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Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
1880-1900
1895-1899
1847
1901
1884
1906
1898
1825
1890
1812
1834
1829
1845-1855
1901
1902
1898
1832
1880-1920
1865
1834
1834
1902
1896
1899-1919
1927
1925
1906
1862
1912
1875
1871
1801-1900
1801-1900
1918-1922
1873-1920
1880-1930
1801-1900
1914
1832-1851
circa 1860
1914
1917
1896
1863-1865
1840-1851
1926
1884
1892-1900
1806