Building Acoustics

220 Building acoustics () 2 0 10 lg 10 lg 1 0.1 2 , c fd σ ⎡ ⎤ ⋅=−⋅+⋅⎢ ⎥ ⎢⎣ ⎥⎦ (6.28) where f is the frequency and d is a typica ...

Sound transmission 221 where kx and ky are the components of the wave number in the medium around the plate (air). This expressi ...

222 Building acoustics This result shows that the important factor for the sound radiation is the ratio of the wave numbers in t ...

Sound transmission 223 where we assume that kB < k. For increasing k, i.e. when the wavelength λB in the plate increases in r ...

224 Building acoustics 2 0 c 2. c m f π B = (6.41) For homogeneous plates we may write 2 0 c L , 1.8 c f ch ≈ ⋅ ⋅ (6.42) where c ...

Sound transmission 225 1 2 2 2 1 (^222). xz x z x z nn n n n n kkk ab ⎡⎤⎛⎞π ⎛⎞π ⎡ ⎤ =+ =+⎢⎥⎜⎟⎜⎟ ⎣ ⎦ ⎢⎥⎣⎦⎝⎠⎝⎠ (6.44) Hence, the c ...

226 Building acoustics In this case, we envisage that the wavelength in the surrounding medium is larger than both partial wave ...

Sound transmission 227 2 2 22 (^62222) 00 cos cos 64 sin 22 sin (, ) sindd. 11 xz xz xz kab nn nn nn ππ αβ σ φφθ π αβ ππ ⎧⎫ ⎪⎪⎡⎤ ...

228 Building acoustics 6.3.4.2 Frequency averaged radiation factor It is not possible to give a simple formula to calculate the ...

Sound transmission 229 connected structure. A typical example of the latter type in buildings is the so-called flanking transmis ...

230 Building acoustics Figure 6.16 Radiation index of a 4 mm thick aluminium panel, 2.7m x 3.4m, measured using different kinds ...

Sound transmission 231 term in the expression. One easily observes that the variability of σf is much smaller than the correspon ...

232 Building acoustics considerably less differences between stiffened and non-stiffened panel. (How would you explain this?) Fu ...

Sound transmission 233 Figure 6.18 Dynamic point force input F to a plate having point mobility M. The mechanical power imparted ...

234 Building acoustics The numerator in this expression represents the power imparted by the force, thereby giving us the follow ...

Sound transmission 235 will be a discontinuity at the driving point, which is called a bending wave near field. This field will ...

236 Building acoustics It could be useful to give an example illustrative of the sound power due to this bending near field. We ...

Sound transmission 237 22 2 2 000 0 c ac 222 2 00 1. 28 2 4 W FcFkB F f cm m cm f ρρ ρ π σ σ πηω π η ⎡ ⎤ =+ = +⋅⎢ ⎥ ⎣ ⎦   (6. ...

238 Building acoustics 6.4.2.3 Impact sound. Standardized tapping machine As mentioned in section 6.2.2, a standard tapping mach ...

Sound transmission 239 loss factor is frequency independent, the impact sound pressure level Ln in the receiving room (see secti ...