Good morning. Welcome to the NPTEL course on course on the Architectural Acoustics.
We are in the the last week, the week number-8 and this is the lecture 38. In this lecture,
we will discuss about the urban noise control and through a planning consideration, the
the urban planning consideration, and this is a lecture 1 on that. If you remember
in the last two lecture, what we have discuss is the the environmental noise in general.
And now we will try to see the the urban noise, and from how the from the planning
aspect, the urban planning and the city planning aspect, how it this can be mitigate this urban
noise, which is day by day this these things are increasing. And creating a huge problem
in the the citizens and the urban's people. The outline the the learning objectives
includes the the outline of the the source classification and the urban nature of
the urban noise, we will try to do the classification, and try to find out what
are the sources and all. And will also going to discuss some of the mitigation strategies
for the urban noise. So, let us compare first the the the
noise level. So, this is this this particular vertical scale indicates the 0 to hundred
140 dB scale. And as you know, the the left hand side about I have put is in in
that the different subjective feeling for any such noise. The 0 dB is threshold
of hearing, and almost to 120 dB is the threshold of pain. Intermediately there are a communication
starts become very difficult to win the noise level is just just just a little above
60. Then the this communication between one people
to the other people will be gradually become difficult that that is the one of the
the benchmark, the the minimum level of that particular communication is required
some kind of a less amount of background noise. And if it is a little more than 80 85 also.
It is can be as a hazard is and that is kind of a dangerous from the health
point of view, if the any person is continuously exposed, within that amount of sound for
a longer duration. Now, let us in the right hand side, let us
see what are the situation in different atmosphere inside building and the outside building,
this around 37, 38 is a quite bedroom really quiet bedroom, and busy office is almost
about 60 also. And a car at a speed of 60 km per hour around 6 to to 7 meter away
is almost about 75 dB or something like that. But, if it is a truck, it is having
almost speed of 40 kilometer or which is a normal speed for a truck, and again 7 meter
away almost gives 80, 85 dB sound. And of course is depend upon the condition of
the truck also the condition of the road condition etcetera. But, if there is a jet aircraft,
and even if you you are 250 meter away from the jet aircraft, its process 100
dB sound limit also. The type of road noise, there are two
types of road noise. And one called from the bulk traffic flow, and it is because of the
mainstream traffic flow. And it is aggregate noise of a particular busier road, which
is have a kind of a continuous noise level also. And there are sometimes there is a peak,
and there is a troughs, but it is depend upon normally it is a aggregate noise source.
The second one is called the from any noisy vehicle from individual noisy vehicle.
Suppose it is a quite road, but there is a vehicle moves, which is a noisy vehicle
kind of a thing with a siren or maybe some kind of a horn or something like that or sometime
which is sports motorbike, very high speed motor bike, and some kind of a commercial
vehicle, so that is actually from a noisy vehicle or noisy source individual noisy source
also. So, it is loud enough and because of
it is a loud enough, and it is a again intermediate kind of a scenario, it is kind of a overshoot,
and then go down, and it is sometime extremely disruptive. And if it is very frequent in
a nature also, then it is a extremely disturbing and because of that in the residential
zone in a quite residential zone, this is going to hamper the sleep. It is
a problematic for the old age people are also for any point of view.
So, there are let us see there in a traffic noise, the individual traffic or individual
a automobile has produce noise because of this particular reasons. The engine produce
noise; the transmission also produce noise; exhaust that also produce the produce noise;
interaction between the the tyre and the road pavement that also produce kind of a noise;
the air turbulence and also the the bodies; and the load rattles and although kind of
things are also produces noise. Then there are some five factors has been
strategically pointed out in are the the central pollution control board by lot of
thorough examination, and the thorough research that that the level of the traffic
noise is also depend upon this five main factor. The first one is the volume of the traffic.
