Has your VoIP conversation ever sounded like bits of voice were missing or have you had a choppy sounding call? How about VoIP echo, where you hear your own voice back in your ear? Have you ever had one way audio? These and many other VoIP problems can be easily understood and corrected by following good basic installation setup practices and then good troubleshooting procedures. We offer you the information and advice on how to correct common VoIP problems. Many VoIP quality issues can be resolved by taking a few easy steps.
Echo can occur in VoIP calls for a number of reasons. Echo actually exists in traditional traditional phone connections as well as VoIP connections, but due to delay that is inherent in VoIP, it can become much more noticeable. Echo that callers experience are most likely the result of the far end where impedance imbalances bounces signals back from where they came. The end result, due to noticeable delays, are voice echoes of one's own words which can be heard.
Even traditional telephone connections have echo that occurs on their lines. A call starts at one telephone and travels on a copper two wire connection, known as POTS (Plain Old Telephone Service), to a trunk line. This trunk line is not a two wire pair of copper lines, so an interface or hybrid is needed to connect the two types of lines. The call will continue to be transmitted over the trunk line and will travel to another point where it will once again travel through an interface or hybrid back to a POTS line and onto the the far end telephone. During the change or travel between the various interfaces a reflection of the signal can be sent backwards to the originating phone. This reflection of the signal will not even be noticed unless the time between the original words or sounds and the reflected sound is greater than approximately 20ms to 50ms and the volume of the echo is large enough. If the echo is greater in time lag than 10ms to 20ms it will become noticeable and as the time gets even greater the more the echo will become noticeable and more annoying.
Phone echoes can happen at several of the transition points along the voice signal's journey. Some echoes could be Hybrid Echo, usually the result of the telephone company's amplification of the signal which then produces electrical leakage. Typically telephone companies amplify the signal and break it out into 2 pairs, one for the transmit and one for the receive signal, (the is referred to as two wire to four wire), so that the signal will be able to be sent over long distances. This two wire to four wire hybrid can also bounce back signal. In an unbalanced hybrid situation part of the signal arriving at the four wire side of the hybrid interface will be sent back on a return path of the four wire circuit.
NAT transversals and firewalls can play havoc with SIP and if you experience one-way audio, the first suspects would be a firewall or NAT router. The issue occurs due the nature of the VoIP protocols, signaling of the device handled by one protocol, with the voice being handled by another protocol. The voice protocol may not be associated with the device, so the router does not know where to send that information and the result can be one-way audio. Many people install VoIP and have two routers on their network each offering NAT addresses to their connections. This "double NAT" can easily cause one-way audio. Double NAT should be eliminated in LAN network design for good basic design, and especially for VoIP installations, as well as, all other LAN installations.
Broken voice typically occurs when there is jitter on the network. here are some fundamental steps that you can take to troubleshoot where the issue is.
Security of an Asterisk installation is a must. Take these precautions to make it more difficult for hackers to access your server and use your system for making calls.