White noise or not?

So my son is 16 months and with us he has always had white noise, for naps and bedtime. Over the months it's fluctuated to different sounds and we tried without too but white noise always seemed a success. Well today while putting him down for his nap I left the room not realizing I never turned it on. He settled himself down and has fallen asleep within 10 mins after leaving the room... pretty much is normal lately but this is without white noise too...my question is though, should I go back in and turn it on or just leave it off. I worry that I might disturb him but if I don't put it on i worry his nap might be short because he's used to the noise...so I'm stuck.