What is sympathetic and parasympathetic tone?

What might cause my son to cry when he hears a song or a certain tone of voice?

• When my son was about 9 months I discovered a certain tone of voice would make him cry. I read in a book babys like to hear their name sang to them. So I sang his name in a soft slow tone. His eyes filled with tears and I never used that tone around him again Well last night we were watching a movie and a song came on and the voice was soft and slow. His eyes filled with tears and he cried until I turned it off. He is 17 months old now Any ideas of why soft low voices in that tone would make him cry? Its not harsh or abrasive at all,I enjoy the tone. I sing to him often so I have no idea

• Answer:

  I have an autistic child and noticed the same thing with my son around the same age as well as other characteristics that are associated with autism. I am not saying that your child has autism. But through all of my research and experience I have learned a lot about my son's auditory sensory issue. I do remember reading about sound-selective auditory impairment. You can google that and there is a bunch of information out there. Again, I am not saying your child may be autistic. What I have learned is that we all may encounter some sort of sensory issue to a degree whether it be by sight, sound, taste, touch,ect.