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 0.154 0.51 0.174 1.126892 40 0.327 1.07 0.368 1.127013 50 0.384 1.26 0.433 1.127050 63 0.436 1.43 0.491 1.127085 100 0.509 1.67 0.573 1.127131 200 0.560 1.84 0.631 1.127161 400 0.596 1.96 0.672 1.127169 630 0.645 2.11 0.727 1.127171 800 0.692 2.27 0.780 1.127172 1250 0.861 2.82 0.970 1.127172 2000 1.262 4.14 1.423 1.127173 4000 2.696 8.84 3.030 1.127178 6300 4.541 14.89 5.118 1.127182 10000 8.013 26.28 9.032 1.127184 12500 10.918 35.81 12.306 1.127186 16000 15.901 52.15 17.923 1.127187 20000 22.978 75.37 25.901 1.127187 40000 81.405 267.01 91.759 1.127188 63000 196.544 644.66 221.542 1.127188 80000 314.677 1032.14 354.700 1.127188
 Frequency(Hz) Absorption(dB/1000 ft) Absorption(dB/Km) Absorption(dB/s) Velocity(1000 ft/s Relative Humidity = 30% 20 0.009 0.03 0.010 1.127976 40 0.034 0.11 0.038 1.127980 50 0.051 0.17 0.057 1.127984 63 0.075 0.25 0.085 1.127987 100 0.151 0.50 0.170 1.127999 200 0.309 1.01 0.349 1.128023 400 0.484 1.59 0.546 1.128037 630 0.682 2.24 0.770 1.128041 800 0.868 2.85 0.979 1.128044 1250 1.552 5.09 1.751 1.128045 2000 3.333 10.93 3.760 1.128047 4000 11.856 38.89 13.374 1.128056 6300 27.626 90.61 31.164 1.128072 10000 62.493 204.98 70.498 1.128105 12500 89.659 294.08 101.148 1.128131 16000 128.814 422.51 145.324 1.128166 20000 171.847 563.66 193.879 1.128204 40000 338.710 1110.97 382.172 1.128316 63000 499.838 1639.47 563.998 1.128361 80000 635.085 2083.08 716.614 1.128375
 Frequency(Hz) Absorption(dB/1000 ft) Absorption(dB/Km) Absorption(dB/s) Velocity(1000 ft/s Relative Humidity = 50% 20 0.006 0.02 0.006 1.128795 40 0.022 0.07 0.025 1.128797 50 0.034 0.11 0.038 1.128798 63 0.052 0.17 0.058 1.128800 100 0.117 0.38 0.132 1.128807 200 0.313 1.03 0.353 1.128826 400 0.563 1.85 0.636 1.128849 630 0.734 2.41 0.828 1.128858 800 0.851 2.79 0.961 1.128860 1250 1.231 4.04 1.390 1.128862 2000 2.176 7.14 2.457 1.128865 4000 6.752 22.15 7.622 1.128867 6300 15.643 51.31 17.659 1.128871 10000 37.521 123.07 42.357 1.128881 12500 57.009 186.99 64.357 1.128890 16000 89.594 293.87 101.143 1.128903 20000 132.719 435.32 149.830 1.128922 40000 382.722 1255.33 432.101 1.129020 63000 654.606 2147.11 739.115 1.129099 80000 844.024 2768.40 953.016 1.129133
 Frequency(Hz) Absorption(dB/1000 ft) Absorption(dB/Km) Absorption(dB/s) Velocity(1000 ft/s Relative Humidity = 70% 20 0.004 0.01 0.005 1.129618 40 0.016 0.05 0.018 1.129619 50 0.025 0.08 0.028 1.129619 63 0.039 0.13 0.044 1.129620 100 0.092 0.30 0.104 1.129623 200 0.284 0.93 0.321 1.129638 400 0.611 2.01 0.691 1.129662 630 0.829 2.72 0.937 1.129673 800 0.947 3.11 1.070 1.129678 1250 1.250 4.10 1.412 1.129683 2000 1.915 6.28 2.163 1.129685 4000 5.056 16.58 5.712 1.129687 6300 11.197 36.73 12.649 1.129689 10000 26.624 87.33 30.077 1.129693 12500 40.758 133.69 46.044 1.129697 16000 65.246 214.01 73.708 1.129704 20000 99.365 325.92 112.254 1.129712 40000 339.153 1112.42 383.165 1.129770 63000 673.667 2209.63 761.137 1.129842 80000 924.481 3032.30 1044.556 1.129884
 Frequency(Hz) Absorption(dB/1000 ft) Absorption(dB/Km) Absorption(dB/s) Velocity(1000 ft/s Relative Humidity = 90% 20 0.003 0.01 0.004 1.130443 40 0.013 0.04 0.014 1.130443 50 0.019 0.06 0.022 1.130444 63 0.031 0.10 0.035 1.130444 100 0.074 0.24 0.084 1.130446 200 0.250 0.82 0.283 1.130457 400 0.621 2.04 0.702 1.130478 630 0.903 2.96 1.021 1.130493 800 1.045 3.43 1.182 1.130498 1250 1.344 4.41 1.520 1.130505 2000 1.892 6.21 2.139 1.130508 4000 4.337 14.22 4.903 1.130511 6300 9.099 29.84 10.286 1.130512 10000 21.133 69.32 23.891 1.130514 12500 32.258 105.81 36.468 1.130516 16000 51.762 169.78 58.518 1.130520 20000 79.424 260.51 89.791 1.130526 40000 290.117 951.58 327.995 1.130561 63000 629.701 2065.42 711.948 1.130612 80000 911.286 2989.02 1030.346 1.130651
 Frequency(Hz) Absorption(dB/1000 ft) Absorption(dB/Km) Absorption(dB/s) Velocity(1000 ft/s Relative Humidity = 100% 20 0.003 0.01 0.003 1.130856 40 0.011 0.04 0.013 1.130856 50 0.018 0.06 0.020 1.130857 63 0.028 0.09 0.031 1.130857 100 0.068 0.22 0.076 1.130858 200 0.234 0.77 0.265 1.130868 400 0.616 2.02 0.696 1.130888 630 0.928 3.05 1.050 1.130902 800 1.087 3.57 1.230 1.130909 1250 1.399 4.59 1.582 1.130917 2000 1.917 6.29 2.168 1.130921 4000 4.140 13.58 4.682 1.130924 6300 8.451 27.72 9.557 1.130925 10000 19.357 63.49 21.891 1.130926 12500 29.461 96.63 33.318 1.130929 16000 47.227 154.90 53.410 1.130931 20000 72.538 237.93 82.036 1.130935 40000 269.598 884.28 304.905 1.130963 63000 601.714 1973.62 680.543 1.131007 80000 888.113 2913.01 1004.492 1.131042

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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