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This picture illustrates the influence of movement on the perception of tone pitch. The author, Rodolphe Radau, explains the shift in pitch using the example of a train passing. The whistle of the engine-driver on an arriving train appears to be higher than on a departing one.

Taken 31 miles per hour as the speed of a train, this equals ¹/₂₄ of the velocity of sound. Hence, a calculation based upon this shows that an observer placed on the railroad will perceive the note of the whistle changed in the ratio of 24 : 25. The observer will either estimate it too high or too low by a semitone. What is a "la" for the engine-driver is a "la" sharp or a "la" flat for an observer, depending on the train's moving direction.

Related Items:

• This book is part of the collection: Staatliches Institut für Musikforschung, Preußischer Kulturbesitz: Bibliothek.
  
• Library resources on the History of Sound and Hearing
• English translation of this source at the Internet Archive: Wonders of acoustics; or, The phenomena of sound