There is no question that Voice over IP has the potential to save us all money and provide greater convenience. While some of these services sound great, others deliver voice quality no better than the walkie-talkies your child recently received for Christmas. So why is the quality so bad sometimes?
Your voice starts out as an analogue wave or vibration. Remember the telephone you built as a child with two cans and a string. The bottom of the first can vibrates; this vibrates the string, which then vibrates the bottom of the second can. In a traditional telephone these same vibrations are used to modulate an electrical signal transmitted over a wire which replaces the string. In VOIP communications your voice is converted from an analogue wave into a series of “Data Packets”, this process is known as “Packet Stripping”. These data packets, which share the Internet with email, web page transmissions and file transfers, are then transmitted from one computer to another where at the destination the data packets are converted back into a sound wave you can hear.
The process of digitizing sound is well understood and as in the case of DVDs can be very high quality. In fact many DVDs are better quality than traditional analogue recordings. Unfortunately, unlike high quality DVDs, which have the capacity to transport a large amount of data, the Internet has limited bandwidth (speed). Therefore when we digitize voice for transmission over the Internet we compress the data significantly more than the music on a typical DVD. This compression reduces the quality of the sound.
There are many standards for the compression of voice. However, in a typical engineering trade off; the more we compress the voice transmission, the more conversations we can transmit over the same Internet connection. The other side of this tradeoff is that the more we compress the voice the worse it sounds.
The vast majority of telephone calls today, even the calls made on your traditional home phone, are digitized. The traditional telephone companies use a compression standard called PCM or G.711. In fact VOIP telephone services that use G.711 sound just as good as traditional telephone calls.
Unfortunately this is not the whole picture. If your Broadband connection is not of sufficient quality or you are using a connection to also carry your Emails and you Internet connection then you will also start to see other issues. And finally some VOIP providers use a “Voice Activity Detection” algorithm to reduce the speed they need for your calls. V.A.D. attempts to listen for silence between the sentences in a telephone conversation and stop transmitting packages when no one is talking. If the V.A.D. algorithm is inappropriately tuned the ends of your words will be clipped and overall voice quality will decline.
So whats the answer? Aside from its limitations there is no question that this is the future of Telephony and should not be ignored when you are looking to invest in your company’s future. Instead do your research on the providers you choose and above all else get some advice from somebody you trust to give good honest advice. If you take the potential issues in to account and design the correct solution then you will be able to improve your communication with your customers while reducing your overheads.
If you have any questions then please give me a call and we can talk through your solution.
Jim
