
Agree with wait ok with the Acme whistles. I’ve always used them with my dogs having tried various other ones over the years. If the website is still the same you can hear what each different whistle sounds like. I’ve tried this with my dogs to see which one had the strongest reaction, not sure if there was a big difference but it was fun trying

I dare say you will know this, but make whatever series of toots on the whistle as distinctive as you can as so many people use a whistle to recall their dogs, many incorrectly. How many times have you been out and heard someone continually blasting on the whistle trying to get their dog to recall whilst it is happily chasing rabbits not taking a blind bit of notice, then they will tell you how great the dogs whistled recall is. Ummm, no. The dog only came back eventually because all the rabbits were gone. Use, but don’t abuse the whistle as with any method of recall.
Total Recall by Pippa Mattinson is a recommended book
The dog I have now has a brilliant whistle recall largely due to something her breeder did when weaning the puppies. When he put down the dish of food he would give several toots on the whistle as the puppies surged towards him so that they learned from a very early age that whistle meant go to human, get food. I continued with this whenever I fed my puppy for several weeks and also practiced a lot in the garden. Her whistle recall now is more or less automatic as she turns and heads back without even thinking. You could start right away using the whistle when you feed your dog.