Study on Infrasound Propagation of Finite Amplitude Wave in the Big Size Horn

This work is aimed at studying changes of acoustic pressure amplitude of the second harmonic in the horn at excitation in horn throat of the finite amplitude wave as well as a determination of the coordinate of the horn’s axial section at which the amplitude reaches its maximum value. The analytical expressions, allowing analyzing the laws of increase and decrease of the second harmonic at excitation of the finite amplitude wave in the air-horn, are obtained. The distance, where the second harmonic propagating along the air-horn reaches its maximum, is determined. Comparative analysis for air-horns of different shapes is performed. All calculations were made for the horn, whose length is 10 meters and the diameter of the outlet section 4 meters. The resonant frequency of the acoustic signal in such a mouthpiece is 20 Hz.