Abstract

Computational modeling (BEM, FEM, and SEA) is often implemented at different stages of the design process to optimize manufacturing and performance parameters. Computational results are typically verified experimentally. Experimental testing standards, particularly those related to vibro-acoustic testing, are defined by various agencies such as ASTM, ANSI, and ISO. An investigation proposing a new computational methodology of analyzing the vibro-acoustic behavior of an aircraft fuselage due to the turbulent boundary layer required verification of the predictions experimentally. In the face of certain limitations, an atypical acoustic facility was constructed challenging conventional standards while complying with the defined criteria of international testing standards. Principal deviations relate to the geometric requirements that recommend large volumes of certain construct, and microphone and acoustic source positioning. The calculated 95% confidence intervals compared exceptionally well against defined criteria (strictest measure is 1 for frequencies greater than 315 Hz) by averaging less than 0.4 for each test product across a frequency range that exceeded is the range specified by ASTM E90. The requirements for qualification of the reverberation chamber according to ANSI S12.51 were also satisfied, with the exception of measurements at 125 Hz and 160 Hz that observed heightened sensitivity due to near field effects and room modes. The calculated permissible ratio of decay variation showed good agreement against ASTM C423 criteria despite the intrinsic challenge of creating a diffuse and reverberant field in a confined, or constricting, volume. The last compliance measure reviewed flanking to ensure acceptable signal-to-noise ratio. It was clearly demonstrated that the silenced sound pressure levels (with the presence of the specimen) were greater than 10 dB above the background sound pressure levels (with the consequences of flanking considered). The investigation confirmed the feasibility of using an atypical acoustic facility to comply with various international testing standards. The noted deviations and shortcomings are not specific to the presented work, but are common challenges that all facilities observe.

This content is only available as a PDF.
You do not currently have access to this content.