Here’s a photo of my low-cost whistle mute. The set up shown reduces the sound level by about 1/2 to 2/3 and is easier on cat ears (and human) … It plays a little sharp, but for practice by yourself, that shouldn’t matter too much.
It looks similar to my Scotch-tape setup, but as I said, everything I’ve tried mutes the low notes (about the lower half of the first octave) until they almost don’t sound, and the high notes barely change in volume. To get the high notes significantly muted, I pretty much have to cancel out the low notes altogether. 
Scotch tape is rather flimsy. The masking tape has worked well on all my Generations and a Dixon, with no problems w/ low notes. The nice thing about tape is that you can control the volume by where you place it across the window. If I close off too much of the window, then some of the notes won’t play well. So you may want to try different kinds of tape and covering less of the window. I’m sure the handy man’s secret weapon would work just as well as masking tape…
This was in our newspaper this morning. I don’t know these people but I bet I know people who know them. This occurred in the most notorious town where I provide social services.
May 24, 2012
Man shot in Lincoln County over music complaint
By Staff reports
The Charleston Gazette
HARTS, W.Va. – A Lincoln County man faces felony charges after he allegedly shot his neighbor with a shotgun in a dispute about loud music.
Fulton Toney allegedly walked to Brian Lee Maynard’s residence on W.Va. 10 in the Compass Point area of Harts and asked him to turn his radio down because it was “too loud and he was getting ready to go to bed,” according to a criminal complaint filed in Lincoln County Magistrate Court.
Maynard, 31, allegedly pulled a shotgun out of his vehicle and shot at Toney’s feet. Toney suffered wounds to his stomach, leg and arm, according to the complaint.
Toney pulled a pistol out of the waistband on his pants and fired a return round at Maynard, according to the complaint. Toney then ran back to his residence and his wife called Lincoln County 911, according to the complaint.
Maynard went inside his residence and “continued to be very violent,” by breaking the butt of his shotgun on the floor while screaming, cursing and punching the walls of his residence, according to the complaint.
Lincoln County Sheriff’s Lt. M. Hatfield and Deputy G.W. Linville arrested Maynard, who is being held in the Western Regional Jail on a $60,000 bond. He faces felony malicious wounding and brandishing charges.
One of the benefits of playing highland bagpipes is no one minds when I practice whistle 
But seriously, in college you ought to have ample opportunities. Thinking back to my college days I could have practiced:
In the stairwell of my dorm.
In the lobby of my dorm (near the piano…)
In the common area outside my dorm.
In a parking lot on campus.
In a green space on campus.
Near the athletic fields.
In a practice room in the music building.
In an empty class room.
I could have practiced in my dorm room too, I suppose. People probably wouldn’t have minded that as much as the loud stereos or electric guitars (think “11”).
Whistle mutes are easy to make. I do mine different from the photo though. I take a narrow strip of card stock and fold it into a V. I hook the V onto the blade of the fipple, with one end going inside the body of the whistle. So the point of the V points towards your face and half of it is inside the whistle. This mute will quiet all the notes to whatever degree you desire (wider paper = less whistle), without impacting tuning. I rarely do that (see opening comment) but I did at a camp two years ago to play after curfew along with my friend, who plays harp, and it was perfect. The whistle responded normally, but it was barely audible.
Way cool !
How is it held in place ? Any chance you could post a photo ?
trill
Good to know that there are lots of practice places. 
Thanks for the list! 
When I’ve done it I just let gravity hold it there, but for a more permanent solution you could use a dab of poster putty or something.
I don’t have a photo, but here’s a schematic:
I think I read about it on David Daye’s old website.