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Building Acoustics

FOREWORD

When an incident sound wave arrives onto a material, part of it can be:

  • • Reflected
  • • Transmitted through the material
  • • Absorbed inside the material

This leads to the definition of:

  • • A reflection coefficient p defined as the ratio of reflected energy over incident energy
  • • A transmission coefficient т defined as the ratio of transmitted energy over incident energy
  • • An absorption coefficient a defined as the ratio of reflected energy over incident energy

p2 + т2 + a2 = 1

One may care to note that those coefficients are frequency dependent. Usually the higher the frequency, the lower the transmission coefficient. More to the point, usually with soft or porous materials, the higher the frequency, the higher the absorption coefficient.

INTRODUCTION

As implied by its name, the field of building acoustics covers all aspects involved in the construction of a building. Usually such acoustics mainly revolve around a same concern: enabling the occupants to be decently protected from the noise and vibration aggressions from the outside environment, ensuring proper sound insulation between the various spaces of the building, controlling the reverberation inside the premises, and controlling the noise from mechanical equipment. In addition, one will also be concerned with the noise radiated to the environment either from the mechanical equipment or from the activities carried out inside the building.

This chapter is devoted to the basic physics of those phenomena. Application of those bases will be done in the relevant following chapters.

 
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