The use of HD Voice is growing exponentially and new research from the Global Mobile Suppliers Association (GSA (News - Alert)) backs that up. According to the GSA, the number of mobile networks compatible with HD Voice has nearly tripled this year to 36.

While this number is still considered relatively low when compared to the 152 High-Speed Packet Access (HSPA) networks in commercial use, interest in HD Voice is definitely picking up.

Improved quality of HD Voice is a major factor in its growth and adoption. The Adaptive Multi-Rate - Wideband (AMR-WB) speech-compression algorithm doubles the range of voice frequencies transmitted. This results in sound quality that has been compared to FM radio by Orange (News - Alert), a French telecom operator and pioneer of the HD Voice movement.

Operators must also use a technology known as transcoder-free operation for HD Voice phone calls to travel across the mobile network without a change in quality, according to Jan Derkson, head of technical marketing at Ericsson (News - Alert) Networks. The usefulness of HD Voice is limited at the moment, due to the fact that calls can only be made between users on the same network, in the same country. The way networks talk to each other must change to move beyond this limitation, according to Derkson, and Ericsson is working to deliver underlying technology to address this during the second half of next year.

Another major factor pushing HD Voice adoption is the availability of a growing number of phones that can make and receive HD voice calls. Only a year ago users were limited to a handful of phones that could handle these types of calls, but today at least 60 models can manage HD voice calls. These include Samsung's Galaxy S II, the Nokia Windows Phone-based Lumia devices and Sony Ericsson's Ray. The Apple iPhone and RIM BlackBerry (News - Alert) have yet to add support for HD Voice.

"There is a business case for HD Voice," said Alan Hadden, GSA president. "Surveys show that people talk longer and also make more calls. In the early days, HD Voice support was mostly limited to mobile networks operated by Orange, but now other carrier groups are also rolling out the technology."

"The launches also create more interest from other operators that we are talking to continuously," added Derksen. The first operators are expected to go live with Voice over Long-Term Evolution (VoLTE) next year, and they will use HD Voice as well, said Derkson.

The GSA is trying to raise awareness about the technology, and introduced an HD Voice logo earlier this year that may be used by both operators and phone makers. Phone (News - Alert) makers need only implement the AMR-WB codec to be qualified to use the logo. Microphone and speaker acoustics as well as on-board signal processing must be up to the same standard in order for HD voice quality to be the best possible.

The GSA also requires improved speaker and microphone acoustics and better audio signal processing on the device to remove noise in order to meet compliance, according to a spokesperson.