mendimen said:
well well well you all replyed like im the agresor remenber the dogs are atacking not me end im not trespasing htrough their yard
but thanks enyway, im not provoking or doing something wromg to them
An ultrasononic device would make you the aggressor, it's just a loud noise that you can't hear, but the dog can. It's never been proven even slightly effective.
Afrighten or injured animal is more unpredictable, aggressive, and dangerous.
Call animal control, if you really must travel these areas, aren't doing anything to provoke these dogs. Pretty sure that most areas have laws about aggressive animals.
Anyway, there are quite a few ultrasonic schematics on the web, dog whistle, dog repeller, bark eliminator, pest control... But you would be wasting your time and money, and gaining a false sense of security, which may make the situation worse.
I use to have 140 lb. rotweiller mix breed, who didn't like getting a bath. He still got a bath every week or two, only a couple of scars for me in over 12 years of fighting with him. I don't what sort of dogs you are having problems with, but most are all noise, and seldom actually attack.