What do you expect in a set of $15 noise - cancelling headphones? If you answered “not a whole lot,” then you might like these Philips SHN2500 earbuds.

Construction

Good news: it uses only one, small AAA battery, and an AAA is included in the box.
Bad news: the earbuds dont work when the battery dies. No, I dont mean the obvious - that the noise-cancelling fails. Of course it fails without power. When the battery dies, the earbuds will not play audio. Hmm. You could compare this to a car’s thermostat failing closed,causing the engine to overheat rather than failing open and causing the engine to run roughly.

Other construction notes are these:
_Battery/on/off switch is large, maybe larger than it needs to be, daresay I, non-engineer.
_earbud ear canal adaptors come in a handy three sizes, but they tend to slip off in bags and pockets, and at the size and weight of Cheerios, are easily lost.
_the mini-jack is not iPhone friendly, unless you modify it by trimming/whittling off a bit of pliable, casing plastic, a tactic I’ve used with success on a half-dozen mini jacks.
_the on/off switch is large and I suspect easily toggled by shit in your luggage, purse or pocket.

Performance

So-so. In a bar/cafe, noise reduction sliced perhaps 10-20% off the general aggregate patron mumble. I’m writing this on my iPhone on a flight to Seattle, and the drone of engines is at least halved, making the value of these earbuds increase quite a bit in my estimation.

The seal the buds provide my ears is quite good, and contributes substantially to their performance.

Constant low frequencies seem to be eliminated best, and when noise-cancelling is active, the audio signal is boosted.

Battery life so far is unmeasured, save for the fact that I’m still on the OEM battery after around five hours. I’d expect 20 or more hours of use per battery.

Conclusion

If you have the money, I’m sure there are better-performing noise cancelling earbuds out there. Go get em. For frequent fliers, the poor, or those who are prone to losing things like this, I consider it a fair trade for something that fits inside a twenty dollar bill.