Author Archives: Roopakrishnamurthy

The conventional movie theater is giving way to a huge mall, with plenty of retail outlets, and the top floors of such places are usually dedicated to a number of small halls replacing the conventional movie theater experience. The large theater had a very different acoustical characteristic and these small halls require a fairly different approach for acoustical treatment.

I’ve worked on the PVR malls at Orion mall, and now at the Vega Mall, and some issues seem to be common across both projects. Let’s begin by looking at common acoustical issues at the smaller halls. (The larger halls are vanishing, and those that are remaining, can be treated similar to large auditoria – coming up in a different post!)

Sound Isolation

This requires maximum consideration. The biggest problems I see frequently are noise coming in from the food courts, gyms sharing walls and floors, air-conditioning chillers on top of the building, and noise from adjoining halls, in some cases! Thankfully, with most of these being located on the higher floors, traffic noise is never an issue. But I know one place where the door to one such hall was separated from the external facade by 6 feet of corridor space, and the glazing was insufficient to contain noise from airplanes passing by!

Reverberation

This is what most people think acoustical treatment is all about. Yes, these spaces need to be optimized for clear speech, as well as music, and of course, deep bass. I’ve watched movies in some really dead sounding spaces.  The speech sounded great, but the songs, the accident, all sounded very superfluous. It didn’t help that the movie was a crashing bore.

While we’re discussing wall treatment, no, absorptive materials on the wall will NOT prevent transmission of sound. Care must be taken to check sound transmission between walls of adjoining halls, and then design acoustical treatment required.

Ringing

This is the other most commonly seen issue. The hall sizes are large enough to allow plenty of LF in the room, but it is a task to ensure they’re sufficiently diffuse,  and it is essential to ensure that room resonances don’t unnaturally colour the sound. There are 5D movie theaters coming up these days!  It’ll be a lovely to write a separate blog post on them, some day soon.

Seating

Actually, the line-of-sight accuracy is all taken care of by the architects, and if the raking is correct and the headrest is not too high, one can ensure there’s good amount of direct sound reaching each row. But we’re more interested in the seating in terms of upholstery. Usually, these places are carpeted, and the seating provides a GOOD amount of absorption. It’s so significant, that the treatment on the walls must be carefully calculated to ensure that the space doesn’t sound dead after the furniture is moved in.

AV

The coverage of the speakers must be plotted to ensure that no place is receiving more than the intended amount of sound. The front seats have it the worst usually. Using logarithmically curved line array speakers can help, but care needs to be taken to add the right number of speakers in each array, else the sound becomes too directional.

Now here’s the other thing about audio. You DON’T NEED to hear it that loud. And if you’re a regular with movies in such places, I strongly advise you to carry a pair of earplugs. Choose how deeply you want to plug them in, and you will hear everything – the HF, the LF, the mids. Just not as loudly as intended. Honestly – I’ve always been most comfortable sitting through a movie when I have my ears plugged. I’ve attended a healthy amount of concerts, and have always maintained comfortable loudness levels by using earplugs. Sounds absurd? I know. Please heed my advise. I speak out of collected experience and foresight. You don’t want to be speaking these words someday, out of bad experience. 

Now there are plenty of other parameters we acoustical engineers calculate, to ensure the right balance of sound, etc. But these spaces lie between glorified home theaters and large auditoria. The importance for each parameter is therefore, determined by the size of each hall.

These spaces are leading to even more novel concepts – a person I know has turned a space into a home theater area. He has a few rooms, and each room is a dedicated home theater. Groups of friends, or family can book a room all for themselves, food is catered, and you can watch a movie with first class acoustics and audio, with only your loved ones! The acoustical challenge is to ensure that there is sufficient isolation between rooms, and of course, to even out the bass response in small rooms. There’s just so much happening on the audio/video front in Bangalore alone! Interesting times ahead!

Actually, there’s no single view to take on this topic. Restaurants are theme-based, these days, and ambiance of older restaurants become their “theme” after a period of time.  Let’s talk about a few ‘themes’, and then we’ll look at some common  acoustical issues at such places.

Eerie Places

I once  went into a restaurant called Gufha. The word means “cave”. True to its name, I walk into seemingly absolute darkness, one bright sunny afternoon. After my eyes got used to the darkness, as the door closed behind me to shut out outside light completely, I realized the whole place has undulated, brown-coloured plaster work all over the walls – made to look like a huge cave we’re entering. The waiters were all dressed like Shikari Shambu.

The undulations on the wall provide for ample diffusion of sound and there are no sharp echoes, no sound of clutter – which is so unlike most restaurants  where “sleek” is the theme. The only downside was that the place had piped music being played – not sweet-sounding chirps, babbling brooks, gushing water etc,  but eerie night-time noises from the jungle. Crickets, the occasional distant roar – what have you. The place provides good quality acoustics, and good quality food, I must add. But you don’t exactly feel appetized listening to sounds of creepy crawlers. The acoustic ambiance is not just about reducing echo and reverberation, and preventing noise going out/coming in. The choice of music goes a long way in attracting certain types of clientele.

