However, the oldest form of speech recognition is the ear witness – accepted in English courts since 1660. But let us think back to the kidnapping of the Lindbergh baby. The son of the world-famous aviator Charles Lindbergh was found dead. Three years later, Lindbergh said he recognized the voice of a suspect. Bruno Hauptmann, of German descent, was executed. However, it was not until doubts about Hauptmann’s guilt surfaced that a systematic investigation was launched into how reliable ear witnesses are. The conclusion was sobering. Two days after hearing a voice, 83 percent were able to remember it, two weeks later 68 percent and five months later only 13 percent. Since then, the preferred practice has been to consult experts.

Incidentally, the most famous voice interpreter comes from the world of fiction, namely Henry Higgins. In George Bernard Shaw’s play Pygmalion, or the musical version My Fair Lady, he can not only tell precisely where the flower seller Eliza Doolittle comes from, but every single person in England to within a few streets.

In 1926 the Berlin police started experimenting with "voice physiognomics" and had convicted criminals sing songs. The idea was to then allocate voices to criminal profiles; but it did not work. Today, in contrast, it is considered more important to be able to listen to a hostage-taker’s voice during the actual negotiations to decipher the degree of nervousness in it – and focus with great care on the sound of lies.