Sound: Periodic and frequency

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A simple vibration has a SINUS shape. If you excite (beat) a tuning fork, then an almost sinusoidal oscillation is produced. The tuning forks oscillate back and forth in a sinusoidal form and transmit this oscillation to the surrounding air.

frequency This sinusoidal oscillation is periodic because the form of the sinusoidal oscillation is repeated at constant time intervals. The same oscillation is repeated in the so-called periods. On the left side of the picture there are two black dots which represent the beginning and the end of a period. The period duration is given in seconds.

The reciprocal of the period 1/s is the so-called frequency in the unit Hertz [Hz]. The frequency indicates how often a periodic oscillation is repeated per second. Example 2Hz means two oscillations per second. This means that one oscillation lasts half a second (0.5s). 20Hz means 20 oscillations per second and 20000Hz means 20000 oscillations per second.

The human being is able to perceive (hear) all frequencies between 20Hz and 20kHz. In old age this frequency range decreases to for example 100Hz to 15kHz. But more about this in the later chapter.

Ultrasound

What is amplitude and what is that? ==>