from people that print add text but failed physics. Even if we do have a higher speed in the leadpipe, it is insignificant because once the air has passed the lips, its gone. Fast air across the lips is also BS. The blow is optimum when the lips are supported by air from the oral cavity and mouthpiece. The cup size and throat determine that degree of "support".