It depends on noise level. You’re right though generally. One can safely listen to 85dB for 8 hours before hearing loss starts. Up that to 91dB and you have just two hours. 97dB quarters it again and one can be exposed to only 30 mins. But once one gets to loud sounds like sirens, gunshots, firecrackers in the 120-150dB range onset of permanent hearing loss can be instant.