The other example I can think of is Cafe Coffee Day at Jayanagar 4th Block. It played such loud music, on such crappy speakers – high on treble, low on bass, and in a room where NO thought had been spent on acoustics, I had to take a disprin at the end of an hour. This was years before I studied acoustics at UK, and so I didn’t imagine bad music could do so much damage. I have sworn not to go into a CCD since.

Noisy Places

Restaurants can be deafeningly noisy – Koshy’s for instance. This one also comes under the category of “Quaint old places, best left untouched”. There are railway canteens that sound quieter than this one! But that’s the ‘theme’ at Koshy’s – old world charm, nostalgia, noise of people, noise of cutlery, noise of the kitchen, bright chequered tablecloth, old fashioned cutlery, etc. There are old, analogue loudspeakers mounted on the corners on top, with cobwebs on them. No point in playing them anyway. 😉 This one should stay as is. 🙂

However, newer places that are deafeningly noisy don’t get the discount of old world charm. Toit micro brewery in Indiranagar is a good example. The weekend I went there, we couldn’t hear ourselves shout. It was so noisy. Of course, noisy restaurants are a sign of good times for the restaurant owners, but I’m not so tempted to go there again if I have to spend a couple of hours shouting myself hoarse over the din for having gone there.

Quiet Places

On a regular basis, we expect “quiet” to be a standard part of a fine dining experience. To provide this feature, the restaurant owners have to make sure the kitchen door isn’t leaking noise, and if the kitchen wall is a lightweight gypsum construction, it shouldn’t leak out noise into the dining area either. Also, the place is to be carpeted for sure – footfalls are irritating when you’re looking for quiet. The other issue we see is a high roof, usually made of gyp, with various designs for diffused lighting. Designs are good – we acoustical engineers are not very fond of flat, parallel surfaces, but high roofs can lead to cutlery noise being amplified. Fine dining places must have heavy upholstery on the furniture, and plenty of carpeting in the open corridor spaces – sleek chairs, smooth floors, high roofs are a bad idea.

Places with Live Music

This one clearly needs specialized acoustical treatment. Thumb rules like the ones mentioned above can backfire rather badly. We’re always talking about money wasted, when we design in hindsight. Such spaces have to be optimized for clear speech, as well as live-sounding music. Too much carpeting will help speech, but kill the high notes, and too little of it will make conversational noise and music mingle with each other unintelligibly. Treatment is not always essential. Hard Rock Cafe in Bangalore is a lovely example. The place is located in an ancient stone building that once housed the Bible Society of India. As was prevalent during that time, the stones of the building  have a natural irregular finish, and so there’s ample scattering of sound at least in the HF range. The various artifacts displayed also help in scattering some mids. It works for speech as well as music.

Common Acoustical Issues

So, it’s not really possible to have a standard view here about acoustical issues, but let’s make an attempt to generalize. For a quick peek into the possible acoustical problems in restaurant spaces, here’s a good read: http://www.restaurantnoise.com/restaurant_article.html.

HVAC: In general, the HVAC duct acoustics must be carefully calculated – certain critical distances can cause them to turn into roaring resonators. That’s not good for any kind of place – noisy, or quiet.

Kitchen Noise: These areas must be strictly isolated, with double doors spaced a few feet apart at the minimum. That way, when one door is open, the other will be shut. The doors must be acoustical doors – 6mm glass will not do much.

Foot falls: Contrary to what you may think, this doesn’t just imply treatment on the floor. It also implies isolating the ceiling from the noise on top, depending on the kind of space above. If the floor above contains a gym, or another restaurant, or an office space, care needs to be taken to isolate that sound.

DG set noise: Seems unrelated? Nearly every restaurant has one, usually right outside the main door. Nobody provisioned space for these things even 5 years back. Now it’s the norm to have one outside. The good news is, road noise will sometimes help to mask it.

Road Noise: At other times, road noise is the problem itself. Glass doors that are not framed, glazing that isn’t thick enough, will cause some noise to filter in. We’re not looking for studio-like quietness, so it’s okay to hear some, but occasionally, it’s bad enough to drown out conversation, especially on rooftop restaurants that aren’t really very high up. The Coffee Day at Jayanagar 5th block is located on the first floor, at the corner of one of the worst traffic signals in that part of town, and they’ve placed tables and chairs outside the room, in the balcony overlooking the signal.  I haven’t bothered to go in, but I can’t imagine myself sipping coffee, inhaling vehicular smoke, and shouting over traffic.

To summarise, for places that solely rely on good user experience for clientele, acoustics can be a big factor to determine how much time people spend at such spaces. Plenty of easy solutions are usually possible, and they don’t have to interfere with the theme that an architect or an interior designer has in mind. And if you thought architects and interior designers were the more creative of the species, I happen to know a couple of really creative acoustical engineers, who’ve worked with the interior designers to come up with spectacular looking furniture, with lighting inside them, which also work as tuned LF resonators to trap bass booms in the room! So there’s always room for some wonderful creativity that accommodates fantastic aesthetics, functionality, and science!

