Potentially VoIP calls can sound radically better than what we are used to even on landline phones. So why don’t they? It may be lack of will. Some say the success of the mobile phone industry proves that people don’t care about sound quality on their calls. I don’t think this is a valid inference. All it proves is that people value mobility higher than sound quality.
The telephonic journey from mouth to ear, often thousands of miles in tens of milliseconds, traverses a chain of many weak links, each compounding the impairment of the sound. First, the phone. Whether it’s a headset, a desk phone or a PC, the microphone and speakers have to be capable of transmitting the full frequency spectrum of the human voice without loss, distortion or echo. Second the digital encoding of the call; it has to be done with a wideband codec. Third, the codec has to be end-to-end, so no hops through the circuit switched phone network. Finally the network must convey the media packets swiftly and reliably, since delayed packets are effectively lost, and lost packets reduce sound quality.
Discussions of VoIP QoS normally dwell mainly on the last of these factors, but the others are at least as important. The exciting thing about dual-mode cell phones is that they provide a means to cut through them. Because they must handle polyphonic ring tones and iPod-type capabilities, the speakers on most cell phones can easily carry the full frequency range of the human voice. Cell phone microphones can also pick up the required range, and DSP techniques can mitigate the physical acoustic design challenges of the cell phone form factor. Smart phone processors have the oomph to run modern wideband codecs. This leaves the issue of staying on the IP network from end-to-end. The great thing about dual-mode phones is that they can connect directly to the Internet in the two places where most people spend most of their time: at work and at home.
So if you and the person you are talking to are both in a Wi-Fi enabled location, and you both have a dual mode cell phone, your calls should not only be free, but the sound should be way better than toll quality.
Check out the V2oIP website for an industry initiative on this topic.