McDewey

−40 50 −50 40 −60 30 −70 20 −80 10 −90 0 DBrnC Noise contains numerous irregular waveforms that have a wide range of frequencies and powers. Although any noise superimposed upon a conversation has an interfering effect, experiments have shown that the interfering effect is greatest in the midrange of the voice frequency band. In order to obtain a useful measure of the interfering effect of noise, the various frequencies that contribute to the overall noise are weighted based on their relative interfering effect. This weighting is accomplished through the use of weighting networks, or filters, within TIMS. Noise measurements through a C−message weighting network are expressed in units of dBrnC (noise above reference noise, C−message weighting). DBrnCO As with test−tone power, noise power can be referenced to the 0 TLP. For example, if the noise objective for the circuit is 31 dBrnC0, what is the noise measurement at the +7 TLP? TLP) + (Noise at the 0 TLP) = (Noise at TLP) (+7) + (31 dBrnC0) = 38 dBrnC The noise measurement at the +7 TLP is 38 dBrnC. What is the noise measurement at the ™6 TLP? (TLP) + (Noise at the 0 TLP) = (Noise at TLP) (™6) + (31 dBrnC0) = 15 dBrnC The noise measurement at the ™6 TLP is 15 dBrnC. Related Information Voice Technology Support • Voice and Unified Communications Product Support • Troubleshooting Cisco IP Telephony • Technical Support & Documentation − Cisco Systems • Contacts & Feedback | Help | Site Map © 2014 − 2015 Cisco Systems, Inc. All rights reserved. Terms & Conditions | Privacy Statement | Cookie Policy | Trademarks of Cisco Systems, Inc. Updated: Feb 12, 2007 Document ID: 8628