1. Acoustical Properties of Materials Chapter 8

2. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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

3. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Sound wave produced by tapping on wall

4. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Wavelength Distance between peaks in a sound wave Speed = Frequency X Wavelength

5. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Sound pressure (loudness) measured on decibel scale

6. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Types of sound: Airborne sound

7. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Types of sound: Structure-borne sound (impact sound)

8. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Airborne sound falling on a building assembly

9. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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

10. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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

11. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Sound transmission loss

12. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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

13. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Decibel scale

14. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Improve STC of light weight assemblies by Adding fibrous insulation in stud cavities Decoupling gypsum board layer Use multiple gypsum board layers

15. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Stud wall assemblies

16. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Resilient Channel

17. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Resilient Clip

18. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Impact Insulation Class (IIC) measure of structure-borne sound

19. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. 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

20. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Ceiling tiles

21. Mehta, Scarborough, and Armpriest : Building Construction: Principles, Materials, and Systems © 2008 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved. Partitions: fabric-wrapped fiberglass panels absorb sound