On Sat, 2011-12-10 at 09:18 -0500, V G wrote:
> http://www.freesound.org/people/vtkproductions.com/sounds/40845/
>=20
> That's what it sounds like. I hear it occasionally wherever I go, anywher=
e
> around the world. What frequencies/devices/protocols are causing it, and
> what data does it represent?

That's GSM. Note that you'll only hear that in 2G ish modes, 3G uses a
CDMA air interface and tends to cause alot less of that sort of
interference.

You actually hear it less frequently in NA since roughly half the phones
use a CDMA air interface (i.e. in the US Verizon and Sprint phones never
were GSM, they use IS-95 and EVO, ATT and TMobile use GSM but will
usually use 3G, which is a CDMA air interface if available).

In Canada the situation is similar, Belus use 3G exclusively (they don't
have 2G fallback to GSM) so their phones are either 3G exclusive, or use
the older IS-95 CDMA (older handsets on the legacy network). Fido/Rogers
use GSM, but again, their phones try to stay 3G as much as possible.

You might hear similar sounds from some phones in a CDMA mode if they
are held in exactly the correct position with the perfect receiver, but
it's pretty rare.

If you have a Fido or Rogers phone it's VERY easy to get this sort of
sound. Set your phone to 2G only and hold it near pretty much any pair
of amplified computer speakers. Establish a call and you'll hear it.

TTYL



--=20
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