Tenant complains neighbor snores through wall!

[Neil Hauger]

I have a TRi plex. The tenant in the middle unit recently sent me an audio recording of his neighbor snoring. Seems their master bedrooms share a wall and the snoring can be heard through the wall an it is keeping him awake. He has tried fans, sound machines, sleeping in a basement room but the snoring persists! A few months ago He sent me a notice of the disruption to which I responded and called the purported offender to let him know of the issue. I also asked the complaining tenant what he expected me to do? Then no response. Three months later I get an audio of the snoring. He is asking if I can install some sort of sound deadening material. Anyone every had this issue? Got a solution?