Mathematical analysis for perceived annoyance of impulsive sounds in terms of physical factors

From the customer satisfaction point of view, sound quality of any product has become one of the important factors these days. The primary objective of this research is to determine factors which affect the acceptability of impulse noise. Though the analysis is based on a sample impulse sound file of a Commercial printer, the results can be applied to other similar impulsive noise. It is assumed that impulsive noise can be tuned to meet the accepTable criteria. Thus it is necessary to find the most significant factors which can be controlled physically. This analysis is based on a single impulse. A sample impulsive sound file is tweaked for different amplitudes, background noise, attack time, release time and the spectral content. A two level factorial design of experiments (DOE) is applied to study the significant effects and interactions. For each impulse file modified as per the DOE, the magnitude of perceived annoyance is calculated from the objective metric developed recently at Michigan Technological University. This metric is based on psychoacoustic criteria such as loudness, sharpness, roughness and loudness based impulsiveness. Software called ‘Artemis V11.2’ developed by HEAD Acoustics is used to calculate these psychoacoustic terms. As a result of two level factorial analyses, a new objective model of perceived annoyance is developed in terms of above mentioned physical parameters such as amplitudes, background noise, impulse attack time, impulse release time and the spectral content. Also the effects of the significant individual factors as well as two level interactions are also studied. The results show that all the mentioned five factors affect annoyance level of an impulsive sound significantly. Thus annoyance level can be reduced under the criteria by optimizing the levels. Also, an additional analysis is done to study the effect of these five significant parameters on the individual psychoacoustic metrics.

Experimental study of physical aging effects on properties of EPON 862-DETDA

Epoxies find variety of applications and during these applications they get exposed to different conditions like elevated temperatures, hydrothermal, chemical, etc. It has been observed that properties of epoxies do get affected substantially if exposed to these conditions for extended period of time and because of the variety of applications, researchers found it necessary to study their effects on the thermal, mechanical, physical and chemical properties. However in this report the focus is on studying effects of physical aging on mechanical properties of EPON 862 with DETDA as its curing agent, where physical aging is aging is the condition which occurs due to exposure to elevated temperatures. A fair amount of computational work has been performed on EPON 862- DETDA to study the effects of physical aging, however very little known work has been done experimentally to study these effects. Young’s modulus, hardness, failure strength, strain to failure, density and glass transition are the properties which have been obtained using various experimental methods - tensile testing, nanoindentation and differential scanning calorimetry. Experimental work on other epoxies have shown no increase or very slight increase in the Young’s modulus and hardness with increased aging time, also decrease in failure strength and strain to failure and through this work on EPON 862- DETDA we can observe similar trends.