During the transmission of speech the relevant sound levels are registered. The peak level threshold is set which is then slowly reduced until a new peak exceeds the threshold. The threshold is then rest to the new peak value, and the procedure repeated. The minimum value is treated similarly, but the set minimum threshold is slowly raised until a lower value again resets the threshold. Maximum and minimum thresholds (SW1,SW2) are operated upon to form a difference threshold value (SW3). When the difference is large the threshold (SW3). When the difference is large the threshold (SW3) tends to the peak value (SW1), when low to the minimum value (SW2). The peak value decay time constant is in the range 3-5 seconds, the minimum value rises with a time constant between 6 and 12 times that of the decay. The choice of times ensures that short pauses between words and sentences have no significant influence on the measurements. 
VERFAHREN ZUR UNTERSCHEIDUNG VON SPRACHSIGNALEN VON SIGNALEN GERAEUSCHFREIER ODER GERAEUSCHBEHAFTETER SPRACHPAUSEN.