Sonic Weapon Targets Youth at Kent Station – And Misses

A few weeks ago I noticed a very annoying high-pitched tone while waiting at Kent Station to board the Sounder Train on route to Tacoma. I didn’t think much of it at the time, but after a few days of the recurring annoyance on my daily commute where the wait time can be up to 30 minutes between trains, realized that this was not just some by-product of the PA system or lighting. After wandering around the depot in an attempt to minimize the audio assault, I realized it was pervasive – and then my suspicions were aroused.

Downloading an audio analysis app for iPhone, I decided to do a little sleuthing to see I could pick out the frequency (see image).

Screen capture of spectrum analysis at Kent Station
Screen capture of spectrum analysis at Kent Station

Sure enough, the meter was pegged at about 12KHz. And my suspicions were confirmed – sort of. You see, high frequency sound has been used to repel youths from areas where they may be prone to commit vandalism, drug deals, or just be generally annoying to adults. Their hearing is typically more acute at higher than 15 kHz frequencies, and technologies such as the SonicScreen (aka The Mosquito in Great Britain) are used to drive them away. Usually, the frequency is set at 17 kHz, outside the range of most folks under 25 years old. Test it out yourself:

  • 11 kHz :
  • 12 kHz : 
  • 13 kHz : 
  • 14 kHz : 
  • 15 kHz : 
  • 16 kHz : 
  • 17 kHz : 

(Hat tip to Jesse for the above sample tones.)

I’ve done some cursory checking to see if this is in-fact what Sound Transit (or the City of Kent) is doing, but can find no additional information on their websites.

There are several issues I have with this – assuming that it is a device being deployed for the stated purpose above:

  1. How in the world did they miss the correct frequency to place it out of hearing range for the typical adult train commuter? I did verify that others could also hear the tone.
  2. Could this be considered a “weapon” for the intent of causing physical discomfort or even pain to the unsuspecting youth?
  3. Because the tone is set so low, are adults actually being targeted in order to cause discomfort? For what purpose?
  4. Does this violate a person’s rights to go unmolested by government in the pursuit of his/her normal activities?

I think this fits the definition of “passive-aggression”, and that it’s dehumanizing. At best it’s just one more annoyance to turn an already strenuous commute into a painful one.


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