UN
D
SO
Something else you have to consider is that all local
networks and accessories, e.g. DECT (wireless) and
Bluetooth®, affect transmission capacity and can
thus also have an impact on sound quality.
LI
TY
Data compression
UN
D
The higher the audio bandwidth and the
lower the data compression, the better the
conditions for good sound quality.
Q
UA
UA
Q
Audio Bandwidth
SO
When investing in telephony solutions, there are a
number of parameters which you must always take into
account. A purely mobile solution provides excellent
flexibility and mobility but is subject to certain limitations
as regards sound quality. Traditional analogue telephony
delivers an acceptable sound quality but with limitations
in audio bandwidth. A VoIP* solution gives you the option
of unlimited audio bandwidth and very good sound quality.
However, some form of data compression is required.
Audio Bandwidth
Sound quality and the importance of networks
LI
TY
Energy
Energy
SOUND AND AUDIBILITY
A young person is able to perceive sounds at frequencies between 20 and 20,000 Hz (20 Hz–20
kHz). This ability changes as we get older and because of other physical factors. An adult is
normally able to distinguish sounds at frequencies between 20 Hz and 12 kHz.
Data
compression
People used to talk about the
concept
of ’telephone quality’, where, owing to technical limitations,
the audio bandwidth only ranges from 200 Hz to 3.4 kHz (i.e. a total of 3.2 kHz). With an analogue telephone system this means losing a large part of the speech content, meaning the sound
becomes less natural and more difficult to make out than if the audio bandwidth had been higher.
Compare this with FM radio which has an audio bandwidth of up to 15 kHz, enabling both voices
30
100
1k
and music to be reproduced much more naturally.
Analog
10k
Analogue Network
Energy
Original signal
Measure points
Digitally compre
Speech
30
100
1k
10k 20k Hz
Speech sounds OK but
that’s about it when using a
telephone with an audio
bandwidth of 3.2 kHz.
* VoIP = Voice over IP, i.e. digital telephony via the data network.
y
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Original signal
Energy
SOUND QUALITY AND THE IMPORTANCE OF NETWORKS
DATA BANDWIDTH AND AUDIO BANDWIDTH
Analogue Network
The term ’bandwidth’ insofar as data is concerned refers to the amount of information that can be
transferred per second in a network. Audio bandwidth refers to the sound frequencies (the range
of sounds) that can be transmitted. The use of the term ’bandwidth’ for both these concepts can
Speech
sometimes lead to misunderstandings.
ANALOGUE TELEPHONY
Sound is compressed in digital
networks. The sound signal is
measured or sampled thousands
of times per second and
converted to digital data.
Energy
Analogue telephony is severely limited in terms of range of sound (approx. 3.2 kHz). Unlike digital
networks, however, the sound signal is not compressed in an analogue network, which means that
the signal remains the same throughout. The analogue signal is perceived by some as ’cleaner’ and
100 tends to contain 1k
10k 20k Hz
’softer’, even though a digital 30
signal generally
more units of sound information.
This is because the human ear is extremely good at perceiving changes in the actual sound.
Original signal
Measure points
Digitally compressed signal
Lowering this sampling frequency reduces the amount of
data to be transmitted, but it also
causes some of the subtleties in
the sound to be lost.
Time
MOBILE TELEPHONY
In mobile networks the sound signal is always more or less compressed. Elements of the sound
which we cannot perceive are simply removed in order to reduce as much as possible the amount
of space taken up by the signal on the network. Advances in technology are helping to increase the
capacity of mobile networks and thus also the ability to distribute good sound using less compression. Sound is currently distributed at about 3.2 kHz in the various mobile networks. Sound is most
compressed in 2G networks, then slightly less for 3G and significantly less for 4G.
Poor transmitting and receiving conditions also have an impact on sound quality. In the event of
poor conditions, the system automatically reduces the size of the information in the network to try to
maintain contact. This has a deleterious effect on sound quality (i.e. compression increases) despite the fact that sound is always given priority in transmissions (over images, for instance).
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SOUND QUALITY AND THE IMPORTANCE OF NETWORKS
VOIP AND CODEC
Telephony over a data network is called VoIP (Voice over IP). As the sound produced by old
analogue technology has traditionally been acceptable with an audio bandwidth of 3.2 kHz
(telephone quality), the sound produced by digital networks was designed to deliver roughly
the same sound quality. This was a necessity in the early digital networks, as back then data
bandwidth was clearly limited.
