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  In flight audio output from the Enhanced Noise Reduction Intercom. Click to listen.     

   In flight audio from a voice operated intercom. Click to listen.

The recorded audio is audio from the intercom output.  Depending on the passive or acoustic noise reduction quality of the headset, some ambient noise will be heard through the ear cup.  The recorded audio is what is heard through the headphone's ear cup speaker.

*These audio clips work best with Internet Employer 5 or later and versions of Netscape above 4.6.

Functional diagram displaying the difference between the Enhanced Noise Reduction Technology and 30 year old Voice Operated technology


*Note: the microphone symbol on the input of the diagrams, is actually the headset microphone, not a separate microphone.

Questions & Answers

  •  What is Enhanced Noise Reduction ?
  •  With a voice operated intercom, wind and engine noise is heard when the headset's microphone audio path is open.  Depending on the intercom and headset microphone, the background sounds can be quite annoying.  With voice operated intercoms, you have to kick start the audio path by speaking and then after stopping,  the microphone is open allowing background noise to be heard until the audio path closes.  This is the case with either manual or auto-squelch systems.

    ENRI eliminates what the open microphone hears and you the pilot don't want to hear -  that rushing wind sound and engine noise.  Since the microphones are open all the time with ENRI, there are no missed words or audio drops between words,  and no background noise,  even while you are talking.

  •  What is the Difference between ENRI and ANR headsets?
  •  In an ANR headset, a small microphone in each ear cup shifts the sound 180 degrees out of phase from the direct sound that the ear hears,  canceling out the noise and giving additional noise reduction to the acoustical reduction of the ear cups.   This ANR reduction works with a small band of the audio spectrum, usually 30 hz to 400 hz.    Above the ANR band pass frequency, the headset is the basic Passive Headset.

The typical headset microphone will pick up sounds ranging from 30 hz to 4000 hz,  leaving a broad noise range above 400hz, not canceled by ANR.   With a Voice Operated intercom,  sounds about the 400hz audio range are passed to the intercom and heard in both ANR and Passive headsets.

ENRI takes over where the ANR headsets leave off, canceling audio noise across the 40hz to 4000hz that is picked up by the headset's microphone, which includes wind noise and high pitch engine sound.

  •  Will I hear additional noise reduction with passive headsets?
  • ENRI will not increase noise reduction of acoustical or passive reduction headsets.


  • Open Cockpit Aircraft
  •  Open cockpit aircraft present the greatest challenge to eliminating or reducing noise during communications.  Because the ENRI circuit works on noise levels,  some cases, such as engines producing very high noise levels during take off, may exceed the threshold of the circuit and will be heard.

Wind blowing across the microphone may also create a beating noise that will be heard.

In either case, it is recommended that wind muffs be added to the microphones.  The foam type will improve the communications in most applications but in some extreme cases, a combination foam and leather muff made by Oregon Aero greatly improves communications.

Oregon Aero Link.




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Copyright 2011 DesignTech Systems, Inc.
Last modified: Jan. 8, 2014