This is a project of useful device for wild animals deterrence. It is a simple acoustic deterrent, which uses sound of barking dogs and howling wolves to scare animals. An old MP3 player was used in this device, the signal is amplified by TDA2003. Attiny13 micocontroller switches the amplifier for about 50 seconds at random intervals (J2 closed – 3-30 minutes, J2 opened – 3-15 minutes). If the jumper J1 is closed, the system responds to light level and switches after dark. Switching threshold can be adjusted by potentiometer PR1. LED indicates the activity of the device by blinking. The whole is closed in a jar and is resistant to weather conditions.

The device should be powered by 12V. The supply voltage cannot exceed 18V. It is good to add small heat sinks for U1 and U2. The system has a supply output that supplies the MP3 player (1,5V). Jumpers J1 and J2 control the operation of the device. By shorting J1 you activate the evening system, when it is opened – the device operates all the time.
J2 jumper is used to set the length of time between activations of the speaker. Using PR1 you can adjust threshold of the evening system. Activation of the system is indicated by blinking LED.

Link to original thread (useful attachment) – Odstraszacz dzikich zwierząt