This was posted to a discussion that has been going on for days on the UDXF mailing list, about a buzzing sound on 11915:
This is indeed a defective Saudi Arabia broadcast transmitter, on
11915, 15205 and others following their published schedule. Not a
jammer, but an example of utter incompetence. It has been going on
for many months but has worsened lately, blanking out entire SWBC
bands. This has been discussed at length recently in DX Listening
Digest,
http://www.worldofradio.com/dxldmid.html73, Glenn Hauser