In July 2019 a number of posts circulated Facebook, all of which linked to video of a 15000 Hz/15 kHz frequency sound that is purportedly only audible to people younger than 40.
One iteration (archived here) accrued a large number of shares. Its original poster wrote:
I need your help! ???? Okay so I nabbed me a younger man, I said it….I am slightly OLDER than Chris #cougar ????❤ BUT I am NOT 40 yet y’all however, I heard on the radio that some businesses and even towns are using a sound wave as a deterrent for teens after curfew, INTERESTING right?! So I looked into it and found a series of sounds that become harder to hear as you *ahem* age. This one in particular cannot be heard by most people over the age of 40.
I CANNOT FLIPPING HEAR THIS!!! But, Chris Helmer can ???? I called all our kids in and they were covering their ears!!! So, I got to know below, help me feel better (or worse) Tell me, are you OVER or UNDER 40 and CAN YOU HEAR THIS SOUND?!?!?
A YouTube video was attached to the post, “15000 Hz 15 kHz Sine Wave Sound Frequency Tone”:
A subsequent post making similar claims was also shared quite a bit:
Incidentally, both posts were shared by individuals recruiting for multi-level marketing (MLM) schemes, commonly described as “huns” or “hunbots” on Facebook. By sharing posts intended to “go viral,” both users boosted their visibility on Facebook — which in turn facilitates efforts to recruit and sell for MLMs. This content was likely shared with the intent to accrue more shares and exposing more readers to MLM pitches.
In this vein, the first poster separately shared a post about the other, in which commenters alluded to its leverage for MLM purposes:
As a reminder, the Federal Trade Commission (FTC) warns [PDF] that less than one percent of MLM victims ever turn a profit at all. Sharing “trojan horse” posts like the ones linked above amplify the reach of MLM recruiters.
In the original posts, the posters said:
I need your help! ???? Okay so I nabbed me a younger man, I said it….I am slightly OLDER than Chris #cougar ????❤ BUT I am NOT 40 yet y’all however, I heard on the radio that some businesses and even towns are using a sound wave as a deterrent for teens after curfew, INTERESTING right?! So I looked into it and found a series of sounds that become harder to hear as you *ahem* age. This one in particular cannot be heard by most people over the age of 40.
I CANNOT FLIPPING HEAR THIS!!! But, Chris Helmer can ???? I called all our kids in and they were covering their ears!!! So, I got to know below, help me feel better (or worse) Tell me, are you OVER or UNDER 40 and CAN YOU HEAR THIS SOUND?!?!?
OMG so I saw a post about some businesses playing this sound to keep younger kids away after curfew. Supposedly people over the age of 40 cannot hear it. I thought yeah right this is some BS ????????
I played it and heard nothing my kids all came screaming running covering their ears!!!! Y’all I’m shook! I can’t hear this shit!!!!! Can you??
Claims that certain frequencies become inaudible as people age are hardly new. A 2010 post to Reddit’s r/science addressed the ability to detect similar frequencies, but did not include an age qualifier:
A top-level comment on that post offered that variations in desktop equipment, speakers, and other factors (not necessarily age) might influence whether that particular tone was audible to everyone:
Oh for fucks sake, you can’t have a 30k tone unless your sampling is at least 60 or you’ll get biasing (correction: aliasing, hat tip to 7e9) and the tone will sound lower than it should. Thats why I could hear them all, and why they started sounding lower after a point.
Also check that your headphones/speakers have a decent output at that frequency. I couldn’t hear 15k on my computer monitor speakers, but had no problem with some nice headphones.
(edit – sweet zombie jesus I’ve just commented on a youtube video. I’M ONE OF THEM) (edit 2 – As 7e9 points out, it’s called aliasing, not biasing)
In the news, claims about the purported ability of certain frequencies to drive teenagers away from malls and other areas in which they might congregate dated back to at least 2008, and possibly earlier still. At the time, reporting centered on a controversial device called “The Mosquito“:
As 15-year-old Eddie Holder sprinted from his apartment for school one recent morning, he held his hand to one ear to block out a shrill, piercing noise.
The sound was coming from a wall-mounted box, but not everyone can hear it. The device, called the Mosquito, is audible only to teens and young adults and was installed outside the building to drive away loiterers.
The gadget made its debut in the United States [in 2007] after infuriating civil liberties groups when it was first sold overseas. Already, almost 1,000 units have been sold in the U.S. and Canada, according to Daniel Santell, the North America importer of the device under the company name Kids Be Gone.
[…]
The high-frequency sound has been likened to fingernails dragged across a chalkboard or a pesky mosquito buzzing in your ear. It can be heard by most people in their teens and early 20s who still have sensitive hair cells in their inner ears. Whether you can hear the noise depends on how much your hearing has deteriorated – how loud you blast your iPod, for example, could potentially affect your ability to detect it.
As noted by CBS News in 2008, ability to hear the frequency has less to do with age, and more to do with hearing loss by any means, such as prolonged exposure to loud music. A 2009 NPR report noted that the sound ended repelling people of all ages, not just teenagers. Similar devices known as LRAD sound cannons have been used to disperse protesters, also of all ages.
In 2015, Yahoo! News compiled a number of frequencies with purported age limitations, but did not cite any information supporting its claims. Two years earlier in 2013, Scientific American examined claims about age and sound, noting that inability to detect the frequencies was attributed to, yes, age-related hearing loss or presbycusis but that there is no exact age at which hearing begins to drop off:
Your results may vary, but you likely found that the Mosquito sound was detected less frequently by older volunteers. Volunteers in their early 20s should have been able to hear the sound. Volunteers in their teens and child volunteers should have been able to hear the sound easily.
[…]
The older age group likely had trouble hearing the Mosquito because as we age, our ability to hear high-pitched frequencies wanes. This process is called presbycusis, the onset of which is sometimes observable in people as young as 18. Presbycusis happens as a result of the cells in our ears aging naturally, so it’s nothing to be alarmed by. Presbycusis is very different than noise-induced hearing loss, which happens as a result of acute or sustained exposure to very loud noises. When you’re at a very loud concert, for example, the hair cells in your ear can become over-stimulated. The body responds by sending oxygen to this region of the ear, leading to oxidative cell death. Curiously, noise-induced hearing loss usually makes it harder to hear lower frequencies, such as those between three kHz and six kHz, whereas presbycusis gradually erodes our ability to hear higher frequency sounds in general.
Based on comments on both posts about the 15000 Hz/15 kHz frequency circulating in July 2019, plenty of people older than 40 were able to hear the frequency. Those comments were not at all representative, since it’s possible people who didn’t hear it were unlikely to comment. In any event, age is only a very rough gauge of who is or is not able to detect certain frequencies. Degradation of the ability to hear, which is not necessarily related to age, was a much larger factor.
- 15000 Hz 15 kHz Sine Wave Sound Frequency Tone
- hunbot
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- Chapter 7: MLM’s ABYSMAL NUMBERS
- I can hear 10000 Hz, but not 15000, what about you? [warning: careful with the volume]
- High-Pitched Device Drives Away Teens
- Can You Hear It? Sonic Devices Play High-Pitched Noises To Repel Teens
- The Mosquito
- Try It: Can You Hear These Sounds Only Young People Hear?
- High-pitched sound used to deter teenagers
- Sonic Science: The High-Frequency Hearing Test
- What Is the LRAD Sound Cannon?