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.

FMI: Learn More About InFO Messages