Circuit arrangement for determining the fundamental frequency from a signal which is not bandwidth-limited and contains harmonics and interference signals, in particular for determining the fundamental voice frequency from a voice and speech signal

摘要

An arrangement is known for determining the fundamental voice frequency for triggering the flash tube of a stroboscope, consisting of the series circuit of a low-pass filter FI1 which has a controllable cut-off frequency, an amplifier having automatic gain control GV1, a zero-crossing detector ND1 and an evaluation and control circuit AS, implemented as a microcomputer, the control of the low-pass filter proceeding in 2 phases, a search phase and the actual control phase. Because of the search phase of about 80 ms, proceeding after each voice interruption, the arrangement has disadvantages for speech analyses. According to the invention, it is proposed to connect in parallel with the series circuit, consisting of FI1, GV1 and ND1 (channel 1), a second identical series circuit, consisting of FI2, GV2 and ND2 (channel 2), on the input side, and to feed the outputs of both series circuits to two separate inputs of AS. The controllable low-pass filters FI1 and FI2 obtain different control signals TFS1 and TFS2 via two separate control outputs from AS. As a result, the search and control phases can be carried out in parallel. The invention is applied in speech analysis, in stroboscopes and in voice diagnostics. <IMAGE>