Is using a distinct pitch or tone in your voice for your hint legal in Codenames? I.e., "colddd" to link "blanket" and "Arctic"
I gave a similar answer to a different question here But this is a different question with almost the same answer.
The rules here say

DON'T BE TOO STRICT

So if the word is a legal clue then there is nothing in the rule to say you can't use a certain voice.  I guess the balance is you couldn't use Western Film accent to say &quot;Paris&quot; to give a clue for &quot;Cowboy&quot; and &quot;France&quot;.
Also its worth looking at the rules for Homonyms which say (emphasis mine).

Some people prefer to allow a more liberal use of homonyms. You can allow knight to be a clue for night-related things if that makes the game more fun for you.

You can apply that rule to making sounds with you clues.  Would saying &quot;colddd&quot; make the make more fun for your group?  If so then yes it would be fine.
In general if you're not sure if a clue is legal ask your self, Do the rules specially say you're not allowed to do it?  If the answer is no, and your group are having fun then the clue is almost certainly fine.