| Name | Range (Hz) |
|---|---|
| Narrowband | 300–3,400 |
| Wideband | 50–7,000 |
| Superwideband | 50–14,000 |
| Fullband | 20–20,000 |
Wideband audio, also known aswideband voice orHD voice, is high definition voice quality fortelephony audio, contrasted with standard digital telephony "toll quality". It extends thefrequency range of audio signals transmitted over telephone lines, resulting in higher quality speech. The range of thehuman voice extends from 100 Hz to 17 kHz[2] but traditional,voiceband ornarrowband telephone calls limit audio frequencies to the range of 300 Hz to 3.4 kHz. Wideband audio relaxes the bandwidth limitation and transmits in theaudio frequency range of 50 Hz to 7 kHz.[3][1] In addition, somewideband codecs may use a higheraudio bit depth of 16 bits to encode samples, also resulting in much better voice quality.[citation needed]
Wideband codecs have a typicalsample rate of 16 kHz. For superwideband codecs the typical value is 32 kHz.[1]
In 1987, theInternational Telecommunication Union (ITU) standardized a version of wideband audio known asG.722. Radio broadcasters began using G.722 overIntegrated Services Digital Network (ISDN) to provide high-quality audio forremote broadcasts, such as commentary from sports venues.AMR-WB (G.722.2) was developed by Nokia and VoiceAge and it was first specified by 3GPP.
The traditional telephone network (PSTN) is generally limited to narrowband audio by the intrinsic nature of its transmission technology, TDM (time-division multiplexing), and by the analogue-to-digital converters used at the edge of the network, as well as the speakers, microphones and other elements in the endpoints themselves.
Wideband audio has been broadly deployed in conjunction withvideoconferencing. Providers of this technology quickly discovered that despite the explicit emphasis on video transmission, the quality of the participant experience was significantly influenced by the fidelity of the associated audio signal.
Communications viaVoice over Internet Protocol (VoIP) can readily employ wideband audio. When PC-to-PC calls are placed via VoIP services, such asSkype, and the participants use a high-quality headset, the resulting call quality can be noticeably superior to conventional PSTN calls. A number of audiocodecs have emerged to support these services, supplementing G.722.
Manufacturers of audio conferencing equipment have introduced wideband-capable models that include support for G.722 over VoIP.
Conference calls are a direct beneficiary of the enhancements offered by wideband audio. Participants often struggle to figure out who is talking or to understand accented speakers. Misunderstandings are commonplace due primarily to generally poor audio quality and accumulation of background noise.
Some listener benefits cited of wideband audio compared to traditional (narrowband):
Despite its reputation for poor audio quality, the mobile telephone industry has started to make some progress on wideband audio. The3GPP standards group has designated G.722.2 as its wideband codec and calls it Adaptive Multirate – Wideband (AMR-WB). More than a hundred handsets have been introduced supporting this codec (for example,Apple,Google,HTC,Nokia,Samsung andSony), and network demonstrations have been conducted.[citation needed]
As business telephone systems have adoptedVoIP technology, support for wideband audio has grown rapidly. Telephone sets fromAvaya,Cisco,NEC Unified Solutions,Grandstream,Gigaset,Panasonic (which brands wideband audio "HD Sonic"),Polycom (which brands wideband audio "HD Voice"),Snom,AudioCodes (which brands wideband audio "HDVoIP") and others now incorporateG.722, as well as varying degrees of higher-quality audio components.
Suppliers of integrated circuits for telephony equipment, includingDSP Group,Broadcom,Infineon, andTexas Instruments, include wideband audio in their feature portfolios. There are audio conferencing service providers that support wideband connections from these and other VoIP endpoints, while also permittingPSTN participants to join the conference in narrowband.sipXtapi is an open-source solution for VoIP media processing engine supporting wideband and HD voice that provides RTP and codecs through a plugin framework for use with SIP and other VoIP protocols.Skype uses an audio codec calledSilk which allows for extremely high-quality audio.
A number of carriers around the world have rolled out HD voice services based on the G.722 wideband standard. In North America, hosted service providers have recently[when?] deployed the Aastra Hi-Q upgrade to its installed user base and as of January 2010 claimed around 70,000 HD voice endpoints. The consumer service providerooma has an estimated 25,000 HD voice endpoints deployed stemming from its rollout of its second-generation Telo hardware.
In cellular communication, "HD Voice" specifically refers to AMR-WB (G.722.2) in VoLTE, but AMR-WB in turn does not specify quality or bitrate. Likewise for HD Voice+ and AMR-WB+.GSMA has an HD trademark and runs two certification program around the HD and HD+ logos.[4]
AMR-WB is natively supported in Android sinceAndroid Gingerbread,[5] and in iOS since theiPhone 5.[6]
As of December 2015, a report announces 117 commercial mobile HD Voice networks launched in 76 countries.[7]
Many mobile networks including AT&T[8] and Verizon are discontinuing support for phones that don't support 4G and wideband audio.
The following are widebandaudio coding standards andaudio codecs used intelecommunication.[9]
| Year | Widebandaudio coding standard | Widebandspeech coding algorithm | Ref |
|---|---|---|---|
| 1988 | G.722 | SB-ADPCM | [10] |
| 1999 | G.722.1 (Siren7) | MDCT | [11] |
| 2003 | G.722.2 (Adaptive Multi-Rate Wideband) | ACELP | [12] |
| 2006 | G.729.1 | MDCT | [13] |
| 2008 | G.711.1 | MDCT | [14] |
| G.718 | MDCT | [15] |
