Why Cell Phone Conversations are Never Crystal Clear
I'm often asked, "How can I eliminate noise in telecommunications transmissions?"
I usually reply that a better question is, "Can we ever completely eliminate noise in telecommunications transmissions?"
And the answer, in a word is – no.
Background noise is always present in all telecommunications transmissions – including point-to-point or point-to-multipoint transmission mediums. These can be either wired, optical fiber or wireless.
Most of the time noise exists at minimal levels and doesn’t cause problems. That said, our cell phones are susceptible to different types of noise and have different noise thresholds.
Types of Noise
White noise is continuous and always present. It can be reduced, or filtered out, but is almost impossible to completely remove. White noise can be the result of passing a cable too close to an electromagnetic source like a refrigeration motor or air conditioning unit.
Impulse noise is the result of a burst, or spike, of energy. It can result from many different sources, including surges in electrical power or energy on a circuit or transmission line or a blast of radiation resulting from sunspot activity. Surge protectors are designed to filter and remove impulse noise from a signal, though high transmission speeds always make this a challenge.
Crosstalk is a problem of conductivity. If two transmission lines are laid parallel to one another for a certain length, the signal from one line can be picked up by the other line. Crosstalk can result in a consistent hum or frequency noise, or data can simply be diverted from one line onto the other.
Using shielding and twisting wire pairs helps prevent crosstalk. It is also important that you do not bundle a large number of wires into one conduit or pipe, as the cumulative voltage from all the wires will increase the likelihood of crosstalk.
Echo, Jitter and Attenuation
Although they are different types of noise, echo and jitter are significant noise problems that affect voice transmissions over internet backbones. Anytime a signal has to pass through large cable distances, there is an increased likelihood that irregularities in both timing and filtering can occur. Echo and jitter can be generated by many issues including improper cable shielding, incompatible repeater or multiplexor devices, as well as crosstalk and electromagnetic interference.
Although attenuation is not in itself a type or source of noise, it can result in the existing noise on a line overpowering the signal. When a cable or transmission media is rated to carry a signal for a certain distance, it is not good judgment to expect that the signal will actually hold up over that maximum transmission range. Because every environment presents different challenges for transmission signals, and you can expect that attenuation will result sooner than the optimum transmission media specs state.
So while noise can never be completely eliminated, it usually can be diminished or lessened to a manageable level. Your best remedy for when you are on a call experiencing excessive noise -- just hang up, and make the call again.
James Dalton is a LearniT! Microsoft Certified Trainer with over 15 years of experience as a solutions developer, consultant, and teacher of networking, applications and Microsoft server solutions for various universities and private companies in the San Francisco Bay Area. His certifications include Microsoft IT Pro for Server 2008, SharePoint, and Windows 7.