We’ve all gone through days when the facts suddenly become too much to handle. That important link between gathering facts and processing them seems to be some kind of bottleneck. That’s when I need to shut out the physical world. I invariably resort to music. It is my first weapon of choice for a mood change.

Why does music make us happy?

Now I’m trying to see if I’m just pleasing my auditory senses here, or whether the relaxation happens because of some other factor. True, some good sounds that hold you in rapt attention can take your mind off the reality you just faced. So temporarily, your energies are devoted to something pleasant. Which means, there was something about the real world that made you tired, de-energized, and there’s something about some well harmonized sounds, that ease out your tiredness, and relax those constricted muscles. This could be natural – because music is by definition a collection of sounds that are harmonically related to each other, and even with distortion, can sound quite pleasant.

What about songs that can make you hit the roof with excitement?

That happens when there’s visible gaining of energy … somewhere some resource is being unleashed in your body and as you get absorbed in the rhythm, melody ( or whatever it is you look for in a song)… and as the intensity of the song picks up, you feel your energies returning full strength, and these keep increasing till the end of the song, leaving you on a high.
This intensity of the song causes your own positive energies to come out and spread themselves on you. This visible gain of energy is worth looking at. It probably doesn’t make sense to rationally analyse these energy transactions, because the very idea of a clinical analysis separates you from that source, but here’s a go at it. Let’s start with the clinical definition of resonance from wikipedia:

In physicsresonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. Frequencies at which the response amplitude is a relative maximum are known as the system’s resonant frequencies, or resonance frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.

Naada Brahma – The Universe is Vibration

The first idea I’d like to talk about is the Sanskrit phrase – Naada Brahma -which means, the universe is vibration. So you, me, the laptop, the dog, the bridge, the building, are all vibrating bodies. Now we know that this is true at least of structures – structural engineers calculate resonant frequencies carefully. Not doing so results in disasters such as the Tacoma Narrows Bridge – where side winds set up vibrations approaching the resonant frequency of the bridge – and this turned into a self-feeding mechanism that resulted in the bridge swinging wildly with larger and larger amplitude, till it broke at the center. Here’s a video:

[youtube=http://www.youtube.com/watch?v=j-zczJXSxnw]

Now if seemingly rigid structures can have resonating frequencies, why not the rest of the world? The songs we listen to are all a combination of instrument vibrations, so the song must have its resonant frequency? What about us? Are we resonant ? On at least some tangible level, yes. Some people we ” resonate” best with, are our close friends. We’re on the same “frequency” with them.  Others cancel out our fond beliefs, so we tend to stay away from the likes.  And so, there are songs we like,and songs we don’t. There are people we like, and people we don’t.  “It’s a vibe thing” …

Least Resistance

At this resonant frequency, the two bodies in question have the least amount of resistance between them. And so there is a maximum transfer of energy – no energy is lost in any kind of impedance/resistance.

Manodharma – Expressing the Inner Energy

Now the other idea about why we suddenly gain energy from some kinds of music.

The song is a collaborative effort of a few people who got together and established contact with their inner energies and instincts and expressed whatever they felt then. It could’ve been their rational minds exploring a technique or a scale, or it could’ve been their feelings taking them up and down the scale. Either way, their rational mind or their emotions, contact with something inside has to be established before their skill can express it. Their skill can only express it. The word for this “something inside” is Manodharma . Carnatic musicians use this word to describe an artist’s ability to express themselves completely – this part of the concert is a mix of skill, intuition, feelings, rational intellect. Wikipedia says ” Manodharma plays such a significant role that a capable artiste may never render a raga the same way twice.” There’s a fixed part of a carnatic concert dedicated to this, while the rest of the concert rendering follows rigid rules of structure.

So when I listen to bands that take off on lovely riffs or ones like Shakti, where each person is spontaneously exploring their domain within the framework of the song, I feel that my reaching a high has as much to do with seeing this contact they’ve established with their inner selves, as with appreciating their skillfulness.

I don’t know yet, but on some level, my inner peace gets unleashed, the frown vanishes, the set jaw relaxes, the gaze softens. Some songs build up on intensity instead of just soothing their way till the end. Then I can actually feel my toes and fingers bubbling with energy towards the end. After these visible energy changes, I feel like I just shrugged off those silly inane worries.

When I listen to a classical piece, I can see the singer so much in contact with the feel of the raaga, and yet retaining judgement to express skill within its framework. In fact, our ancestors have classified raagas so accurately according to the feeling they induce, that one wonders how they gauged all this rationally – it really deserves a separate post. Maybe it wasn’t all rational.  Maybe it’s not just music. Maybe it’s directly rejuvenating to see anyone establish a moment’s connection. Music is more instantaneous to me because I posses some basic skill.

But I’d be wrong if I tried to limit all my happy moments to music. Resonance happens with us on many levels. 

