Answer:
First, let us remember that the sound transmitted to the listener is found from a vibration created in the bowl of the mouthpiece and filtered by the instrument which transmits certain frequencies better than others. The typical transfer function has been studied by Arthur Benade. It varies according to the nuance played: the harder you play, the richer the sound is in high harmonics. To put it simply, the spectrum of perceived sound depends on three factors:
• the sound spectrum created in the mouthpiece
• the transformation of the sound spectrum by the trumpet
• transmission of the sound spectrum to the listener or trumpeter
Explanation:
note: the sound perceived by the trumpeter is different from the sound perceived by the listener.
Indeed, the trumpeter is in a particular listening position, very close behind the instrument and not a few meters in front; in addition, part of the sound it perceives is transmitted by bone conduction from the mouth to the inner ear. You can easily see this when you play despite a good sinusitis or by covering your ears with earplugs: the sound perceived is nasal and unpleasant, because the transmission by bone conduction becomes predominant.
The vibration of the instrument, in particular of the horn, gives the sound a color perfectly perceptible by the one who plays it but little perceived by the listener. The reason is that the energy transmitted to the surrounding air by the vibration of the metal is weak compared to that transmitted by the air column, but since the trumpeter is just behind the pavilion, which partially masks the vibration of the column of air, the proportion of sounds coming from the two sources is different for him. To convince yourself, read Jim Donaldson's testimony * ("The Schilke Loyalist").
