Verification builds:
1.2.2.3

Summary:
When travelling through the nether after changing the difficulty to Peaceful, Ghast sounds continue to play.

Repro Steps:

1. Travel through a section of the nether in Hard difficulty
2. Change the difficulty to Peaceful
3. Now travel back to the original point
4. Observed Results:
5. Ghast sounds can still be heard, presumably as they exist for a split second before despawning.

Expected Results:
If the game is set to peaceful, no hostile mobs should be heard.

Screenshots/Videos attached: No

Notes: