This is the sound of my 2-year old son jumping up and down in his crib, which kind of resembles the sound of. . . A baby being made if you know what i mean. I placed a roland r-05 digital recorder under the crib while he bounced.
Zoom h4 held immediately at the opening of a thermos. Hot tea building up air pressure, escaping air evenly producing this squeaky sound. Low cut 1000hz for filtering out street noise.