Direct answer
For the Bose QuietComfort Earbuds II, fit/seal, microphone obstruction, mode, adaptive settings and hardware should be separated. First, clean approved microphone areas and confirm fit.
What this covers
- Bose QuietComfort Earbuds II (870730)
- Bose product; Bluetooth multipoint, app generation, wired input and spatial/ANC features vary.
- The specific fault this record addresses: noise cancellation or transparency is not working correctly
What it does not cover
- ×The same symptom on a different Bose product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The ear tips do not seal
What separates it Weak cancellation and thin bass, both of which improve when the bud is pressed gently into the ear.
How to confirm Seal is the single largest factor in perceived cancellation. Try the other tip sizes supplied — most people have differently sized ear canals and many never change from the default medium tips.
- 2
The microphones are blocked
What separates it Cancellation degrading over time, with visible debris in the small microphone openings.
How to confirm ANC microphones are tiny external openings that collect wax, dust and lint. Clean them carefully with a dry soft brush.
- 3
The noise is speech or sudden sounds
What separates it Good cancellation of engine and fan noise, poor cancellation of conversation nearby.
How to confirm ANC works best on steady, predictable low-frequency sound. Speech is neither, so it is deliberately much less affected — this is inherent rather than a defect.
- 4
The mode has been switched
What separates it Cancellation absent entirely, or outside sound unusually loud.
How to confirm Most models cycle between cancellation, transparency and off, often on a touch gesture that is easy to trigger accidentally. Transparency deliberately amplifies outside sound.
- 5
Wind is overwhelming the microphones
What separates it A loud rushing or roaring outdoors in wind.
How to confirm Wind across the ANC microphones is amplified by the system itself. Most models have a wind-reduction mode or work better with ANC off outdoors.
- 6
Firmware needs updating
What separates it Cancellation behaving differently after a change, or a known issue in a specific release.
How to confirm See app-update. ANC tuning is frequently adjusted in firmware.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- Whether cancellation improves when the earbud is pressed gently into the ear, which identifies seal as the limiting factor.
- Which mode is actually active — cancellation, transparency or off.
- What kind of noise it is failing on: steady low-frequency, or speech and sudden sounds.
- Whether the microphone openings are clear.
Try every ear tip size supplied
ReversibleSeal is the largest single factor in cancellation, and most people never move off the default medium tips even when another size fits better.
Press the bud gently into the ear and listen for the difference
ReversibleA clear improvement confirms seal rather than the ANC system as the limiting factor.
Confirm which mode is active
ReversibleTransparency deliberately amplifies outside sound, and the gesture that switches modes is easy to trigger by accident.
Clean the external microphone openings with a dry soft brush
ReversibleThey are tiny and collect wax and lint, which degrades cancellation gradually.
Judge cancellation on steady low-frequency noise, not speech
ReversibleANC is inherently far less effective on voices and sudden sounds; that is the technique's limit rather than a fault.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- 870730. Bose product; Bluetooth multipoint, app generation, wired input and spatial/ANC features vary.
- Type — ANC Bluetooth earbuds (battery)
- Bose's standard flagship-ANC earbuds (no Immersive Audio — that is the Ultra) with a charging case. Battery/ANC/Bluetooth and earbud-specific symptoms (fit, tips, case contacts) apply.
- Fit & CustomTune
- Fit bands plus ear tips, with CustomTune calibration at insertion; ANC and bass depend on the seal, so wrong-sized tips/bands are the usual cause of thin sound or weak ANC.
- Case & battery
- Buds charge in the case; dirty case contacts leave a bud starting low. ANC on at high volume shortens runtime.
- Power path
- Internal or removable battery. Every capability that costs current — night vision, higher stream quality, longer recordings, frequent events — is paid for in runtime, so a change in behaviour after a settings change is usually a power consequence rather than a fault. Cold weather reduces usable capacity sharply.
- Symptom boundary
- This record covers Bose QuietComfort Earbuds II when it noise cancellation or transparency is not working correctly. A different symptom on the same hardware, or this symptom on a different Bose product line, has its own record with its own causes and its own cited source.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. Bose Support publishes this as "QuietComfort Earbuds II: noise cancellation is not working". Bose's own article for this symptom on this product. The title here is read from the article's URL slug: support.bose.com serves the <title> "Customer Support" on every page, so there is no published title to copy. Probed 2026-08-23: 200 against a hard-404 control, which is what discriminates on this host. What that article does not carry is the model boundary — it is written for a product line, and 870730 is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
One of my Bose QC Earbuds II won't charge in the case.+
Clean the charging contacts — earwax and lint on the bud's contacts and the matching pins in the case are the common cause of one bud not charging, so wipe both with a dry cotton bud. Make sure the bud seats fully in its slot (a magnet should pull it in). If a bud still will not charge or connect, reset the earbuds per Bose's steps and re-pair. The buds also pair to each other, so a dropped link between them can leave one silent.
Noise cancellation seems much weaker than it should be.+
Try the other ear tip sizes in the box. Seal is by far the biggest factor in how much cancellation you actually get, and most people stay on the default medium tips even when a different size would fit better. A quick test: press the bud gently further into your ear — if the cancellation and the bass both jump, seal is your limiting factor, not the ANC system.
Why can I still hear people talking?+
That is inherent to how ANC works rather than a fault. It cancels by generating an inverted copy of incoming sound, which works very well on steady, predictable low-frequency noise like engines, aircraft cabins and fans — and much less well on speech, which is neither steady nor predictable. No headphone cancels conversation the way it cancels an aeroplane.
Does this answer apply to every Bose model?+
No. It is scoped to 870730. Bose product; Bluetooth multipoint, app generation, wired input and spatial/ANC features vary.
What should I record before troubleshooting ANC or noise cancellation?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing ANC, noise cancellation. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Stop for loud feedback, pain, heat or liquid damage.
Answer for the exact device and software version shown above.