I'm a native speaker who used to commute to work by train every day but have been living in Japan for 3 years (rural area, no other English speakers in my town)

I'm a native speaker who used to commute to work by train every day but have been living in Japan for 3 years (rural area, no other English speakers in my town). I was a bit curious because after hearing the phrase, I could only hear the resemblance and not the full phrase. So I did an experiment. I replayed it a second time to try and remember the sounds. Then I went and did some work for 2+ hours before coming back to HN. I played the clip and the sounds became gibberish again until I reheard the phrase. I'm going to try this again tomorrow (if I remember), but my guess is that the ability to hear & unhear the sound is dependent on how much natural English is used around you. The less it is used around you, the less your brain is actively trying to match sounds to an English pattern. In my case, my brain is most likely trying to map sounds to Japanese rather than English because that is all I hear around me.