Sound transmission loss Sound transmission loss
Sound transmission loss Sound transmission loss
Sound transmission loss Sound transmission loss
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©<br />
Prof. B.A.T. Petersson<br />
©<br />
Prof. B.A.T. Petersson<br />
<strong>Sound</strong> <strong>transmission</strong> <strong>loss</strong><br />
• Double wall <strong>transmission</strong><br />
» Normal incidence<br />
d<br />
<strong>Sound</strong> <strong>transmission</strong> <strong>loss</strong><br />
• Diffuse <strong>transmission</strong><br />
» Double gypsum wall on separate stringers<br />
12 dB/octave<br />
p inc p 2<br />
p 3<br />
p t<br />
p1<br />
v 1 v2<br />
x = 0<br />
Frequency, Hz<br />
1
©<br />
Prof. B.A.T. Petersson<br />
©<br />
Prof. B.A.T. Petersson<br />
<strong>Sound</strong> propagation<br />
• Measurement of sound <strong>transmission</strong><br />
• <strong>Sound</strong> reduction index<br />
<strong>Sound</strong> propagation<br />
L S<br />
• <strong>Sound</strong> reduction index<br />
S<br />
L R<br />
R d = L S - L R - 10log(A R /S) ; A R = S R R<br />
Reference curve R w , dB<br />
R w<br />
38<br />
42<br />
20<br />
100 400 1000 3150<br />
Frequency, Hz<br />
i 3dB<br />
i 32dB<br />
2
Prof. B.A.T. Petersson<br />
©Reference curve Lp, dB<br />
<strong>Sound</strong> propagation<br />
<strong>Sound</strong> propagation<br />
• Measurement of footfall noise<br />
62<br />
57<br />
42<br />
100 315 1000 3150<br />
Frequency, Hz<br />
L p<br />
• Flanking paths<br />
1. Direct path<br />
2. Wall to wall<br />
3. Wall to floor<br />
4. Floor to wall<br />
R res = 10log( S i / S i I )<br />
3
©<br />
Prof. B.A.T. Petersson<br />
<strong>Sound</strong> propagation<br />
• Leaks<br />
» Big gaps (d ) broad band <strong>transmission</strong><br />
» Small gaps (d < ) high frequency <strong>transmission</strong><br />
» 1 significant increase of <strong>transmission</strong><br />
4
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