Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) SAKAMOTO Syuichi and ICHIMIYA Ryoichi and SUZUKI Yuji,A new measuring method of displacement by means of variations of sound frequency and the length of air column in a small pipe. A resonant method by using speaker and electric feedback loop.,TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series C,03875024,The Japan Society of Mechanical Engineers,1990,56,530,2562-2566,https://cir.nii.ac.jp/crid/1390282681273405312,https://doi.org/10.1299/kikaic.56.2562