Passive Isolation
Noise reduction from the physical seal of an earphone or earcup, before any electronics.
Last revised
Definition
The mechanical blocking of sound by the ear tip or pad. It is most effective at high frequencies, where active cancellation is weakest.
Why it matters when buying
Fit matters more than the noise-cancelling specification for blocking voices and sharp sounds.
Where you will see it quoted
It appears on almost every specification sheet in this space, usually without the context that makes it meaningful. Here is the same class of figure across hardware we have measured, so you can see the spread a single number hides.
| Device | Headline figure | Price | Our score |
|---|---|---|---|
| Pixel 9 Pro | 6.3in LTPO OLED, 120Hz | £999 | 4 / 5 |
| iPhone 16 Pro | 6.3in LTPO OLED, 120Hz | £1,099 | 4 / 5 |
| Galaxy S25 Ultra | 6.9in LTPO AMOLED, 120Hz | £1,249 | 4 / 5 |
| Nothing Phone 3 | 6.7in AMOLED, 120Hz | £579 | 4 / 5 |
| OnePlus 13 | 6.82in LTPO AMOLED, 120Hz | £899 | 4 / 5 |
Common misunderstanding
Poor fit cannot be compensated for by better ANC — the two work on different parts of the spectrum.
Why the term exists at all
Most specification vocabulary starts as engineering shorthand and becomes marketing language on the way to the box. That journey matters, because the engineering meaning is usually narrow and conditional while the marketing use is broad and unqualified. When a term feels like it is doing a lot of work in a product description, it is usually being asked to carry more than it originally meant.
How to spot it being misused
- It is quoted without the conditions the measurement was taken under
- It appears as a single number where the honest answer is a range
- It is compared across manufacturers who do not measure it the same way
- It is given prominence on a product whose weaker specifications are harder to find
How to weigh it against everything else
Treat it as one input among several rather than a decider. A specification only earns its place in a decision when you can name the task it changes — if you cannot, a better figure will not improve anything you actually do with the device. The reverse is also true: where it does map onto something you do daily, it is worth paying for and worth ignoring the rest of the sheet over.
In one line
Noise reduction from the physical seal of an earphone or earcup, before any electronics.
Behind this page
This reference page is written from the same testing notes as the reviews it supports, and it is revised whenever the hardware or the software underneath it changes. Where a figure appears here it has been measured rather than quoted from a specification sheet.
If something on this page no longer matches what you are seeing, it is out of date rather than disputed — tell us and it gets checked again.
Related reading
The reviews this page supports go into the measurements behind these figures, and the knowledge base collects every reference page we keep.
Elsewhere in glossary: Peak vs Sustained Brightness, PoE and Refresh Rate.