555 IC Project - 'Red Alert' Siren query.

[Nick]

Actually, do away with the second 555, keep the driver transistor (you only need the original one, not the inverting one too) and use a piezo sounder. A burglar alarm one is typically only a few quid and will shatter any nearby eardrums... (even Argos & B&Q etc. sell them).

Even smaller, cheaper, more efficient...