The crack of the bat: Material properties, dynamic response, and sound radiation of baseball bats

Abstract

The crack of the bat on contact with a fastball is one of the special effects that contribute to the enjoyment of baseball. The objective is to establish relationships between the dynamic mechanical material properties, vibration characteristics, and acoustic radiation of hardwood, aluminum, and composite material baseball bats. Results of structural analyses are compared with laboratory and field experimental vibration and acoustic measurements. The aluminum bat characteristically exhibits a series of lightly damped resonant frequencies, relatively high handle vibration levels, and a distinct narrow‐band radiation signature. Traditional hardwood bats have fewer, lower Q, low‐frequency resonances, resulting in relatively low handle vibration levels and an impulsive sound signature governed by low‐frequency components. A recently developed composite materials hat has a specially configured high‐strength core integrated with a hardwood exterior shell. The dynamic and acoustic response of the composite bat is similar to that of hardwood bats. Field testing of the three types of bats provides performance measures that can be related to structural acoustic and vibration characteristics for parameter modifications and design improvements.