This is Morning sun alarm circuit using IC-4011 that hobby It will have sound alarm when morning like a normal clock alarm with lighting sensor same clock.
Use high frequency out of the piezo speaker and IC-556 is base as oscillator between 22kHz and 56kHz This projects is safer and more convenient.
Simple electronic drum circuit project is an Instrument of this era really, various sound effects and many others, using digital IC and more
This is High power siren circuit with small PCB size, using CD40106 and four transistor TIP31-TIP32 increase current to horn speaker 20W, 4-8ohm. , and
This morse code generator circuit is suitable for learning basis of communication. Unbelievably, short and long tone can be decoded into letters and text.
This is buzzer circuit easy to build with small size,cheaper using normal transistor and small piezo speaker can use for 3V to 12V as use parts resistors[...]