It may be a piece of art, it may be a deed of kindness, or it may be a program that worked after you spent all your energy on it trying to make it work, or just something you cooked that turned out well. If we only took time to take a step backwards for just a second, and savour that moment – the very next moment, you’re already smiling.

Music, art, work, anything… they’re all reflective of human thinking, and of human transcendance, and are a direct expression of the vibrational energy that exists around us. Regardless of what moves you –  please take a moment off to step aside and shake hands with it.

This is the time of the year all Hindus wait for – houses are spring cleaned weeks in advance, sweets are made, customary gifts are exchanged, etc. Grandiose is the theme of the festival’s new dresses –  people drop in at each other’s places, huge get-togethers happen for Lakshmi pooje performed by women, followed by plenty of feasts. And of course, the crackers. Now I don’t quite know what ancient history or religion has to do with cracker bursting – but we’ve all been mighty excited about it since we were kids – till many of us grew out of it.

The crackers come with a huge story behind them – of the many children forced to work with unsafe materials, working in unsafe factories, of the many fire accidents that are reported, of the many more accidents that go unreported, of the shameful salaries they get, of the heavy price they pay – risking their health, life and limb.  Now if this isn’t enough reason for people to stop using crackers, I don’t know what else could be. Surely, people who burst crackers despite knowing the abovesaid, won’t be dissuaded by the idea of noise pollution, or the distress it causes to humans, and especially to animals. My infant is already being jolted out of sleep – the cracker bursting sometimes starts earlier than the festival itself. The sound scares the living daylights out of her – it’s an explosion, for god’s sake. She wakes up screaming and crying – can’t expect her to understand “it’s merely fireworks”. Given the decent density of infants in any pocket of India – people bursting crackers should perhaps display some consideration. I will not even mention the sheer physical distress that animals must be going through – their range of hearing is much higher than ours, and they hear everything a lot louder than we do.

The number of accidents that happen at this time of the year is shocking – and many more go unreported. Children suffer burns, injuries, scars, and of course, ear injuries. So many children are rendered permanently deaf  – for your ear drum is a tiny, delicate membrane  – stretched taut. I wonder why people think the thrill of lighting crackers is worth the risk. There are toddlers and infants in half the households in India. The lifetime of suffering is not worth the thrill  – and somehow no amount of highlighting this seems to work. There’s always a fresh crop of youngsters, waiting to have their go at the crackers. There’s even some kind of graduation scheme – starting with the small ones – and when you become ‘big’, go for the loud ones. The noise levels in the proximity of such a cracker can be close to 120 -140 dB. How loud is that? Actually, it’s really hard to tell you that without resorting to swear words for accurate expression.  If you think that’s not to worry about –  the explosion is just for a brief second, hear this –  people join such things till this chain extends all around an apartment complex, and then you’ll hear this for 10 mins. Experience your ears ringing after that – and other sounds seem strangely tolerable, because your threshold of hearing just suffered a temporary shift. A few of these in succession, and your hearing will be just a little bit worse off than it was. You’ll only know in your later years.

On a more rational note, clearly, this is a modern phenomenon – this cracker bursting – Prince Rama didn’t have these in his days, I’m guessing. This is more of a social thing – one that really should be done away with.

Now, in case I’m sounding like a doomsday soothsayer, I must clarify – I love festivals myself. I’m very fond of the enthusiasm they bring, of all the sweets and savouries that go around, of all the customary meeting and greeting, of all the new clothes, of people turning up in their finery, of all the long-lost relatives we get to meet, of all the catching up, the feasting and merrymaking, and of course – the holidays! Quite the mood!  I just wish there wasn’t the firecrackers angle. There’s just plenty to enjoy without that one!

So season’s greetings everyone, have a safe festival!

Usually, acoustic engineers are never consulted for this part of the design – we all think this has only to do with the Electrical contractors for the building, and all we need are specifications on how much power backup a building needs – which determines the number of DG sets for which to provision space.

Manufacturing Specification

Even more so, because all DG sets now come with an acoustical enclosure. The mandate below, out in 2002, clearly states that DG sets must come with their own enclosure. This actually mercilessly threw a lot of people out of business – these guys used to be design and build contractors for DG set enclosures. I know one of them personally. Very depressing times for them. Now they’ve all been forced to look for livelihood elsewhere. Click on the image below for a larger view of the text. 

Excess Noise in Residential Layouts

The funny part is, this mandate does not take into account the fact that DG sets confirming to 75 dB of noise at 1 m is only good for commercial or industrial areas. Residential areas need them to be quieter than 60 dB during daytime, and 45 dB during night time. Who on earth is now responsible to fill that gap? 

Case Study: This was exactly one of the cases we handled – a fertility clinic had opened up in the heart of a residential layout. The layout is one of the most beautiful, well planned layouts –  planned by the legendary Sir. M. Vishweshwaraiah, no less! – with lovely boulevards lining one of the most beautiful, tree-lined roads in Bangalore, and the layout on both sides of it. The residents refused to put up with the noise levels  – given that Bangalore faces a lot of power cuts in summer – the DG was required to be in use for good portions of the day. The Clinic people contacted us, and we asked them to move the DG set to the terrace, build a 4-inch thick enclosure around it, leaving enough open for ventilation, but blocking line of sight from nearby houses – what they don’t see daily won’t seem obvious to complain about. :).

