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Great. Now that we’ve largely taken care of soundproofing in the previous post, let’s look at what happens in the interiors.

All Glass 

Glass is something we can’t avoid these days, and the challenge is to ensure that the sound field in a room is sufficiently diffuse, despite perfect planar reflections from large panes of glass all around you. This poses trouble even for the mids and highs, let alone the LF.  How do you introduce time and phase shifts? How do you reduce the spot intensity of standing waves forming peaks and nulls at the same spots ALL the time? Well, clever options are possible if you lay down the fundamentals of the concept/solution to the architect, and let them play with it. They ARE the creative of the species. In Mumbai, a lot of old industrial sheds have been successfully converted into music lounges – despite the theoretical odds.

Mixed Usage

Here’s a very generic scheme of what sound should sound like, for various usages:

Frequency  Movies Live Music Gaming
Bass Loud, but not boomy Tight Loud and Boomy
Mids Short Long, resonant Short
Highs Dead Long, Short

Now lounges have another category    – DJ music. The kind of absorption you need for these scenarios is really different, but we always have to strike a balance. There is always a mixed usage. The kind of bass you need for DJ music is thumping, compared to the kind of tight bass you need for say, smooth jazz. Actually, for those who know their music, within EDM ( Electronic Dance Music), there are so many sub-genres each of which have a typical characteristic feel – all contributed to by the balance of highs, mids and lows.

Now while it’s great to experience this variety, at the design level it is not really possible to alter a room’s response to suit different scenarios. So broad generalizations are made, keeping in mind the primary use, the secondary use, etc. Sometimes the extremes are too far away to bridge – such as one project I’m pitching for where I will need to design for typical lounge music, DJ music, and the space also doubles up as an exhibition area, or ( hold your breath) – a conference room!  The ambience for an exhibition area must be a quiet one  – low noise, piped music, etc, and for speech – deadly quiet. HVAC hum, etc are factors to monitor here. Now for the volume of the space, speech is going to sound terrible if music is to sound awesome. Variable acoustics is the key here. There will have to be additional absorption brought in when there is a speech event going on. The design must be modular, easy to assemble and move, and sturdy.

Such a situation also requires variable sound systems. You can’t be playing piped music through a line array meant for live music. Sound system engineering is also critical for soundproofing. Choice must be made between having a distributed system or a line array-like system. Distributed systems must be chosen to ensure their coverage isn’t much more than needed – to avoid excess sound pressure at the walls. Compared to distributed systems, for the same power configuration, a line array system will beam all energy along the main axis – while keeping smaller amounts of energy in the side lobes. This makes it suitable for long halls, marginally/significantly reducing soundproofing needs for side walls, but surely increasing the soundproofing requirement for the opposite wall. However, low frequency response is nearly similar to that of a distributed system. So soundproofing requirements for LF stays the same.

Mixed usade presents another issue in that seating plays a very important role in acoustics, and we are unable to take that into account for such cases. Seating accounts for a significant absorption, and so does the crowd – we design for 2/3rds occupancy typically. If furniture is going to be modular, to be shifted in and out for various scenarios, our calculations have to buffer for that. Also, the place could have 150 people for a DJ session, and only 25 for an exhibition. The challenge lies in making intelligent estimates, and in knowing the broad ranges of parameters within which these estimates are true.

Concluding each such article leaves me excited about the variety of cases we get to solve in the ever-evolving melting pots that our cities have become.


I’ve been often asked these questions by a host of people, and considering most of these conversations run into at least an hour if any justice is to be done, I thought writing down the basic information would be useful. This is by no means exhaustive, just a starting point.

Scope of Acoustics 

The most beautiful thing about acoustics is that it is a very multidisciplinary subject. There are fields coming together at all levels – pure math or pure physics, statistics ( perceptual audio and psychoacoustics), electronic engineering ( transducer design – loudspeakers and microphones), mechanical engineering ( noise, vibration and harshness  – NVH), and not to mention music ( tuning spaces for music, musical acoustics etc).  The field that I’m working in is called Architectural Acoustics – I work with architects and builders to design spaces for optimal acoustics and soundproofing. Let’s cover these one by one.

