Directional Sound:
Improving Airport Terminal
Evacuation
Kim O'Neil
Advanced Aviation Technology
Ltd.
Abstract
Several recent events have highlighted the need to
significantly improve evacuation from buildings such as Airport Terminals.
Directional Sound enables rapid, effective and guided evacuation from Airport
Terminal buildings and associated facilities, including car parks. This new
evacuation technology ensures that people are guided to the nearest and most
efficient rapid evacuation route - even in dense smoke - when evacuation is
most urgent. No special passenger training is required.
Directional Sound has very special properties that
make it easy for human hearing to both locate and follow the source of the
sound and even to navigate obstacles such as stairs in zero visibility.
Directional Sound can direct passengers along optimal evacuation routes - a
property that is especially useful Airside where safety and security can
sometimes come into conflict.
Directional Sound will help airports cope with the
rapid growth in passenger numbers, helping to improve and maintain public
safety in already crowded Airport Terminal buildings. Directional sound is also
language independent - an important fact given the many nationalities passing
through Airport Terminal Buildings.
Figure 1: Airports are getting busier
1. Introduction
Conventional evacuation technologies rely on detectors
to identify hazards such as fires, alarms to alert people to the presence of
danger and signs to direct people to exits. Whilst detectors and control
systems are getting smarter, less progress has been made on the limitations of
conventional alarms and signs. There are many occasions when conventional
solutions are simply ineffective or just not enough. For example, not all exits
will be safe to use during a fire or in the presence of toxic smoke - yet
conventional signs will have little effect on what exits passengers actually
try to use.
Figure 2: Airport fires can be terrifying
Sophisticated control systems can also be ineffective,
when they rely on visual signs alone. There is also a great deal of visual
confusion in many buildings - with people, displays and obstacles obscuring
exits and exit routes and the signs leading to them. Especially as most signs
are unreadable at distances of over 25 metres. This makes it difficult for
anyone under stressful evacuation conditions to find the most efficient and
safe exit - even when visibility is good.
Figure3: Even a small amount of smoke quickly
obscures signs
If smoke is added, then visibility drops rapidly -
even relatively low levels of smoke can drastically reduce visibility. Acrid or
toxic smoke will also make eyesight virtually useless - as it is simply too
painful to even open the eyes - and visibility would be too poor to see anyway.
Yet these are just the conditions where evacuation must be rapid if people are
to survive. Indeed, most fatalities are caused by smoke inhalation rather than
by burns.
All the more surprising then, that conventional
evacuation technologies tend to rely almost entirely on vision - despite
evidence indicating that in a real fire emergency, vision is perhaps the one
sense that cannot be relied upon.
2. Directional Sound Technology
Directional Sound is a new technology that has gained
rapid acceptance by fire industry professionals and independent safety experts,
as an essential evacuation technology. It is entirely complementary to
conventional solutions. It can be introduced quickly, and at low cost and is
complementary to technologies such as PA/VA systems. Sound and Light combined
are particularly effective in emergencies.
Perhaps the greatest benefit of Directional Sound, is
its ability to improve evacuation in ways not achievable by other technologies
and in all visibility conditions. Directional Sound technology makes it
possible to guide people to safety, even through complex routes (up and down
stairs, round corners, avoiding hazardous areas via the most efficient safe
exit route) in zero visibility.
Directional Sound has very special properties. These
properties have been very carefully tailored to ensure that they contain all
the aural cues required for human hearing to be able to fully locate the
direction and source of the sound. There are three key elements to Directional
sound, which give it very special directional qualities:
3. How We Locate Sounds
Directional sound has been the subject of significant
research and many operational trials. Research has enabled us to understand how
we hear and how information from what we hear is processed in the brain. This,
in turn, has made it possible to generate the specific sounds that provide the
exact information the brain needs to accurately identify the source of a sound.
This is Directional Sound.
Human hearing extends across the range from 20Hz to
20kHz but is optimized for speech, which lies in the more limited range between
500Hz to 3,500Hz. Human hearing is capable of identifying the source of sounds
(a good survival trait!) by using a number of aural cues. Timing information
(i.e. the time difference between a sound arriving at each ear) can be
extracted from low frequency sounds in the range up to 1000Hz. Similarly, the
difference in the intensity of sounds at each ear (i.e. a sound appearing
louder in one ear than the other) can be measured at 3000Hz and above.
Both these cues together provide important information
- but this is still not enough for the brain to identify the source of a sound.
In particular, to determine whether a sound originates from in front or behind
us. This last aural cue is obtained from the complex shape of our ears, which
amplifies some frequencies and attenuates others (esoterically called the Head
Related Transfer function - HRTF!).
If the right kind of sound is used, the human brain's
ability to locate a sound can be optimized. This is the simple but effective
secret of Directional Sound. Pure tones or narrowband sound simply cannot be
localized. For example, and somewhat surprisingly, conventional emergency
vehicle sirens cannot readily be localized! It is not easy for the brain to
work out whether an emergency vehicle using a conventional siren is in front or
behind us. New sirens are now being produced containing directional sound, so
fixing this problem.
Directional sound contains broadband sound across a
range of frequencies providing all the aural cues the brain requires to
accurately pinpoint the direction of the sound source. This is effective even
if the hearer has partially impaired hearing.
4. Applications for Directional Sound
The properties of Directional Sound are finding
applications in many areas. These include:
5. Evacuation Trials
Rigorous practical trials have demonstrated the
effectiveness of Directional Sound. Trials have included buildings, ships and
ferries, and aircraft evacuations. In each case, significant improvements in
evacuation times and therefore survivability have been demonstrated. Perhaps
most significant of all, is the way in which Directional Sound can be deployed
so that evacuation takes place through the nearest and most efficient exit
route for each individual. This ensures that people do not all try to escape
from the same exit or otherwise become lost and confused inside the building.
