Måling og analyse av støy- og vibrasjonsmiljøet i stormpanservognen CV90

This report has been written as a contribution to FFI’s project “Technologies for network integrated combat vehicles” (TEKNISK), but it is also meant to serve future activities involving Infantry Fighting Vehicles (IFV), and in particular the CV90. The report deals with the noise and vibration measurements executed in a CV90 at the military camp at Rena on two occasions, May 27th 2008 and August 6th 2008. These measurements were conducted in order to examine the operational environment for the computer equipment to be installed in the vehicle for the common field tests which are to be carried out by the FFI projects TEKNISK and TAURUS during the fall of 2008. The purpose of the field tests is to test and demonstrate a BMS (Battlefield Management System) with new AR functions (Augmented Reality), and to examine how a MUAS (Mini-UAV) should be integrated and operated to support the BMS optimally. The noise measurements were primarily conducted with respect to a possible future speech recognition system, which will be installed in the vehicle. The system will be used to give oral commands to the BMS, and it is crucial that it functions in the noise environment inside the vehicle. The speech recognition system that has been chosen, DynaSpeak® from SRI International, is equipped with a noise filtering design tool and dynamic noise compensation, but the question is if that is sufficient. To examine the noise environment, sound pressure level measurements and sound recordings were conducted in different places in the vehicle during various gunfire and driving conditions. The measuring results are presented in tabular form and graphically. In addition, frequency and spectral analysis have been done on the measured data. The results show that the unweighted effective sound pressure level is in the interval 90-125 dB, and it reaches its maximum during driving at high speed on a hard surface. The maximum unweighted peak value is 142.7 dB, and it is of course obtained during gunfire. The constant background noise energy in the vehicle is concentrated around 100 Hz, but an important exception is idling, where the noise energy is situated at certain frequencies in the interval 0-800 Hz. The dialogue on the intercom is in the frequency range 200-1,200 Hz with rapid variations in amplitude. Both firing with the 30 mm main gun and the 7.62 mm machine gun result in noise that covers a large frequency range, primarily in the interval 0-4,000 Hz. As we do not know anything about the limitations of the noise environment in which the speech recognition system can function, we cannot draw conclusions as to how the system will work in the vehicle, but the results presented here form a basis for further investigation and tests. The purpose of the vibration measurements was to examine the vibration environment in the vehicle in order to be able to conduct vibration testing of the equipment which is to be mounted inside the vehicle. The measurements were done at the four fixation points of the vibration damped rack which will contain the equipment when driving at different velocities. The measuring results were then processed statistically by use of so-called PSD estimates (Power Spectral Density), in order to produce the input data for the vibration tests. The PSD-graphs show clearly the harmonic track frequencies of the vehicle, which correspond well with the theoretical values, and that the vertical vibrations are the most significant ones. The vibration tests will be conducted at FFI’s Environmental Laboratory.