# Sound Velocity of Material

The speed of sound in air is around 768 mi/hr (1,125 ft/sec, 343 m/sec), or about 5 seconds per mile, or 3 seconds per kilometer. That is the reason for the rule of thumb where when you see a flash of lightning, count the number of seconds until you hear the thunderclap, then divide by five. That gives you the approximate distance (in miles) away from the lightning. Divide by three for kilometers. Speed of sound very important for an application to ultrasonic flow meter or ultrasonic level sensor.

The speed of sound in any medium is dependent upon the coefficient of stiffness (modulus of bulk elasticity for gas mediums). Density and/or compressibility alone does not determine the speed of sound.

• Vl = Velocity of a plane longitudinal wave in bulk material.
• Vs = Velocity of a plane transverse (shear) wave.
• Vext = Velocity of longitudinal wave (extensional wave) in thin rods.

### Solids

Substance
Density
(g/cm3)
Vl(m/s)
Vs(m/s)
Vext(m/s)
Metals
Aluminum rolled
2.7
6420
3040
5000
Beryllium
1.87
12890
8880
12870
Brass (70 Cu, 30 Zn)
8.6
4700
2110
3480
Copper, annealed
8.93
4760
2325
3810
Copper rolled
8.93
5010
2270
3750
Gold, hard-drawn
19.7
3240
1200
2030
Iron, Armco
7.85
5960
3240
5200
11.4
2160
700
1190
11.4
1960
690
1210
Molybdenum
10.1
6250
3350
5400
Monel metal
8.90
5350
2720
4400
Nickel (unmagnetized)
8.85
5480
2990
4800
Nickel
8.9
6040
3000
4900
Platinum
21.4
3260
1730
2800
Silver
10.4
3650
1610
2680
Steel, mild
7.85
5960
3235
5200
Steel, 347 Stainless
7.9
5790
3100
5000
Tin rolled
7.3
3320
1670
2730
Titanium
4.5
6070
3125
5080
Tungsten, annealed
19.3
5220
2890
4620
Tungsten Carbide
13.8
6655
3980
6220
Zinc rolled
7.1
4210
2440
3850
Various
Fused silica
2.2
5968
3764
5760
Glass, pyrex
2.32
5640
3280
5170
Glass, heavy silicate flint
3.88
3980
2380
3720
Lucite
1.18
2680
1100
1840
Nylon 6-6
1.11
2620
1070
1800
Polyethylene
0.90
1950
540
920
Polystyrene
1.06
2350
1120
2240
Rubber, butyl
1.07
1830
Rubber, gum
0.95
1550
Rubber neoprene
1.33
1600
Brick
1.8
3650
Clay rock
2.2
3480
Cork
0.25
500
Marble
2.6
3810
Paraffin
0.9
1300
Tallow
390
Woods
Ash, along the fiber
4670
Beech, along the fiber
3340
Elm, along the fiber
4120
Maple, along the fiber
4110
Oak, along the fiber
3850
Human Body Tissues
Soft Tissue

### Liquids

Substance
Formula
Density
(g/cm3)
Velocity at 25°C
(m/s)
-δv/δt
(m/sec °C)
Acetone
C3H60
0.79
1174
4.5
Benzene
C6H6
0.870
1295
4.65
Carbon tetrachloride
CCl4
1.595
926
2.7
Castor oil
C11H10O10
0.969
1477
3.6
Chloroform
CHCl3
1.49
987
3.4
Ethanol amide
C2H7NO
1.018
1724
3.4
Ethyl ether
C4H10O
0.713
985
4.87
Ethylene glycol
C2H6O2
1.113
1658
2.1
Glycerol
C3H8O3
1.26
1904
2.2
Kerosene
0.81
1324
3.6
Mercury
Hg
13.5
1450
Methanol
CH4O
0.791
1103
3.2
Turpentine
0.88
1255
Water (distilled)
H2O
0.998
1496.7
-2.4