The second one is the speed of the traffic, the average speed of the traffic its vice
versa. Sometimes volume of the traffic if it is
high, quite normal that the the noise is also going to be high. The speed is
also it is again, it is not directly proportional, but it is if it is heights also going to be
high the noise. But sometimes if it is a day speed also, it is a congestion kind
of a thing, which is also sometimes give you kind of a noise because of the exhaust
and some kind of a motor always running, so that also gives a noise.
So, even though if there is a traffic congestion that does not mean that there is no noise
pollution or the know, it is also produce some kind of a noise. Then the the traffic
composition is a also one of the issues. It is a issue like the traffic composition
is a mix traffic scenario. It is a slow moving cares, slow moving vehicles, so slow moving
some rickshaw, and all those kind of a and all and with that there is a car or may be
some kind of a lorry and busses, and all those kind of a thing bikes, which is bit of high
speed. So, if this kind of a compositions are
there, and normally there are noise scenario more noise scenario. So, a composite
kind of a character of the traffic gives you a noise. If it is uniform kind of a
traffic, it is may not give you that I mean there may be a less amount of noise.
Of course, there are also some different opinioned about that or may be some you should not
be on only this factor there are other factors also. In general again a a the the road gradient
is also one of the issue. The gradient of the road, how it is a steep or it may
be a flat road also. The pavement type and the pavement type texture surface quality
is a definitely one one of the factor that also import the noise, I mean the the
amount of the noise. Again so those are the the first what I
have discussed is the the the which component of a particular automobile produces the
noise. And then the five those factors of a road or the compositions of the traffic.
And then the six major factor also identified in our code are the this pollution control
literature that which actually propagate the from the propagation point of view, which
six major factor contributes in more. The first one is the road profile, the grade,
the depressed or the elevated road on the depressed road also. The distance from the
source to the the the reception point that is also important if you are further away
from the noisy road, so definitely you are less exposed to the noise also.
The nature of the ground between the source and the reflection the the reception point.
If the the nature of the ground is very much hard, it is reflective stay back. If it is
if it is kind of a soft, the greenery is an all definitely it is absorptive, it
will not propagate that much amount of sound. The angle of view of the traffic stream from
reception point. So, is it a direct angle of view, the view and sound are actually correlated,
very strongly correlated. If the line of sight, and the line of hearing or the line
of sound, actually going to match with each other.
So, if you cannot we shall I, if you cannot see that particular noise source because of
some kind of a barrier in front, it may be natural barrier or it may be a magnate
barrier, it will reduce the sound also. The presence of bus screening on how you are
going to screen out, the particular noise source barriers or building and all will discuss
in detail in the next lecture on that. And the meteorological effect like the the
winds and the strength of the wind, and the direction on the of the wind also, in sometimes
rains also can create a kind of a the the changes of the the propagation of the sound.
So, those are the six factor, which from which a noise propagation will going to here.
Though now in the traffic noise mitigation measures. So, in that but now our objective
of this particular lecture is are maybe, this subsequent lecture is how to mitigate that
traffic noise, how to minimize, how to you you cannot just avoid the traffic noise,
now it is it is impossible. Of course, you can actually reduce down the impact
of that, because with the some strategies. And in this mitigation strategies or the
measures of the mitigations is broadly classified into three categories. One at source, you
can control the noise from they the emission point or the emitted emitted point from the
source of the noise source that is from the vehicle itself you can actually control.
And if you want to do that, you can you can minimize the huge amount of sound as
such. Sometimes we can go to the second category,
which is along the path of the transmission. The along the path of the transmission means
from the source to the transmission, source of the noise may be a road. And the the
transmission there is a transmission path. And the finally there is receiving in which
is my building, my my may be hospital may be a residential zone. So, this travel
this particular portion of the travel portion, this travel path also we can do some kind
of interference, we can do some changes, we can do some kind of a the the barriers.
And lot of the the the some kind of a landscaping or maybe some kind of a the the human barriers,
and all that can also help us from the I am the reducing the noise.
