sentences:  TCA received its fleet of twenty DC-4M-2 North Stars during 1947 and 1948 and operated them on routes within Canada and to the USA until 1961.Starting in 1954 the North Stars were replaced on TCA's routes to Europe by Lockheed Super Constellations.To deal with passenger complaints about noise, TCA engineers developed a cross-over for the fuselage-side exhausts that reduced cabin noise by 6-8 decibels.