You should look for places that have a natural echo that will bounce the sound of the whistle back to you. This natural reverb or return echo is a sound your whistle lacks and will give you the missing link to getting great sound from your whistle.
Look for hard surfaces that echo or amplify sound and give a good sharp whistle return. Use a clear loud shout to see if you get a quick return echo. The quicker the return echo the better your music will sound.
There are bandstands that have been constructed in a lot of communities that are perfect for an impromptu concert in the afternoon. In Maine almost every town has a bandstand available for community use and folks gather there to talk, tell stories and make music.
Be prepared to draw a crowd of folks passing by that like your whistle music. Most likely, you will get a round of applause at the end of your performance. Play what you like and folks generally like what you play. I suggest a short medley of familiar tunes that your are confident in playing to finish up your concert in the park.
Playing music in the city provides lots of chances to find places to play your whistle. Brick buildings and alleys are excellent backdrops. Over passes, outside on an open porch, your garage with the doors open, a grassy knoll with surrounding hard surface buildings, are just a few spots to try out some music and find out how differently your whistle sounds outdoors.
Read my article on playing whistles at the Standpipe in Arlington Heights, MA for more insight on where to go to play outdoors.
Highways have lots of flood culverts with huge openings that are dry and accessible along the side of the road. I see folk playing, singing and recording music on their phones all summer in these types of places. There is a Trans Canada hiking trail and the Appalachian Trail in the US that will take you to places to play your whistle that are really unique. The two most common instruments that hikers like to play around the campfire are harmonicas and whistles and they both can be played while marching along the trail for company and to warn the bears that you are coming to visit.
Avoid things that interrupt the air in and around your whistle playing area. Inside the house stay way from air conditioners, fans, washers and dryers that are running, wood stoves and furnace registers. Try to play where the temperature is about 70 degrees and avoid extreme temperatures above 90 degrees because that will make the whistle play sharp. Warm air travels faster in the whistle bore, therefore the pitch will be faster and higher in the heat.
Overhead lights that have slow moving fans will make your whistle out of tune or hard to play slower tunes. Acoustic ceiling tile will absolutely cut the volume off the whistle you are playing by at least 30%. Acoustic ceiling tile is made to absorb sound and it is excellent at it’s job.
Your whistle will be at it’s best if you find a spot to play that has natural reverb and you will quickly notice how you whistle responds with better sound.
I have noticed that many players can play better with their eyes closed when learning new repetitions or when playing a new song and committing it to memory. By totally concentrating and shutting out everything around you, it is easier to memorize the music.