And the third and the final one, at the reception point itself that means, at the
building level itself. So, you may not do anything on the source, you may not you
may not do anything on the the path or may be path is too small that your building is
very near to the sources. There is no amount of path is available for a trees, spinning
or anything. So, you what you have to do is that other reception point, you have you have
to actually design your building such away, architecturally you are the way architecturally
some way are that many from the orientation point of view some kind of the site, landscaping
are the site planning point of view such a way that you reduce the sound.
So, if I want to do the first one at the source level, I need to do some kind of a
the act, I need to do put some kind of a very strong act maybe some kind of a traffic
guidelines. Those at the source level, so you can reduce the source sound. If
I want to do the second one the along with the transmission path in between the receiver
and the source, then I need to have some kind of a town planning act that this much amount
of area to leave, you this much I cannot construct anything, this has to be this much of are
the wall and whatever, you can do some impose some kind of the urban design guidelines
by virtue of that you can actually reduce the the transmission of the noise or you can
sometimes forget. The noise in the other directions also which will not going to actually
disturb you are sensitive zone, my sensitive zone.
And if you want to do the third one is the that the reception point, so you have to actually
back on the architectural design. Because, in that case the third case you have to receive
a reception point that is a building you have to think, so it is the the duty of an architect
to design a building, and the shield that noise the shield in the building from the
noise the out outdoor noise point of view. So, in a nutshell this is the traffic noise
mitigation technique. So, in this particular lecture, we will discuss
on the first one only the at source how we will we will do. In the next lecture,
in the the lecture number 39, we will do the second one the urban noise mitigation
through the the transmission path and all. And in the last lecture, in the lecture number
40, we will do with the architectural consideration. So, the noise control at source yes I have
already told you, it is some kind of a most effective way to reduce the noise. Because,
if the source is weak definitely weak in the sense of the from the noise producing
point of view it is weak, then definitely you are all problem solve though though,
but though it is very tough to do. It has to do some with some kind of a city rules
implementation, and due to some kind of a traffic management system.
It control of this reduction has to be implemented both for the bulk flow for the
noise and also from the the vehicle noise. And those are the following subdivisions
can be made from this particular point of view. This noise control at source one
is research and innovations, then the city planning, then the traffic management and
also from the citizen. So, what is the research and innovation
point of view is that the development of the some kind of a new low noise emitting machines,
automobile machine some kind of a new tyre technology. Even some kind of a new road surface
material those are the the areas, which the research and innovations can be thought of
or may be implemented in our automobile industry or maybe in the construction road
construction sector that can reduce the noise.
The second one is the city planning, city planning the town planning. And the the city
planners are actually may do some kind of a zoning or maybe some kind of a by
I mean the distribution of the noise sensitive zone. And the proper use of the the the
the land use planning that two which actually areas of a city is very noisy. So, you have
segregate the in the master plan that this part of will be used for the commercial
zone. And this part will be the residential are the noise sensitive zone, so that kind
of a things, they can the implement or propose. They can do some kind of a development control
rules also. Development control rules in the sense that this area this particular
building type is not permitted or this particular area if you have to construction some building,
you have to give minimum amount of this much amount of setback.
All those kind of a development controller or maybe sometimes, you know the high rise
buildings also may be exposed to the noise, because there may be a boundary wall or there
may be some kind of the barrier. So, the upper floors are very much exposed to the noise.
So, you can also develop some kind of a development control act for the the high rise. The
what will be the the height of the buildings, definitely city plane has do those, but may
not be a for the noise point of view, but they control the height of the building because
of the some the vicinity of the airport sometimes or sometimes, it is because of the
gradation from one point to the other one point to the deeper point from the road point
of view. And for the further sometimes it if it is
a commercial zones, utilize an a maximum fi are and all. For those kind of a area
cases the do the limit the height, but may not be from the noise point of view. Sometimes
we can they can also think of are they they definitely do some kind of a micro zoning.
In a zone and in between there are some kind of a micro zoning a suppose kind of a satellite
city, a part of the city is actually now look into in the various micro sectors.
