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damping factors   n [eta]

I have re-assessed the results of the damping factors already given, and by adjusting calculations and changing bandwidths on some of the tested higher valued materials, I have found that some materials have higher values than previously given. Those below 0.2 are unchanged, those above 0.2 have been re-assessed.

 

Here are the revised data. Any new values have the centre of the bandpass region quoted, all attenuation out of band at 24dB/oct, as before, at a Q of 0.7071.

 

Wood    
material frequency damping factor
     
balsa wood   0.013
bamboo (resinated)
  0.200
chipboard   0.228
cork 850 0.127
low density fibreboard 113 0.257
hardboard 134 0.062
mahogany   0.032
mdf   0.017
oak 540 0.102
olive wood (oiled) 264 0.273
'Panzerholz' 150 0.599
  900 0.898
'Permali' 6mm 250 0.671
'Permali' 18mm 220 0.688
pine 226 0.064
rosewood
365 0.104
Russian 7 ply   0.040
'Torlyte'   0.088
walnut  

0.014

 

metals frequency
damping factor
aluminium   0.004
brass   0.013
copper 175 0.01
lead   0.032
steel   0.008
titanium    

 

 

plastics

     
material frequency damping factor  
acetal (delrin) 121 0.013  
carbon fibre twill   0.020  
carbon fibre rod (non-twill)
239 0.061  
expanded polystyrene   0.055-0.168  
perspex (acrylic)   0.070  
polyethylene terephthalate   0.043  
polyethylene (high density) 200 0.050  
polypropylene   0.052  
ptfe ('Teflon')   0.021  
vinyl foam (hard)   0.046  
vinyl floor tile 272 0.145  

 

 

Ceramics      
material frequency damping factor  
       
fired clay   0.012  
glass, strengthened   0.033  
'Pyrotek' 6mm 100 0.376  
'Pyrotek' 20mm 340 0.395
 
marble   0.009  
slate   0.017  
soapstone 1338 0.027  

 

 

visco elastics and soft foams    
material frequency damping factor
     
blutack (white) 15 0.166
closed pore foam   0.151
expanded polyethylene   0.167
foam for glass bricks   0.288
foam board (paper) 94 0.030
polyurethane foam 120 0.054
polyurethane foam block 141 0.109
above, reconstituted 82 0.149
Plasticine' 77 0.304
'Newplast' 160 0.635
rho C' [polyurethane]   0.287
smart putty'   0.134
sorbothane   0.197
tungsten loaded putty 80 0.725
Wickes' 'lead' flashing   0.161

 

 

complex materials and structures      
material frequency damping factor  
Ikea platter mat   0.062  
dilatant fluid 260 0.109  
recycled rubber crumb 109 0.348  
aluminium + polyalkane composite   0.240  
glass 'Butacite' laminate 150 0.391  
glass 'Sentryglas' laminate 247 0.317  
Al/mdf/Al composite ('Sole') 203 0.218  
glass fibre pcb (copperclad) 445 0.013  
'Trespa Meteon' 30 0.126  
'Alucobond' (Al/ldpe/Al) 300 0.187  
Page Lacquer' acrylic over mdf 100 0.315  
compressed rockwool   0.089  
candle wax 618 0.269  
vinyl record 281 0.020  
above on bare platter 181 0.054  
above, on Ikea mat 194 0.118  
above, with record clamp 117 0.100  
Shellac '78' [HMV] 330 0.014  
above on Ikea mat 287 0.257  
video disc 12”(polycarbonate?   0.033  
above on Ikea mat   0.079  
bentonite powder filled resin 100 0.518  
lead filled resin 100 0.592  
bentonite filled resin 48 0.618  
(bentonite is dry cat litter)      
resin is isophthalic polyester resin **
     
       

 

** the type of polyester resin seems important, it is of the isophthalic variety, but only from certain suppliers.

see here for data sheet: enter code 6398

 

acknowledgements, thanks:

Resin/clay mix researched and developed by Rap.

polyester resin samples prepared and provided by François LEBEAU, Annecy, France

panzerholz and aluminium laminate supplied by François LEBEAU, Annecy, France

smart putty and carbon fibre sheet  from Middlesex University, UK

'Alucobond', 'Page Lacquer', 'Trespa', compressed 'Rockwool' and DuPont samples from 's&p' Architects, London, UK

fired clay sample from 'Angela Wallwork Ceramics' Devon, UK

Aluminium/mdf/aluminium section of 'Sole' sub-chassis supplied by 'Analogue Innovation'

Pyrotech cement board samples supplied by Haydn, Australia

Permali Deho Permali ® (Densified Wood Laminate) samples supplied by Haydn, Australia

 

Thanks to everyone.