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II Acoustic Reality II.1.2 (W Sept 17) The Piano

II Acoustic Reality II.1.2 (W Sept 17) The Piano. Some History In 1709 harpsichord (cembalo) constructor Bartolomeo Cristofori in Florence invented the instrument, he called gravicembalo col piano e forte. Here an instrument built in 1720 at Metropolitan Museum of Art

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II Acoustic Reality II.1.2 (W Sept 17) The Piano

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  1. II Acoustic Reality II.1.2 (W Sept 17) The Piano

  2. Some History In 1709 harpsichord (cembalo) constructor Bartolomeo Cristofori in Florence invented the instrument, he called gravicembalo col piano e forte. Here an instrument built in 1720 at Metropolitan Museum of Art (sound_example_1)

  3. Some History string The historical instrument’s action looks like this hammer (leather on wood) key

  4. An exploded grand piano

  5. Modern piano‘s anatomy

  6. The action of a modern piano Have also Erard‘s repetition action on grand pianos!

  7. The agraffe and the bridge terminate the free strings tuning pins

  8. The pull forces for Cristofori‘s and for modern pianos 70N versus 830 Nper string total: 7,500 N versus210,000 N ~ 30 x more! Since 1855 (Steinway) need no more wooden, but cast-iron string plate, 160-180 kg

  9. The durometer to measure hammer hardness

  10. Where to hit the strings L d hammer

  11. The soundboard (spruce), 6.5-9.5 mm, 4 modes 49Hz 67Hz 89Hz 184Hz

  12. Modes mobility = velocity/force without strings and plate fully equipped

  13. The piano case/rim 80-90 mm150-200 kg maple or beech wood, important for massivetermination of vibration of the soundboard

  14. The interaction of strings and soundboard string(s) exchange of energy bridge/soundboard strong coupling —> high energy transfer —> loud, fast decay weak coupling —> low energy transfer —> quiet, slow decay need „trade-off“!

  15. Three directions of string and bridge vibrations vertical horizontal longitudinal

  16. Longitudinal vibrations E1 = 41 Hz Sound Level Frequency sound_example_4, 5, 6, 7

  17. Horizontal and vertical vibration for decay function

  18. Horizontal and vertical vibration for decay function strong coupling caused by vertical vibration, loud, energy transfer to bridge —> fast decay weak coupling —> low energy transfer —> quiet, slow decay the second is caused by horizontal vibration and coupling with second string

  19. coupling with second string and mistuning uncouple second string strong energy exchange via bridge/soundboard

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