The 10 seconds ghostly voice is a woman singing "Au Clair de la Lune".

From Wikipedia:

In 2008, the New York Times reported the discovery of a phonautogram from 9 April 1860.[7] The announcement of the discovery was accompanied by an announcement that the visual recording was made playable — "converted from squiggles on paper to sound — by scientists at the Lawrence Berkeley National Laboratory in Berkeley, California."[7] The phonautogram was one of Leon Scott's forgotten images in Paris; they were scanned then processed by a sophisticated computer program developed a few years earlier by the Library of Congress. The recording was a ten-second snippet of a singer, originally thought to be the daughter of the inventor, before it was discovered that the recording was played at twice normal speed and was probably his own voice,[8] performing the French folk song "Au Clair de la Lune". This phonautograph recording is now the earliest known recording of a human voice and music in existence, predating, by twenty-eight years, the longest surviving Edison phonographic recording of a Handel chorus from the oratorio "Israel in Egypt", made in 1888.[9] A phonautogram by Scott de Martinville containing the opening lines of Torquato Tasso's pastoral drama Aminta has also been found. Recorded around 1860, probably after the recording of Au Clair de la Lune, this phonautogram is the earliest known recording of human speech to be played back.[10] Earlier recordings made in 1857 contain Scott's voice, too, but are unrecognizable due to the irregularity of speed. There is an urban legend that a recording was made of Abraham Lincoln's voice, supposedly made using Scott's Phonautograph in Washington D.C. in 1863.[11] The legend claims that a phonautographic tracing of Lincoln's voice was supposedly included among the artifacts kept by Edison. According to the researchers at FirstSounds.org, Scott did not travel to the U.S. in the 1860s. Scott de Martinville's phonautograms were selected by the Library of Congress as a 2010 addition to the National Recording Registry, which selects recordings annually that are "culturally, historically, or aesthetically significant".[12]