Eagle have you heard it since?, I went through this last summer and it was driving me nuts.I live by skellys market and it was haunting me for almost a month.It started only at night and was high pitched like a girl screaming and change directions quickly but never heard it moving(rustling leaves,etc.) At one point i assumed it was bigfoot in the ossippee mountains because I had never heard anything like it-lol. Then it happened in the morning so I followed the sounds through the woods and never saw it.Not a fisher cat or owl as I went through all the sounds on the internet at the time also. My closest guess would be a red fox. Listen to the howl-#6 and see if there is any similarity
http://www.soundboard.com/sb/Fox_Sounds_audio.aspx
What I heard was very much like a sonar blip from a submarine