Whilst these are often very effective at repelling birds, ultrasonic sound machines have absolutely no effect at all when it comes to repelling snakes. This is primarily because snakes rely on purely vibrations to hear sounds, which is entirely different to how mammals and birds hear. Snakes use their underbelly to detect vibrations and adapt accordingly, and as a result, pitches do not really exist. Therefore, whilst snakes may detect a sound coming from your ultrasound machine, it will not cause any sort of discomfort, as it will just feel like another noise. The harmful pitch, whilst affecting other animals in the vicinity, will simply pass the snake by. Ultrasonic machines are also notoriously unreliable, and it is very difficult to tell if they are working or not. The whole point of ultrasonic machines is that they cannot be heard by humans, and as a result cause no discomfort. However, this is a problem if you want to check whether the machine is working or not. You cannot tell if it is on or off! As a result, we recommend that ultrasonic machines should be avoided when it comes to snakes, especially as they are advertised at often high prices, and end up doing nothing at all.