In evacuation trials in buildings with only conventional signs and alarms, many
people try to leave the building by the way they entered - this being the most
familiar route to them. Yet this route may not be the quickest or safest exit
for them.
6. Directional Sound and Building Evacuation
Directional sound works well in good or bad
visibility, but is far more effective than any other system in poor visibility.
Not only does it serve to draw people towards exits in poor visibility, but it
can also help them negotiate obstacles such as stairs. It can make sure that
people are attracted toward only valid exits - i.e. exits that are not blocked
and exits that are safe to use. It can guide people round corners and around
obstacles and help them negotiate even complex routes - especially when
combined with modern addressable fire systems which can identify both the
source of a fire and the preferred optimal exit routes.
Conversely, there is little benefit in modern
addressable fire systems if people cannot see the exit signs or if the signs do
not indicate the best route. Even when visibility is good, directional sound
ensures that people use the best route for them, rather than trying to retrace
their steps or following the crowd. This ensures a more even evacuation of
buildings, with the correct and nearest exit being used by evacuees.
Figure 4: Visual clutter obscures fire exit
signs
Loss of life in building fires is rarely the direct
result of burns. Most die from the inhalation of toxic smoke and fumes. In
these cases rapid evacuation is essential if lives are to be saved. It is also
in just these conditions that vision is of little use. Directional sound
measurably improves evacuation times up to 60% in such circumstances. This
saving in evacuation time translates directly into the saving of lives. 
Figure 5: Dusseldorf - Unfortunately airport fires
do happen
7. Safety and Security Airside
The ability to guide people directly to safe exits
even over complex routes in poor visibility, makes Directional Sound
particularly suitable for solving difficult Airside problems. It is a simple
fact that safety and security can sometimes come into conflict - especially
Airside, where the needs of Customs, Immigration and Airport surface operations
can become severely compromised during fire evacuation. Fundamental problems
arise when merely pressing a fire alarm can void much of airport security.
Passengers can spill onto the airport surface, where other safety issues also
arise. Legitimate Police, Customs and Immigration problems can occur as large
numbers of people make their way - with limited supervision - to safety
(possibly out of Airside altogether).
At the very least, Airport operations can be severely
affected as the impact of a fire alarm can spread far outside the immediate
environs of the alarm itself. It is not unusual for all airport operations to
be suspended in the case of a fire emergency (real or otherwise) for a
considerable time. Directional sound makes it possible to guide people directly
to exits that are both safe AND secure. It allows Airport Authorities to
develop contingency plans to contain and minimize the disruptive effects of
emergencies and attempt to maintain normal operations in a safe and secure
manner. This can be done without compromising safety.
8. Munich International Airport
Munich International Airport has commissioned and
installed Directional Sound evacuation system in its car parks to assist people
in finding their way out in the event of smoke or emergency. Directional Sound
systems are needed to combat the unusually high number of smoke-related
incidents that occur in the Munich Airport Car Parks. High speed driving on the
autobahns in hot weather, can result in spontaneous combustion of tyres when
the cars are left in the car park (this is a regular occurrence!).
Figure 6: Munich car park installation
Each car park floor is a very large open space but
without forced ventilation. This means that during a fire, smoke will not
dissipate. 28 directional sounders draw people towards the most suitable of the
12 exits available on each floor. The cost of fitting the Directional Sound
system is estimated to be just one eighth of the existing system. Munich is a
rapidly expanding Airport with a second terminal building (and car park)
planned to be in operation in the Spring of 2003. Being safe in the face of
this rapid growth in passenger numbers is extremely important to Munich
airport.
9. Aircraft Evacuation Trials
Aircraft evacuation trials with a major aircraft
manufacturer has been successfully carried out, showing significant
improvements in evacuating passengers from smoke filled aircraft. Not only did
passengers leave the aircraft more rapidly, but they did so via the most
efficient exit for each individual. This is a remarkable result - and one that
may have significant implications for some of the very large aircraft planned.
Video recordings of the evacuation trials are particularly impressive.
10. Industry Awards
Directional Sound has won the UK Fire Industry Council
Product Innovation Award, the Prince of Wales award for Innovation and the UK
Dept of Trade and Industry SMART award and has also been declared a 'Millennium
Product'. The International Maritime Organisation (IMO) has also recognised the
significance and benefits of Directional Sound and ship and ferry operators are
fitting the technology.
In an equally rare accolade, the UK Business Design
Centre (BDC) has installed Directional Sound Evacuation systems. The BDC is one
of London's premier Exhibition and Conference Centres. UK Television programmes
(Tomorrow's World, Channel 5 and Discovery Channel) have documented the
benefits of directional sound in dramatic reconstructions of evacuation
exercises.
11. Summary
Directional Sound has proven to be an effective
solution for improving evacuation. The benefits in improved evacuation times
can be very significant indeed. Directional sound works even when visibility is
reduced to zero, but is equally effective in improving evacuation in good
visibility. Even the best-planned airport buildings contain a lot of visual
clutter that may obscure exits and exit routes.
Directional Sound has the ability to draw people
toward the correct exit route for them. In a fire emergency, the benefits of
Directional Sound translate directly into saved lives, leading people out of
buildings quickly, minimizing confusion and reducing the risk of exposing them
to the disabling and life threatening effects of toxic smoke. Directional sound
can also be deployed to help maintain normal airport operations, where
possible, during emergency evacuations. |
