Says Pilots Should Check They Can Still Hear Alarms
The Federal Aviation
Administration has issued an Information For Operators (InFO)
message advising operators, pilots, and flight crewmembers who may
be using noise-canceling headsets of the potential for misdetection
of audible alarms and other environmental sounds.
Ordinary, non-noise-canceling headsets reduce ambient noise
levels through a physical means by providing some acoustical
quieting -- often by use of low-density padding, which is effective
against low-frequency noises (think engine noise) but, in most
cases, still allows the user to detect higher-pitched
tones.
Noise-canceling headsets block noise through a combination of
physical 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.
As noise-canceling headsets are most effective over a narrow
frequency range -- though specific frequencies may vary by make and
model, and are often proprietary to the manufacturer -- the FAA
says 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.
The FAA recommends all affected flight personnel should evaluate
their use of noise-canceling headsets. The agency recommends
sampling the available manufactured makes and models when
performing such evaluations, since performance and attenuation
properties vary.
The InFO states
evaluations should be conducted while both on the ground, and
inflight 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.
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.