Acoustic impedance of various materials table
Table shows acoustic impedance of various mediums such as air, water or marble.

# metals#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ aluminum (pure) Al 16650900 brass - 36777900 cadmium - 24220000 copper (pure) Cu 42018000 gold Au 61824000 iron Fe 46433000 iron, cast - 33152200 lead Pb 22228360 magnesium Mg 10126800 molybdenum Mo 64890000 monel - 46926000 nickel Ni 49784000 platinum Pt 70785000 silver Ag 37764000 steel, carbon - 46472000 steel, stainless 304 - 44660000 tin Sn 24090000 titanium Ti 27694000 tungsten W 97864000 uranium U 63580000 zinc Zn 30004800

# liquids#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ glycerin C3H5(OH)3 2394000 ethanol C2H5OH 2366400 liquid helium He 120625 oil, petroleum - 1394000 mercury Hg 19017600 water 25°C H2O 1475664 water, sea - 1576960

# alcohols#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ ethanol C2H5OH 2366400

# other materials#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ ice (frozen water, 0°C) H2O 3666800 organic glass (plexiglass) - 2006000 quartz glass - 9860000

# gases#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ hydrogen H2 106 carbon dioxide CO2 505 dry air (standard conditions, 25°C and 100 kPa) - 385 oxygen O2 452

# oxides#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ carbon dioxide CO2 505 aluminium oxide Al2O3 39303000

# plastics#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ nylon - 4420000 polyethylene - 4370000 rubber, hard - 2133000 neoprene (polychloroprene) - 1968000 teflon (polytetrafluoroethylene, PTFE) (C2F4)n 3080000

# wood#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ fir wood - 2200500 pine wood - 2618000

# solids#

 Substance Molecular formula Acoustic impedance $\left[\frac{kg}{m^2 \cdot s}\right]$ neoprene (polychloroprene) - 1968000 teflon (polytetrafluoroethylene, PTFE) (C2F4)n 3080000 marble - 10328910 concrete - 9500000

# Some facts#

• The acoustic impedance is a measure of resistance to the propagating sound wave.
• The acoustic impedance is specific for a given medium. In the case when the medium consists of one substance (the medium is homogeneous) it is identical with the acoustic impedance of the substance.
• The acoustic resistance depends on the density of the medium and the speed of sound in this medium:
$Z = d \cdot c$
where:
• The acoustic impedance is most often denoted by a capital letter Z or capital letter R.
• The unit of acoustic impedance in the SI system is kilogram per meter square per second:
$\frac{kg}{m^2 \cdot s}$
• The acoustic impedance depends to the greatest extent on the density of the medium. For example, the acoustic resistance of gases is several orders of magnitude smaller than solids. Similarly, in the case of two solids materials, the medium with higher density have greater acoustic impedance (e.g. concrete) and vice versa (e.g. wood or polystyrene have poor acoustic impdedance).
• In the case of two solids of similar density medium in which acoustic wave moves faster have higher acoustic impedance. For example, teflon and concrete have a similar density (approx. 2000-2500 kg/m3) but concrete has greater impedance - sound moves almost three times faster in the concrete.

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