Large quantities of ultra low‐frequency acoustic data accumulated over long periods of time can be analyzed by several methods. Preliminary analysis of the analog waveform determines specific areas of primary interest prior to digital‐computer analysis. Data of no consequence can be discarded; or, the worth of such data may be graded, to scale their importance for computer processing. This technique also provides a means of expediting initial findings, and primary conclusions can be deduced. This study was conducted by the University of California, Los Angeles, and entitled, “Ionospheric Disturbance Experiment.” The raw tape‐recorded data are played back through an electronic system. Some important parts of this system are narrow bandpass filters and a Missilyzer (sound spectrograph). Some sample results are summarized.