HUMAN HEARING
The range of human hearing covers
frequencies from 20Hz to 20,000Hz [7],
while the human voice spans a
frequency range of at least 50Hz to
12,000Hz [8]. However, traditional phone
calls (both fixed and mobile) transfer
sounds in a smaller spectrum band of
roughly 300Hz to 3,400Hz.
Consequently, the voice quality of
today’s calls is limited. For example, the
auditory information needed to
consistently distinguish F sounds from S
sounds is contained in frequencies that
are higher than conventional calls allow.
The potential for misunderstanding is
one reason for the development of
phonetic alphabets for use in critical
telephone or radio communications,
such as air-traffic control.
HD voice removes this limitation. It
conveys a wideband spectrum from
50Hz to 7,000Hz and uses wideband
codecs such as AMR-WB or G.722 that
are tailored for this purpose – resulting in
better quality, more natural sound, and
improved intelligibility and voice
recognition.
USER BENEFITS OF HD VOICE
The voice quality of traditional telephony
is perceived to be at its worst when
people call while using public transport,
such as the subway [9]. An important
factor for this is the high background
noise of trains, which makes it difficult
for both parties of a call to hear each
other well. The clarity gained from HD
voice allows users to make calls in noisy
environments, such as near a busy road,
on a construction site or in extreme
weather conditions, where normal calls
would simply not be feasible. In addition,
the technology enables clear voice-mail
playback, more effective conference
calls and better speech-to-text
applications. This reduces stress and
offers users a greater voice experience.
HOW TO DEPLOY HD VOICE IN
A MOBILE NETWORK
To enable HD voice, operators need to
ensure their core and radio networks are
capable of providing the service. Both
users in a call need to have devices that
support the service with the AMR-WB
codec and other improved device
acoustics suitable for the wideband
spectrum, including higher quality
microphones and loudspeakers. Many
2G and 3G phones are already HD voice
capable. All VoLTE-capable smartphones
have HD voice as the default codec, and
the service is supported over LTE
networks.
WHAT IS HD VOICE?
EVOLVED HD VOICE FOR LTE • INTRODUCTION 3
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