Headphones

It doesn't matter if it's all bass, since bass can travel through the cochlea as well, any frequency above say 250Hz can damage the hair cells and even with earplugs with 25dBNR many frequencies above 250Hz can travel through the plug and straight into the hearing organs, so something like 300Hz can travel through and still cause damage. Generally frequencies below 200Hz are of lesser consequence but you need to be careful since vibrations can also damage the microvascular and tubular structures within the cochlea. How do I know this? From years of study.