Direct Field Acoustic Testing (DFAT)

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  • NASA

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  • Office of the Chief Engineer

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The information in this handbook presents an overview of Direct Field Acoustic Testing (DFAT). DFAT is a relatively new aerospace acoustic testing method, first used for acoustic qualification of a spacecraft in the late 1990s. DFAT has certain advantages over the conventional reverberant field acoustic testing (RFAT) approach, in particular, reduced facilities development and maintenance costs and portability of the acoustic test equipment. The major disadvantages are a lack of coherent acoustic field that results in spatial variation; and the current technology limitation of not being able to produce sound pressure level (SPL) in excess of 147 dB. Even with the advancement of the control systems using DFAT for acoustic qualification testing, the pressure field and measured structural responses can differ significantly from an RFAT test, even if the control microphones are kept within the test tolerances specified. Significant advances in the DFAT control systems have been made in the last few years, which alleviate many of the previous concerns with this test method. However, application of DFAT varies widely among the NASA Centers and their contractors. Therefore, this NASA Technical Handbook provides the best current guidelines for implementation of the DFAT test method.

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