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Session 1526

Teaching Awareness about Pollution from Sound and Combustion Emissions

Luis M. Bocanegra, Jose L. Rivera Department of Mechanical Engineering University of Puerto Rico, Mayagüez Campus

ABSTRACT

This paper intends to communicate what is being taught at the University of Puerto Rico regarding pollution from noise and exhaust gas emissions. These two topics are addressed in the senior level Mechanical Engineering Laboratory II course in which students get exposure to subjects otherwise not covered in other courses.

NOISE POLLUTION AND CONTROL EXPERIMENT

Introduction

Sounds are always present in our daily environment. Depending upon their level, sometimes these become unwanted and are known as “acoustic noise”. The latter may be originated from different sources such as pumps, compressors, pneumatic equipment, traffic or just a group of people talking loud. Despite its origin, it has undesirable effects that affect human behavior and health such as hearing damage, disturbance, annoyance and distraction, interference with speech communication and at high levels, can even damage material structures by acoustic fatigue1-3.

Awareness of such effects is important for an engineer that frequently has to make decisions that affect the environment such as pollution created by unwanted sounds. One way to reduce the effect of these sounds is by attenuating them using acoustic absorbers that ultimately transform sound energy into heat. Sound absorbing materials are used in rooms, to reduce excess reverberation, which leads to poor speech intelligibility; in ventilation spaces; in loudspeaker cabinets, to suppress undesirable cabinet resonance; and in machine enclosures to reduce the buildup of reverberant noise inside, and thus to improve their performance.

The behavior of such materials is related to the frequency of the sound. Adult males respond to sound waves in the frequency range of 20 to 16,000 Hz. The speech zone lies in the frequency range of 500 to 2000 Hz. The most critical subrange for control of noise purposes is within frequencies from 2000 to 5000 Hz.

Class Management

In this course, during a semester, students get a total of three hours of theory related to acoustics. Topics covered are sound waves, effect of sound waves in people, sound rating measurement, transmission of sound, attenuation of sound with distance and noise control. During the class students use a sound level meter to measure different levels of sound around campus and in a

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Bocanegra, L. M., & Rivera, J. L. (1997, June), Teaching Awareness About Pollution From Sound And Combustion Emissions Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6812