Switching Arm Research Articles

Method for Measuring Fine Details of Differences in the Structure of Various Speech Sound Spectrums

Fine details in the spectral differences of various speech sounds can be distinguished by comparing envelope curves. In a Scanvocoder the differences can be found instantaneously if the envelope signal is distributed to (for example) 100 equal condensers by a switching arm that rotates synchronously with the analyzer switching arm. If the envelope curve does not change between two consecutive rotations, no difference charges have flowed to or from the condensers during the second rotation. If the envelope curve does change, its difference in direction and size corresponds to the difference in charge of the several condensers. A small pulse transformer in the link to the distributing switching arm picks up pulse voltages corresponding to the difference charges. Smoothed in a low-pass filter, these voltages are linked to the y deflection plates of an oscilloscope. If the electron beam is also deflected in the x axis synchronously with the rotating switch, the difference between consecutive envelopes appears as a difference curve. Because the condensers have a long discharge time, it is possible (by special switching arrangements) to compare the envelope curves of sounds spoken by the same person or by different persons. Variations of such difference curves with time also can be measured.