Information Technology Reference
In-Depth Information
In general it is said that automated female voice output is easier to understand.
If you are designing a system that requires voice output, the rule of thumb is
usually to prefer a clear, slightly high, female voice if you can only choose one. If
you have a system that produces multiple voices in the same task context, how-
ever, you will need to think more deeply about your choices. First, and foremost,
however, you will need to choose voices that are easily discernible from each
other. If your system has a sophisticated speaker system, you may also be able to
separate the voices spatially.
You will also need to take account of the geographical context in which your
system will be used. If your system is being deployed in the UK, for example,
users may prefer the system to use a voice that has a British accent. Personal
preferences can play a role too, so you may want to allow your user to select which
voice output should be used. Indeed, many motor vehicle satellite navigation
(satnav) systems now allow you to choose the voice that will be used to offer you
verbal directions on how to reach your travel destination.
Like sight, hearing generally diminishes with age. If you are designing a system
for a population that will include older users, you will need to take the possible
reduced hearing levels into account when selecting voices and sounds to use as
output. Some mobile phones by default include ring tones that can compensate for
hearing loss in older people.
Audible alarms are supposed to be designed to alert the user to abnormal or
undesirable situations. In many cases the audible alert is used in addition to a
visual alert. If you want to quickly attract your user's attention in an emergency
situation, the easiest way is to use square-ended, sudden onset waveforms such as
klaxons or bells to provide audible alarms. The problem is that they evoke a startle
reaction, and if the sound is at high volume it can even cause panic. The design of
audible alerts requires great skill because you want to make sure that your users
process the meaning of the alert rather than focusing on trying to stop the loud,
incessant noise. The alarm sound needs to be distinctive so that users can recog-
nize it and recall its meaning. If you are trying to convey urgency, you should
avoid high intensity sounds, and instead consider the speed of the alarm sound: a
tri-tone alarm, for example, which doubles in speed, will suddenly sound very
urgent.
4.7 Motivation
4.7.1 Introduction
Now that you know some of the basics about how humans behave, it is also
important to be aware of why they behave in particular ways. Generally there are
two reasons why people act in a particular way. The first is governed by the central
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