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Mobile phones: the poor, the bad and the truly
abysmal
You hear them in public, on Trains, in
Restaurants and on the street. Mobile phone users speaking very loudly
into their phones....
Well it may (or may not) come as a surprise to find that
it is not entirely their fault, but rather is due to several serious design
flaws that most (if not all) mobile phones have (certainly every mobile I
have used in the last ten years has had at least two of these problems).
Mobile phones (aka Cell phones), they come with all sorts of
features functions and facilities: GPS, Camera, Internet browser,
Television, MP3 player, organiser, Games to name but a few....
It seems odd really that with
all the effort going into developing and pushing mobile phone technology
further and further, that so little effort seems to be put into making
them useable as Telephones.
The
first major design flaw is that mobile phones do not have Sidetone.
What is Sidetone? I
hear you ask.
In order to answer this
question lets go back to the early days of telephones.
Originally telephones were fairly
simple devices and essentially had the Transmitter (microphone) and Receiver (speaker)
in the same circuit - this
meant that was said into the Telephone could be clearly heard in the
receiver.
This effect actually caused a bit of trouble because it
was found that people who could hear themselves loudly in the earpiece
would speak into the Telephone much more quietly (anyone see what I
am getting at here?).
While the addition
of a specially wound coil called an ASTIC or Anti-Sidetone Induction
Coil reduced this problem, it was found that this coil could be too
effective as while lots of Sidetone made people speak too quietly, Too
little Sidetone on the other hand made people speak too
loudly.
when people cannot hear themselves while they are
speaking, they tend to speak louder - try it yourself, get someone to wear
headphones and see how loudly they speak - try getting them to cover one
ear and see how loudly they speak.
People need a feedback mechanism
like Sidetone,
since mobile phones have no Sidetone they encourage people to speak
louder.
Unfortunately the next design flaws come about because it
seems Manufacturers of mobile phones could not be bothered making their
phones useful but are more interested in adding spurious functions and
making them small and trendy.
Unfortunately it takes a bit of imagination,
ingenuity and dare I say it a small amount of engineering skill in
order to make a compact phone that is compact but still large enough to be
useable all unfortunately characteristics that mobile phone designers seem
to shun.
Early Telephones had a
fixed transmitter (usually mounted on the side of the telephone) while the
receiver was attached to a short piece of cable. The idea was that you could
hold the receiver up to your ear while you spoke into the Transmitter.
while this worked well it did mean that the user had to stand up
next to the (typically wall mounted) Telephone and it was soon decided to
fit the transmitter and receiver into a common unit. The question then was
how big do you make the hand piece in order to accommodate most, if not
all people ?
Much research was carried out and it was decided that
a handset of approximately 8 inches (200mm) in length worked well for most if not
all people as this placed the Transmitter in the front of or near
the mouth when the Receiver was conveniently located next to the
ear.
Modern mobile phones are a lot shorter than 200mm, meaning
that when you hold one up to your ear the microphone is nowhere near
your mouth.
Since the microphone does not point at your mouth a directional microphone cannot be used, so
most Mobile phones use an Omni-directional microphone which picks up noise
all around you.
Now if that was not bad enough, extra circuitry
is then added to make sure things get
worse......
Since the mobile phone does not employ
Sidetone, the level coming into the microphone can be variable, because of
this a circuit called an AGC (Automatic Gain Control) is used.
What the AGC does, is if the incoming
level is too low the gain (volume) gets turned up, if the volume
is too high the gain gets turned down.
Now the problem with this arrangement is that AGC is
unintelligent and unable to tell the difference between your voice and
background noise so that when you speak the gain gets turned down and
when you stop speaking the gain is turned up in order to amplify the
background noise. the result of this that the person at the other end is
going to have more trouble than they otherwise would hearing what you are
saying and they are likely to ask you to speak up.
Is it any wonder mobile phone
users speak so loudly?
Unfortunately, mobile phone manufacturers seem
either ignorant or, completely unconcerned about the issues
involved and the only phones you can buy are
designed to encourage you to speak loudly. Even if there was a phone on the
market that did work well, no-one seems to consider sound quality when
they buy a mobile phone anyway.
Is it possible to make a mobile
phone that would work adequately?
Yes I believe that it is - I
would start by using a noise cancelling microphone, (similar to those
used on aviation type headsets) these are a bit bulkier and slightly more
expensive than an omni-directional electret microphone, however they
are not that enormous and probably no more expensive than a CCD pickup for
a camera.
To keep the phone compact this microphone would be on a
slide out arm made from one of the less brittle plastics.
The
gain of the microphone would be fixed (no AGC) with manual adjustment
available.
The phone would have Sidetone.
The phone would
have a headset socket using a standard 2.5mm jack NOT one of those
flimsy, unreliable edge connectors that certain mobile phone manufacturers seem to
love so much.
I
would have to go through the extra functions to decide what can fit in and
what to drop, since the primary focus is to provide a working mobile phone
any other facilities would be only of secondary importance. Having said
that I can see that some extra functions such as a GPS and maybe a Camera could be very handy.
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