An analysis of different thermodynamic properties as a function of temperature provides valuable information about their characteristics. The ultrasonic velocity of the ternary mixtures ethanol+water+1-pentanol at the range 288.15-323.15 K and atmospheric pressure, has been measured over the whole concentration range. The experimental ultrasonic velocities have been analysed in terms of different theoretical models, an adequate agreement between the experimental and predicted values both in magnitude and sign being obtained, despite the high non-ideal trend and partial miscibility of the ternary mixture studied in this work. The obtained experimental values indicate varying extent of interstitial accommodation among unlike molecules as a function of steric hindrance attending to 1-pentanol as key component and as a function of hydrogen bond and temperature attending to ethanol as key component.