Is the ikhfa always an empty noise from the nose?

Question
 Salam. Is the ikhfa always an empty noise from the nose?.
Answer
Wa alaikum assalaam wa rahmatullahi wa barakaatuh.
If a  نون ساكنة or تنوين is followed by one of the 15 letters of إخفاء , we hide the  نون. To hide the  نون, our tongue moves close to, but not at the articulation point of the next letter which is the letter causing the إخفاء.  We then produce a complete nasalization (ghunnah) from the nasal pharynx area. A small sound from the mouth accompanies the nasalization due to the incomplete closing of the mouth portion of the sound. This is the technique of the إخفاء with all the letters except the letter قاف and كاف.
The articulation points of the قاف and كاف are far from the articulation point of the نون, for this reason the way of doing إخفاء with these two letters is slightly different. While doing إخفاء of the نون when it is followed by a قاف or a كاف, we do not just move our tongue close to their articulation points (like we do in case of other letters), instead we touch the articulation point of the قاف or كاف and close it off completely. We then prolong the sound with a nasalization (ghunnah) and this sound emits from the nose only. 
Therefore, the sound while doing إخفاء does not always emit from the nose only. It is emitted from both the nose and the mouth in most cases and from the nose only when the نون ساكنة or تنوين is followed by a قاف or a كاف.
The complete إخفاء rule can be found on the following link:
http://www.abouttajweed.com/index.php/tajweed-rules/47-the-noon-saakinah-and-tanween/40-hiding-ikhfa-rule-of-the-noon-saakinah-and-tanween