  • Psychoacoustics/Perceptual Audio : This is more research oriented,  and there is very little work being carried out in India on this. ITC Sangeeth Research Academy is one place that does regular research work on this. Audio manufacturers  and mobile phone manufacterers are also interested in this field, but to my knowledge there’s only sales and marketing going on here. Philips has some acoustics-related work here in their product development facility.
  • Electro-acoustics Commercial/Private Sound System Design: This field has broad applications, and the two companies that actually do product development in India are Sonodyne and good ol’ Ahuja. Most others have manufacturing lines in China or elsewhere and at best hire software engineers to design computer interfaces here. The significant bit is always sales and marketing, and execution – which involves project management, client account management, design, installation, testing and commissioning.
  • ElectroAcoustics – Microphones, etc: This throws up a whole lot of mobile phone manufacturers as potential employers.
  • Electro-Acoustics -DIY: This aspect is something that needs highlighting. I know people with fantastic talent in this area. There are plenty of projects to execute if you know the indispensable art of negotiating, project management, and marketing. There is, of course, stiff challenge from the branded products that are sold by equally agressive AV vendors who also offer automation, but there’s always place for talent.
  • Mechanical Engineering: Knowledge in this field will give you an edge when working on industrial acoustics projects. The scale of problem solving is stupendous, as is the cost of basic transducers you need for vibration measurement. I know firms that deal with such a huge variety of problems – from the nanoscale (hearing aid devices) to ocean acoustics. Basic knowledge of finite element modeling, boundary element modeling, meshing etc is vital, and there is investment in terms of procuring some relevant software. Other applications are aero-acoustics, and automotive NVH analysis. With Boeing and plenty of aero-acoustics firms setting up engineering establishments in India now, and with automotive firms moving similar research to India, there’s a big thumbs up for this side of acoustics.
  • Music: Now I started out with this, and my basic love of the sciences. It turns out that the place where you experience maximum music is in live sound acoustics, and electro acoustics, where you test loudspeakers, or even in perceptual acoustics – where you may be playing music to check its effects, etc. Not so in the field I’m in! Now I know a lot of sound engineers who can just listen to sound and and tell you exactly what the problem frequencies could be. Sound engineering, however is different from the study of acoustics, and they have a different skill set. It is important not to mix the concept of music production and sound engineering with the study of acoustics. There is a mild overlap, but the rest of it is quite divergent.
  • Architectural Acoustics: I spend some part of my week taking noise measurements ( – irritating traffic, deafening train horns, machinery noise, stuff that grates on your years), and many of them at night hours. In the other part of the week when I’m on a desk, I look at dry numbers, excel sheets, formulae, impulse responses, CAD drawings, software models etc.It’s REALLY dry – the only music you hear is that on your ipod if you can work side by side – so getting into this profession because of your love for music is a very overrated idea. I do design spaces for sound, but time management tells me that I have to be more interested in running swept sines or MLS sequences, or blasting white or pink noise in a place instead of joblessly hanging around on a site listening to music!   You need to enjoy calculations and analysis to be able to hang around in this field long enough. I’ve climbed 16 storeys of of a building in my third month of pregnancy, assessing noise issues floor by floor, with no place to sit, and debris strewn everywhere (construction sites build lifts after EVERYTHING else is done. The other option was to use a precarious-looking service lift outside the building). Of course, I was all excited and had no complaints, but my folks freaked out, as did my doctor. Long hours of standing on sites is a given. This is true of any construction-related field.
  • Environmental Acoustics: Again, overlaps with Architectural Acoustics and Industrial Acoustics sometimes when it comes to soundproofing projects. Building noise control is increasingly important as residential and commercial zones are overlapping in growing cities.
  • Naval/Ocean Acoustics: This is for the seriously technically inclined. Needless to say, most work locations will be located on coastlines. You can’t choose to live in a place, should you make this choice.

Scope of Working in India

This deserves a first mention because people ask me this before they’ve even thought about why they wish to work on acoustics, and rightly so. The field is still nascent in India.

