Description / Abstract:
This Aerospace Recommended Practice (ARP) defines quantities
that may be used to describe various attributes of the sound field
in the interior of aircraft. For a particular aircraft, or for a
specific situation in a particular aircraft, it may not be
necessary to utilize all the quantities included here to provide an
adequate description of an aircraft's interior acoustical
environment.
The scope of this document includes frequency-band sound
pressure levels, wideband sound pressure levels, frequency-weighted
sound pressure levels, and quantities that may be calculated from
band sound pressure levels. The primary frequency bandwidths are
those of octaves and one-third octaves.
This ARP does not include recommendations for specific
quantities to use in a given situation, nor does it include
specific numerical values of any quantity for use in evaluating the
acceptability of the acoustical environment in the interior of an
aircraft.
Definitions in this document are compatible with procedures in
SAE ARP1323A (Reference 1), ARP1964 (Reference 2), and the
International Standard ISO 5129 (Reference 3) for measurement of
aircraft interior noise. The definitions are also compatible with
standards on acoustical terminology (References 4 and 5) and with
standards on preferred abbreviations, quantity symbols, units, and
unit symbols (References 6 and 7). If no abbreviation or quantity
symbol is given, then, for the purposes of this document, none is
recommended.
Quantities defined in this document may be used to describe the
acoustical environment in the interior of any kind of a aircraft
including jet-propelled and propeller-driven airplanes and
rotorcraft. The quantities are applicable to measurements of
aircraft interior noise where the sound pressure levels are
relatively steady so that valid time-averaged measurements may be
obtained in a reasonably short measurement period. If the sound
pressure level is not relatively steady, then additional quantities
other than those in this document may be needed for an adequate
description of the acoustical environment. Example of nosteady
sounds include those that occur during takeoff, climbout, descent,
and landing.
Abbreviations are most useful for column headings in tables and
for printing by machines not able to print lowercase letters.
Quantity symbols are recommended for us in equations.