2.1 Scientific Measurements of Brass Instrument Behaviour
33
Each type of experiment has its own advantages and disadvantages, which are
discussed fully in Chaps. 3 and 4. It is important to note at the outset, however,
that scientists and musicians agree that the behaviour of a musical instrument can
only be fully understood when the nature of the human player’s involvement with
the instrument is taken into account. The ultimate goal for scientists working on
the musical acoustics of a brass instrument is to explain fully how the instrument
functions in a musical performance, which normally involves four linked and
interacting elements: the player, the instrument, the performance space and the
listener. Progress towards this goal will require much further research, including
contributions from physics, physiology, neuroscience, psychoacoustics and room
acoustics. In the case of brass instruments, the interaction between the player and
the instrument is crucial even at a very basic level, since the sound generating
mechanism is provided by the lips of the player.
To illustrate the nature of the scientific approach to brass instruments, we review
briefly some of the topics which will be studied in more detail in following chapters,
outlining the methods of measurement used to gain scientific understanding of the
phenomena involved.
2.1.1 Sound Radiated from a Brass Instrument
First we look at the sound radiated from a trombone during a musical performance.
The signal illustrated in Fig. 2.2b was recorded by a microphone 50 cm in front
of the bell of a tenor trombone. Just under 1 second after the recording started,
the player sounded the note F4, shown in staff notation in Fig. 2.2a. The note was
maintained at a constant piano level for around 1 second; the player then made a
crescendo to forte, followed by a diminuendo. Since a calibrated instrumentation
microphone was used in the recording, the signal shows the changes in the pressure
p rad of the air due to the sound wave radiated by the trombone.
During the sounding of the note, the pressure was rising and falling several
hundred times every second. On the time scale in Fig. 2.2b, it is impossible to
distinguish these very rapid variations in the sound signal, which are all contained
within the solid blue area. To see the detail of the pressure changes corresponding
to the sound of the trombone, it is necessary to look at a much smaller time segment
of the signal. The red box in Fig. 2.2b marks a time interval of 230 ms starting at
t = 0.92 s. The zoom into this time interval shown in Fig. 2.2c reveals how the
sound begins. The tiny wiggles in the horizontal blue line around t = 0.93 s are
the first signs of a developing note. At this stage, the signal is fluctuating between
+5 mPa and −5 mPa, so the peak-to-peak pressure amplitude is only 10 mPa. This
amplitude grows, at first slowly and then more rapidly; by t = 1.03 s it has reached
a value of 0.46 Pa which remains more or less constant for around 1 s. The initial
part of the sound, in which the amplitude is continuously increasing, is called the
‘starting transient’; in musical terms this corresponds to the ‘attack’ of the note. The
33
Each type of experiment has its own advantages and disadvantages, which are
discussed fully in Chaps. 3 and 4. It is important to note at the outset, however,
that scientists and musicians agree that the behaviour of a musical instrument can
only be fully understood when the nature of the human player’s involvement with
the instrument is taken into account. The ultimate goal for scientists working on
the musical acoustics of a brass instrument is to explain fully how the instrument
functions in a musical performance, which normally involves four linked and
interacting elements: the player, the instrument, the performance space and the
listener. Progress towards this goal will require much further research, including
contributions from physics, physiology, neuroscience, psychoacoustics and room
acoustics. In the case of brass instruments, the interaction between the player and
the instrument is crucial even at a very basic level, since the sound generating
mechanism is provided by the lips of the player.
To illustrate the nature of the scientific approach to brass instruments, we review
briefly some of the topics which will be studied in more detail in following chapters,
outlining the methods of measurement used to gain scientific understanding of the
phenomena involved.
2.1.1 Sound Radiated from a Brass Instrument
First we look at the sound radiated from a trombone during a musical performance.
The signal illustrated in Fig. 2.2b was recorded by a microphone 50 cm in front
of the bell of a tenor trombone. Just under 1 second after the recording started,
the player sounded the note F4, shown in staff notation in Fig. 2.2a. The note was
maintained at a constant piano level for around 1 second; the player then made a
crescendo to forte, followed by a diminuendo. Since a calibrated instrumentation
microphone was used in the recording, the signal shows the changes in the pressure
p rad of the air due to the sound wave radiated by the trombone.
During the sounding of the note, the pressure was rising and falling several
hundred times every second. On the time scale in Fig. 2.2b, it is impossible to
distinguish these very rapid variations in the sound signal, which are all contained
within the solid blue area. To see the detail of the pressure changes corresponding
to the sound of the trombone, it is necessary to look at a much smaller time segment
of the signal. The red box in Fig. 2.2b marks a time interval of 230 ms starting at
t = 0.92 s. The zoom into this time interval shown in Fig. 2.2c reveals how the
sound begins. The tiny wiggles in the horizontal blue line around t = 0.93 s are
the first signs of a developing note. At this stage, the signal is fluctuating between
+5 mPa and −5 mPa, so the peak-to-peak pressure amplitude is only 10 mPa. This
amplitude grows, at first slowly and then more rapidly; by t = 1.03 s it has reached
a value of 0.46 Pa which remains more or less constant for around 1 s. The initial
part of the sound, in which the amplitude is continuously increasing, is called the
‘starting transient’; in musical terms this corresponds to the ‘attack’ of the note. The