A person who's a drug addict stas hearing light and seeing voices. The substance is:

LSD is a hallucinogen. There is often a 'cross-over' of perceptions (synaesthesia) so that sounds are 'seen' or 'felt' and colours are 'heard'. Distoions of body image are common: a limb may appear to shrink, or become enormous and may seem completely separate from the rest of the body. Ref: Ghodse's Drugs and Addictive Behaviour: A Guide to Treatment By Hamid Ghodse, 2010, Page 93; Kaplan and Sadock's Concise Textbook of Clinical Psychiatry By Benjamin J. Sadock, Virginia A. Sadock, 2008, Page 127