The author of the passage, Julia Casey, regrets not protecting her hearing and aims to alert others to the hazards of loud music, which can cause irreversible hearing damage.
Based on paragraph 12 of the provided reading passage from Julia Casey's "Once It's Gone, It's Gone," the reader can conclude that the author regrets not taking better care of her hearing and now seeks to warn others about the dangers of loud music.
The author describes her personal experiences with hearing loss and tinnitus due to exposure to loud music through headphones, car speakers, and concerts.
Moreover, the author suggests that such damage to hearing is irreversible as the tiny hair cells in the cochlea, which are critical for our hearing ability, do not grow back once destroyed, leading to permanent hearing loss. Therefore, the author emphasizes the importance of protecting our hearing from loud sounds, likely by using earplugs or other protective measures.