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Dec 15, 2016

QC35 ANC Troubleshooting and Informational Guide

Hello everyone!


We have split this post into two segments beginning with troubleshooting steps followed by a section on ANC.  

Thank you for reading and we hope that you will find this useful!


Troubleshooting steps for poor noise cancellation on the QC35:


  • Be sure the headset is turned on. The switch on the right earcup should be in the "On" position with the green LED illuminated. The headset must be turned on to cancel noise.
  • Double check that the cushions are securely attached to the earcup. If the ear cushion is not affixed to the ear cup properly, the noise reduction may be affected.
  • Check to make sure the headset is fully seated and the ear cushions are in good shape as the seal they provide is extremely important for noise cancellation performance.
  • Verify the noise cancellation mode you are in through the Bose connect app.  These modes are designed to customize the noise cancellation effect for different environments and may sound very different from one another.  A video detailing these modes can be found HERE.


The “hiss” that may be heard with some noise reduction headphones is the electronic noise floor. This noise can be annoying and can take away from listening enjoyment. QuietComfort 35 headphones use electronic circuitry to minimize the noise floor.


How Acoustic Noise Cancellation technology works :


Acoustic Noise Cancelling headphone technology is a method of reducing unwanted noise by electronically creating a signal that is the mirror image of the unwanted noise. Microphones in the earcups monitor sound at the user’s ear and externally. The monitored sound (music and noise) is compared to the sound the user wants to hear (the signal coming from the audio input—this could be music or silence). The difference between the monitored sound (from the earcup’s microphone) and the sound the user wants to hear (music or silence) is noise. The electronics in the QuietComfort 35 wireless headphones instantly process the noise signal, and a precisely equal and opposite signal (correction signal) is created. This opposite signal is then sent to the speaker in the earcup along with the sound the user wants to hear (again, this could be music or silence). The result is three signals being presented to the user’s ear: Noise from the environment, the sound the user wants to hear and the correction signal from the electronics. The noise and the correction signal nearly cancel each other, providing a clean, high-fidelity sound signal at the ear.


ANC is most effective in environments with lots of low-frequency "droning" type sounds (Examples: Buses, air-conditioning, airplane engine noise, etc).  We find that the noise cancellation effect may not be quite as effective on "transient" or "sharper" sounds in some environments. (Examples: The human voice, quick loud noises, babies crying, etc.) 


We do not make any claims to cancel 100% of sound because it is difficult to establish one number that is valid for different environments and situations. QuietComfort 35 headphones compare very favorably to other noise reduction headphones and reduce unwanted noise to a level that is noticeably more comfortable when compared to the same situation without using the headphones. We encourage consumers to try it for themselves in a variety of situations, both with and without an external audio source.


Noise reduction in the QC35 headphones is achieved by utilizing both active and passive noise reduction technologies. They use a proprietary electronics approach to active noise reduction, placing microphones both inside and outside of the earcups. The electronics system senses the sound in an environment and then measures, compares and reacts—instant by instant—to produce an opposing cancellation signal. Through a combination of advanced active electronics and passive attenuation, QuietComfort 35 headphones reduce noise across the full range of human hearing. The passive noise reduction is achieved by the combination of the acoustic design and materials chosen for the earcups and cushions.


Believe it or not, the positioning and condition of the headset's ear cushions are a critical factor in the performance of ANC. Obviously ensuring that the headset is positioned properly on the user's head (with the power switch on the right) is important, but the seal around the ears is incredibly important as well. 


A common cause of non-performing ANC relates to the integrity of the ear cushion's contact to the headset itself and its condition. We've recently come across a QC35 where the scrim of the ear cushion became dislodged slightly from the teeth that hold it in place. The headset had a significant drop in their ANC performance. When we investigated, pulled back the ear cushions a bit, this is what we found:




Once we removed and reseated the ear cushion properly, it was as good as new.  Here's a great video we found that gives a great step-by-step instruction of the process:


Other instructions can be found at our own Support Page


It's also worth noting that replacement cushions are offered in the event that the cushions become excessively dirty or damaged in some way.  Contact your local support team or go to to order them. 


Thank you all again for taking a look at this information, we hope that it helps! 


Be well,

Mohsin - Community Support