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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 | 0.154 | 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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Kirt
