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

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

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

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

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

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

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

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

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:
- Z - acoustic impedance (wave resistance) of the medium,
- d - medium density,
- c - the speed of sound in the medium.
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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