Can acoustic waves travel through human body? If I stand inside a perfect anechoic chamber in front of a unidirectional acoustic waves emitter, I would hear the tone played either using my ears or using a microphone for ultrasonic waves. But what happens if I put my hand in between my head/microphone and that emitter? Or if a person stands between me and the emitter?
Would I still hear/detect something?
And on what properties does the propagation or blocking depends on? frequency, signal energy?
 A: First, some fraction of incident sound power will pass thru any object, human body or not, so your title makes no sense.  The real question is how much this body will attenuate the frequencies of interest.  Below some attenuation, you either don't care or it's below the noise floor of the sensors to detect it.  However, this depends on what you care about, how good your sensors are, and how much ambient noise there is, so there is no single yes/no answer.
The other part of what you are missing is that "blocking" by your hand isn't the issue.  A human body, even just a hand, will likely attenuate to oblivion audio frequencies coupled air to body and then back out body to air.  However, that won't prevent you hearing the sound in the setup you describe.  That's because of diffraction around the edges of this body, even if you assume it absorbes everything incident upon it.
If you figure audio frequencies are from 20 Hz to 20 kHz, and sound propagates thru normal air at about 3 ms per meter, then the wavelengths are 17 m to 17 mm.  Even at 17 mm, there will be easily audible diffraction that will go around the edges of the blocking object.  You will be able to hear significant attenuation as you hold your hand between your ear and the source, but you will still be able to hear the original.
Let's say your hand is about 100 mm across.  100 mm sound wavelength means about 3.3 kHz frequency.  That's roughly the limit below which the hand will have diminishing affect.  At 300 Hz, for example, you probably won't notice any affect from puting your hand in the way when it's arm's length from your head and the sound source.  At 1/10 wavelength, the sounds waves will mostly just go around it without getting attenuated.
