INSUL is a program for predicting the sound insulation of walls, floors, roofs, ceilings and windows. Impact sound and rain noise of floors and roof. The software provide good estimates of the Transmission Loss (TL) or Impact Sound (Ln) in 1/3 octave bands and Weighted Sound Reduction Index (STC or Rw) or Impact Rating (IIC/LnTw) for use in noise transfer calculations or acoustical design or specification.