The pulse method is used to measure the ultrasound velocity Win stable and metastable liquid nitrogen at 95-125 K. The depth of entries into the metastable range amounts to 0.1-0.8 MPa. The ultrasound velocity on the Line of attainable superheat is determined. The behavior of Win the neighborhood of the spinodal curve is studied, and a unified (for the stable and metastable ranges) equation of ultrasound velocity is derived.