The mosquito tone
A tone around 17 kHz, audible to most teenagers and to few adults, with an unusually contentious history.
What it is
The mosquito tone is a continuous high-frequency sound, usually quoted at 17 kHz and in practice anywhere between 16 and 18.5 kHz. It is loud and irritating to anyone who can hear it, and completely inaudible to anyone whose hearing has retreated below that frequency — which is most people past their mid-twenties.
The name comes from the whine it resembles. You can test yourself in a few seconds on the tone generator: the 17 kHz preset is there for exactly this. Keep the volume low, because a tone you can barely hear is still reaching your ears at full power.
Why age decides who hears it
High-frequency hair cells sit at the entrance of the cochlea and experience every sound that passes on its way in. They wear with exposure and do not regenerate, so the top of the hearing range retreats steadily through life. By 25 many people have lost 18 kHz; by 40 many have lost 15 kHz. The hearing range by age guide has the usual figures.
The spread is wide enough that some adults hear it clearly and some teenagers do not. Loud-music exposure moves the line, and so does simple individual variation.
Two uses, one controversial
The tone became widely known through a deterrent device marketed in the mid-2000s and installed outside shops and public buildings to discourage young people from gathering. It works by being unpleasant to the group that can hear it and invisible to everybody else, which is precisely what made it contentious: it cannot distinguish between loitering teenagers, babies, or anyone else with intact high-frequency hearing, and it affects people who have done nothing at all.
Children's commissioners and human-rights groups in several countries have criticised such devices on those grounds, and some local authorities have restricted them. The underlying objection is not about the sound but about applying a penalty to a whole age group indiscriminately.
The second use inverted it. Students turned the same tone into a mobile ringtone that teachers could not hear, which spread quickly and briefly made 17 kHz a subject of staff-room discussion.
Testing it properly
A fair test needs three things. Use wired headphones, because several Bluetooth codecs discard content up there before it ever reaches the driver, so a wireless negative result may say nothing about your ears. Sit somewhere quiet, since a faint tone disappears under room noise. And keep the volume moderate and unchanged, because audibility at the top of the range trades directly against level.
Play the tone for several seconds rather than a moment. Near the limit, a tone can be present but easy to lose track of, and you may notice it only as a slight pressure or tension rather than a clear pitch.
Things that sound like the mosquito tone but are not
Old cathode-ray televisions emitted a real 15.6 kHz whine from the line-output transformer, which is why some people remember being able to tell whether a television was on from another room. Some LED drivers, switched-mode power supplies and phone chargers do something similar at audible frequencies when a component vibrates.
Persistent ringing with no external source is tinnitus, which is a different thing entirely and worth discussing with a professional if it does not settle, particularly after loud exposure.
Where the limit sits for you
If 17 kHz is inaudible, the hearing range test will find where you actually stop — sweeping upwards and stopping at the point the tone vanishes is more informative than a single yes or no at one frequency. And whatever the answer, losing the top of the range says little about how well you hear speech, which is the part that matters.
Last reviewed 2026-09-22.