The Mouse and Rat repellent circuit using astable multivibrator which use sound waves or ultrasonic so it escaped away. Use transistor and piezoelectric.
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 tone generator circuit,it is small size. I use IC digital CMOS 4011 quad NAND gate.