Abstract
This discussion compares two common siren types. They are the diaphragm driven horn based upon an improvement to Edison’s original gramophone, referred to as an electronic siren, and the rotary air-shock siren based upon an improvement to the Carter type WW2 air raid siren, referred to as a rotary siren. Differences in performance, practicality and economic viability between the two are identified, with emphasis on how a spherical atmospheric wave-front dispersal influences cost escalation for electronic sirens. The validity of a new National Standard for sirens promulgated by the New Zealand Ministry of Civil defence and Emergency Management (MCDEM) is questioned.