Testing an Extremely Large Payload

Using a sound field that is uniform and incoherent in both the horizontal and vertical axis.

Challenge

This customer requested support from ARS to test an extremely large payload with sound field that is uniform and incoherent in both the horizontal and vertical axis. Sub-goals were to significantly reduce scheduled test time, and reduce time spent reconfiguring between bare circle and flight hardware test configuration. There was also an impetus to improve safety and update best practices versus legacy industry practices and compromises for concert line array and subwoofer systems. The customer as well requested hands-on support for 3rd party facility test-readiness process and a supply high channel count data acquisition system to support capture of customer sensors during DFAN test.

Approach

  1. Utilize truly uncorrelated drive sources so a large number of Neutron™ devices can be driven by a similarly large number of uncorrelated sources, eliminating the problems encountered by large vertically coherent line source arrays when testing large, tall test articles.
  2. Establish the requirement for 90 Neutrons™, less than half of what would be required by legacy systems, which when combined with exceptionally efficient proprietary suspension and stability solutions, enables a reduction in setup and reconfiguration time of 50%.
  3. Configure circle to allow entry and exit of the test article from the circle with the removal of only two Neutron™ columns.
  4. Supply engineering support from ARS from a team of acoustical, structural, and health and safety experts to ensure 3rd party facility test-readiness process was successfully completed to the satisfaction and approval of all parties. From ARS’s inventory of data acquisition solutions, a 450ch DAS was supplied, and was integrated with the acoustic control system allowing for all microphone and accelerometer time histories to be delivered to the customer in their raw unprocessed form and fully time-aligned to each other.

Results

The extremely large payload was successfully tested to its required level of 142.dB OASPL. The large Neutron™ deployment provided the expected uniform and diffuse field, demonstrating exceptional incoherence and a lack of standing waves both horizontally and vertically. Setup time vs previous large payload DFAN tests was 50% faster and safety was increased significantly through the use of pre-built microphone attachment frames and lateral bracing support structures. Additionally, various suspension points were provided to the customer for the safe suspension of umbilical and sensor cables from the test article to the ground. All facility and human safety requirements were met or exceeded during all phases of the test campaign. All data acquisition activities were completed successfully and raw time history files from all microphones and accelerometers were delivered to the customer following each run, the alignment of transients and the single source file expedited the test analysis process and saved time to schedule.

Specifications

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