Chapter 6 — Sources and radiation

What a vibrating object emits into the medium.

We have studied the wave in flight. Now we look at where it comes from. Every sound in the world is launched into the medium by some vibrating object — a vocal fold, a string, a speaker cone, a colliding pair of surfaces. This chapter is about how such sources couple to the acoustic field they create.

• 6.1 A pulsating sphere — the monopole
• 6.2 Spherical waves and the inverse-square law
• 6.3 Cylindrical waves
• 6.4 The dipole as two opposing monopoles
• 6.5 The piston in a baffle