This circuit is from a 1968 publication. Here we have several types of resistive sensors with individual adjustments triggering a single SCR. Power depends on the type of sound device to be triggered.
Published in Popular Electronics with the curious name of Obnoxious Noisemaker, this 1968 circuit...
This simple converter does not use a transformer and the transistor can be the BD135 for currents up...
This circuit is from a 90's publication but uses components that are still common in our market....