Your hearing attenuates to the environment, takes a while but something that is quiet will be perceived as becoming louder over time as your brain adjusts. There's also the fact that as we age slight deafness begins to creep in, at 63 my hearing is still pretty good despite working in noisy environments and attending more live music 'gigs' than I could count. As an example if we're sat in the dining room with my HiFi up pretty loud I can still hear if the doorbell or the phone rings whereas Maz can't, another example of failing hearing is if you are in a noisy environment you struggle to hear a conversation.