Here is a link giving the status of the bill in US Congress:
https://www.congress.gov/bill/115th-congress/house-bill/367/all-actions?overview=closed#tabs
Hearing Protection Act of 2017
This bill amends the Internal Revenue Code to: (1) eliminate the $200 transfer tax on firearm silencers, and (2) treat any person who acquires or possesses a firearm silencer as meeting any registration or licensing requirements of the National Firearms Act with respect to such silencer. Any person who pays a transfer tax on a silencer after October 22, 2015, may receive a refund of such tax.
The bill amends the federal criminal code to preempt state or local laws that tax or regulate firearm silencers.