acoustics - Is there an upper frequency limit to ultrasound?

Wikipedia has this diagram of the acoustic frequency spectrum:

Is there an upper limit to the frequencies you can transmit through the air? Are they absorbed more and more at higher frequencies, resulting in shorter travel distances? Are there "windows" of absorption and transmission like there are for radio waves?

Update:

This says

An additional problem is created by the strong absorption of ultrasound in air, at least for frequencies higher than 250 kHz. As a consequence, ultrasound of e.g. 1 or 2 MHz can propagate in air over a distance of not more than a few centimeter

Also found some references, but I can't access them: http://scholar.google.com/scholar?q=Atmospheric+absorption+of+sound