Institutet för rymdfysik

BASIC DATA ANALYSIS

Background information

Infrasound stations & network

Our infrasound stations consists of 3 microphones connected to an amplifier and a low-pass filter card, which is then connected to an A/D-card inside a computer. The microphones have good low frequency response down to DC. The filter cuts of everything above 8 HZ, and the signal is then sampled at 18 HZ.

The data is then collected by a central server for storage and analysis. Here is a schematic over the infrasound network.

Schematic over the infrasound network

Files and file format

The entire day is divided into 48 30-minutes files. Files are written in a binary format (.bin). Within the file data are written in 512 samples blocks, each block containing the timing information and A/D readings from all 3 microphones. The sampling frequency is approximately 18 Hz, so that 32k samples (exactly 32256) is obtained from each microphone during 30 minutes. Time information in all files is the Internet-time (or in some stations GPS-time) with an accuracy of about 0.1 sec.

File names:

Additional software:

il2tmseries.exe may be used to convert .bin files into ASCII time series files. That software is also available at the above html-address.

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