Acoustical Design is a relatively niche field in India, but things have changed significantly in the last five years alone. When I studied my course, I was still comforted by the fact that I had experience in the IT industry and could always get back to it if I wanted to.  Now there are paid jobs available, and of course the option to do freelance consulting is always there. I chose the consultancy option because it gives me the flexibility I need with a 2 year old toddler.

Salaried Jobs:   A lot of audio video companies are looking for an in-house acoustical designer, and there are acoustical product vendors who also need in-house design services before they can quote for a project – so these are typically the kinds of salaried posts people can expect.

Consultancy: Technical skills are about 20 % of what you need to run your own business. Business skills are equally important. Consultancy has its ups and downs – you sometimes have to spend time recovering money from delayed payments when you’d rather be doing fundoo design, and it can get difficult to plan your finances if you don’t know how to hold your own. Work always needs to be done ASAP, but there are always processes for payments.  Construction itself is a rather unpredictable area – there are unforseen delays and projects rarely get done in time. It takes some getting used to. Also, in the Indian mindset, people like to pay for tangible things – such as products, or installation – it’s rare to find someone who gives importance to design.  But all this takes some getting used to. A few projects down the line, you learn to draw up your set of rules. It is fair to say that while there are enough freeloaders on this planet, there also nice people who think other people’s labour is to be paid for. You learn to tell the difference, but it’s always a trial and error method.

There is also the issue of managing time, especially for women in the Indian context. I’m incredibly lucky, to have a fantasic support system, but not every one else can be so fortunate, and this profession has its share of multiple projects landing up together – and this entails nightouts. It also has its share of multiple projects being in a state of execution and your support being sparingly needed. It’s important to stay productive all the time.

Most acoustical consultants I know are not into pure consultancy. I know only a handfull ( including myself), who relies entirely on the Indian construction market. I couldn’t have done this without my family supporting me till I reached steady levels. One person I know  ( and work with) who does pure consultancy also works half time with a U.S firm, and that’s his steady source of income. Most others tend to take on turnkey installations ( which means they charge for project management, have margins on materials, etc). Others have ventured into offering a complete auditorium package –  lighting, audio and video, along with acoustical design AND installation, and even audio renting. These are the qualified ones.

While I am a believer of learning on the job, the bulk of acoustical consultants in India are those who can’t tell absorption from isolation. Simply because there is no opportunity to study the science here. Most are forced to offer acoustics as a freebie to clients, while selling either wall panelling, or AV products.  I can count on my fingertips the number of acoustical consultants here who are qualified, who are independent ( do not take commission for recommending products or for vendor referrals), and who do only pure acoustical consultancy. It’s a big decision to take – the turnover is bigger if you take on bigger jobs – simple. Turnkey Interior vendors do business worth crores – it is a very tempting proposition.  As problem solvers, independant acoustical consultants cannot quote their fees as a percentage of the project cost, or on a per-square foot basis for ethical reasons. Instead, we quote for our expertise and time. There is a direct conflict of interest. More on this in a separate page on Independent Consulting.

The upside is that consultancy allows you to work at your own pace like nothing else does. I know how important that can be – on days when the toddler falls sick, or when the babysitter falls sick. I restrict travelling on site visits to two days a week – which helps to ensure that I get uninterrupted periods of time during the other days to get important design work done. Once work starts flowing in, days and nights can get merged into one. Growth is required – you will need assistants for CAD, for site visits, for marketing, report writing, software modeling, measurements, etc.  But I have yet to see a firm that is larger than 6 people.  I haven’t done any marketing so far, but have required help for all others aspects I just outlined. As with any business, you need to ensure you’re covered for a year of regular and random expenses so that you don’t fret or get a panic attack when payments are delayed – as they inevitably will be.

Studying Acoustics in India

In India, the options are fairly limited. A couple of IITs and IISc have some courses in technical acoustics, but I’m not sure of what the entrance criteria is.  Institute of Acoustics has started a chapter in India, and they offer diplomas, but I’m not sure of any further details. I had no choice but to go abroad.

