Graph (a) represents the male voice. Usually the male voice has less pitch as compared to female.
The faster the vibration of the source, the higher is the frequency and the higher is the pitch, as shown in fig. (b). Thus, a high pitch sound corresponds to more number of compression and rarefaction passing a fixed point per unit time.
In fig. (a), the vibration of the source is slower, the frequency is lower and therefore pitch is also lower.
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