Catalyzes the hydrolysis of membrane sphingomyelin to form phosphorylcholine and ceramide. a sphingomyelin + H2O = an N-acylsphing-4-enine + H(+) + phosphocholine H2O + N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine = H(+) + N-hexadecanoylsphing-4-enine + phosphocholine Activated by anionic phospholipids, specially cardiolipin and phosphatidylserine. Optimum pH is 7.5. Lipid metabolism; sphingolipid metabolism. Highly expressed in testis, pancreas, epididymis, and brain. Belongs to the neutral sphingomyelinase family.