Tennis ball degradation

Despite anecdotal evidence of changes to tennis ball characteristics and play properties, little research has\nbeen directed towards understanding the causes and effects of tennis ball degradation. Improved racket\ntechnology and player fitness have contributed to an increase in the speed of the game, yet balls have\nseen few advancements over the same period. There are several obvious factors contributing to tennis ball\ndegradation: natural pressure loss in pressurised balls, changes to the cloth covering due to court and\nracket impacts, and precipitation and environmental factors. As recent tennis research has focused on the\nproperties of new balls, there is a need to investigate other ball conditions present in the game of tennis.\nThis thesis provides a structured investigation into the causes and effects of ball degradation, an objective\nassessment of the effects of degradation on ball performance, and incorporates subjective perceptions of\nball aesthetics and play properties noted by players. Particular attention is given to ball fuzziness. Excessive\nfuzziness can occur from manufacturing variability, court and racket interactions, and environmental\nconditions - though there is currently no standardised method to assess ball surface condition.\nAn objective measure of ball fuzziness has been developed and used in the analysis of nearly 4000\nindividual ball images. The effects of court and racket impacts, precipitation, natural pressure loss, and\nrepeated impacts have been analysed for their effects on ball degradation. An assessment of ball performance\nutilised ball impact and aerodynamic data to determine significant differences between balls and\ndevelop an improved ball trajectory model.\nSeveral player perception investigations were conducted using professional, elite, and standard club\nplayers. Two internet based investigations incorporated aspects of sensory evaluation studies to produce\nnew techniques in evaluating products for the sports industry. An investigation into ball aesthetics was\nused to determine the relative importance of ball attributes on ball playability and important areas of\nperceived ball feel and performance were assessed during testing with elite players. Significant differences\nin perception were then combined with objective data to establish perceptible thresholds of wear and\ndegradation in tennis balls and significant areas in player perception. This thesis presents a large body of work on tennis ball degradation. Results provide a mechanism\nto structure future investigations, new analysis techniques, and objective and subjective analyses of ball\ndegradation. The developed digital fuzziness metric shows good agreement with player perception and\naerodynamic data and provides a method to objectively compare ball conditions. Naturally aged and\nfuzzy balls produced the most noticeable differences in ball impact properties, though the aerodynamic\ndata used in the development of an improved trajectory model suggests that ball spin could play a more\nsignificant role in ball flight than drag force differences.\nSubjective assessments of ball appearance suggest ball fuzziness is nearly twice as important as the\ncondition of the ball's logo in determining ball playability. Player testing indicated inconsistent responses\nand limited differentiation in the perceived feel and performance properties of naturally aged balls. The\nvisible differences in the fuzzy balls improved player responses, indicating the importance of aesthetics in\nperceived ball properties. Flight speed, hardness, liveliness, bounce speed, and bounce height are areas of\nperceived ball feel and performance that show good agreement with measured ball properties and usefulness\nin future work.\nDirections for future work include developing a ball performance model, expanding the digital fuzziness\nmetric to produce an overall measure of ball degradation, and further laboratory and perception testing.