A Photographic Study of Sound Pulses between Curved Walls and Sound Amplification by Horns

Abstract

Photographic Study of Sound Pulses Passing between Walls Corresponding to Sections along a Straight Tube, a Crooked Tube, a Megaphone and a Conical Horn Receiver.—Using the photographic method previously developed by the author, four pairs of brass plates, each of the proper section, were arranged radially about the axis of the sound-producing spark so as to provide the four passages to be studied. As the sound pulse progressed through these passages, instantaneous photographs registered its position at various stages. Six of these are reproduced. They clearly show that whenever a pulse moves at an angle to a wall there is reflection in exact accord with Huygen's construction. Sound pulses, therefore, do not glide around bends in tubes without appreciable reflection. In the case of a pulse emerging from the open end of a tube or horn, the per cent. of the energy reflected is small, while much of the energy of a pulse entering the large end of a conical horn is reflected back out of the end it entered.