FAA paper Noise Attenuation Properties of Noise-Canceling Headsets

InFO

Information for Operators

U.S. Department InFO 07001

of Transportation DATE: 1/5/07

Federal Aviation Flight Standards Service

Administration Washington, DC

http://www.faa.gov/other_visit/aviat...ne_safety/info

An InFO contains valuable information for operators that
should help them meet certain administrative, regulatory, or
operational requirements with relatively low urgency or
impact on safety.

SUBJECT: Noise Attenuation Properties of Noise-Canceling
Headsets

Purpose: This InFO alerts operators, directors of operations
(DOs), chief pilots, and flight crewmembers who may be using
noise-canceling headsets of the potential for misdetection
of audible alarms and other environmental sounds.

Background: Ordinary (non-noise-canceling) headsets reduce
ambient noise levels through a physical means by providing
some acoustical quieting. Noise-canceling headsets cancel
noise through a combination of physical means and electronic
means. While this technology can have many beneficial
effects such as providing clearer communications, reduced
pilot fatigue, and added comfort, electronic attenuation of
important environmental sounds and alarms may occur.

Discussion: Noise-canceling headsets are most effective over
a narrow frequency range, but the specific frequencies may
vary by make and model. Also, these electronically
attenuated frequencies are often proprietary to the
manufacturer and may not be publicly available. Therefore,
it is difficult to assess any effects the headsets may have
on discerning environmental sounds such as:

.. Vital communications between flight crewmembers or flight
attendants, other than those attainable through interphone
operations;


.. Abnormal mechanical noises or abnormal engine sounds;


.. Audible alarms other than those discernible by electronic
means;


.. Vibrations or wind noises; or


.. Other aircraft during ground operations.

Recommended Action: Operators, DOs, chief pilots, and
crewmembers of aircraft should evaluate their use of
noise-canceling headsets. The FAA recommends sampling the
available manufactured makes and models when performing such
evaluations, since performance and attenuation properties
vary. Evaluations should be conducted while both on the
ground and in flight during normal operating conditions to
ascertain if any audible alarms or other environmental
sounds, or combinations thereof, can be detected while
electronic noise attenuation is on and active. If any
audible alarms or environmental sounds cannot be discerned,
operators should elect to find other solutions to discern
such alarms or sounds, or discontinue the use of
noise-canceling headsets.

Approved by: AFS-200