I have a pair of Sony's noise cancelling headphones and they seem to only cancel out constant or piercing loud noise like HVAC or a power saw. They let voices t

I have a pair of Sony's noise cancelling headphones and they seem to only cancel out constant or piercing loud noise like HVAC or a power saw. They let voices through clearly without muffling it like you would expect a regular pair of headphones to do. I haven't tried them outside, the sound of an approaching car seems like something they would filter out but they might have some smarts to them.