Path: utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!bu.edu!att!cbnews!cbnews!military From: oink!jep@cis.ohio-state.edu (James E. Prior) Newsgroups: sci.military Subject: Re: Offensive use of Sound possible? Message-ID: <1991Feb4.065220.21503@cbnews.att.com> Date: 4 Feb 91 06:52:20 GMT References: <1991Jan21.041118.5204@cbnews.att.com> <1991Jan22.021825.22248@cbnews.att.com> <1991Jan24.044530.26622@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: Random Prime Research Institute Columbus, Ohio Lines: 61 Approved: military@att.att.com From: oink!jep@cis.ohio-state.edu (James E. Prior) In article <1991Jan24.044530.26622@cbnews.att.com> rubin@cis.ohio-state.edu (daniel j rubin) writes: ...>I would think that a super high power ultrasonic >transducer array of some sort could be placed on top of very tall towers all >across the nation in a grid with one every several miles. If there was a >national nuclear or whatever attack these transducer would direct a powerful >wave of ultrasonic sound upward with every one of the stations in phase >with each other. This huge ultrasonic wave generated in the middle-atmosphere >would break up any warheads, plane or whatever that was in the atmosphere >directly over US territory. > > - Dan Rubin Sound at high frequencies attenuates greatly over distance. The air would heat up. At best, rapid heating of the air by ultrasound would cause it to expand rapidly, i.e. boom. I list some data concerning absorption of sound in air from 56th Ed. of CRC's Handbook of Chemistry and Physics: The follow data refer only to the temperature 20C (68F). Ther were abstracted from an extensive compilation prepared by L.B.Evans and H.E.Bass. The entire report, Tables of Absorption and Velocity of Sound in Still Air at 68F (20C), AD-738 576 is available from National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Va. 22151 Frequency Absorption Absorption @ 0% Rel Hum @ 100% Rel Hum Hz dB/Km dB/Km 20 0.51 .01 40 1.07 .04 50 1.26 .06 63 1.43 .09 100 1.67 .22 200 1.84 .77 400 1.96 2.02 630 2.11 3.05 800 2.27 3.57 1250 2.82 4.59 2000 4.14 6.29 4000 8.84 13.58 6300 14.89 27.72 10000 26.28 63.49 12500 35.81 96.63 16000 52.15 154.90 20000 75.37 237.93 40000 267.01 884.28 63000 644.66 1973.62 80000 1032.14 2913.01 Note the extreme attenuation of high frequencies. Note how music, thunder, cars and gunshots sound more muffled and boomy the further away they are. This means that high frequency sound weapons must generate their sound close to their target. The loudest sound generators remain to be explosives. The trick remains to be placing them close to their targets. -- Jim Prior jep@oink osu-cis!n8emr!oink!jep N8KSM