Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Hase Kettweisel Tandem (redundent recumbent), Merin Bear Valley (The gopher).
My experience with those has been 1 for 1.
Mrs. Grouch and I were following another tandem couple when a German Shepherd size dog came running out to greet us. The other stoker calmly used some sort of gizmo that emitted a high pitch "eek". The dog acted like he had run into an invisible wall and walked back in the direction he had come from.
Based on that one experience I'd buy one if I stumbled across one for sale in about the $15.00 range, but I'm not interested enough to seek one out.
A guy is working from home.
His neighbor has dogs that keep barking during the day.
Talking to the neighbor does no good, so being an IT geek, he resorts to technology;
He gets an ultrasonic dog repeller, and a sound-activated switch, and installs them in a weatherproof enclosure in his backyard.
Dog barks -> switch closes -> ultrasonic repeller turns on temporarily -> dogs ears hurt -> dog stops barking.
He said he even saw one dog bite another when it tried to start barking.
Just a general observation based on my pair of dogs.
There is a world of difference between what works to stop them when they are merely interested in something and trying to stop them when they have decided to chase something. In the first case a word from me is plenty, once they start the chase it takes a whole lot more.
I would not be at all surprised if something like this works just fine, until the first time you use it an a chasing aggressive dog and then it is like nothing happened.
Do not confuse this with an implied endorsement of chemical means, one of my data points is skunk spray. Excited dogs and it was like nothing to them.
I'm really interested in this as well. I just learned about sonic dog repellent recently, and *if* it is something that can keep the friendly, curious, but tire-chaser dogs away, then I'd be all for owning one. In that case, I don't want to injure the dog by spraying pepper-spray, and I certainly don't want to run over the animal, and furthermore, I don't want to get hurt by having to avoid the dog with ultra-tight maneuvering.
There are maybe 2 aggressive dogs on my usual country routes. If something like this would be a deterrent, that would be a bonus. As it is now, I have some pepper spray as a backup (haven't needed it yet), but I do need to dismount the bike and use the bike as a shield until the owner comes out to reclaim the animal, or until small game re-directs its attention.
Edit: would a dog whistle be something that's useful to keep away the playful, but nuisance dogs? I've never had a dog so I don't really know how they work.
Cannondale T600, Scattante R-660, Diamond Back Response Sport
+1 on dog squealer.
Years ago I bought one.
Made the neighbor's dog bark all the harder (he hated that noise).
Which convinced the cops to write a ticket for noise pollution (police couldn't hear the squealer).
My experience: Works well on dogs whose ears stand up (dobermans, shepards, etc.), doesn't work very well all on floppy-eared ones (beagles, great danes, mastiffs, etc.). When I was reading meters for the utility co. they tried them, but they didn't seem to work out. Good pepper spray is better, but it'll burn you if you get it on your skin.