Owen PalmerBy Owen Palmer

Updated November 2026

The Bose QuietComfort 20 acoustic noise cancelling headphones are wired in-ear earbuds that use a small battery-powered circuit to reduce steady background sound. If your pair seems to block less noise than expected, the cause is usually a poor seal, a dead or low battery, a tangled or damaged cable, or an ear tip that does not match your ear canal. Most of these problems can be fixed at home in a few minutes.

Why the QuietComfort 20 Seems to Block Less Noise Than Expected

The QuietComfort 20 is an in-ear model, so its noise reduction depends on two things working together: the passive seal your ear tip makes with your ear canal, and the active circuit that generates an opposing sound wave to cancel low-frequency rumble. When either part is compromised, the result feels like weak cancelling. Owners often report that the difference is most noticeable on airplane engine drone and subway rumble, while sharp, higher-pitched sounds such as voices or keyboard clicks pass through more easily.

Shopping for one? See our guide: Bose QuietComfort Ultra Noise Cancelling Headphones Review: Is It Worth It?.

Because the active circuit is designed mainly for steady, low-frequency noise, you should not expect it to erase conversations or sudden noises. Setting that expectation early makes it easier to tell whether your pair is actually faulty.

The Main Factors Behind Weak Noise Cancelling

Ear Tip Fit

The ear tip is the single biggest factor. The QuietComfort 20 ships with multiple tip sizes, and a tip that is too small will let air leak past the seal. Insert the tip gently, turn it slightly, and check that it sits snugly without causing pressure. A correct fit usually makes a clear change in bass level within seconds. For another angle, check out Quietcomfort 20 Acoustic Noise Cancelling Review: Is It Worth It?.

Battery and Power Source

The noise cancelling circuit draws power from a small internal battery that is charged or replaced depending on the model variant you own. Bose specifies that the battery should be checked before every extended listening session. A low battery typically produces a noticeable drop in cancelling strength, sometimes with a faint hiss or a change in tone.

Cable and Connection Condition

Because these are wired, the cable carries both the audio signal and the power connection to the control unit. Cable strain near the earpiece, a bent plug, or a loose connection at the jack can cause crackling, intermittent cancelling, or one side that sounds quieter than the other. Check each end of the cable before assuming the electronics have failed.

Environment and Noise Type

Steady, low-frequency noise such as engines, fans and air conditioning is where active cancelling does its best work. Speech and sudden impacts are far harder to reduce, so a pair that handles a bus engine well may still let coworkers’ voices through. Testing against the right kind of sound gives a fairer picture.

What to Do About Weak Cancelling

Work through these checks in order. Most owners find the problem in the first two steps.

  1. Clean the ear tips and the mesh openings with a dry cloth. Earwax and dust reduce the seal and can muffle sound.
  2. Try each ear tip size and choose the one that gives the deepest bass with no discomfort.
  3. Check the battery level or replace the battery according to the instructions for your variant.
  4. Inspect the cable for kinks, cracks or fraying, and reseat the plug firmly in the jack.
  5. Test on a steady sound such as a fan or engine to isolate whether the cancelling itself is working.
  6. If one side is weaker, swap the earpieces to see whether the fault follows the earpiece or the cable.

If the problem continues after these steps, contact Bose support or an authorized service center. Avoid opening the control unit yourself, since that can damage the circuit and affect any warranty coverage.

What we’d use

If you want a replacement for the ear tips or a clean cable, look for tips that match the original size and material so the seal stays consistent. Owners who rely on these headphones for travel often find that a foam or silicone tip set in a small size improves the seal on smaller ear canals. You can search for these directly:

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For a more complete setup, a replacement cable in the same connector style can rule out a damaged lead. Confirm the connector type matches your model before buying.

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Are the Bose QuietComfort 20 acoustic noise cancelling headphones wired or wireless?

They are wired. The cable connects the earpieces to a control unit that powers the noise cancelling circuit and carries the audio signal.

Why does one ear sound quieter than the other?

This usually points to a poor ear tip seal, a damaged cable on one side, or a loose connection at the jack. Swapping earpieces helps you locate the fault.

Do these headphones cancel voices?

They are designed mainly for steady, low-frequency noise. Speech is only partly reduced, so expect the best results on engines, fans and similar constant sounds.

How often should I check the battery?

Check it before long trips or extended listening sessions, and follow Bose’s guidance for your specific variant when replacing it.

Should I open the control unit to fix it?

No. Opening it can damage the circuit and may void your warranty. Contact Bose support or an authorized service center instead.

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Owen Palmer

About Owen Palmer

Owen Palmer is part of our editorial team and reviews and edits our brand headphones & noise cancelling guides, checking product details against manufacturer specifications and owner feedback.