Determining when a worksite exposure should be considered impulsive is a problem which has complicated both research into mechanisms of auditory pathology and protection of the exposed worker. An ideal solution requires that a definition of impulsive noise be developed which is independent of specific characteristics such as duration and amplitude. As an alternative to duration independence, a fixed time window over which a statistic is calculated may also serve as a basis for classification. Additionally, selecting this window on the basis of TTS production in the ear provides a biological basis for the definition of impulsiveness. Classification of impulsiveness based on the sample kurtosis meets the requirements of a generally applicable impulse definition.