I've been tearing my hair out regarding this audio issue, and I've noted that this has been a known issue for quite some time. Since D-Link hasn't seen it fit to run a resolution to ground, I thought I would provide some additional tips and information to see if they'll get their act together on this.
So, after doing a lot of work testing to see if there was any RF interference, I came up with a decent workaround. Using a ground loop isolator that I had picked up at Radio Shack for a few bucks (for an unrelated matter), I pulled up the stream on my iPad, plugged in the ground loop isolator, and plugged the audio cable into my computer and voila! The static/hissing noise was greatly diminished.
I then unplugged the ground loop isolator and plugged the audio feed directly into my computer, recorded a few seconds of room tone, and analyzed the sound in spectrogram view. It appears that the hiss is fairly constant and concentrated in the 5hz to 180hz range, concentrated at 50-60hz, confirming what I suspected... Mains Hum. That's all it is. You won't hear a lot of this on most webcams because they plug into the USB port, rather than the electrical system of your house
If you EQ the audio file and lower the audio for 180hz and below, the hiss is gone and the audio quality is preserved. I'd imagine that would be an easy fix for our friends at D-Link, if they took the time to either update the App or the firmware to eliminate this.