The frequency of a sound wave refers to the number of cycles or vibrations the wave completes per second. It is measured in units called hertz (Hz).
In the case of your example, a sound wave with a frequency of 70 hertz (Hz) means that the wave completes 70 cycles or vibrations in one second. This measurement indicates the pitch or tone of the sound. A lower frequency, such as 70 Hz, corresponds to a lower pitch sound, whereas higher frequencies result in higher-pitched sounds.
To give you some context, sounds in the lower frequency range are typically associated with deep tones, like the rumbling of thunder or the lowest notes on a musical instrument such as a bass guitar. Sounds with higher frequencies are associated with higher-pitched sounds, such as the chirping of birds or the tinkling of a wind chime.