High Pass Filter Application to Reduce Voice Communication Delays on IP Phones

VoIP technology is equipped with several functions, namely, the signalling function, meaning the VoIP is in charge of receiving the network from the caller, after which the conversation delivered. This technology is capable to pass voice traffic in the form of packets over an IP network. Packets of sound undergo a long process or delay to get to the destination it can damage the voice’s quality being heard. It happened because there is continuous delay in the communication between IP phone set on VoIP technology that causes echo in the receiver’s voice. Echo can occur during communication with IP phone set with average delay capacity above 5ms. The delay on the delivery and reception as in the results of communication between telephones can be adjusted for sound frequency of 300 Hz to 1000 Hz as a cut off by adding High Pass Filter (HPF) application. HPF filter application is able to stabilize the amplitude of about -21 dBm from the set of transmission test on the receiver when there is weakening at low frequencies, but when the frequency is raised to 1500-2250 Hz the amplitude strengthens to -12,2 dBm or increases the value of about 8.8 dB. Meanwhile, for the lower frequency such as 300 – 950 Hz, the filter would not pass it since the frequency is designed to be cut-off at 1000 Hz. The value of delay is narrower to 0.08ms by HPF application at the frequency of sound upper limit received by any 1000-3400 Hz telephone set. Keywords: VoIP technology, echo cancelling, HPF filter, delay, voice quality

Research of the Passive Information Protection Device in the Acoustoelectric Leakage Channels Using Matlab Environment

Purpose: design of the passive device of the speech information protection from acoustoelectric leakage channels and study of the characteristics of protection device using a virtual laboratory bench developed in the Matlab environment. Methods: mathematical modeling using Matlab environment. Practical relevance: designed in the Matlab modeling environment: an equivalent circuit of the telephone set, which makes it possible to simulate acoustoelectric information leakage channels, schematic diagrams of passive protection devices for telephone sets that implement protection methods: limiting low-amplitude signals, filtering high-frequency injection signals and disabling acoustoelectric transducers, a virtual laboratory stand for research of the characteristics of protective device. Using a virtual laboratory stand, the main characteristics of the developed protection devices were studied and their performance was assessed when connected to the telephone network.