Waves of Irritation
By Tesfu Tilahoun
 Our sensory
organs, all five of them, are delicate to be protected of nature
and deserve to be protected from excessive exposure.
This five part series, launching this week with the auditory sense,
will examine the sources of sensory pollution and what we can do
to protect ourselves.
As recently as 80 years ago, foreigners visiting the then 50 year
old Addis Ababa routinely described it as a large agglomeration
of neighborhoods with no real center except for the emperor’s
palace and the houses of the nobility. This was not the best endorsement
of a capital of an historic empire. Visitors to our Addis had refrained
from calling it a city.
More currently, Lonely Planet’s 2000 edition “Ethiopia
and Eritrea” describes our city as: “Addis Ababa at
first sight as noisy, dusty, sprawling and shambolic. But it is
also a colorful and vibrant city (finally!) that grows on you quickly
… (here comes the kicker). Despite its huge size – it
is the third largest city in Africa, with an estimated population
of over five million – it retains a small town feel. And further
down the guide book notes “most travelers can’t wait
to hurry out of the capital the moment they hurry in(Italis supplied).
Seven years on, the compilers of that Lonely Planet guidebook would
probably want to do some heavy editing. Very noisy – even
chaotically so, would be one edit and also an apt beginning for
our topic at hand, the growing problem of noise pollution in Addis
Ababa.
The guys who peer into eyes, ears and nostrils inform us that the
human ear – though not as amazing an organ as that of say
your mongrel dog’s , is nevertheless one of the finest pieces
of natural engineering. The ear is a wonderfully balanced precision
instrument that does quite more than just pull in sound waves –
what we mistakenly call hearing. You see, the ear actually doesn’t
understand. We just have the illusion of our ears hearing sound
when in fact that task is performed by an even more fantastic and
perhaps, the ultimate product of God’s laboratory, our brain.
It is this central processing unit that intercepts and interprets
the signals piped in from the five senses (more if you are either
blessed or damned) which are in comparison to the brain, mere components
of boring hardware. In other words your eyes are like cameras with
no clue about the images streaming through them. The nostrils have
no idea how good your girlfriend smells tonight nor of the awful
stench of Sunday morning post soccer practice socks.
The ears are but simple antenna and yes, the basic design and function
of satellite dishes and the decoding receiver replicate the ear
to brain analogy and physical dynamics. For convenience though,
we will go along with the masses and pretend the ear can ‘hear’.
As surley as sun spots and solar radiation can overload and even
fry your satellite feed, so it is when the human ear is flooded
with sound waves. The instinctive reaction is to squirm in discomfort
and clamp your ears to muffle the painful noise in vain.
Addis Ababa has become a cacophony of discordant noises that are
often direct assaults on private space and an abuse of human rights.
This article deals with the main sources of the escalating noise
pollution and what if any regulation exists, whether noise restrictions
apply to certain noise sources and on how the average resident can
deal with the rising decibel levels of a rapidly developing city.
Science describes sound as vibratons of an object which transmits
itself by varying the increase and decrease in pressures that radiate
outward through a material media of molecules. The favorite analogy
of physics teachers is much simpler to digest. Sound is according
to our lecturers, like those waverlets emanating across the surface
of a pond after a pebble has been thrown into it.
Sound has frequencies depending upon the number of times the vibrating
waves pass per second. This is known as cycles per second. If the
cycle is slow the sound will have a lower (deeper) frequency while
higher cycles produce correspondingly higher pitched sounds.
The human ear is sensitive, (to varying levels among different individuals),
to between sounds of as low as 20 vibrations (cycles) per second
and almost as high as 20,000 vibrations a second.
The loudness of sound is called intensity and is described as the
strength of the pressure of the radiating waves. Intensity of sound
is measured by decibels (dB) which are the measure of the relative
loudness or intensity of sound.
A 20 decibel sound is 10 times louder than a 10 decibel sound; 30
decibel is 100 times louder 40 decibel is 1000 times louder, etc.
One decibel is the smallest difference between sounds detectable
by the human ear. A 120 decibel sound is beyond painful. The following
approximations will help to lelate to decibel revels at home, in
public and at our workplaces.
No. Noise Source Average Decibels Regulation: v = Yes; × =
No and ? =Undetermined
1. Sound Trucks operated by advertisers Power amplified by A.C.
from on-board generator 80 X
2. Houses of WorshipPower amplifiers mounted at elevated points
60 X
3. Music/Audio –Video retailers 60-80 ?
4. Boutiques – yes, they also contribute to the auditory attack
40-60 X
5. Monster Stereos 50 ?
6. Beeping Weighing 40 X
7. Inter-city and Anbessa bus horns, also the harsh Lada squeal
60 ?
10 Decibels = a soft whisper
20 = quiet conversation
30 = normal conversation
40 = light traffic
50 = manual typewriter, loud conversation
60 = noisy office
70 = normal traffic, quiet train
80 = rock music concert
90 = heavy traffic, thunder
100 = jet aircraft taking off
We have then taken these decibels level approximations and applied
them to seven randomly selected sources of noise in any given area
of Addis Ababa.
The list is long of noise nuisances found on any given day. A random
selection of several of these will reveal that our sense of hearing
is under veritable attack by apparently legal activities –
some even perhaps beyond criticism.
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