The term 'SOUND FROM A FAN' can be broken down into four crossword solutions: WHIRR (5 letters), HUM (3 letters), RAH (3 letters), and WHIR (4 letters). WHIRR is a sound made by a fan that is similar to a low-pitched buzzing. HUM is a low, continuous sound made by a fan that is similar to a humming noise. RAH is a sound made by a fan that is similar to a loud, vibrating roar. Finally, WHIR is a sound made by a fan that is similar to a high-pitched whirring noise. All of these sounds are commonly heard when a fan is running.