Acoustical properties of materials
Sponsored Links
This presentation is the property of its rightful owner.
1 / 21

Acoustical Properties of Materials PowerPoint PPT Presentation


  • 71 Views
  • Uploaded on
  • Presentation posted in: General

Acoustical Properties of Materials. Chapter 8. Sound. Response of human ear to pressure fluctuations in the air caused by vibrating objects. Sound wave is a back & forth vibratory motion passed from particle to particle through a medium

Download Presentation

Acoustical Properties of Materials

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Acoustical Properties of Materials

Chapter 8


Sound

  • Response of human ear to pressure fluctuations in the air caused by vibrating objects.

  • Sound wave is a back & forth vibratory motion passed from particle to particle through a medium

  • Sound frequency is the number of back and forth cycles that occur in one second ( measured as Hertz)

  • Audible frequency range lies between 20 Hz & 20,000 Hz


Sound wave produced by tapping on wall


Wavelength

Distance between peaks in a sound wave

Speed = Frequency X Wavelength


Sound pressure (loudness) measured on decibel scale


Types of sound: Airborne sound


Types of sound: Structure-borne sound (impact sound)


Airborne sound falling on a building assembly


Airborne sound & building assembly

  • Sound is reflected, absorbed & transmitted

  • Transmission rate varies with weight of assembly

    • Heavy-weight assemblies are poor transmitters - good insulators

    • Light-weight assemblies, poor insulators


Sound transmission loss (TL): the loss of sound pressure level as sound passes through an assembly

  • Measured in decibels (dB)

  • Difference in sound pressure level between the source side and receiver side

  • The greater the TL of a wall, the better it is as a sound insulator

  • TL varies with frequency, generally higher TL with higher frequency sound


Sound transmission loss


Sound Transmission Class (STC)

  • Single number index- average of TL over frequencies ranging from 125 Hz to 4 kHz

  • Used to compare building assemblies

  • Regulated by code in some building types


Decibel scale


Improve STC of light weight assemblies by

  • Adding fibrous insulation in stud cavities

  • Decoupling gypsum board layer

  • Use multiple gypsum board layers


Stud wall assemblies


Resilient Channel


Resilient Clip


Impact Insulation Class (IIC)measure ofstructure-borne sound


Sound absorption

  • Sound originating within room attenuated only through sound absorption

  • Noise reduction coefficient used to compare efficacy of materials (0-1)

  • Higher NRC, the more sound absorptive the material

  • Materials .2 NRC or higher are sound absorptive


Ceiling tiles


Partitions: fabric-wrapped fiberglass panels absorb sound


  • Login