Guides · Audio and hearing
What noise cancelling can and cannot do
It silences the drone of an aeroplane and not the child in the next seat.
How it works
Small microphones on the headphones listen to the sound around you. The electronics then play the opposite sound into your ear, so the two cancel. This works best on steady, low drones: the roar of an aeroplane cabin, a fridge, an air conditioner, the hum of a train. The sound has to be steady for the electronics to keep up with it.
What it leaves alone
Voices, cutlery, a door, a dog, a child: anything sudden or high is largely untouched. A sudden sound is over before the electronics can answer it. A high sound changes too fast for the answer to line up. What you get for those sounds comes from the seal of the earcups or the tips, which is the old kind of quiet. That is why a well-fitting pair with no cancelling at all can beat a loose pair with it. Nothing is wrong with your headphones when a conversation still gets through.
Why it matters for your hearing
Loudness climbs by multiplying. Ten decibels more is ten times the power and about twice as loud to the ear. Much of the time, people turn music up to beat the noise around them, not because they want it loud. Headphones that shut the world out let you turn the volume down, and over the years that is what protects your hearing. A rule of thumb worth keeping: under about 60 per cent of the maximum, and a break after about an hour.
Hearing loss usually takes the high notes first, and the high notes carry the consonants. Speech turns to mumble before it turns quiet, which is why turning the television up does not always help. If people seem to mumble more than they used to, a hearing test is quick, and it will say which notes have gone.
In the shop
Try the pair somewhere noisy, not in a quiet shop. Check that the cups or tips seal without pressing. Ask whether the battery can be changed, because in most earbuds it cannot, and the pair lasts only as long as the cell does.
More guides
- Network and Wi-Fi Where to put the router
The engineer left the socket in the cupboard. What to do about that, and when a second unit earns its money.
- Smart home Before you buy a smart plug
A lamp comes back on; a television just sits there. The guide sorts the house into those two piles, and asks one question about the broadband first.
- Health and personal care What a bathroom scale actually measures
Strain gauges, a small current and an equation: what each number on the screen rests on, and how to get something useful from it anyway.