Whether the issue is called ‘Hyperacusis’ or ‘Hypersensitive Hearing (of Unique Frequencies)’, there is evidence of these types of issues in many people with Autism Spectrum Disorders. One of the treatments that is ment to be especially effective for these kinds of issues is the combination of Vitamin B6 with Magnesium. While studies in the past have not always been conclusive (as to the combination’s merits for treating Autism), they have virtually all utilised the non-active form of Vitamin B6, Pyridoxine Hydrochloride. This version, in addition to requiring conversion by the body to its active form, is toxic at high doses. I believe that combining Pyridoxal-5-Phosphate (P5P), the ‘active’ form of Vitamin B6, with Magnesium supplements would be more effective…
(sources: http://www.europharmausa.com/DBFiles/Greensheet/138.pdf; http://naturopathicanswer.com/spectrum/wp-content/uploads/2010/11/6_10AutismNewsletter.pdf)