I use a whistle for Cassie and Sky.We started using it when we first brought sky home,we used it when we put there food down,Cassie was 10 months old at this stage so the whistle has been more effective with Sky but it does work well when we are out for either dog.We use the acme gundog whistle with a pitch of 210-1/2 .Sky is very food orientated so training to the whistle was quite easy,Cassie on the other hand will finish sniffing before returning to my side.