I've been learning about VoIP lately. I'd like better sound quality for my calls than what my cell phone offers...however, that remains an elusive goal. I could try an IP Phone or a VoIP ATA (analog telephone adapter) for high audio quality.
Here's what I've learned so far:
You can test your Internet connection (or here) to see if you have enough bandwidth. Skype calls from my PC to their testing service sound great, but calls to my own voicemail or my parents' landline were terribly muffled. At first I thought this might be caused by my ISP maliciously tampering with VoIP packets, but poor audio quality remained even after signing up for and installing HotSpotVPN (an OpenVPN implementation). You do have to tell the VPN to use UDP instead of TCP.
I also tried VoxOx, but couldn't sign-in to my account with the program. Considered signing up with RingCentral.com, but $28/month would be overkill in this case. VirtualPBX.com looks very reputable, but is way too pricey for me at $50/month. Next, I looked at Google Talk, but for now it only does PC to PC calls (not landlines). Supposedly you can combine it with a free DID (Direct Inward Dial) number from GroovyTel to receiving incoming calls.
So, I signed up with IP Communications and purchased one SIP line (with one DID) for $10/month. This allowed me to receive calls on my new Bellevue, WA number, but not make outbound calls - for that, you have to sign in here and purchase a minimum of $10 credit. I think they debit your credit at the rate of 2 cents per minute or less. I'm using Counterpath's free X-Lite softphone. The audio quality isn't too bad, but isn't as good as I want it to be. I test it by calling my own voicemail.
IP Communications isn't the only SIP provider...VoicePulse.com and CallCentric.com both look interesting. VoicePulse may be less expensive than my current host.
This all-in-one $225 ooma Core VoIP Phone System (with no monthly fee) is big on Amazon.com - 717 reviews so far, with the vast majority being totally positive.
Reading up on "codecs" this evening...according to X-Lite's user manual, PC-only VoIP traffic can use "wideband" codecs that sample at 16 KHz, wheras calls into the PSTN require "narrowband" codecs (G711 only, in fact) that have a lower sampling rate. That explains why my test call into Skype sounded so much vastly better than to a landline. Maybe a Cisco IP phone would sound better...but that's a $100, so...not right now. :-)