Heating and Ventilation Issues

Now the other problem with DG sets in mid-size to large buildings may again seem unrelated to acoustics These large buildings could be office spaces, commercial outlets or residential buildings. I know of a case where a 17-storey residential complex wasn’t able to sell the houses in the ground floor of a building, because their DG area was located in the basement below that. The noise was so deafening that while taking measurements, my colleague and I had to use sign language to indicate dimensions to the other person to write down. We couldn’t hear ourselves shout over it!

What exactly is the problem? 

Now DG sets in buildings are almost always considered a necessary evil. Nobody wants to provision the space they really need, because it means giving up precious car parking space. As a result, these are often crammed into some corner of the basement, mostly as an afterthought.

But as it stands, correct provision must be made for the emitted hot air to be vented out either by giving space around it, or by providing artificial ventilation. Merely standing around such a DG set will tell you how hot these can get, and that you will feel most comfortable nearly 2.5 metres away from it. Not in the stipulated 1m space around it. Now usually, nobody affords that kind of space around a DG set these days – which means that in the absence of a ventilation system, these sets heat up and the DG operator walks over to the set and opens the door of the enclosure to let some air in for cooling. Now what’s the purpose of the acoustical enclosure again? Here is where a heating and ventilation issue becomes an acoustical issue. 

Now basements are usually bare bones by design, and provide ample empty space and bare walls for the sound to echo and reverberate in. I’ve heard huge basements echo with large amounts of noise, annoyingly audible 3 floors up. Three hotel floors up. Acoustical engineers are then required to design secondary enclosures based on the noise reduction needed.The good part is, unless you have staff sitting in the basement, you’re okay with having decent amount of noise there.

To summarise, noise is not the primary issue, but becomes one after a few months of the building’s commisioning.  The life of the engine is affected by these design decisions. The owner of the building spends time maintaining the set, replacing parts, etc, long after the building is up. In terms of acoustics, you only need to ensure that the sound reaching your compound wall and your building interiors is within the specified limits. This is easy to do, but is best done in foresight, not in hindsight.

This note is for mall owners / mall managers. Let’s start with looking at a few aspects of the mall.  The first is about the kind of crowds that come in.  At least in the Bangalorean context, with gardens and parks being turned into parking spots for malls (ironically),  play area and lung spaces are fast disappearing. People have no place to go if they just want to go out and get some air, and get a feel of the city’s mood.  This is quite unlike a few places in other countries I’ve seen – there are vast areas in the city center, meant for people to just sit around and bask in the sun (when they do get some).  You’re not compelled to be visiting shops there – you can go there without a shopping list, and just hang around.

In Bangalore, Lalbagh and Cubbon Park used to be those kind of places, and people went to regular markets/santhes/petes for their shopping needs. Parks and churmuri were the mainstays when it came to relaxing outside.

Now malls have become those places where people just go and hang out, as well as shop.  I think more than 80 % of the crowd that goes to mall does so for socializing. Most don’t have shopping on their list. Shopping is usually only incidental. I personally prefer the local shops for my grocery shopping – those kids can do fractions in their head! But being this new mom, sometimes I want all my work to get done in one place, so malls are useful there.

So what are the acoustical issues at malls?

Now here we hardly worry about acoustics – malls are fundamentally supposed to be abuzz with noise, quiet malls are a sign of bad times! But you’ll be surprised to know a few things.  A visit to the mall might be a thrill or a nightmare, depending on how sensitive to sound you are.  I know people who can’t handle the weekend buzz in malls, and finish all their shopping during weekdays – not just to beat the rush. My own husband is such an example – wild horses can’t drag him to a mall on weekends. 🙂

From an acoustical perspective , the expected sources of noise are:

  • noise from conversation
  • noise from events run by companies – more during weekends
  • noise from toys meant for children – play horses, play cars, etc – placed outside shops
  • noise from bowling alleys
  • noise from kids play areas – soft zones
  • noise from the PA system
  • noise from the food court
  • and rarely, noise from the HVAC ducts and vents.

Now, this post assumes that the cinemas, gyms and spas have been acoustically treated and there isn’t noise leaking in and out of those sites. So we’ll only discuss noise sources  listed above.

Why is noise a problem again?

It won’t kill anyone, yes. But people can choose how much time they want to spend at a place that sounds like a huge bathroom. As mall owners/product marketing guys, you’d would like them to hang around and witness publicity events.

Any studies conducted on mall noise? 

Here are a few:

If you really want to study this before you take a decision, contact me and I’ll be happy to provide more sources to you.

So what happens to customer experience at a noisy mall?

The problems are

  • low speech intelligibility
  • ringing sounds
  • general clamour

Low Speech Intelligibility

People will often strain their ears trying to listen to some DJ or someone on the mic trying to engage the crowd.  Most might just find it easy to move away to a quieter place.  But for having organized the show, mall owners/ product marketing managers would want people to hang around to ‘engage’ them.

