I'm interested that some ULF (ultra-low frequencies, especially the 17 HZ zone) can cause humans to experience sensations of fear, trembling, or even claims of seeing ghostly apparitions. What an interesting ability to grant a fantasy or sci-fi race. But what physiological tools would a humanoid need to actually generate and hear those frequencies for an extended time?
Fairly easily done.
You need a long neck and a barrel chest. It just needs to be long enough and shaped to create the necessary resonance.
Humans can create a very broad range of pitches with a more or less standard set of apparatus (chest cavity, throat, vocal chords, and mouth). Ever noticed how a tall guy tends to have a deeper voice than the shorter person? Same apparatus, just different pitch resonance based on size.
The deeper the pitch, the longer the wave length. The larger and longer the resonance chamber needs to be. So, long neck and a big chest cavity.