UPDATE 2023

Sputnik 1 (Russian: “Спутник-1”, “Satellite-1”, or literally “Co-traveler-1” byname ПС-1 (PS-1, i.e. “Простейший Спутник-1”, or Elementary Satellite-1)) was the first artificial satellite to be put into geocentric orbit. Launched by the Soviet Union on October 4, 1957, it was the first satellite of the Sputnik program.
The satellite helped to identify the density of high atmospheric layers by its orbit change and provided data on radio-signal distribution in the ionosphere. Because the satellite’s body was filled with pressurized nitrogen, Sputnik 1 also provided the first opportunity for meteorite detection, as losses in internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data. The unanticipated announcement of Sputnik 1’s success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War.
Sputnik-1 was set in motion during the International Geophysical Year from the 5th Tyuratam range in Kazakh SSR (now Baikonur Cosmodrome). The satellite travelled at 29,000 kilometers (18,000 mi) per hour and emitted radio signals at around 20.005 and 40.002 MHz which were monitored by Amateur radio operators throughout the world. The signals continued for 22 days until the transmitter batteries ran out on October 26, 1957. Sputnik 1 burned as it fell from orbit upon reentering Earth’s atmosphere, after traveling about 60 million km (37 million miles) in orbit.

Listen to the original signal from Sputnik 1
Qui potete ascoltare il segnale originale dello Spuntnik 1
[fonte NASA]