Catalyzes, at least in vitro, the hydrolysis of sphingomyelin to form ceramide and phosphocholine (PubMed:10608884). Also hydrolyzes 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lyso-platelet-activating factor) in vivo (PubMed:10608884). Also acts on 1-acyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PC) and sphingosylphosphocholine (PubMed:10608884, PubMed:14741383). a sphingomyelin + H2O = an N-acylsphing-4-enine + H(+) + phosphocholine an N-(acyl)-sphingosylphosphocholine + H2O = an N-acyl-sphingoid base + H(+) + phosphocholine 1-O-octadecyl-sn-glycero-3-phosphocholine + H2O = 1-O-octadecyl-sn-glycerol + H(+) + phosphocholine 1-O-hexadecyl-sn-glycero-3-phosphocholine + H2O = 1-O-hexadecyl-sn-glycerol + H(+) + phosphocholine 1-hexadecanoyl-sn-glycero-3-phosphocholine + H2O = 1-hexadecanoyl-sn-glycerol + H(+) + phosphocholine a sphingosylphosphocholine + H2O = a sphingoid base + H(+) + phosphocholine Lipid metabolism; sphingolipid metabolism. Belongs to the neutral sphingomyelinase family.