And those micro sectors can be segregated or may be differentiated because of the
noise sensitivity point of view. The third one is the traffic management. This
is another important area, where we can thought of and that can be actually minimize
some kind of the the noise from the source. Some traffic rules, some kind of over speeding
rules for over speeding. So, then driving a noisy vehicle, so there may be some kind
of a penalty, no horn zone can be created in some areas. The city traffic movement,
and then no entry zone or re-routing zone can be think of in a particular area.
And definitely the last point is very much important, this point is very much important
that is a development development regular maintenance of the road, some sometimes you
develop some kind of a road. And forget to maintain it properly, so that is very much
sometimes problematic in sense of that also give you a directly penalty to the
vehicles, which is actually going are on on the particular bad road. Penalty in the
sense of that the wear and tear and all and also it create noise noise scenarios.
And the last one what is that is the the change of citizens attitude. And this is another
one, we just cannot ignore that one so. Citizens sensitization some kind of the the
the kind of a participate reactivity is required particularly in from the very beginning,
f rom the very school or the kindergarten age to a particular class or may be in
a in a the the the with the matric standard are the the board standard students. Because,
if you sensitize the children, then the next generation is prepared to take care of yours
all those issues and all. So, those are required, of course the the the raw material
is doing so. Lot of endures are also doing and our the administrative police and all
those things are also doing, but citizen is also has to be change their attitude.
So, from the city planning point of view there are few fundamental things, which
I have noted for this lecture. So, there are some road pattern, and from that road pattern
there are some grid iron road pattern. And the cities fall in a grid iron way. Sometimes
there is a radial pattern, if you see the the so plan of new Delhi is a radial pattern
road, if you see the the the the Chandigarh is a grid iron kind of thing.
So, out of these two if I want to compare these two particular kind of a situation or
the road network situation from the noise point of view, I must say this grid iron is
good. Grid iron is good in the sense of that its provide less concentration of the
noise. Whereas in case of a the radial pattern, so all vehicles actually a concentrated
in a rotary or in a particulars concentrated area. So, the noise concentration is more
practically in this particular area. So, there you own get a the silent zone or
the noise sensitivity zone over here. Here because of that may be in the central pocket
in each sector you may get a kind of a school, space for the schools may be
this particular can be one school or one central space may be for some kind of a park,
and another one may be for some kind of the hospitals or residential zone also.
Now, next one suppose you take a grid iron pattern. And in that grid iron pattern,
you have two type of traffic scenario. One is a two-way traffic, so from this road.
So, this the this arrow, this is black color arrows are actually indicating the road.
And this arrows are indicating the direction. So, here suppose there are the two-way
traffic. So, in this road both way traffic cab flow.
And here suppose this is an one-way. So, from this road only the the upper direction, and
the from this two-way the lower direction an the right and left side direction flows
are possible. So, out of these two choice, let us see if I want to see that what will
be the the effect of the noise, then the we must preferred the the the the two-way traffic
system, because the two-way traffic system you will get I mean its theoretically.
If you concentrate a two-way over here, so will get my larger area larger pocket area,
where there are will be a smaller pocket area that is number one.
Number two as we know that from our very beginning, if two equal sources added together, the decibel
level increased by only 3 dB. So, suppose this is source a, and this is source b
this is again a source, suppose another source c. So, if this two sources are add
added together, and put one source the only this particular road will be increased by
3 dB. If I assume that both road output is same, so it is nothing it is just only
3 dB increment in one you can our a central road of the the other direction road also.
