Salt Lake Telegram | 1928-09-23 | Page 15 | Aviation Experts Tussle to Vanquish Engine Noise

Aviation Experts Tussle To Vanquish Engine Noise By ANDRUE BERDING Associated Press Pres Staff Write LONDON AP Aeronautical engineers engineers en- en the world over are working work work- ing long hours day and night to solve one ot of the greatest problems ot of commercial aviation Tho carrying ot of passengers by byall all air they they believe will never be a a. complete success until the Incessant incessant inces- inces sant throbbing and pounding ot of the great motors is e Engineers are on only y beginning to approach a solution of the Their difficulty consists in Ing the discomfort to passengers oJ of traveling g In close Iose proximity to two or 01 three engines aggregating from to 1 explosions a minute These engines moreover are rigidly rigid rigid- ly connected to the ot of the airplane by materials which are highly sound The stay stay- wires wings and cabin walls are ot of god resonant material Tho cabin itself reverberates and becomes It a sound box AU All these points create considerable difficulty With regard regald to the engines It the frequencies ot of the motor exhausts exhausts ex- ex are arc not exactly alike beats result which Impinge unpleasantly unpleasant unpleasant- ly upon the passengers passengers' ears The propeller itself Is a considerable source ot of noise noie and its own po- po C- C cullar culiar sound like lIko that ot of the motor exhaust is rich In harmonics actually ac- ac producing a complete series Substitution ot of metal for wooden propellers has eliminated some noise because wooden screws were mor more subject to slight bending known as flexural vibration One ot of the first means experts are employing to lessen noise Is to change the tho construction ot of the cab cab- Ins It Is most important to make the walls oJ of the cabin nonflexible so that they cannot vibrate Some cabins are nOw being lIned with balsam wool and the floors are beIng being be- be Ing covered with carpets The Imperial Airways com company pan which operates a service between London and the continent provides its passengers with a cotton wool plug for tor their ears cars which has been found quite effective In absorbing sounds ot of high frequency Engineers are trying to eliminate eliminate nate a fruitful SOUrce ot of uneasiness uneasiness ness to the inexperienced traveler production ot of beat and its varla- varla tion A passenger soon gets accustomed accustomed ac- ac to constant rhythmic noise nole and loses thought ot of danger But Dut when the engines get out ot of step with each other and vary their beats from sa say one In five I seconds to two a second the passenger pas pas- enger at once notices the change chan and becomes alarmed Expert mechanics are now working on this problem ot of synchronizing motors Considerable attention has been devoted to silencing the engine exhaust ex- ex haust on airplanes Some progress I I has been made but no silencer has come into effective use because of the Increase of weight Involved Addition ot of weight Indeed seems to be more or less the crux ot of the problem The three ply cabin material material ma- ma adds several hundred pounds alone Until Inventors can devise ways ot of decreasing noise without Increasing weight aircraft manufacturers manufacturers manu manu- will be slow In making use ot of the new devices