Chaparral Physics Research Jay Helmericks, Duncan Marriott, John Olson Wilson Infrasound Observatories Geophysical Institute, University of Alaska Fairbanks Presented at the Infrasound Technology Workshop Bermuda 3 Nov 2008 This presentation does not necessarily reflect the policies or views of the United States Government.
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Chaparral Physics Research Jay Helmericks, Duncan Marriott, John Olson Wilson Infrasound Observatories Geophysical Institute, University of Alaska Fairbanks.
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Chaparral Physics Research
Jay Helmericks, Duncan Marriott, John OlsonWilson Infrasound Observatories
Geophysical Institute, University of Alaska Fairbanks
Presented at the Infrasound Technology WorkshopBermuda 3 Nov 2008
This presentation does not necessarily reflect the policies or views of the United States Government.
CP Research • ITW 2008 2
AbstractThis talk will cover two areas of research that Chaparral
Physics has been pursuing, both of which are of interest to the general Infrasound community. The first is an investigation of the linearity of Chaparral Physics sensors. The testing shows that there are three regions: with small-amplitude signals the sensor is fully linear; then, as the signal amplitude increases, there is a point where the linearity of the sensor depends on the shape of the incoming wave; and finally, as the signal exceeds 150 Pa peak-to-peak the sensor response completely departs from linearity. The second area of research looks at both the effectiveness and frequency response of wind noise reduction systems, from ~5 Hz to 100Hz. The effectiveness of wind noise reduction systems have been studied extensively, but little work has been done on the frequency response of such the systems. Preliminary results from this research will be presented.
CP Research • ITW 2008 3
Introduction
▫ Linearity of Chaparral Physics sensors
▫ Frequency response of soaker hose▫Large area vs small area wind noise
reduction systems
▫ New Chaparral Physics sensors
CP Research • ITW 2008 4
Linearity Setup▫ Constructed a test chamber with
heavy plywood with a subwoofer as the signal source
▫ Standard audio power amplifier and sound card to drive the speaker
▫ Pressure reference was a G.R.A.S 40BF ¼” microphone
▫ Able to test from 1 to ~ 200Hz, and 0.5 Pa p-p to 700 Pa p-p
CP Research • ITW 2008 5
Test Chamber
CP Research • ITW 2008 6
Test chamber opened
CP Research • ITW 2008 7
Single Tone Test
▫Drove the chamber with a sine wave of varying frequency and amplitudes
▫Compared the output of the G.R.A.S. microphone to the Chaparral microphones