1. Making sounds virtual G. Karwasz, L. Gratton, E. Rajch
Dipartimento di Fisica, Università di Trento, Italy
and Pomorska Akademia Pedagogiczna, Słupsk, Poland

2. Sounds
Sounds, i.e vibrations

3. Everything plays
Depending on the source and the mode, the whole variety
of sounds can be generated
What makes the difference between them: why some
of them are pleasant, other sharp or dull?
· Can we see the variety of these sounds?
freeware Oscilloscope 2.51
(K. Zeldovich).
The program allows visualization
of registered sounds and
their Fourier analysis

4. Sound wave
The fundamental quantity describing a simple sounds – a monocromatic sine wave are the frequency, length and velocity of propagation. 

5. Glass music In practice, generating a single frequency is not easy.
Surpisingly, monocromatic sounds are generated by glasses.
What determines the frequency of glass?

6. Glass music

7. Blow instruments
Sounds can be generated in different type tubes and whistles. Also bottles can play.
The “pitch” of the sound, first of all depends on tube length.
But the pitch depends also on the power in the blow
P= ½ vρω2A2
where v is the sound velocity, ρ gas density, ω – frequency, A – amplitude of the wave

8. Trumpets
Infinite ways to generate sounds in tubes of variable length.

9. Flutes
Infinite ways to generate sounds in tubes of variable length.

10. Closed flute
W piszczałce zamkniętej fala stojąca ma na jednym końcu węzeł, na drugim strzałkę

11. Open flute In open tube knots are formed inside.
Frequencies scale like 1:2.3 etc. i.e. “octave” intervals
But: 1) even the ligthest blowing generates
higher harmonics
2) Exact scaling does not hold for the
strongest blow – the dominating frequency
belongs to the “closed tube” series

12. Strings
The frequency of the strings depends on the tension F, mass linear density  and string length l.

13. Sounds of a rod
A metal rod creates a variety of sounds, depending on the mode of excitation.
In the rod, these are longitudinal waves which give the sound

14. Psalm book from Reims cathedral, now in St John’s College, Cambridge
Evil’s music
As seen from this XIth century psalms book, vibrations of mebranes are much more complex than those of strings.
Psalm book from Reims cathedral, now in St John’s College, Cambridge

15. Thunder drums

16. Painful noise

17. “White” noise
White noise, differently from “glass music” has a wide spectrum of frequencies. Waterfalls is a good example.

18. Physics is fun