Infrasonic Microphones

J4	Popocatepetl Colima New Mexico	The J4 microphone is similar to the McChesney4 microphone, but all four microphone elements are co-located within the enclosure. Its modularity allows external or internal power supply (single-ended), easy swapping of microphone elements, and variable gain/filtering controls. Two variants currently exist, the J4 New Mexico, which is deployed in New Mexico and at Colima, and the J4 Popo currently deployed at Popocatepetl, Colima, and in New Mexico.
J1 Basic	Stromboli Villarrica Santiaguito Fuego Colima Erte Ale	The J1 Basic is a very simple, extremely cheap (less than $10), unamplified, single-element (WM-034BY) microphone with corner frequencies between 0.5 and 0.8 Hz. It has an unbuffered output, but is extremely low-powered (6 months on two alkaline AA's). Different versions have single-pole anti-aliasing filters at 12 Hz and 38 Hz. The low cost and compact size enables deployments in multi-element arrays. Very successful array deployments have been conducted at Stromboli, Villarrica, Santiaguito, Fuego, Colima, and soon Erte Ale.
ISLA4	Erebus	The ISLA4 is a variant of the ISLA14, but with only four microphone elements. It was built for permanent deployment at Erebus
ISLA14	Kilauea	The ISLA14 microphone was adapted from the McChesney microphones, but utilizes 14 individual co-located WM-034BY Panasonic electret condenser elements. These buttons, which are used in the Seattle P and Q microphones (designed by Chris Hayward, Southern Methodist University), appear to have a much lower corner frequency (0.5 to 0.8 Hz). Positive and negative power supplies are required. Design and construction by Jeff Johnson with support from Infrasound Laboratory (ISLA), HIGP, UH. Deployed at Pu'u 'O'o, Kilauea.
McC#	Erebus Pichincha Tungurahua Stromboli	The McChesney1, McChesney4, and McChesney16 element microphones consist of a variable gain amplifier, low-pass RC filters (~20 Hz), and 1 to 16 individual WM-52BM Panasonic omnidirectional condenser elements. Each Panasonic condenser element has a slightly different sensitivity and corner frequency (~1 to ~5 Hz) which limit their application for infrasonic waveform modeling. However, the spatial wind filtering abilities of the McChesney 4 and 16 boxes allow identification of acoustic pulses in windy conditions (see section on noise in this appendix). Of all the McChesney units used in this study, only the microphones deployed at Erebus have undergone careful laboratory calibration tests to determine sensitivity and corner frequency so that instrument responses may be removed. McChesney microphones deployed at Karymksy were calibrated only by temporary co-location with the Larson-Davis microphone. Frequency response of the McChesney microphones resembles a single-pole high-pass filter to first order. Design and construction of the McChesney microphones is by both the author and Pat McChesney (University of Washington). Deployed at Erebus, Pichincha, Tungurahua, and Stromboli.).
Larson- Davis	Karymsky Erebus Erte Ale	The Larson-Davis free-field precision microphone is a commercially available electret condenser microphone suitable for engineering purposes and sensitive to near infrasound. The instrument deployed at Karymsky and Erebus consisted of a one-inch electret condenser element #2570, preamp PRM900C, and a power supply 2200C. Specifications are provided by Larson-Davis and verified in the McChesney laboratory calibration box. Laboratory calibration tests reveal a behavior which closely resembles a single-pole high pass filter with corner frequency at 0.27 Hz. In many experiments, the Larson-Davis microphone was temporarily co-deployed with other electret condenser microphones to assess the relative response of the other instruments. Deployed at Karymsky and Erebus.
Venema	Karymksy Sangay Pichincha	The Venema microphones (low and high gain) use Radio Shack omnidirectional electret condenser elements (catalog number 270-092B). The attached variable-gain amplifier and low-pass filters (~20 Hz) were designed and built by Brian Venema and the UW Physics electronics shop. Unfortunately, laboratory calibration tests conducted in 2000 may reflect deterioration of the sensing elements during their long life span. Absolute sensitivity at Pichincha is entirely unknown because signals were conveyed by telemetry atunknown gain. Deployments at Karymsky, Sangay, and Pichincha
Ramey	Karymsky	The Ramey microphone is a replica of the Dibble microphone in that it uses a similar enclosure and a pressure transducer with one of the differential pressure ports blocked. Pressure sensing element is a SenSym LX06002D transducer. Construction of microphone is by Jim Ramey (University of Washington). Deployment at Karymsky in 1997.