Drum sound from floor coverings - objective and subjective assessment

Abstract: Drum sound is the sound produced when an object, such as a foot, hits the flooring in the room in which the receiving ear is located. Drum sound has attracted interest in recent years, particularly due to an increased use of thin floating floor constructions, such as veneer or laminate flooring, which can produce loud and sharp walking sound. A prediction model of the subjective response, in a paired comparison test, to drum sound based on differences in objective measurements is developed. The difference in 10-percentile loudness, N10, between two stimuli is shown to predict the subjective perceived disturbance better than, for example, A-weighted sound pressure level. A difference of about 8% in N10 resulted in 50% of the assessors noticing a difference. A comparison of different existing approaches to analysing the result from a paired comparison test is made. The main focus is set on the basic models by Thurstone-Mosteller and Bradley-Terry and extensions of these concerning ties. Procedures for testing if the responses and calculated ranking values are statistically different are presented. The advantages and disadvantages of these methods are discussed. These methods are illustrated with examples from tests on drum sound from floor coverings. A branch norm has been established for measuring drum sound on laminate floor coverings. The norm evaluates the subjective perception of the drum sound's loudness using the ISO tapping machine. A round-robin study of the norm is reported along with the results of a paired comparison listening test using the same floor coverings. General aspects of evaluation measures, tapping machines, test environments, etc., that need to be considered when measuring drum sound on various floor coverings are discussed. It is concluded that loudness as measured according to ISO 532B correlates the best with the subjective perception of the drum sound's loudness. The tapping machine can be used to excite hard floor coverings to produce the drum sound, but should be used with caution in studying low-level drum sounds due to the tapping machine's inherent mechanical noise.