WASHINGTON (AFP) — Irreverent US comedian George Carlin, who became known as a voice of the 1970s counterculture and was one of the country's best known funny men, died on Sunday aged 71, US media reported. The Grammy award winner, whose career spanned five decades, died of heart failure, his publicist Jeff Abraham told the New York Times. Carlin had a history of heart problems and passed away in Santa Monica, California after checking into the hospital with chest pains. He won four Grammy Awards, including one for his 1972 comedy recording "FM & AM," in which he combined his older, more conventional material that entertained audiences in the 1950s and 60s, with his new, edgier and more controversial style. Gray-bearded and often dressed in black casual attire, Carlin frequently admitted to drug use and shocked 1970s audiences with his hit "Seven Words That Can Never Be Said on Television." When a radio station played the album on air, Carlin's use of numerous swear words sparked a legal case over obscenity regulations that made it all the way to the Supreme Court. The material was judged indecent, though not obscene, and a 1978 high court ruling upheld the government's right to penalize stations that broadcast such material during hours when young people may typically be tuned in. Carlin, who also collected five Emmy Awards, was considered in the same class of influential comedians as Richard Pryor and his predecessor Lenny Bruce, the Times said. The first host of the popular comedy show "Saturday Night Live" when it debuted in 1975, he went on to sell more than one million recordings of his stand up acts and also became a best-selling author. "I think it is the duty of the comedian to find out where the line is drawn and cross it deliberately," Carlin once said. Earlier this year, Carlin was named the winner of the Mark Twain Prize for American Humor, and was to accept the award at a ceremony in November. He performed as recently as last weekend in Las Vegas. "In his lengthy career as a comedian, writer, and actor, George Carlin has not only made us laugh, but he makes us think," said Kennedy Center chair Stephen Schwarzman. "His influence on the next generation of comics has been far-reaching." He was an Air Force veteran and got his start in entertainment as a disc jockey at a radio station in Shreveport, Louisiana. Carlin was born in New York and had a daughter, Kelly, with his first wife Brenda who died in 1997. He is survived by his second wife, Sally.