One of my projects was based on such a case – the mall owner who approached us was convinced he could drive up the revenue on weekends by almost 40%  if we could just take care of the speech intelligibility. You hear lots of noise everywhere – all around you – you hear people talk, but despite high amplification (high enough to drown out ambient crowd noise), you can’t make out what they’re saying.

Ringing Sounds

Stand around one of those events, and you’ll hear music unevenly – even if you’re right in front of the huge speakers put up. Some notes hang on forever, muffling others. The bass sounds muddled and is usually all over the place, merely adding to the noise. Hearing bands perform at malls has never been anything but torture for me.  My favourite guys have played at malls close to my place, and I’ve had to turn back and come home because their words, lines, songs blended into one another due to echoes.

General Clamour

There are people who don’t hang around watching those events, but do go to malls to have a cup of coffee with friends  -such people might find themselves shouting over the din. The noise does get to them after a while.  My husband, for instance, forever prefers quiet, fine dining to eating at the food court. Typically high roofs provide for ample space for reverberation – so the sound energy tends to just hang on forever, in the absence of anything to absorb it. People do absorb noise, and we acousticians take that into account when designing auditoria, but in malls, they’re also the source of noise :).

That seems common across malls. What causes this? 

Smooth interior finishes – huge glass showrooms in most places, smooth gypboards everywhere else. Large empty spaces waiting to get excited with sound and echoing on forever.

Right. The solution is…?

The best part is, the acoustical treatment need not be seen.  These days, there’re so many products available, and for malls with a tight budget (if there’ such a thing 🙂 ) local carpentry is always an option. If some of the treatment areas are unavoidably conspicuous, they can be used for publicity banners.

The amount of treatment must be carefully calculated – a dead-sounding mall is as uninviting as a painfully noisy one.  Here’s a study actually recommending a decent amount of buzz.  http://www.retailcustomerexperience.com/article/196427/Study-Background-noise-inspires-innovative-purchases

So in summary, all other factors remaining the same, the time people spend at a mall is a function of how comfortable they are with the ambient noise – among other things.  And it’s so easy these days to make a mall  sound  more chirpy and less like a glorified, reverberant bathroom – without marring the interiors.   People would spend more time catching up with each other on the food court if those didn’t all sound like “noisy railway canteens.”. I quote because a friend once described Koshys that way. Now some quaint old places just have to be noisy. I won’t have them any other way.  🙂 But our malls could do with not sounding like deep, bottomless, echoing wells.

This post was long in the making – the seeds of it sown during the recent Ganesh Chaturthi  celebrations, and now culminating in the Durga Pooja celebrations. This note is for the organizers of such festivals. Having been on both sides of the fence, I expect this post to be a balanced view.

Indians love noise. 

Let me begin by Indianizing the context – we love noise during festivals. Bustling preparations that set the whole household abuzz a week before the festival contribute majorly to the excitement – and they’re all needed to take one away from the drone of daily routine. All this has been happening for thousands of years – and frankly, not just in India – festivities involve huge preparations all over the world – and are always accompanied by noise/music/gatherings/storytelling/rituals, etc.

Festivals are ages old. So is noise. Why this hue and cry about Noise Pollution now?

So why this brouhaha about noise pollution now? What’s changed is that loudspeakers now transmit sounds over long distances, and communities are more widely spread out than they used to be.  This means there’re always a mixture of people living around you – some who don’t share that festival with you, and some who do.

What can one or two days of noise do to you anyway?

We’re talking noise 24/7 on those days.  Eight hours of exposure to 85 dB of noise can be the beginnings of permanent ear damage. And noise at a loud dandiya hall,  or near some cultural programme can exceed 100 dB on an average. In general everyone faces irritation and annoyance, students face anxiety due to their inability to concentrate, and  some exam or the other is always looming near, the older folks face raised blood pressure, the infants are  repeatedly startled out of deep sleep, and disturbed sleep makes everyone cranky – infants and adults alike.

The Legal Angle

A little bit of consideration can save you from legal action. These days people don’t take things lying down, and there are android apps available for every passer by to measure the noise levels leaving your venue.  Along with GPS mapping to pinpoint location, it’s easy to gather proof and lodge a police complaint.

Any solutions here? 

I’ve mentioned enough about what noise pollution can do to your health, so here let me only speak of the solutions we can think of.  There are strict mandates by the courts of law about acceptable noise levels in urban areas being less than 55 dB uptil 10 p.m., and less than 45 dB after 10 p.m. Organizers of the events are bound by law to adhere to these norms.  Here are some things they should do  – these will ensure

  • that you enjoy your festival while not causing physiological distress to others who don’t share your festive mood
  • that you don’t get on the wrong side of the law.

