What could cause someone to suddenly go deaf?

Most often wax: Fortunately, the most often reason is wax. People have a near complete blockage and can hear ok, when it becomes complete they feel "deaf." if not wax it can be middle ear fluid and rarely a viral illness that truly causes deafness. The key is is to see an ENT doctor right away as viral sudden deafness needs to be treated within 72 hours to have the best chance of recovery.

Sudden deafness: Barotrauma- sudden explosion, even a slap on the face can result in sudden deafness, it could either be conductive deafness or sensorineural loss of hearing.

Sudden deafness: An otologist sees sudden sensor i-neural hearing loss quite often. Although noise and acute infection may be causative factors, possibly the most common cause is what is known as idiopathic sudden sensori-neural hearing loss (issnhl). This is an otologic emergency and may be the result of a viral infection or autoimmune cause. Intra-tympanic injection of steroids or high dose oral steroids.