PERU, Ind. (AP) – A new study has found that noise pollution around northern Indiana's Grissom Air Reserve Base has fallen significantly over the past two decades.

A study by Air Force officials found Grissom's overall noise impact has fallen by 20 percent since 1994, when the site was demoted from Air Force base status to a reserve base.

Base commander Col. Doug Schwartz tells the Kokomo Tribune Grissom isn't as noisy because the number of flight operations has fallen significantly in that time. He says quieter engines in the base's KC-135R Stratotankers refueling planes also contributed to the noise reduction.

The noise pollution drop has occurred even though civilian air traffic has increased at the base about midway between Indianapolis and South Bend.