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This paper describes a procedure used to aid in the control of IC engine knock, an autoignition phenomenon that results in customer annoyance, loss of power, and potential engine damage. Since a control system can only function as well as the signal it is provided, input signal optimization is critical to the robustness of the system. Optimization of the input signal starts with a properly located physical transducer on the engine block. The locating process begins with laser holometry to evaluate compliant regions of the block. Holographic data, block vibration spectra and empirical engine data are then used to identify the most promising sensor locations. These locations are then verified with a broadband accelerometer mounted on a dynamometer engine. This process allows the highest available signal to noise locations to be found in a systematic and efficient manner.

This paper describes a test-based process used to identify structural characteristics of a vehicle windshield wiper system that contribute to customer impression of the sound. The method of paired comparisons determined which wiper system sounds customers preferred. Annoyance ratings of sound components then identified contributors to customer preference. Wiper motor noise was identified as the major annoyance factor affecting system sound quality. This information guided a study of the structures responsible for radiated motor noise. Laser based test methods were used to interrogate the structures clearly identifying transmission paths into the surrounding structure. Paths were then modified reducing structure-borne motor sound as measured with acoustic retests. Thus, a logical technique for hardware testing and modification guided by customer perceptions is presented allowing efforts to be focussed on the most critical aspects of vehicle sound quality.

Panel acoustic contribution analysis (PACA) is an advanced engineering tool to improve the NVH quality of vehicles. Using PACA areas of vehicle body panels are categorized according to their contribution to the total sound. Positive contribution areas increase the sound level as vibration amplitude increases, negative contribution areas decrease the sound level as vibration amplitude increases, and neutral areas have no significant effect on the sound level. This knowledge is important to guide vehicle NVH refinement. This paper presents the technical approach of PACA and the results of an experiment used to validate the PACA techniques. Vehicle application results to improve NVH quality and reduce weight are also included.