Ken Wood wanted his employees to better understand the struggles and frustration people with a hearing loss encounter every day. So about three years ago, at a staff training, Wood outfitted them with custom earplugs and silenced their world. Wood, born with a hearing defect, believes people can sympathize with a physical handicap because they see the person in a wheelchair or the blind person walking down the street with cane. “But it’s hard to understand somebody with hearing loss,” said Wood, who’s owned UpState Hearing in Redding since 1990. The company provides hearing aids and other instruments to assist the hearing-impaired.