From: jameshartman@tsrcom.com Date: Aug 26 1996 AUDIO1.ASC -------------------------------------------------------------------- The following appeared in the prestigious Electric Spacecraft Journal - Issue #8, Published May 3, 1993. Page 40. 旼컴컴컴컴컴컴컴컴컴� � Information from � � Charles A. Yost � 쿏ynamic Systems Inc� � 73 Sunlight Drive � 쿗eicester, NC 28748� 읕컴컴컴컴컴컴컴컴컴� After James Hartman described making a loud- speaker levitate (ESJ#6, page 43), I decided to see if a loudspeaker could produce a net thrust. Apparently it can. I used a ten-inch diameter, eleven- pound Altec woofer suspended in pendular fashion by a pair of 38-inch long strings. (See Figure 1.) A constant 20 to 40 Hz high amplitude sine wave input didn't cause the slightest movement. However, quick pulsing of the sound in this frequency range was able to cause the woofer to swing in pendular fashion. The amplitude of the swing could be progressively ______________ 3 ^ | 8 | <-- | --> 1/2"| | /| air flow \ / | / | --- 栢 | 컴컴�> \ | 11 lb.\| Figure1. Speaker suspension increased if the sound pulses were timed to occur as the speaker was swinging through center. The maximum amplitude was about 1/2 inch. The voice coil chamber of the speaker was about three inches in diameter and two inches deep with a 3/4-inch central hole through which the air pulsed. A fine thread on a small stick allowed the airflow to be distinguished. (See Figure 2.) It is my thought that a very transient sound pulse sets up a brief unbalanced air flow and projects the equivalent of a smoke ring away from its face. Is there an equivalent electrostatic pulse phenomenon?* | | /| | / / Inward | / / Pulsed 栢賽N / air flow 幡___. . . . . 栢 S . ---> .---> .---> ----> 栢 S . .. .. Outward 幡___. pulsed 栢 N\ air flow 栢複 \ \ \ \ \ \| internal construction Figure 2. Speaker Design