Low Frequency Coils and AF

Hi guys'

Ive been wondering of late about building a coil in the 20km range.
15kHz is in the audio frequency band! Is it possible that a coil
like this might actually produce sound? I cant imagine it would be
very much. (I'me not suggesting it would put out 'pure' AF or anything 
weird like)I just wonder if the streamers might 'shake' the air, or
perhaps the cap might act as strange kind of 'transducer'. Caps 
certainly 'hum' with 50Hz, why not with 15kHz ? Hmm....just a thought.
Anyone tried a coils with AF  frequencies?
It could be interesting if the effect exists. Monitoring with a mic
for instance! 


ps. Coils are deafening enough as it is! 15kHz AF of only a few watts 
output is pretty loud.