So, you will get much more wider space of road to road concentration, road to
road distance. So, there is a much more noise sensitive area can be found
out from there. So, the this is very obvious a bypass road
is always good a bypass road is always good, because that will not go through in your
the the zone, which is demarcated as a noise sensitive zone. Then for a city
guidelines point of view also follow this particular rule sometimes. This is in segregate
the industrial zone in the outer direction of you are city. And then put you are all
the express ways and the the corridor the transportation corridor. And that that can
be shielded from through a green zone or the dense green belt, which will help you actually
shield in the noise. And also purify any kind of air movement because of the the the
dusty air from the industry also. And your noise sensitive city zone or city areas can
be the other side of this green zone, so that is also one of the way city planners actually
make for any kind of a new cities also. So, traffic management systems also is also
one of the impartment issues. So, suppose this is the this are the street, and these
the red color this blocks are you are noise sensitive zone or noise sensitive
building. So, this is your main road wider. And those blue color buildings are of some
commercial building, which is in the periphery which is near to the main road. This will
be the tentative distribution of the the the the zoning, the micro zoning of this particular
level and there some lines. And maybe what we can do is that we can put
some kind of a no entry point here for the heavy vehicles. For those streets at least
for sometimes in the the night hours or may be some kind of the hours, day hours or maybe
depending upon what are the the activities around here. And that will going to help you
in reducing the noise and from the source point level itself.
Then suppose you have a main road, and there is a noise sensitive zone in between and there
are commercial zone. Those buildings or nor that much sensitive. So, you can provide
hump or the the the speed breakers over here, and you reduces speed of this things
we can put some kind of a no horn signal signage also. Just to provide there should
not be any kind of a disturbance in between this patch of the road near to the noise sensitive
zone. So, again CPCB gives are some kind of a
criteria of our noise, which in day time the industrial area should not be exposed
more than 75 nine night time 65. Commercial area 65, 55. Residential area is important
this 55 in the day time and the night time it is consider as a 45 degree not more than
that. In fact, the silent zone which is actually 50 and 40 day and night
time. In as for the our Indian standard and this day time and night time also mention
from 6 to 9 and 9 to 6 in the night. And silent zone includes as for then as for the code
is the hospitals, educational institute like school, college and all an also courts.
And though this is the some of the category of the vehicle passenger car, commercial
vehicle from how much distance 4 meter, 4 to 12 meter, or above 12 meter and what is
the noise limit. So, if you want to just to check that this particular passenger car is
producing 82 dB or 85 dB at 4 meter also, so it is ok. If it is more than that, so
this is noise producing more than that limit. Similarly, we have some kind of a limit
for the trains also for electric diesel and the steam train steam trains are actually
nowadays not used in Indian Railway, but diesel and the electric train in at 60 kilometer
per hour should be less than are maximum up to 77 and 83 dB A that is the limit are
of our as per our standard. The aircraft noise are also very important.
And this aircraft noise is also considered as one of the the the annoying noise in those
who live near the air the the airport the actually can you tell better. I mean
it is the if they in the very near to the aircraft, and it is very near to this landing
or the for the flight the take off zone, so it is really annoying. And the and this
noise has has two type of noise has been the classified as a aircraft noise is
concerned, one is called the flyover noise. The flyover noise at is actually occur due
to the flight path which is actually because of the the takeoff and the landing.
And another one is called is a ground noise flight noise or the flyover noise is having
a high peak and there is a drop, and high peak and a drop if you take a large amount
of a time segment or so. Because it is due to the the high peak and a drop and again
again a high peak because of the landing or the the the takeoff activities. But the
ground noise is for the the emitting the sound emitting from the the aircraft when it is
a ground operation, the movement and all other activities during and that is little bit low,
it is not that much sharp of all this is kind of a static kind of a scenario.
So, it is harmful to the health of course, and this is sometimes go as much as 100 to
110 dB A. And it is it is important that a strong development development act control
act has to be implemented very nearby areas of the airport, air traffic zone or the airport.
And if it is still there are some development need to be happened of that you have to be
adequate insulate your building from that sound.
And this aircraft zone which is in the vicinity of any airport actually you need
to major that way how actually what is the noise, and the what is the amount of this
particular noise effect and all. So, it a single number evaluation system is developed
by the U. S. Federal Aviation Agency and that has been followed by almost everywhere and
that is called a noise exposure forecast NEF, which is a single number . And the procedure
of achieving the particular single number is little elaborated and little complicated.
