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[...]
The mosquito repellent circuit to generates small sound frequency using transistors as bistable multivibrator. It is economical, safer than using chemicals.
The cricket sound effect circuit which is an another Sound effects generator byLM324 op-amp and emit by a buzzer. And they have sound similarly the cricket
Here is The 4 Sound effects generator using UM3561 and a few parts only. It can make siren, Ambulance sirens, Police car sirens, Fire truck siren and Space
Here is the tone generator circuit,it is small size. I use IC digital CMOS 4011 quad NAND gate.