The public has nearly a month to weigh in on Marine Corps plans to station MV-22 tiltrotor Osprey and H-1 Cobra and Huey attack-utility helicopter squadrons at Marine Corps Base Hawaii, but any community opposition likely will boil down to a single topic, according to the secretary of the Kaneohe Neighborhood Board.

"In one word," said Bill Sager, "it’s the noise."

The Osprey can take off vertically, switch to airplane mode for forward flight, then switch back to helicopter mode for landing.

But Kaneohe neighbors have no idea how the Osprey will sound when the noise from its engines and rotors bounce off of the Pali cliffs, Sager said.

"Several people have expressed concerns to me," he said.

While the Marines opened a 30-day comment period on their proposals last week, "People will have no way of evaluating the noise impact of an Osprey until they actually hear it," Sager said.

Kaneohe Neighborhood Board Chairman Roy Yan­a­g­i­hara has asked the Marines to fly an Osprey over Kaneohe to let residents hear the sound themselves.

"The Marines indicated that right now they have no spare aircraft to bring over," Yana­gi­hara said.

The environmental impact statement says fixed-wing aircraft — Navy P-3C Orion patrol planes, C-17 cargo jets from Joint Base Pearl Harbor-Hickam and transient fighter jets — "will continue to be primary contributors to noise to the environs."

A spokeswoman for the Marine base, 1st Lt. Diann Olson, said Monday that flights of the Osprey and new helicopters would make up only 28 percent of flight operations.

And she added that noise perception is relative.

"What makes me crazy — motorcycles going by — doesn’t make other people crazy," said Olson. "It’s sort of in the ear of the beholder."

If their plans are approved, the Marines will bring in two Marine Medium Tiltrotor squadrons — or 24 MV‐22 Ospreys — from Camp Pendleton in California; a Marine light attack helicopter squadron of 15 AH‐1 Cobra and 12 UH‐1 Huey attack and utility helicopters; about 1,000 active‐duty personnel; 22 civilian contractors and government employees; and 1,106 dependents from this summer through 2018 as the aircraft arrive.

One plan would put all of the new facilities — including new bachelor enlisted quarters, taxiways and aprons — on the southeast side of the base runway, to be built over six to 10 years. The other plan would put Osprey facilities on the northwest side of the runway at West Field, requiring construction of a runway underpass.

Both Sager and Yana­gi­hara said the Marines have generally adjusted their operations in the past to reduce noise.

Yanagihara, 58, grew up in Kaneohe, where Marine and Navy flights "were a lot noisier" during the height of the Vietnam War.

"Those F-4 Phantoms, they had some big, noisy engines," Yana­gi­hara said of the fighter jet of choice for the Navy and Marines during the Vietnam era. "Since then the noise levels have come down quite a bit."

Sager lives two miles across Kaneohe Bay from Marine Corps Base Hawaii and still hears loud noises "occasionally," including last month when helicopter rotors and engines "rattled the windows, drowned out the television for three minutes and left me with a headache."

Representatives of the Marines attend almost every Kaneohe Neighborhood Board meeting and sometimes get an earful of noise complaints from neighbors, Sager said.

"Usually they’re able to tell people what was happening and why it was necessary," Sager said. "When people understand the necessity for the noise, most people are quite understanding. If the noise from the new mission becomes unacceptable, I’m sure the Marines are going to hear about it."