This is nothing new. It has been in the audiology literature for decades that sustained noise above 75dB causes (concerts hit 90-100dB) noise-induced hearing loss due to shearing of the hair cells along the basilar membrane in the cochlea. "Sustained" is considered to be longer than 30 minutes. OTC foam earplugs mitigate the noise by about 20dB, bringing the noise down to only a 10dB louder than conversational levels; certainly within the safe range.
Earplugs May Help Prevent Hearing Damage from Concerts — Physician’s First Watch
Earplugs May Help Prevent Hearing Damage from Concerts
By Kelly Young
Wearing earplugs during a loud music concert might help prevent hearing loss, according to a small, industry-conducted, single-blind trial in JAMA Otolaryngology—Head & Neck Surgery.
Fifty adults attending an outdoor music festival in the Netherlands were randomized either to wear or not wear earplugs for 4.5 hours at the festival. Their hearing was assessed before and within a half hour after their festival visit.
Roughly 8% of the earplug users had a temporary threshold shift on audiogram, indicating hearing loss, compared with 42% in the unprotected group. The authors estimate that three people needed to wear earplugs to prevent one case of temporary hearing loss. After the festival, reported rates of new tinnitus were higher in the unprotected group (40% vs. 12%).
The authors conclude that earplug use "should be actively promoted and encouraged" to help prevent noise-induced hearing loss.