Chapter 3
Buzzing Lips: Sound Generation in Brass
Instruments
This chapter is concerned mainly with the vibrating lip sound source, which is the
defining feature of every instrument in the brass family. Section 3.1 identifies some
of the major muscles which control the embouchure of a brass player and presents
the results of experimental studies which reveal the nature of the lip motion when
a note is sounded. Measurements on human players have been supplemented by
studies using artificial lips to generate the sound in a brass instrument, and some
insights derived from these experiments are outlined. Section 3.2 describes the
simplest possible mathematical model of the lip valve, often called the one degree
of freedom model. The equation describing the behaviour of this model includes
a term representing the net force exerted on the lips by the surrounding air; the
subtle fluid dynamics of the air flow through the lips turns out to be of crucial
importance in understanding why the lip vibration generates a fluctuating pressure
in the mouthpiece. The mechanical behaviour predicted by the simple lip model is
compared with experimental measurements on artificial and human lips in Sect. 3.3.
In Sect. 3.4 some of the processes through which air flow generated by the player’s
lungs can initiate and sustain the vibration of the lips are explored. An equation
relating the volume flow of air through the lips to the pressure difference across them
is derived in Sect. 3.5; this equation is an important constituent of the elementary
model of brass playing constructed in Chap. 5.
3.1 The Nature of Lip Vibration
3.1.1 The Brass Player’s Embouchure
To get a well-controlled buzz from the lips, it is necessary to use the muscles which
form the embouchure to obtain the correct lip configuration. Figure 3.1 illustrates
some of the facial muscles which are important in achieving a good embouchure
© Springer Nature Switzerland AG 2021
M. Campbell et al., The Science of Brass Instruments, Modern Acoustics and Signal
Processing, https://doi.org/10.1007/978-3-030-55686-0_3
63
Buzzing Lips: Sound Generation in Brass
Instruments
This chapter is concerned mainly with the vibrating lip sound source, which is the
defining feature of every instrument in the brass family. Section 3.1 identifies some
of the major muscles which control the embouchure of a brass player and presents
the results of experimental studies which reveal the nature of the lip motion when
a note is sounded. Measurements on human players have been supplemented by
studies using artificial lips to generate the sound in a brass instrument, and some
insights derived from these experiments are outlined. Section 3.2 describes the
simplest possible mathematical model of the lip valve, often called the one degree
of freedom model. The equation describing the behaviour of this model includes
a term representing the net force exerted on the lips by the surrounding air; the
subtle fluid dynamics of the air flow through the lips turns out to be of crucial
importance in understanding why the lip vibration generates a fluctuating pressure
in the mouthpiece. The mechanical behaviour predicted by the simple lip model is
compared with experimental measurements on artificial and human lips in Sect. 3.3.
In Sect. 3.4 some of the processes through which air flow generated by the player’s
lungs can initiate and sustain the vibration of the lips are explored. An equation
relating the volume flow of air through the lips to the pressure difference across them
is derived in Sect. 3.5; this equation is an important constituent of the elementary
model of brass playing constructed in Chap. 5.
3.1 The Nature of Lip Vibration
3.1.1 The Brass Player’s Embouchure
To get a well-controlled buzz from the lips, it is necessary to use the muscles which
form the embouchure to obtain the correct lip configuration. Figure 3.1 illustrates
some of the facial muscles which are important in achieving a good embouchure
© Springer Nature Switzerland AG 2021
M. Campbell et al., The Science of Brass Instruments, Modern Acoustics and Signal
Processing, https://doi.org/10.1007/978-3-030-55686-0_3
63