This 1968 U.S. Navy film SUBMARINE SOUND AND VIBRATION MEASUREMENT shows the techniques used to conduct airborne and structureborne noise surveys, in hopes of producing quieter and stealthier submarines. The film begins with an overview of the noise problem, with subs giving away their position to the enemy, and causing various crew problems including deafness.
As the narrator describes: Noise is a potential hazard by which a submarine might give away its location to the enemy, it shows malfunction for some years now, and its also an incoherent sound that could cause deafness as seen at mark 1:28. the navy has been developing equipments to combat noise as seen At mark 2:00 . The different kinds of noise measurement surveys are seen at mark 2:18; the airborne noise with two sub categories. At mark 2:58 is the structure-borne noise. At mark 3:20 is the total airborne noise survey. Before the survey is carried out, you must check your instruments. At mark 3:48, there are 2 equipments seen; sound level meter and an active bar analyzer. These two are combined and both has its functions as seen at mark 4:00. The survey is started at mark 4:25. The internal calibration is check. The next procedure is for the accuracy on the meter readings. The equipments needed for this are seen at mark 5:20. The calibrator is connected to the oscillator and also adjusted as seen at mark 6:20. At mark 7:00, the sound level meter is now ready. Next is the analyzer as seen at mark 7:05. With all the settings, the analyzer should now give the same readings as the sound level with the pointer at 0. That completes the calibration at mark 7:35.
The internal noise of each instrument is then checked at mark 7:40. Now the airborne survey is ready. At mark 8:10, readings are taken at compartments. At mark 8:35, an ambient reading is taken; a measure of the background noise. At mark 9:00, the background noises are modified by the analyzer. At mark 9:40, same reading is taken again with the machines in operation. At mark 10:10 is the ventilation system noise survey. For this, same gears can be used but this time, the ventilation noise is for the air conditioning system.
The structure borne noise survey is carried out next as seen at mark 11:00. The instruments used are also seen such as the accelerometer at mark 11:45. The accelerometer is attached to a side of the disc. At mark 12:03, the calibrator is turned on and all adjustment are made. At mark 12:40 is the calibration excitor which can produce calibration at any frequency. It requires some auxiliary equipment. At mark 13:05, the accelerometer s attached to a washing system. The background reading and new readings are taken. 3 readings are taken on each machine, acceleration, velocity and displacement as seen at mark 14:00. Broadband structure borne noise survey checks if any machine has become excessively noisy as seen at mark 14:12.1/3octave surveys do the same thing in a more thorough way. At mark 14:28 is the octave survey which requires more equipment. At mark 14:45, the functions of each equipments are discussed starting with the accelerometer. At mark 15:30, the narrowband data is written out inform of a graph on a paper sheet by the graphic level recorder. The system is prepared for use at mark 15:40 with all connections appropriately set. The analyzer is calibrated to match the reading of the sound level meter at mark 17:00. But it does not show, hence you must note the dB. At mark 18:12 is the diehard drive unit, a new system. At mark 18:48, you take the octave data. At mark 19:00, a graph of the broadband noise is obtained. The analyzer is also set at mark 19:35. This is what happens in the case of an off scale reading at mark 20:30. Turn till you get an on scale reading. You must remember to write down every change in attenuation machine.
In this film, the equipments, methods for measurements and analysis for these surveys has been seen. Before you begin, consult handbooks as they are as always your best guides.
This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com