There is no specific technical limitation for sound quality in digital networks but this is determined
primarily by the chosen codec. A codec is a function in the telephone that converts sound into data
and vice versa. The sound from the transmitting telephone is converted to data packages using a
codec, whereupon the data packages are sent to the receiving telephone where they are converted
back to sound by a corresponding codec. The telephones normally try to transmit sound using
the best possible common codec. Modern telephones, which support broadband codecs, tend
therefore to be better able to achieve the best possible sound. The last decade has seen incredible
advances in the capacity of VoIP.
Common designations for various codecs are: Wideband codec (7 kHz); Super Wideband codec
(14 kHz) and Full Bandwidth codec (20 kHz).
WIRELESS SOLUTIONS
A network’s distribution capacity to the office is naturally fundamental to ensuring good sound quality. It is also important to remember that additional wireless solutions added outside the telephony
network can interrupt the chain and reduce the capacity of the audio bandwidth. These issues can
be caused by wireless systems, such as DECT and Bluetooth®, or even old network products.
BLUETOOTH® (BT)
Bluetooth® is a standard that was originally developed to enable various accessories to connect
wirelessly to a mobile phone or PC. BT only works over short distances between a mobile phone
and accessories. There is additional data compression of the sound signal, leading to a deterioration in the sound quality.
DECT
DECT solutions for wireless telephony in offices and industrial premises were originally developed
for use with analogue telephony. Regardless of the capacity up to the DECT transmitter, it is not
possible to produce anything more than normal telephone-quality sound, i.e. 3.2 kHz, in a DECT
network. If using a Wideband codec (7 kHz) in a VoIP network, you lose more than 3 kHz for all
calls transmitted via the DECT system. This hardly matters for normal telephone calls, but if you are
using such a combination and want to hold meetings where sound quality is particularly important,
it may be a good idea to use direct connections (cables) to the VoIP network.
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SOUND QUALITY AND THE IMPORTANCE OF NETWORKS
CAT-IQ
Put simply, CAT-iQ is a digital enhancement of DECT. A CAT-iQ system uses a 7 kHz audio bandwidth and thus offers excellent capacity for wireless connections to a VoIP system.
KONFTEL’S SOLUTIONS
Konftel’s products always deliver optimum sound quality in relation to network capacity. This brief
review of sound distribution shows that there are grounds for analysing activities and the organisation before choosing a network and updating your telephony and data infrastructure. Clearly, a
VoIP network with Wideband codec (7 kHz), for example, is better equipped to deliver good sound
every time than a mobile or analogue network. On the other hand, mobility can be an important
consideration in many contexts.
A number of Konftel’s products offer more than one connection option, giving you the opportunity
to choose between practical applications (e.g. mobile) and optimum sound quality (VoIP). For
instance, the wireless Konftel 300W with its analogue DECT connection can transmit a 3.2 kHz
audio bandwidth, while the USB connection for a computer is compatible with a Wideband codec
(7 kHz). It is also possible to connect this unit to a mobile phone using a cable.
Irrespective of your chosen solution, there are products in Konftel’s range which simplify and improve opportunities for both rapidly improvised teleconferences at your desk and large meetings in
conference rooms and so on. Please contact one of our resellers for more information.
Visit our KNOWLEDGE CENTER to find tips for simple ways to guarantee the best possible sound
quality for your virtual meetings.
ABOUT KONFTEL
Konftel AB is Europe’s leading manufacturer of conference telephones and is a subsidiary of
Avaya, which is a global leader in business communication systems. Since 1988, Konftel has been
developing conference phones with the patented audio technology, OmniSound®, that provides
crystal-clear sound. Konftel’s products are marketed worldwide under the Konftel name. Our head
office is in Umeå, Sweden, with sales companies in the USA, the UK, France and Germany.
You can find more information at www.konftel.com.
HEAD OFFICE KONFTEL AB Box 268, 901 06 Umeå
Tel: +46 (0)90 70 64 89 Fax +46 (0)90 13 14 35 info@konftel.com marketing@konftel.com
LOCAL OFFICES W EMEA – emea@konftel.com. DACH – dach@konftel.com. North America – na@konftel.com
UK – uk@konftel.com. India – india@konftel.com
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