1. if the frequency of the sound is increased then the pitch will

The pitch will increase because high frequency have high pitch and low frequency have low pitch pitch is directly depend on the frequency .For example, soprano singers stretch their vocal cords, so they vibrate more quickly as the air rushes by them, which creates higher-frequency sound waves that have a higher pitch.

Ibelieve the topic sentence is [1] keeping my mind on my writing is not easy when i stay at my grandfather's ocean-side cottage. hope this : )