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Absorption and Velocity of Sound in Still Air

Sound is a vibration that travels through an elastic medium as a wave. The speed of sound describes how much distance such a wave travels in a certain amount of time. In dry air at 20 °C (68 °F), the speed of sound is 343 meters per second (1,125 ft/s). This equates to 1,236 kilometers per hour (768 mph) or about one mile in five seconds. This figure for air (or any given gas) increases with gas temperature, but is nearly independent of pressure or density for a given gas. For different gases, the speed of sound is dependent on the mean molecular weight of the gas, and to a lesser extent upon the ways in which the molecules of the gas can store heat energy from compression (since sound in gases is a type of compression).

Although "the speed of sound" is commonly used to refer specifically to the speed of sound waves in air, the speed of sound can be measured in virtually any substance. Sound travels faster in liquids and non-porous solids than it does in air, traveling about 4.4 times faster in water than air. Additionally, in solids, there occurs the possibility of two different types of sound waves: one type is associated with compression (the same as usual sound waves in fluids) and the other is associated with shear-stresses, which cannot occur in fluids. These two types of waves have different speeds, and (for example in an earthquake) may thus be initiated at the same time but arrive at distant points at appreciably different times. The speed of compression-type waves in all media is set by the medium's compressibility and density, and the speed of shear-waves in solids is set by the material's rigidity and density. - Wikipedia

     Speed of Sound = (Coefficient of Stiffness / Material Density )

The tables of data below refer only to the temperature 20°C (68°F). Values are provided for relative humidities of 0%, 30%, 50%, 70% 90%, and 100%.
 
Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/km)
Absorption
(dB/s)
Velocity
(1000 ft/s)
Relative Humidity = 0%
     
20 0.1540.510.1741.126892
400.3271.070.3681.127013
500.3841.260.4331.127050
630.4361.430.4911.127085
1000.5091.670.5731.127131
2000.5601.840.6311.127161
4000.5961.960.6721.127169
6300.6452.110.7271.127171
8000.6922.270.7801.127172
12500.8612.820.9701.127172
20001.2624.141.4231.127173
40002.6968.843.0301.127178
63004.54114.895.1181.127182
100008.01326.289.0321.127184
1250010.91835.8112.3061.127186
1600015.90152.1517.9231.127187
2000022.97875.3725.9011.127187
4000081.405267.0191.7591.127188
63000196.544644.66221.5421.127188
80000314.6771032.14354.7001.127188

Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/Km)
Absorption
(dB/s)
Velocity
(1000 ft/s
Relative Humidity = 30%
     
200.0090.030.0101.127976
400.0340.110.0381.127980
500.0510.170.0571.127984
630.0750.250.0851.127987
1000.1510.500.1701.127999
2000.3091.010.3491.128023
4000.4841.590.5461.128037
6300.6822.240.7701.128041
8000.8682.850.9791.128044
12501.5525.091.7511.128045
20003.33310.933.7601.128047
400011.85638.8913.3741.128056
630027.62690.6131.1641.128072
1000062.493204.9870.4981.128105
1250089.659294.08101.1481.128131
16000128.814422.51145.3241.128166
20000171.847563.66193.8791.128204
40000338.7101110.97382.1721.128316
63000499.8381639.47563.9981.128361
80000635.0852083.08716.6141.128375

Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/Km)
Absorption
(dB/s)
Velocity
(1000 ft/s
Relative Humidity = 50%
     
200.0060.020.0061.128795
400.0220.070.0251.128797
500.0340.110.0381.128798
630.0520.170.0581.128800
1000.1170.380.1321.128807
2000.3131.030.3531.128826
4000.5631.850.6361.128849
6300.7342.410.8281.128858
8000.8512.790.9611.128860
12501.2314.041.3901.128862
20002.1767.142.4571.128865
40006.75222.157.6221.128867
630015.64351.3117.6591.128871
1000037.521123.0742.3571.128881
1250057.009186.9964.3571.128890
1600089.594293.87101.1431.128903
20000132.719435.32149.8301.128922
40000382.7221255.33432.1011.129020
63000654.6062147.11739.1151.129099
80000844.0242768.40953.0161.129133

Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/Km)
Absorption
(dB/s)
Velocity
(1000 ft/s
Relative Humidity = 70%
     
200.0040.010.0051.129618
400.0160.050.0181.129619
500.0250.080.0281.129619
630.0390.130.0441.129620
1000.0920.300.1041.129623
2000.2840.930.3211.129638
4000.6112.010.6911.129662
6300.8292.720.9371.129673
8000.9473.111.0701.129678
12501.2504.101.4121.129683
20001.9156.282.1631.129685
40005.05616.585.7121.129687
630011.19736.7312.6491.129689
1000026.62487.3330.0771.129693
1250040.758133.6946.0441.129697
1600065.246214.0173.7081.129704
2000099.365325.92112.2541.129712
40000339.1531112.42383.1651.129770
63000673.6672209.63761.1371.129842
80000924.4813032.301044.5561.129884

Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/Km)
Absorption
(dB/s)
Velocity
(1000 ft/s
Relative Humidity = 90%
     
200.0030.010.0041.130443
400.0130.040.0141.130443
500.0190.060.0221.130444
630.0310.100.0351.130444
1000.0740.240.0841.130446
2000.2500.820.2831.130457
4000.6212.040.7021.130478
6300.9032.961.0211.130493
8001.0453.431.1821.130498
12501.3444.411.5201.130505
20001.8926.212.1391.130508
40004.33714.224.9031.130511
63009.09929.8410.2861.130512
1000021.13369.3223.8911.130514
1250032.258105.8136.4681.130516
1600051.762169.7858.5181.130520
2000079.424260.5189.7911.130526
40000290.117951.58327.9951.130561
63000629.7012065.42711.9481.130612
80000911.2862989.021030.3461.130651

Frequency
(Hz)
Absorption
(dB/1000 ft)
Absorption
(dB/Km)
Absorption
(dB/s)
Velocity
(1000 ft/s
Relative Humidity = 100%
     
200.0030.010.0031.130856
400.0110.040.0131.130856
500.0180.060.0201.130857
630.0280.090.0311.130857
1000.0680.220.0761.130858
2000.2340.770.2651.130868
4000.6162.020.6961.130888
6300.9283.051.0501.130902
8001.0873.571.2301.130909
12501.3994.591.5821.130917
20001.9176.292.1681.130921
40004.14013.584.6821.130924
63008.45127.729.5571.130925
1000019.35763.4921.8911.130926
1250029.46196.6333.3181.130929
1600047.227154.9053.4101.130931
2000072.538237.9382.0361.130935
40000269.598884.28304.9051.130963
63000601.7141973.62680.5431.131007
80000888.1132913.011004.4921.131042



Information from CRC Handbook of Chemistry and Physics, 7first Edition, 1990-1991, David R. Lide
Minor corrections made 8/17/2005 - thanks to Andy H.

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