NASA-HDBK-7010, NASA TECHNICAL HANDBOOK: DIRECT FIELD ACOUSTIC TESTING (DFAT) (01-FEB-2016)

NASA-HDBK-7010, NASA TECHNICAL HANDBOOK: DIRECT FIELD ACOUSTIC TESTING (DFAT) (01-FEB-2016)., This NASA Technical Handbook is published by the National Aeronautics and Space Administration (NASA) as a guidance document to provide engineering information; lessons learned; possible options to address technical issues; classification of similar items, materials, or processes; interpretative direction and techniques; and any other type of guidance information that may help the Government or its contractors in the design, construction, selection, management, support, or operation of systems, products, processes, or services. This NASA Technical Handbook is approved for use by NASA Headquarters and NASA Centers and Facilities. It may also apply to the Jet Propulsion Laboratory and other contractors only to the extent specified or referenced in applicable contracts. This NASA Technical Handbook establishes a common framework for consistent practices across NASA programs, addressing the application of the direct field acoustic test (DFAT) method for acoustic testing of spaceflight hardware. 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