“NOISE DETECTIVE”

Wairarapa Times-Age, 20 May 1938, Page 9

“NOISE DETECTIVE”

EXPERIENCES OF POLICE SOME UNUSUAL ADVENTURES. TRACKING DOWN CRIMINALS. Noise has come to be recognised as one of the criminals of the modern world, and detectives are engaged in tracking down harmful sounds in much the same way as policemen track down evildoers, says a writer in the “Adelaide Chronicle.” In the course of some years as a “noise detective” I have had many interesting and not a few amusing experiences. Perhaps the quaintest adventure was at a house which had been divided into flats, where a tenant complained that every evening, between 10 and 11, he was disturbed by a regular tapping noise. I went to the house and examined the noise. I found it was rather percussive, had a fairly regular periodicity of about four seconds; but several hours’ search failed to reveal any clue as to its origin. I was not prepared to admit that it might be a workman who had accidentally been walled up during rebuildings. (I have had this theory put to me about a noise at a London theatre), and I decided to investigate the flat next door.

There I was admitted by a lady in a dressing-gown who told. me she never heard the noise, but gave me a free hand to look round. She watched me for a few minutes, then returned to her chair and began to read. Suddenly I heard the noise, this time much louder! I looked round, and there was the lady snapping the garter on her leg with one hand as she read. It was an entirely unconscious habit she had acquired, and by some acoustical peculiarity the sound of the elastic snapping travelled to the next flat. We all laughed, and none of the elaborate sound-absorbing blankets I had suspected might be necessary were required to stop the noise! The way in which sound travels along girders and through concrete in certain circumstances astonishes many laymen. If you try the experiment of putting a watch upon an iron bar ten feet long and listening to the ticking at various points you will appreciate why careful insulation for sound is necessary in modern buildings. I was once called to a hotel in which it was found that the whispering of two people in a certain position in one, room could be distinctly heard in every room down the corridor! A guest in a hotel once complained of a creaking sound every morning and evening, as if there was a board loose in the room above. The boards were examined, but found to be in order, and I was asked to track down the noise. I found it eventually in a room two floors above, being made by a man who used a spring muscledeveloper. He had screwed the developer into a piece of wood which was touching a girder. The sound travelled down two floors in the girder and then was “broadcast” by the whole side of the room acting as a loudspeaker diaphragm. In another case it was found at a certain restaurant that the acoustical properties of the room were such that the lowest whisper at one table could be clearly heard at every other. When the diner learnt romantically across the table and whispered, “Darling, you look absolutely wonderful tonight!” every diner in the restaurant looked up! That noise was quickly tracked, and the trouble cured by altering the acoustics of the room. It cost hundreds of pounds that could have been saved by a simple experiment before the roof was built. There was at one time a certain position on the stage of the old Alhambra Music Hall in London .where the sound was reflected from the gallery to the pit, so that an actor’s voice sounded in certain seats of the pit exactly as if it was coming from the gallery. A famous comedian discovered the acoustical eccentricity, and worked some “gags” which made the pit very angry with the completely innocent people in the gallery!

Every car owner knows that noise can be a great help in the detection of faults in the engine. Experts whose ears have been trained will detect imperfections where the ordinary man finds nothing unusual. More than a century ago Fulton, the famous steamboat builder, walked into a building in New York where a perpetual motion machine was being exhibited to the public. Immediately he said: “That is not perpetual motion. I can hear it being worked by a crank.” He risked his reputation and a considerable amount of money on his statement; and sure enough, when various boards were torn away, the “perpetual motion" machine was shown to be connected by a crank to a hidden engine!