What is CustomTune technology on the Bose QuietComfort Ultra Earbuds 2nd Gen?

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You might have noticed your earbuds play a quick sound every time you put them in. That's CustomTune doing its thing—and it's actually pretty clever technology.

What's Actually Happening

Everyone's ears are shaped differently. Like, really differently. And that affects how sound reaches your eardrum. What sounds perfect for one person might be bass-heavy or tinny for someone else, even with the exact same earbuds.

Bose's solution? Measure your specific ears and adjust accordingly.

The Quick Science

When you pop in the QuietComfort Ultra Earbuds 2nd Gen, you'll hear a brief tone—just a second or two. During that moment, tiny microphones inside the earbuds measure how that sound bounces around your ear canal. Then the earbuds adjust their output to compensate for your unique ear shape.

It's like having a sound engineer fine-tune your audio setup, except it happens automatically every time you use them.

What Gets Adjusted

Sound Quality: The frequency response changes to deliver balanced bass, mids, and treble specifically for your ears. What the engineers intended you to hear is what you actually get.

Noise Cancellation: The seal between your ear tips and ear canal matters a lot for ANC. CustomTune measures that seal and optimizes the noise cancellation to work with whatever fit you have.

Transparency Mode: Even the Aware mode gets tweaked so external sounds come through naturally.

Getting the Best Results

The calibration is only as good as your fit. Make sure you've got the right ear tip and stability band sizes before you start. If things sound off, try a different size and let CustomTune recalibrate—it happens automatically each time you insert the earbuds.

Pro tip: A quiet environment helps the calibration work better, though it's usually fine in most normal conditions.