IMS Infrasound Monitoring Test Site at Trafelberg, Austria: Preliminary Results from In-Situ Response Measurements of Infrasound Elements
Abstract
The International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) has a unique infrasound test site (I99AT) with four wind-noise-reduction pipe-array systems in close enough proximity to allow simultaneous measurements under similar environmental conditions. It was designed as a facility to study the effectiveness of various wind-noise-reduction systems so it is clear of trees, vegetation, or other wind breaks. The persistent winds presented a challenge for response measurement by reference-microphone comparison however, there were several suitable periods during the eight days of continuous recording from 19 May to 27 May 2010. Reasonable estimates for the magnitude and phase response of all four infrasound elements at I99 were made from 0.008 Hz to several Hz. For all four elements, from 0.01 to 0.1 Hz, the measured magnitude and phase correspond closely to the manufacturer?s specifications for the MB2005. Above 1 Hz, the effects of the pipe system produce a significant change in the phase response compared to the MB2005. Below 0.01 Hz, the phase also changes somewhat faster than expected. A preliminary investigation of the effects of non-acoustic turbulence and the associated scale sizes was performed and an apparent drop in the magnitude response of the larger elements below 0.08 Hz was tentatively associated with area-averaging of non-acoustic pressure fluctuations. Finally, in windy conditions, the large hexagonal element showed higher spectral levels from 0.2 to 3 Hz than the small element.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2010
- Accession Number
- ADA569457
Entities
People
- Georgios Haralabus
- Stefi Stefanova
- Thomas Gabrielson
Organizations
- Pennsylvania State University