Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
Paper and pulp manufacturing are forest-based industries. The basic raw material for the pulp and paper industry isthe wood. Softwood of the temperate forests is especially suitable for making pulp and paper.
EXAMIANS