Vibroacoustic Coupling of Cylindrical Structure with Both Excited End Plates
Vibroacoustic coupling phenomena occur in a variety of different situations and are generally studied with the goal of controlling noise. However, we also expect that they are applied to new technologies based on energy stored in each system. In this study, we investigate vibroacoustic coupling between structural vibrations and the internal sound fields of thin structures. We consider a cylindrical structure with thin plates at both ends and investigate the coupling between the plate vibrations and the internal sound field when external periodic forces are applied to respective end plates. This coupling is theoretically and experimentally investigated by considering the behavior of the both plates and the acoustic characteristics of the internal sound field with variations in the periodic forces. In the analytical model, the end plates are supported by springs in circumference to make those support conditions close to actual conditions in the experiment due to adjustments of spring stiffnesses, and then the cylinder is assumed to be structurally and acoustically rigid at the lateral wall between the structure and the sound field to simplify this problem. The acoustic characteristics are evaluated by the sound pressure level, which is maximized with changing the phase difference between the both plate vibrations, when the phase difference and relative amplitude between both periodic forces are varied. The behavior of the plate vibration is studied from changing the phase difference with the cylinder length. In comparison between characteristics of the both systems, it is clarified that vibroacoustic coupling is effective in increasing acoustic energy and the phase difference depends greatly on the acoustic mode, which contributes the formation of the sound field.
Mazda's New V-6 Gasoline Engine and Its Innovative Induction System
Mazda succeeded in the development of a new V-type 6-cylinder engine series comprising 2-liter JF naturally aspirated and turbocharged units and also a 3-liter JE naturally aspirated unit. This engine is 60-degree-banked and has 18 valves: two intake valves and one exhaust valve per cylinder. Various techniques, such as High Rigidity Cylinder Block and HLA, are adopted to upgrade quietness and smoothness. The Dynamic Charge Effects system, a combination of inertia and resonance charge effects, is modeled on the principle of two-degree-of-freedom system. The application of this principle helped develop the Induction system that is compatible with the three engine types. The turbocharger adopted on the JF engine is of a twin scroll type to considerably improve power response quality and increase torque at low speed. Triple Port Induction Control System is used to help improve fuel economy and running performance.
Comparison of Binaural Release from Forward Masking in Animals and Humans. Electrophysiological Studies
Evoked potentials in the inferior colliculus and auditory areas of the cortex were studied in anesthetized guinea pigs and long-latency auditory evoked potentials (LAEP) were studied in waking humans using sequential binaural presentation of pairs of clicks – the masker and the masked signal – with a variable interval between them, to provide the conditions needed for the psychophysical phenomenon of direct forward masking. Introduction of phase differences between the masker and the masked signal led to decreases in suppression of responses to the masked signal and to faster recovery of the reaction types recorded. The greatest relative differences between response magnitudes to antiphase and synphase masked signals were seen at the beginning of the recovery process, and were 1.6, 1.5, and 1.4 respectively for responses from the inferior colliculus, auditory area of the cortex, and LAEP at stimulus intensities of 50–65 dB sound pressure level, differences subsequently decreasing to zero. There was a positive correlation between this measure and the stimulus intensity. The greatest differences between the time at which the recovery process ended for responses to antiphase and synphase masked signals were 4, 250, and about 2000 msec respectively for the inferior colliculus, auditory area of the cortex, and LAEP.