The Smithsonian's National Zoo in Washington, D.C., is serving as a living laboratory for a product still under development by 3M Co., a specialized acoustic film to reduce noise levels in buildings.

Since May, the din in the zoo's Great Ape House has been significantly lowered thanks to the film, which is mounted on tiles installed high on walls. "It was something we all had noticed and lived with," said Ed Brinikowski, the zoo's senior curator. He said the acoustic tiles have resulted in "an admirable improvement" in noise levels.

The gorillas and orangutans weren't to blame. When they're inside, they're in cages behind thick plate-glass panels.

It was the noise from people who stream into the ape house, one of the zoo's most popular attractions. Their conversations and screams of delight have been bouncing off the ape house's glass panels, concrete walls and ceramic tile floors since it was built about 20 years ago, Brinikowski said.

That's what made the building the perfect setting for evaluating 3M's film, which is specifically calibrated to lower the noise from human speech, said 3M senior scientist Tom Hanschen.

3M is still working on the film, which it hopes to market mainly to buildings with open-office layouts. Hanschen said it has been modified from another 3M acoustical material for the auto market designed to reduce engine and road noise inside cars. That product is expected to be on the market next year, he said. 3M has patents and patents pending on the film for buildings and automotive material, he said.

Both products stem from 3M's long-standing expertise in acoustical insulation. For years the company's Thinsulate acoustic insulation has been used to reduce noise levels in automobiles, aircraft and appliances.

Nate Pearson, a senior design-phase manager at Golden Valley-based Mortenson Construction, said he wasn't aware of any products currently on the market that would be similar to 3M's acoustical tiles.

"Often we used just good old-fashioned insulation, but more and more there's a need for specialized products," Pearson said. Open-plan offices and historic-renovation projects, whose interiors often have exposed rough block or brick walls, are especially challenging to acoustically insulate, he said.

Hanschen said the ape house's acoustical problems were immediately apparent when Smithsonian officials gave him a tour of several areas of the museum and zoo last year.

"It was really poorly set up acoustically. It was hard to carry on a single conversation, much less two conversations," he said.

Hanschen and other researchers conducted tests to measure noise levels before and after the acoustic tiles were installed. One involved popping a balloon in the ape house when it was empty and recording how long the sound echoed.

"It was stunning," Brinikowski said. He said the tiles have cut the reverberation time by at least half.

"Don't get me wrong, it's not a library," Brinikowski said. "But now families can communicate with each other in reasonable tones." The strongest positive feedback has come from zoo volunteers who work as guides at the ape house, he said.

Other 3M innovations used in the tiles include flame-retardant resins and a new variety of adhesive, so the tiles can be installed without drilling into the ape house's concrete walls. That also makes the tiles easier to move if necessary.

3M, a Smithsonian corporate sponsor, donated the tiles for the ape house. A company spokesman said it's not possible to estimate the cost, since the product is still being developed and not yet on the market.

In addition to the ape house, future installations of the acoustic tiles are planned at the zoo's Amazonia Science Gallery, an experimental science education center, and at the Written in Bones exhibit at the Smithsonian's Museum of Natural History. Brinikowski said both sites have noise-level issues.

Susan Feyder • 612-673-1723