Sonicrest 90db piezo sound generator 5v sonicrest hpa17f 821 b sonicrest b have produced a sound generator that operates using the piezoelectronic effect producing a loud 90db of sound this 5v sound generator is suitable for use in alarms sirens audio alerts telephone ringers industrial household appliances control modules high end toys medical instruments etc sonicrest hpa17f 821 piezo sound generator 5v