My Amer. Std. 4A6H5030G1 2.5T has a recip. Per the latest literature I was given, 3.5 ton or higher you get the "Duration" scroll. I have never figured that one out! Thank goodness the sound is not reverberating upstairs. I can hear barely hear the sound when I stand next to the unit outside but in the basement it is a little louder. Once you close the basement door I can faintly hear it on the first floor. When I recorded that clip, the microphones were placed 1/4" from the liquid line in the basement.