This device provides for rapid analysis of short samples of speech and other sounds. It permits direct viewing of the energy‐frequency distribution of the sound at instants of time in a two‐dimensional pattern, and also over intervals of time as a three‐dimensional pattern. Magnetically recorded on a disk at slow speed, and speeded up 200 times on playback, the sample of sound is analyzed rapidly by a broad band high frequency system.
The three‐dimensional portrayal (in time, frequency and amplitude) shows the whole sound sample, including an interval of about , on one cathode‐ray tube, together with a movable indication of the point in time at which the “instantaneous” or two‐dimensional frequency‐amplitude section, appearing on another tube, is taken. This two‐dimensional pattern displays amplitude on a decibel scale and covers about a 40 db range. The complete pattern is made up of 190 amplitude values for the 100 to 4000 cycle frequency range so that the pattern is formed by 190 vertical lines. The effective band width of the resolving filter is 45 cycles. The patterns are scanned at a rate of 2/sec. so that a slow phosphor screen is used for viewing. Successive sections approximately , 5, 10, 20, or 40 milliseconds apart may be established and photographed automatically. Or for direct viewing manual selection of any desired point of analysis is provided.
