What hides this stereogram?

Murphy and his wife went for a stroll in the park. They sit down on a bench to rest for awhile. Soon they overhear voices coming from a secluded spot nearby.
Suddenly, Mrs. Murphy realizes that a young man is about to propose. Not wanting to be eavesdropping during such an intimate moment, she gently nudges her husband and whispers, "Whistle, to let that young couple know that someone can hear them."
To which Murphy replies, "Whistle? Why should I whistle? Nobody whistled to warn me?"