Lawn Mowers Cut Decibels For a Price

March 25 -- How much will Americans pay to avoid annoying their neighbors?

Briggs and Stratton Corp. hopes they will cough up roughly $40 to $50 extra for a quieter lawn mower. The Milwaukee-based company this spring is introducing a mower engine that it said is 64% less noisy than standard versions.

So far, this quieter engine is available only on two Craftsman mowers sold at Sears stores. Briggs, the world's largest maker of gasoline engines for outdoor power equipment, based on sales, said the new engines may be installed in other mower brands eventually.

Rival engine maker Kohler Co. said it also has made its motors quieter but declined to provide details. A Honda Motor Co. spokeswoman said she lacked the data needed to say whether that company's mowers had become less noisy in recent years.

Briggs said it has been able to reduce the racket mainly because it has found a way to slow the spinning of the blade without sacrificing cutting ability.

Mowers are noisy partly because much of the time they are running faster than necessary to cut the grass. Standard engines typically run at about 3,100 revolutions a minute when they are started, then slow as the blade hits resistance in slicing through grass, Briggs said. The rotation of the crankshaft varies from around 2,800 rpm when the blade is cutting thick or wet patches of grass to more than 3,000 rpm where the grass is less dense.

A fuel governor on the new Briggs engine increases the flow of gas to the engine when it runs into denser patches of grass, so the speed remains steadier at around 2,800 rpm, Briggs said, and the use of a flatter blade reduces noise further. The two Craftsman mowers offered by Sears with the quieter engine are priced at about $340 and $450.

Briggs's chief executive, Todd Teske, hopes to achieve further sound improvements by "tuning" mower mufflers to make the noise less harsh. Still, he conceded, "it's never going to sound like Bach."

It isn't clear that many people will pay a premium for less noise. Stihl Group, a Germany-based maker of power lawn equipment, introduced in 2008 a quieter leaf blower known as the BG 66 L. Baffles inside the blower smooth air flow to eliminate whistling noises. This model, also available in other parts of the world, typically retails in the U.S. for around $230, or roughly $60 more than a similar model that makes more noise. Sales of the lower-priced model remain much higher than those of the quieter one, Stihl said.

Malcolm Crocker, a soft-spoken acoustical engineer who directs the International Institute of Acoustics and Vibration at Auburn University, said he wears ear-protecting muffs when he mows. He likes the idea of a quieter mower but thinks some people may be wary.

"Humans tend to equate loudness with power," Dr. Crocker said, "so if you make it quieter people think it's not so powerful."

James R. Hagerty         http://online.wsj.com/