<DOC>
<DOCNO>
805
</DOCNO>
<TITLE>
ground measurements of the shock wave noise from airplanes
in level flight at mach numbers to 1. 4 and at altitudes
to 45,000 feet .
</TITLE>
<AUTHOR>
maglieri,d.j., hubbard,h.h. and lansing,d.l.
</AUTHOR>
<BIBLIO>
nasa tn.d48, 1959.
</BIBLIO>
<TEXT>
  time histories of noise pressures near ground level were measured
during flight tests of fighter-type airplanes over fairly flat, partly
wooded terrain in the mach number range between 1.13 and 1.4 and at
altitudes from 25,000 to 45,000 feet .  atmospheric soundings and radartracking
studies were made for correlation with the measured noise
data .
  the measured and calculated values of the pressure rise across the
shock wave were generally in good agreement .  there is a tendency for
the theory to overestimate the pressure at locations remote from the
track and to underestimate the pressures for conditions of high tailwind
at altitude .  the measured values of ground-reflection factor averaged
about 1.8 for the surfaces tested as compared to a theoretical value
of 2.0 .  two booms were measured in all cases .  the observers also
generally reported two booms,. although, in some cases, only one boom
was reported .  the shock-wave noise associated with some of the flight
tests was judged to be objectionable by ground observers, and in one
case the cracking of a plate-glass store window was correlated in time
with the passage of the airplane at an altitude of 25,000 feet .
</TEXT>
</DOC>
