Do all ANR headsets work the same?

In general, they all utilize the same acoustic theory of 180° out-of-phase signal to cancel engine noise.  In truth, performance varies significantly among active headsets so it's important to compare them, both with technical specifications and in actual flight.  Manufacturers make a variety of tradeoffs in dome cavity design, ANR mic position, electronics complexity, and earseal size, shape, and materials in developing a product.  Many are constrained by an existing passive design, leading to suboptimized efficiency and effectiveness.  Ultimately, the headset delivers a curve of cancellation that can be characterized by depth, breadth, and position of cancellation.  Manufacturers should be able to supply you with that information for comparison.
 

How does ANR work?

The ANR microphone located inside the dome senses noise frequency and amplitude at an instant in time.  The Active Noise electronics "processes" that noise and relays it to the speaker driver.  That speaker adds a signal that is 180° out of phase with the initial noise sensed by the microphone, and the two signals sum to zero canceling each other out.
 

Which headset is quietest?

This is a very subjective question that only partially depends on the characteristics of the headset itself.  Much of what the user calls 'quietness' is related to individual characteristics of hearing and ergonomics that depend on user experience.  Certainly, the most important element of quietness is the acoustic properties of the headset - how well it attenuates noise passively and actively.  Other factors include: how an individual headset fits your head, your hearing acuity (the efficiency and capability of your ears), the noise environment you are in, whether from piston or turbine driven aircraft.  Beyond just the technical parameters of quiet, each individual has personal preferences relating to weight, side pressure, and user interface issues such as battery size/usage and auto shutoff.  You will need to experience the sound of silence to decide for yourself.

Customer Service Innovations

  5 year warranty
  48 hour service turnaround on most repairs

Convenience Innovations

  Independent volume adjustments for left and right ears
  Stereo and mono switchable
  Up to 40 hours battery life from just two AA's
  All models come with protective carry and storage case
  All models come with mic wind muff
  Bass and treble boost on Zulu series
  All models feature Bluetooth or Jackcord (supplied) cell/sat phone or auxillary audio connectivity