To start with,

  1. Ensure that noise levels at the boundary of your event is less than 55 dB. This is easily possible these days, and it doesn’t have to cost you an arm and a leg. Talk to an acoustical consultant. Solutions can be easier and cheaper than you think, and they may cost you less than a  twentieth of the average budget for such events.
  2. Tilt your speakers. Rock shows use line array speakers which are tilted at an angle – this ensures that the main beam of sound coming out of a speaker does not run parallel to the ground, but will surely hit the ground at some point, minimizing the direct energy leaving the area.  The reflected sound leaving the venue is easier to contain with barriers. Your sound engineer or acoustical consultant can help you with this.
  3. Cut out celebrations at 10 p.m .  Everyone needs their shut eye after a tiring day. Ask tired moms whose infants wake up 4 times an hour thanks to your mood. The solution is simply to celebrate during the day. If you can’t do that, please spend more from your budget on soundproofing. It’s not as expensive as you think, and a lot of features of the venue can be used to mitigate sound after a certain boundary.
  4. Avoid mounting horn loudspeakers on streetlamp poles for half a mile on each side. In other words, there’s no need to tell the whole town about your celebrations. Use posters/hoardings to publicize, if you have to. Keep all your loudspeakers within your venue.
  5. Use ear plugs yourself. Quite honestly, your ears aren’t made of sterner stuff  compared to those who get disturbed by noise at a distance.  Before you find out the wrong way, please do things to protect your hearing. You will be able to dance quite well to the music despite ear plugs in your ear – they only reduce the direct sound hitting your ear. Try it.

So is it really possible to contain noise in such venues? 

The simple answer is yes. Distance does a great deal to help attenuate, so if the venue is large, it is more easily possible to contain sound at the edges. I was once posed with a client’s requirement – they wanted me to think of some kind of enclosure that tests audio setups for live sound. So this enclosure is to have about 50 dB of sound on the outside, while the inside sound levels would be about 120 dB. The catch is, because this enclosure tests live sounds, it has to be completely modular – one should be able to dismantle, transport, and assemble it.  Now THAT’s a difficult project. Only heavy mass can block sound over short distances.

So, controlling noise levels from leaving a fixed area meant for large gatherings is decently possible.

Acousticians speak physics. They don’t speak convenience. :). But here’s a post outlining the basics of what you’ll hear them talk about.

Loudness
Yes, I know you know what loudness is. You may even know that we measure this in decibels. But what you should know is that the human ear perceives loudness logarithmically, not linearly. What does that mean to you? It means that we humans therefore use a logarithmic scale to measure loudness. And that means, that a 10 dB increase in noise levels means a doubling of the noise you hear. Similarly, to bring down noise to half of what you’re hearing, you need a 10 dB loss.

Frequency
This is roughly the ‘pitch’ of the sound you hear. Buses, bass guitars, bass drums, and all rumbles in general are ‘low’ pitches. Most vocals figure in the ‘mid’ frequency range. Shrill voices, instruments, female opera singers figure in the ‘high’ pitch range. Generally, if you have a piano before you, low pitch is to the left, and high pitch is to the right.

Why do you need to know this? When you get a room acoustically treated, you must know that high frequencies scatter more easily and predictably around a room. Low frequency sounds tend to bend around life-size objects such as chairs, sofas, etc, producing irregular shadow regions. Absorption helps kill most high frequencies, but it can’t keep the low frequencies from bouncing around the room. Trying to ‘absorb’ low frequencies would eat up most of the space you have – around 3 feet on all sides.

Reflection
Of course, this is about how sound bounces off walls. High frequencies bounce off walls and surfaces like light does. Low frequencies have a mind of their own. They bend around objects, ignore most wall treatment, and pretend that your single partitions don’t exist. These are what your neighbours will most often complain about. Quite simply, sound acts like a particle at high frequencies, and like a wave at low frequencies.

Absorption
This really needs a separate post, but we’ll stick to the definition for now. So absorption is the fine art of reducing sound energy in a room. Absorber materials are essentially porous in nature – sound goes where air goes, and then while passing through a maze of pores, being  in frictional contact with maximum surface area, sound energy gets dissipated into miniscule amounts of heat.

Diffusion
This is the process of scattering sound around a room. Egg crates work here, only for high frequencies, though. Nowadays, there are products available which absorb as well as diffuse.  Again, space constraints in most site conditions make it difficult to build diffusers for low frequencies. These constraints are sometimes marginally overcome by making the opposite wall surfaces non-parallel.

Reverberation
This is a measure of how long it takes for sound to die out in a room. Well, not exactly die out – reduce by a certain amount.

Isolation This may seem too elementary to define, but the number of times people confuse this with reverberation treatment makes this worth mentioning. Isolating is to prevent sound from leaving a certain space.  Materials that ‘absorb’ sound seldom ‘block’ it.

