I hear my nieghbor flush

[Billm9555]

I live in a side by side 2 story new home in NJ. Whenever my nieghbor flushes his toilet I hear the drainage noise through my tub next door. Our master bathroom share the same firewall, meaning that the homes are idenetial but opostie layouts.No pipes are shared between the homes firewall so how is this possible? I blleive the only places our sewagre may share is in the mian pipe that goes out to the street. Could it be pssoible that the noise is traveling that far back to my tub shower drain. It is all PVC

[phishfood]

Why are you certain that there is not shared piping through the firewall?

[LeakFinder]

Where exactly do you hear the flush? In the tub drain itself or in the wall near the tub?