Early deafness has been a reported problem in some Cavaliers for many years.
I once had a dog who was poor at recalls. In the park he would look up when called, stare around, and then continue sniffing or trot in the other direction.
I used to get so angry at him. It did not occur to me that he may be hearing some indistinct sound, but be unable to locate where it was coming from.
There was nothing in his behaviour at home to spark off any suspicion that he could not hear.
When he went to live with friends they said he did not seem to hear them when they called his name. I walked into their lounge and called him & he immediately looked up. When they called he seemed uninterested.
It became apparent that he could hear my higher pitched call but not their lower tones.
That taught me that selective deafness may actually be intermittent deafness. Loss of hearing can be gradual and a partially deaf dog may hear some sounds better than others.
Cavaliers......Tommy Tuppence 2000-2012 and a half share of Faith.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.