New-ish tactics used by the police force are a great way to use force to contain people without leaving evidence of what they did.

From the Guardian’s article on the use of the sonic cannon:

Sonic weapons or long-range acoustic devices have been used by the US military overseas, notably against Somali pirates and Iraqi insurgents.

But US security forces turned the piercing sound on their own citizens yesterday to widespread outrage. Pittsburgh officials told the New York Times that it was the first time “sound cannon” had been used publicly.

[Warning: the video below contains very loud audio from the start]

BoingBoing has even more on the sound cannon:

Click here to see more footage from the BBC on police intervention and peaceful protesting.