ABSTRACT
This chapter focuses on basics – what sirens are and how they work – as well as history. It presents practical information on the making of sirens as musical instruments. As an acoustical device, a siren takes what would otherwise be a continuous flow of air and converts it into a series of pulses. These pulses, occurring at some frequency within the hearing range, propagate out into the surrounding atmosphere as sound. In its simplest form, the heart of the siren is a rotating disk. The musical intervals available from a siren disk will be determined by the relationships between the numbers of holes in each ring. The numbers of holes will not determine the actual pitches, because pitch depends on the disk’s rotational speed. On a siren disk with multiple concentric rings of holes, the ratios of the pitches available will correspond to the ratios of the numbers of holes in each ring.
