1. II Acoustic Reality
II.4.1 (M 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. hammer (leather on wood)
Some History
string
hammer (leather on wood)
The historical instrument’s action looks like this
harpsichord action:
key

4. An exploded grand piano
cast iron plate
sound board, spruce
rim, maple

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
versus
830 N per string
total:
7,500 N
versus 210,000 N
~ 30 x more!
Since 1855 (Steinway) need no more wooden, but cast-iron string plate, kg

9. The durometer to measure hammer hardness

10. Where to hit the stringsL d
hammer

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

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

13. The piano case/rim 80-90 mm 150-200 kg maple or beech wood,
important for massive termination of vibration
of the soundboard

14. string(s) bridge/soundboard The interaction of strings and soundboard
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. vertical horizontal longitudinal
Three directions of string and bridge vibrations
vertical
horizontal
longitudinal

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

17. Vertical and horizontal 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