I have two Clare whistles, a two-piece and a nickel one-piece.
On both, they came out of the box with the kind of sound you describe: edgey, raspy, squeaky.
On both, looking through the fipple showed a LARGE amount of plastic flashing. Carefully cleaning that up improved both whistles drastically.
The result, in both cases, is a whistle that is a very smooth, responsive player, sounding a lot like a Gen but much easier than a Gen to play.
Those are now my two best cheapies.
Just thought I’d share my experience; your mileage may vary. Your whistles may vary. You may vary. Void where prohibited or taxed. Do not eat. Not to be confused with wearable clothing. May cause upset stomach. Do not expose to ferrets or they may attempt to steal.
I’ve just purchased my first Clare…fipple was clean as a whistle (hummmm), the instrument was not squeaky or raspy. Gosh, I really enjoy it save for the high b.
Somehow I have a problem keeping it to play in tune, but that me and the after hours I suppose!
seriously, I was quite impressed, but this is my newest toy and most knows what that means.