lec16 - Noise control Sound components reflected...

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Unformatted text preview: Noise control Sound components reflected (reverberated) absorbed transmitted Transmission loss TL TL = 10 Log(1/ ) = -10 Log Reverberated sound Incident sound Absorbed sound Transmitted sound Noise control 20 30 40 50 60 70 10 100 1000 Surface density [kg/m] Attenuation [dB] . 565 Hz Theor. 565 Hz Exp. 20 30 40 50 60 70 10 100 1000 Surface density [kg/m] Attenuation [dB] . 565 Hz Theor. 565 Hz Exp. Mass law (Bergers law) theory: doubling of surface density S [kg/m 2 ] - 6dB i.e. TL 20 Log S practice: - 5 dB i.e. TL 17 Log S Noise control Mass law (Bergers law) Frequency law doubling of frequency f [Hz] - 6dB i.e. TL 20 Log f TL 20 Log (0.08 f S ) 10 20 30 40 50 60 70 80 90 100 100 1000 10000 Frequency [Hz] Attenuation [dB] 1000 500 200 100 50 20 10 s [kg/m] 10 20 30 40 50 60 70 80 90 100 100 1000 10000 Frequency [Hz] Attenuation [dB] 1000 500 200 100 50 20 10 s [kg/m] Noise control For low and high frequencies: resonance coincidence 100 Hz 1000 Hz 10 kHz r e g i o n r e g i o n r e g i o n Sound reduction index : dB C o i n c i d e n c e M a s s l a w R e s o n a n c e Resonance Effect in a Panel Coincidence Effect in a Panel Images by MIT OCW. Noise control Sound paths 1 - direct air transmissio 2 - reverberation 3 - lateral transmission of airborne sound 4 - re-emission of impact sound 5 - transmission " Weakest path n A 1 2 1 3 4 5 1 5 5 2 B Noise control Sound paths Weakest path + = 1 10 S ' S 1 log 10 TL TL...
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This note was uploaded on 12/11/2009 for the course ARCHITECTU 4.401 taught by Professor Marilyneandersen during the Spring '06 term at MIT.

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lec16 - Noise control Sound components reflected...

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