1.1 This standard specifies the conditions for laboratory testing of the resistance to acoustic vibrations of on-board equipment in subsonic and supersonic civil aircraft. Two types of tests are specified: equipment operation tests and sonic fatigue tests. Functional tests are carried out during the development of the devices for certification. Sonic fatigue tests are generally used to detect structural defects in equipment during its development stage. 1.1.1 Equipment performance tests may be carried out according to each of the following methods:
——broadband noise testing;
——rehearsal of harmonic sounds. Sonic fatigue tests are carried out according to the broadband noise method. 1.1.2 The choice of the degree of severity of the test is up to the user, according to each of the following methods: a) If there are measurements of the acoustic pressure levels in the place where the equipment is going to be installed, either due to the conditions flight or by calculation, the user can use them to determine the test acoustic pressure levels by the method proposed in this Standard. This is designated as method "A" (see 4.4.1, 5.2.1 and the Annex). b) If these measurements are not available, or you do not wish to use method "A", the test levels according to this Standard can be obtained, based on the type of aircraft in which it is going to be installed, and the location of the equipment in the aircraft in relation to noise sources. According to this method, which is designated as "B", the test sound pressure level can be determined by means of the tables and formulas given in this Standard (see 4.4.2, 5.2.2 and the Annex). 1.2 The tests are planned for equipment sensitive to acoustic vibrations. The characteristics necessary for performance and fatigue tests by broadband noise or harmonic sound methods, as well as the sound pressure level, must be indicated in the equipment specifications. 1.2.1 Equipment on board aircraft, located at points where overall sound pressure levels do not reach 125 dB, should not normally be subjected to environmental acoustic vibration tests.