In the amazing advance of technology of the past half century or so, there’s been one unfortunate constant. The audio quality of phone calls today is pretty much what it was in the mid-1930s. Just about everything involved in the transmission of phone calls during that time, but because the public switched telephone networked is locked into audio protocols that allow just 3 kHz of bandwidth, voice quality is frozen in time.
A loose confederation of hardware makers, software companies, and service providers, including tele- and videoconferencing specialist Polycom, voice-over-IP chipmaker DSP Group, and VoIP service provider phone.com is aiming to change this. Flying under the banner of Connect HD–yet another bad analogy to HD television–their plan is to take advantage of abundant bandwidth and digital technologies to improve voice quality.
They make a good case. Human speech typically ranges from about 80 to 14.000 Hz, but traditional phone systems chop off everything below 300 and above 3,300 Hz. That’s a wide enough frequency response to provide intelligible speech–barely, but our brains are remarkable good at making up for what our ears don’t hear. Most of the time, we can differentiate between a “b” and a “p” sound over the phone, even though the audio cues that make the difference between these voiced on unvoiced plosive consonants live in the higher frequencies that are lost over phone circuits. HD Connect wants to provide at least 7 kHz of frequency response, though this can often be provided in less actual bandwidth through the miracles of digital signal processing.
HD Connect is wisely not trying to impose a single standard. It will support multiple codecs–the software that encodes and decodes audio as digital signals so that two HD Connect handsets, speakerphones, or other endpoints should be able to negotiate a common protocol. Where necessary, systems such as conference bridges can convert, or transcode, signals.
Both intelligibility and overall audio quality of speech were greatly enhanced in the HD Connect demos that I tried. There was also a much great sense of presence, the feeling that the person you are talking to might actually be in the same room. In a conference call, individual voices are much easier to differentiate and some accents are much easier to understand.
Still, I think the HD connect folks face a tough road ahead. We have managed to create a wireless phone system that reproduces the miserable voice quality of the landline network it is rapidly replacing. The wireless carriers are not about to change their protocols, which in any event would require all of us to replace our mobile handsets. in theory, we could all be making VoIP calls on our smartphones, and with VoIP, software alone can determine the audio quality. But the wireless carriers have a vast investment in voice infrastructure and terrible quality or no, they are not going give it up without a fight.
My guess is that Connect HD technology will make its first inroads in what amount to walled gardens, such as speakerphones and conferencing systems that run on internal corporate VoIP networks. For telephony at large, however, lousy audio quality, though easily preventable, is likely to be with us for a long time to come.