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Minimizing Noise on VoIP Calls

written by: George Garza•edited by: Linda Richter•updated: 6/1/2010

Voice over IP or VoIP is the capability to carry on a normal telephony-style call over an IP-based Internet connection with Plain Old Telephone System (POTS)-like voice quality, reliability and functionality. You can minimize noise on VoIP calls to transmit a high quality phone call.

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    What is VoIP?

    The telephone has been around for over 100 years. Obviously many improvements took place over the years, but through it all, it was an analog-based system, where voice frequencies are transmitted over the phone line. With VoIP, the technology is radically different. It is digital. It is based on packets that contain the audio frequencies that one hears. The audio frequencies are broken down and converted into a digital format. Then they are transmitted over the Internet line, like data. At the receiving end, the packets are de-coded and converted back to an analog signal which the hearer then interprets as a telephone call...loud and clear.

    VoIP can be just as convenient to use as a regular phone. You can make a phone call directly from a computer, or a regular phone with special VoIP equipment attached, or a VoIP phone. There is nothing challenging or intimidating about the VoIP phone system; moreover, it can be used anywhere that there is an Internet connection.

    voip HowItWorks 0203v2 

    Source: FCC

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    What is Noise?

    Noise is any interfering sound in a phone call. In VoIP, noise can be classified as distortion. It can degrade the transmitted signal. So in a VoIP environment there are two types of distortion: subtractive and additive.

    As noise goes, VoIP does not present a “new” source of noise or distortion that does not already exist. There are analog versions as well as digital versions. Analog communications networks, for example, have always exhibited packet loss and jitter (delay variation). Other forms of noise and echo in analog channels have existed for a while.

    In digital channels, other forms of noise exist such as quantization distortion (the difference between the actual analog value of the signal and the quantized digital value). Another noise generator is the attenuation/level problem (reduction in the strength of a signal). Finally, low bit rate codec distortion (whereby more users are allowed onto the IP network system, but create more distortion in the process), has existed for some time. Because of these problems, noise avoidance in VoIP is as important as noise reduction.

    Original And Quantized Signal 

    Image Source Quantization distortion

    Source: Noise and Voice Quality in VoIP Environments

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    How Do You Minimize Noise on Voip?

    There are numerous physical conditions that will cause the voice signal to be noisy. One common way is when the signal level is too low at some point along the voice path. If the signal is amplified along the path, then the noise is also amplified. Other problems are due to bad equipment or bad electrical connections.

    One way to reduce noise on VoIP calls is by correlating the noise incidence with pieces of equipment (including telephone handsets) or to specific routes. If the problem appears to be correlated with an identified route that connects to an analog system or TDM trunk, then look at the loss plan where you have a subscription. On the other hand, if the problem appears on a noted packet path then look for excessive packet loss or jitter.

    Another way to reduce noise is to use a software application, SoliCall, which is intended for that purpose.

    SoliCall Real-Time Graphs 

    The graph from the software shows frequency problems before and after the application of the program.

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    Summary

    VoIP is a digital method of transmitting telephone calls over a network. It can also be used over the Internet The transmission mechanism uses the IP protocol with an IP address. Special equipment must be used to convert the analog signal into a digital one.

    Noise is an interference with the quality of the signal. Noise can be caused by a variation in the signal, packet loss, reduction in the signal strength, or by having additional users on the system.

    Elimination of noise on VoIP calls can be done by reviewing the equipment used, correlating the signal with the route taken by the call or by excessive packet loss.