I purchased the lightning striped model.
I plan to try it out tomorrow.
According to the video that Scott Mann posted on the forum from the factory with him in the video operating the T motor and also one operating on a layout in his area the sound is one of a diesel locomotive and diesel horn. He had told me that he is at the mercy of Lionel as to what sound boards that Lionel sends him. The sound board used in the Lionel S motor would be a much better match for the T motor. Again one of my friends who purchased a T motor ran the locomotive in the late 60s and said that the sound was almost no sound at all.