336 Lecture 17 
dB re 
1pw 
ean 
160 
150 
reverberant room 
Cee 
Pp 
140 
130 
120 
fo) 
—————= power level ( Lp) 
wo 
fo) 
80 
1 2 & © i SB Ge 165 eae ccs) | 2.7 '4h Nemihe i is2mes) 
—_sf Hz kHz 
Fig, 17.11. The power levels Lp due to the plate in Fig. 17.8 were measured; however, the veloc- 
ity of the point of excitation was 1 m/sec for two values of the loss factor. For constant velocity 
excitation, damping layers do not reduce the radiated sound power appreciably (cf. Fig. 17.10). 
QO_kHz 
\mi/s 
reverberant room 
150 
140 icon 
et Wate air-borne excitatio 
130 
1W 
—————=_ power level (Lp) 
[e} 
fo) 
0 
{e) 
80 
iS ane Pis2 cs 2519250 Sco Ni ea oe iicmmesotacs 
———af Hz kHz 
Fig. 17.12. Again the power levels Lp due to the plate in Fig. 17.8 were measured. The velocity 
level averaged over various points on the plate was 1 m/sec for point excitation and for area 
excitation (loudspeaker at 2 m from plate). 
