The oscillations of a body can generate sound waves in air. This is the case of musical instruments, but is also the case of other objects, as we can see in the following experiment.
from IPython.display import Video
Video('./video/KostaBoda.mp4', width = 600)
The sound produced depends on the characteristics of the body, which behaves as the source of mechanical waves.
from IPython.display import Video
Video('./video/Kristall.mp4', width = 600)
Now we can analyze the sound. To this aim we can use the Audacity app.
We can import the file and look at the signal that has been recorded. The audio wave forces the membrane of the microphone to vibrate. The microphone acts as a transducer, generating a time dependent voltage that is proportional to the displacement of the membrane.
Looking in greater detail, we observe a kind of complex fluctuation.
For comparison, using Audacity, we show it in the figure here below, along with a pure sinusoidal function.
We can describe the recorded sound as a superposition of different sinusoidal functions, applying the Fourier analyis.
This plots (obtained using Audacity) represents the amplitude of the sinusoidal functions at different frequencies, whose sum will better describe the given signal.
We can observe that the sound has an intense component at about 823 Hz, and other components at 342 Hz, and 1440 Hz, respectively.
Now we can use te Audacity App to generate a continuous wave at 823 Hz, and play this sound close to the object that we have considered above. Suppose that we play the sound for 3 seconds
We have put the object in oscillation. The sound wave makes the object vibrate at this particular frequency, that is a frequency at which that body can oscillate. Once the body oscillates, it can itself generate a sound wave at that frequency, since it can transfer its motion to the air molecules near to its walls.
(c) 2022 Andrea Mandanici, Giuseppe Mandaglio, Giovanni Pirrotta, Valeria Conti Nibali, Giacomo Fiumara. All content is under Creative Common Attribution CC BY 4.0 and all code is under BSD 3-Clause License.