An IP rating is two digits, and each digit is a different test.
The first covers solid objects, which in practice means dust. The second covers water.
IPX4 therefore reads as: not rated for dust, protected against splashes from any direction.
IP55 reads as: protected against dust in useful quantities, and against low-pressure water jets.
The letters stand for Ingress Protection, and the tests are set out in the international standard IEC 60529.
The X is not a zero, and that distinction costs manufacturers money
An X means the manufacturer did not run that test, not that the product failed it.
Most earbuds are IPX-something for a straightforward commercial reason.
Dust testing is expensive, and dust is rarely what kills a pair of earbuds.
So the first digit is skipped and the second is certified, which is why IPX4 appears on so many boxes.
Sony's flagship carries IPX4, as our Sony WF-1000XM6 review: the 5 numbers that decide whether it's worth ยฃ300 notes, at around ยฃ300.
Anker's Soundcore Liberty 5, at roughly ยฃ110, carries the fuller IP55 โ dust included, for a third of the money.
Each water level is a specific laboratory procedure
Level 4 is a spray test: water from every direction, for ten minutes, with no harmful effect.
Level 5 steps up to a jet from a 6.3 mm nozzle at a defined pressure and distance.
Level 7 is complete immersion, one metre down, for thirty minutes.
Levels up to 6 build on one another. Levels 7 and 8 are separate immersion tests and do not guarantee jet resistance.
Every one of those tests uses clean, still, room-temperature fresh water.
That single detail is where most of the misunderstanding lives.
Sweat is a harder problem than rain
Sweat is salty, mildly acidic, and it arrives warm and stays put.
Salt water conducts, corrodes and creeps into seams in a way that tap water does not.
No IP digit tests for it, which is why some manufacturers quote a separate sweat-resistance claim.
IPX4 is nonetheless the sensible floor for anything worn in a gym.
Rain is the easier case. A shower on the walk to the station is squarely within IPX4, and a downpour is closer to the edge of it.
Water resistance is a description of one product, on one day, in one laboratory. It is not a permanent property.
The rating describes a new earbud, not a two-year-old one
Rubber gaskets harden. Adhesives fatigue. Mesh screens clog and hold moisture against the shell.
A single drop onto a hard floor can break a seal without leaving a mark on the casing.
Charging a damp earbud is the other classic mistake, because current plus moisture plus metal contacts corrodes quickly.
Dry the buds properly before they go anywhere near the case.
Water damage is also excluded from most manufacturer warranties, IP rating or no IP rating.
Many earbuds carry a moisture indicator inside, and a repair centre will check it before anything else.
The case is unrated, and it is the expensive half
Almost no charging case carries an IP rating of any kind.
It has a hinge, a lid seam and exposed metal contacts, none of which seal.
A case left in a coat pocket during a downpour is at considerably more risk than the buds inside it.
Which is the small irony of the whole system: the rated component is the one you could most easily replace.
