2.1 Scientific Measurements of Brass Instrument Behaviour
39
0
1
2
3
4
5
6
Time (s)
0
1
2
3
4
5
Pressure (kPa)
0.95
1
1.05
1.1
1.15
Time (s)
1.5
2
2.5
Pressure (kPa)
4.25
4.26
4.27
4.28
4.29
4.3
Time (s)
3
4
5
Pressure (kPa)
(a)
(b)
(c)
Fig. 2.5 (a) Pressure measured in the mouth of a trombonist playing the note F4 illustrated in
Fig. 2.2a. (b) Zoom to 230 ms of the mouth pressure signal starting at t = 0.92 s. (c) Zoom to
50 ms of the mouthpiece pressure signal starting at t = 4.25 s
mouth pressure. The frequency of this signal is 350 Hz, which is the same as the
frequency of the acoustic pressure variations in the mouthpiece and the radiated
sound. The amplitude and waveform of the acoustic pressure signal in the mouth
can be modified by changes in the upper windway of the player (see Sect. 6.3). The
zoom to a time interval from 4.1 to 4.25 s shows that, for the note studied here,
the acoustic pressure measured in the trombonist’s mouth when playing forte had
a peak-to-peak amplitude of 1.4 kPa, corresponding to an SPL above 140 dB. This