770 mi/hr. Velocity of sound in the open is influenced by air temperature more than by atmospheric pressure. At 21 degrees C, speed is 344 m/sec (1,100 ft/sec); at 50 degrees C, 360 4m/sec, or 42 ft/sec faster.
"I am very pleased with the overall results of all three transfers. The "Hall of Presidents" and "Country Bear Jamboree" transfers were outstanding, with almost no hiss or pop. The "Tiki Room/Jungle Cruise" soundtrack had some minor hissing in the first couple of tracks, but side 2 was superlative. Given that that album was over thirty years ..."