So, we are not going to going to detail in that. So, this single number is something
like a contour kind of thing. It is actually a primary used for some kind to develop a
noise counter; that means, this area is having high noisy zone.
And then next rein is having little less and then there is a next rein is a little less
than that. So, those are the some numbers has been created because of due to the number
of aircraft and the number of other peaks and throbs and peaks and throbs due to
the landing and the the takeoff scenario. And this total this particular NEF that
is the noise exposure forecast are given with some number like any 40. If it is any 40 or
more than that is unacceptable I mean any kind of a development over there is on acceptable.
So, it is very noisy zone. So, only the aircraft and those of the this the particular
may be um some particular airport, and those activities can be happened, but not
any kind of the day to day the hospital or may be residential area or may be school
or may be anything cannot be accepted in the particular area anything. Anything NEF less
than 25 is normally accepted. So, there are situation, suppose this is
a a city map, I will just draw is sketching form a city map and this is suppose a landing
steep and this is you are airport area . So, if you do this NEF, you will find this
is the red zone which NEF is 40. So, there should be some kind of a developmental control.
So, there are should not one. Mostly it will common that the airport zone itself may be
here may be some part of the since may be go little bit away which may be there are
may be some kind of a residential area, but still there should be some kind of a
development act. Next we will be a another ring which is again
a kind of a stretched ring a contour which is green color. I have not here suppose it
is if it is in 40 is a red one, this is n 35, and then third one is little bit soft
and larger also, and this is N 30. So, and this is suppose the the blue one is the N
25, so which is which can be thought of that yes any kind of a residential area may
start from this this yellow blue boundary an also. This part can be have the your growth
of the city. So, this is the real of the sound exposed to a huge amount of sound
and gradually it diminishing down. So, this is the the NEF and that will be demarcated.
And then the the town planners and the they will actually do some kind of a development
contour act on it. So, anything like NEF is more than 40 is high impact which is
equivalent almost 80 more than 80 dB A. And in between 35 to 25 NEF that is my this
probably this yellow to this green zone, which is medium impact 65 to 75. And NEF less
than 20, which is beyond this zone is less than 55 dB A, there is small mistake this
should be capital A. So, from the mapping point of view, the
the mapping of the noise is concerned with the specifically with this. I have already
told you have to find out the L equivalent, L 10, L 50, L 90. And then you have to identify
the noise hotspot which is maybe a road crossing, narrow roads, a roundabouts mixed traffic
zone busy road etcetera. And then in the third stage in the mitigation process you to overlay
the the other sensitive zone like park, residential zone - school, hospital on this
map. So, overlay you are on the noise map overlay your sensitive zone map.
Next you find out the demarcate the conflict zone. So, if your hospital is under the
silent zone, not noisy zone, fine no problem, but if it is in a noisy zone then there is
a conflict demarcated that conflict zone. Now, you have to take the strategies whether
you go for any kind of a entry control, whether you rule it re-route the traffic. Whether
there should be no parking if suppose there is a very narrow road, and due to narrow
road people are parking over there, road become much more narrower and there is a when
there is a kind of sound so you may go for no parking zone over here and you can increase
the width of the road and give the the passage away. And sometimes it may be restricted
entry for the trucks and heavy vehicles for that so you can take some kind of suggestions.
So, those are the typical stage or the steps we will follow for mitigation process.
I think that is all for this lecture. So, I will give you the small exercise as as
you from the different city of my country. You are locate your noise source of your city
you think. Locate your noise source of your city whether the noise what are the sources
of the noise in your city or in your town . And take a map of your town, map of your
city, locate the hotspots point of your noise hotspot of course, point or so. And second
one is that and with the some example you can actually you can link this with
your the first assignment that how to reduce the impact of the urban noise, what are the
methods and what are the examples you can think for your city for any may be
a for a school not may be a whole city, but for a stretch of the road or stretch
of the some the noise hotspot point like a roundabout or so.
So, thank you very much for hearing me in the our the lecturer number 38 the
urban noise control planning consideration. So, thank you.