sub-zero 642 hissing

(This was previously posted on rec.food.equipment, but I thought I would see if alt.home.repair had any input. Is there a more appropriate group?).
Hi, During a recent kitchen remodeling project, we had a sub-zero model 642 side-by-side installed. So far, it is everything we expected, but I have an "Is this normal?" kind of question. Every time the freezer door is opened and then closed, a vacuum is created by the warm air contracting as it cools. The air that equalizes it enters through the main seal around the door making a hissing noise for 15 to 30 seconds during which time, the door can't be opened. I am impressed that the freezer is sealed well enough to cause that to happen, but I would think sub-zero would have added some sort of check valve to control it rather than having it hiss at you for 30 seconds. The manual has a "noises that are normal" section, but doesn't describe this. Is there something that got blocked off during installation that I should open up? The installers mumbled something about "That's to dehumidify the moist air that entered the freezer while the door was open", but that doesn't make a lot of sense to me.
One more detail. About 20% of the time, a gurgling sound is made in addition to the air entering through the seal as though air was also entering through the defroster drain line.
Thanks, Pat     
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

the hissing is a normal sound it is the vacuum seal that will keep your fruits and veggies fresher longer.
the gurgling sound is probably from your ice maker.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.