can ultrasonic wave (20khz.?) really repel pests like mice, insects, bugs, etc? it is a fact that animals have different audible frequency range compared to us but i'm quite sure that this method is effective enough to be applied for such purpose. i saw a lot of products here in the internet selling such kind or related products like that. i'm not planning to purchase one but i'm looking forward to use it in my research. to build one. i need a reference for this one for me to know the effectiveness of such method...
thanx in advance...