The number of troubled U.S. homeowners receiving assistance with their mortgages fell in the third quarter as the government’s foreclosure-prevention effort tapered off. Federal bank regulators reported Wednesday that about 470,000 homeowners received loan assistance in the July to September quarter, down 17% from the second quarter and down 32% from the same quarter a year earlier. Banks have largely sifted through a big pool of eligible borrowers who weren’t getting any assistance before the Obama administration launched its effort to combat foreclosures in early 2009, officials said.