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# Module 1 - Physical Acoustics

### Introduction

If a tree falls in a forest...

An old riddle is often heard, "If a tree falls in the forest and no one is present, will there be sound?"

What do you think? Will there be sound?

Though this riddle has stumped philosophers for many years, the answer is actually straight forward. There are two approaches to sound. One is called physical acoustics, the other psychoacoustics. Physical acoustics (the topic of module one) deals with sound as physical quantities, such as pressures, amplitudes, frequencies, and spectra. If the tree falls in the forest there will be sound waves produced with physical properties. Psychoacoustics (the topic of module two) deals perception of sound, such as loudness, pitch, and timbre (no pun intended). If no one is around there will be no perception of sound.

Therefore, if a tree falls in a forest with no one around there will be physical sound but no psychoacoustic sound.

In this module on physical acoustics, you will learn how to describe sound waves physically and mathematically. The module is divided into four lessons. In the first lesson you learn an old vocabulary with a new twist, the language of physics. The second lesson discusses vibrations of springs, strings, bars, etc. The next lesson introduces the properties of waves, including sound waves. The final lesson describes how physical systems respond to a periodic force by resonating. During each lesson you will learn new vocabulary, physical concepts, and use algebra to solve simple problems.

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, January 25). Module 1 - Physical Acoustics. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Electrical_and_Computer_Engineering/Science_of_Sound/Module_1_-_Physical_Acoustics_1.htm. This work is licensed under a Creative Commons License