Studying Acoustics abroad

Studying abroad is a great idea. It’s also the rich experience of interacting with people from very diverse backgrounds that helps you become a lot less judgemental, than cocooned home birds. However, one needs to plan finances very carefully before embarking on such a journey. It can get difficult to start out on your own while having an education loan EMI to take care of. I was lucky to get away with 8 % – that doesn’t happen anymore – it’s now at 11 or 12 % – that can get crazy. This made sense earlier when the job markets abroad were good, and acoustics being a rare field, the visa or residentship application for this comes under the category of highly skilled migrant workers in most places. With job markets not doing so good in EU and the US, construction takes a nose dive, and with it, so does construction-related work.  So it makes sense to study abroad only if you are able to manage the finances well.  With my frugal lifestyle ( studying acoustics will usually not leave you with much time to have a life, as the course tutors themselves had advised us 🙂  ), a lucky 8 % interest on loan, and the fact that I came back home after finishing my coursework and completed my thesis from here, supported throughout by parents, husband, parents-in-law – I ensured that my loan was only 10 lakhs – course feels, flight tickets, living expenses, combined. This still means an EMI of 17k every month. I knew many even back then whose lifestyles just couldn’t be brought down to less and they had serious issues managing their finances.

At the current rate of interest, and with rents, course fees, etc on their way up since I went there last, I’d say the monthly EMI will easily be around 25-30k a month. Think very carefully about this. Most loans now offer 10 year repayments also, though 7 years is the norm.  To a lot of people, studying abroad makes sense if you can work abroad and make some money for a few years before thinking of coming back to India. The equation is no longer true – due to various factors – general down turn,  it’s not as easy to find jobs as it used to be, stricter immigration laws, significant taxation, higher living expenses to start with, etc.

I must point out that it is easier to get a salaried job abroad than in India – because there the building norms are very clear on the certifications and compliances, and more importantly – they are strictly followed and enforced. Here there is no such thing. People worry about soundproofing only when they are in danger of having their place shut down due to complaints. But even there, acousticians lament that the field is very rare and many just don’t even know such a thing exists. But for sure, organized work is much more easily available there than in India.

Courses Abroad 

I studied at Univ of Salford, and we were privileged to be interacting with the best minds in the field. The course gives a fantastic introduction to the field and we were left in awe at the end of most classes. The course is very intensive and you’d be left with nearly no time to have a part time job, unless you’re a genius and can comprehend lessons in half the time it takes the rest of us to grasp concepts. A strong numeric background is required. You could opt for the audio acoustics module if you’re good with electronics, or the environmental noise modules if you’re interested in noise control. These are two modules each, and the other six modules stay the same. For most current information, please visit the website of the university.

There are many other universities in US, EU, and Australia.

To conclude, the field is nascent in India, and that is both a good and a bad thing, depending how lofty your aims are. Getting into acoustics is a tougher decision to take compared to thinking of other mainstream areas, and this decision takes a good amount a planning. I am personally driven by the joy of experiencing how good a place sounds, but that alone is not enough to keep up a healthy tempo. Though the field is related to music, experiencing music is not really a part of the work – experiencing noise and balloon bursts is :).  The romantic illusion that led me to this was that this is the perfect amalgam of my interests in music and sciences. I’d like to burst any such bubble right now. 🙂

Things have looked up significantly in the last 5-6 years and there are now firms offering paid jobs in the field for those unwilling/unable to take a plunge into consultancy. I cannot emphasize enough on how unorganized the construction industry is in India, and there are no standards on processes and payments.  It takes serious passion some major family support to keep going forward. To work in architectural acoustics, one must surely have a sense of music, but can do just fine without it, as long as you understand material science and wave propagation well.   Also, consulting works well for women, and it feels good to see things taking shape and the money rolling in – for much less the time you’d spend in a regular 8 to 8 ( 9 to 5 doesn’t really happen anymore, does it). For those willing to endure the rest of what freelancing/pure consultancy entails, it can be a rewarding experience to see a building come up from out of nothing and to hear it sound the way you designed it.

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!


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.


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.


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.


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 advice. 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!