INFLUENCE OF THE THICKNESS OF THE BACK WALL OF A WOODEN ORGAN PIPE AND THE AIR PRESSURE IN THE WIND CHEST ON ITS SOUND PROPERTIES

Abstract

The paper presents the results of the study of the influence of the back wall thickness of an organ pipe made of resonant spruce wood and the air pressure in the wind chest on its frequency spectrum. A wooden organ pipe with a replaceable back wall was used in the experiment. The wooden plate used for the back wall had an initial thickness of 7 mm. The plate was gradually thinned in 1 mm decrements to a thickness of 1 mm. For each plate thickness, the frequency spectrum was scanned at four different air pressures, namely 588 Pa, 716 Pa, 814 Pa and 941 Pa. The results of the experiment showed that at a given back wall thickness, the fundamental tone frequency increases with increasing air pressure. The decrease in the back wall thickness was manifested by a decrease in the fundamental frequency. At an air pressure of 716 Pa, the intensity of the fundamental as well as the second harmonic component of the pipe acoustic spectrum increased slightly at all wall thicknesses. With increasing air pressure, the intensity of higher harmonic frequencies also increased. The decrease in the back wall thickness of the wooden organ pipe had only a minimal effect on the intensity of the individual harmonic components of the frequency spectrum. Changing the thickness of the back wall of a wooden organ pipe will not significantly affect its final sound.