There are plenty of other terms – depth, clarity, speech intelligibility, etc. There are also terms describing what sound sounds like – warm, cold, bright, mellow, intimate, etc. These will be dealt with in another post.  For now,   the above terms should lessen some of the the geek (!) and latin in your conversations with your consultant. 🙂

I’ve only just started freelancing on my own. Unlike the initial  romanticised impression of acoustics being the perfect mix of music, maths and physics, I really spend most of my day listening to noise :). So I thought I should get my hearing tested for two reasons:

  1. To have a point of reference for a ‘before’ and ‘after’ scenario of my hearing sensitivity.
  2. To understand what frequencies I am sensitive to, and any hearing losses I may have for other frequencies – so that I can accurately tune listening spaces.

I went to this institute near my place and found out two things that didn’t suit my needs.

  1. I could hear road noise very clearly inside their listening room! This is past 3 doors, no less – the entrance door, the door to the audiologist’s room, and the door of the listening booth.
  2. They test only 5 frequencies from 250 Hz to 8 kHz, because this is primarily for old people to hear speech.  For my purpose of tuning spaces for music, I need to be tested for a much wider range – 50 Hz to 18 kHz.

Anyway, I went ahead and turns out my hearing is normal, but I suspect it won’t stay so for long. I am a tad sensitive to vocal high pitches – the Lata Mangeshkar types – playing those at normal volumes can grate on my ears. But I did have difficulty in listening to low pitches – the 250 Hz thing. This would’ve been critical information for me to have found out – except that I will have to take it with a pinch of salt, pending more accurate tests. There was plenty of low noise infiltration through the doors, and I could hear them despite the on-ear headphone.

Anyway, the point is, that critical spaces such as these must not have any type of noise coming in. They had even used thermocol for acoustical isolation. Thermocol, styrofoam are easily and cheaply available, but they are not acoustical materials at all – they can at best be used for impact isolation.  There was also some masking effect happening due to road noise intrusion. I could clearly tell the sound of an auto, a bike, a bus, and some local vegetable vendor hawking at a loud voice.  This is also because the glazing they had used was rather thin. It is critical for listening booths to have glazing because they are to be closed, and the only way for the audiologist to know that you are able to hear a certain test frequency, is when you raise your hand. They have to be able to see you. Glazing itself is not a problem, but the right thickness must be used. Also for such applications, either in-ear earphones, or supra-aural earphones must be used. On-ear headphones are not very effective for blocking out sound.

These and many other defects can be solved right at the design stage.  Eventually, the kind of hearing aids that are prescribed are primarily influenced by the extent of the patient’s hearing loss, and the budget.  The first factor – the extent of the patient’s hearing loss can be accurately gauged if external interference is zero. In this case, it is critical to avoid masking effects.

The right technical advice will take into not just that, but also the hum of your HVAC, the type of earphones you must use, the influence of nearby buildings and their DG sets, etc.  It should also prescribe materials from a rough-use point of view (for instance, the rubber linings of the door had peeled off – leading to a compromise in sound isolation). For a place primarily meant for accurate testing of hearing loss, the noise constraints posed by the location can be easily overcome with correct acoustical diagnosis, testing and recommendation.

Studios are critical listening spaces. The noise levels have to be as low as 10-20 dB.  The hum of the HVAC, the rumble of the ceiling fan, the structural vibrations of all the houses/buildings nearby, the rumble of trucks on the road, the cross talk through the HVAC duct, the hum of the machines, all make a rather big difference to the quality of the sound. Also, since most studios are rather small spaces, the the bass response must be carefully evened out.

I’ve seen studios that have sound leaking in and out of the rooms, studios that are somewhat reverberant because the glass wool sagged over the years, and studios that were about 50m from the nearest bus stop but you could hear the squeal of the breaks and even the horns all the time, even if there wasn’t an obvious air path from there.

The purpose of outlining this scenario is to mention common issues faced by a lot of studios in this area. Structural vibration is the biggest grouse. And increasingly, pavements are laid joining the road and residential areas. This, despite there being a mandate not to do so for longer than a certain width ( wide enough for your car to roll out of your house). This leads to added coupling.

That said, in India, the advantage is that most structures are still brickwork/RCC, unlike gyp/wood partitions in the west. Internal walls are usually 4 inches wide, and external walls are 8 inches. Older houses have thicker external walls.  So, a decent amount of isolation exists between rooms, if you ignore flanking.

All this is was about the sound isolation bit. Now when it comes to reverberation treatment, and the frequency response of the room,  studios again are the most critical sound spaces.  It is vital to even out nulls and peaks for bass frequencies, and diffusers must be optimally used.  If the absorbers are carefully and specifically designed, one gets much more benefit out of the treatment than by randomly experimenting with off-the-shelf stuff. Faulty room acoustics leads to the sound engineer falsely believing the sound spectrum to be something it is not, and equalizing to correct what they think they’re hearing.

Sound technical planning should make sure that you avoid all these pitfalls, and the expensive corrections they entail. The right treatment should make the ambient sound crisp and clear, with accurate and predictable colouration from the room.   The quality of sound you hear can then safely be subject only to the quality of the equipment. I have a personal affinity towards sound studios, because these test so much of our skills, and these are also the places where some of the best works of art are immortalized. As someone whose interest in music primarily led her to acoustics, I do have a thing for these little rooms.  🙂