Hearing a persistent whistling sound when no one is around or present in the room is frequently caused by environmental drafts, structural settling, wind blowing across exterior architectural features, or HVAC ductwork pressure differentials. In homes with forced-air heating and cooling systems, air pressure imbalances between rooms can force air through small cracks under doors, around window seals, or through gaps in electrical outlets, creating an acoustic whistling tone. Additionally, thermal expansion and contraction in metal flue pipes, plumbing vent stacks, or roof structures during temperature changes can produce sudden whistling sounds. You can verify the source by checking if the sound stops when you turn off the HVAC system or seal drafty doors and windows.
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