Creating Good Acoustic environment in a World-class Auditorium
The blog is contributed by Ar. PANKAJ MALHOTRA – (Principal Architect) at KLM DESIGNS INDIA , New Delhi.
With over 23 years of Multidisciplinary experience in more than 300 projects handled since
inception, Mr. Pankaj Malhotra has designed numerous Auditoriums , Cinema Multiplexes ,
Conference Rooms , Seminar halls , Lecture theatres , Audio / Video / News & Film Studios.
He has participated in many workshops conducted on the design of AV systems and Green
Building principles conducted by IGBC.
Today everyone is talking about sustainability which aims at creating better environment. An environment where one experiences all sorts of comfort – Visual, Thermal, Acoustic and Indoor Air quality. This multicomfort approach is one of the key differentiating factors among architectural buildings that directly questions the effectiveness of the structure for the purpose it is build.
When it comes to designing an auditorium, acoustics becomes a major decisive parameter compared to the other 3 multicomfort requirements.
A place with good acoustics not only ensures appropriate focus but also enables a soothing experience inside the premise.
One of the most challenging facilities for a consultant is to design an auditorium. An auditorium is no ordinary room. It is a space that hosts activities holding the power to influence. For e.g. lectures, seminars, convocations, conferences, live dance, drama, cultural activities, film presentation, music concerts and award ceremonies. All these put together demand for high acoustic performance combined with superior aesthetics. The design and modelling of an auditorium requires a mix of elements of building design, architecture and technical performance. The ultimate motive while designing such architecture is that the audience seated, irrespective of their location in the auditorium, is able to see and hear everything that is being performed on stage.
One such challenging yet a masterpiece in itself is the design of Swarn Jayanti Auditorium, at Lady Hardinge Medical College, New Delhi.
Situated at the heart of Delhi, this hall was renovated, restored and retrofitted recently with following aims:
1.Retrofit specific materials that cater to the high needs of auditorium design and
2.Create a visual delight by designing aesthetics to the next level
To add up to the prestige of this master piece, the auditorium was inaugurated by the President of India – Honourable Shri. Pranab Mukherjee in the wake of the centenary celebration of the Lady Harding Medical College, New Delhi.
So, what should be the acoustic criteria while designing an auditorium of this stature?
To ensure smoothness and clarity of sound, it is critical that there should be no echo. Technically,it is a measure of reverberation time (RT) (optimum RT is prime concern for speech intelligibility).
As per the mathematical modelling specific to this auditorium taking into account the size of the hall and activities happening, an ideal reverberation time for appropriate speech intelligibility should be in the range of 1.5 - 1.8 seconds and a Noise Criter ia of NC40( i.e. Ambient noise level measured in dB within the room should conform to NC 40).
Right products to choose when you need a mix of high performance and visual appeal?
The above design requirements call for use of wide variety of performance oriented materials. Starting with consideration of reverberation time, there is a requirement of highly absorptive surfaces and finishes that absorb sound and ensure that it doesn’t get reflected back. Moreover,the positioning of such materials and aesthetic appeal pose a question on selection of the right product for the same.
After thorough evaluation, it was found that Gypsum based perforated boards were the right fit because of their aesthetic appeal and robustness compared to conventional soft acoustic materials. The uniform perforations on the board along with tapered edges together enable a smooth finish with an appearance of continuous endless pattern. The boards were wrapped in fabric and used a fascia on GI Gypsteel® framework with insulation. The placement of these boards were important as the lower part of the hall was designed with stone, hence the absorption for the Mid frequency and High frequency were placed above 2400mm.
The lower portion of this hall upto 2400mm lvl from the floor level was designed using Dholpur Stone. Above 2400 lvl upto the false ceiling FR fabric panels intermediated with MDF jali niches were used.The use of Stone along with MDF jali gives the auditorium a rich look symbolising strength and robustness. Moreover, use of less wooden materials protects the structure from termites since the area is prone to termite attacks.
The ceiling was designed with Fire Resistant Fireline ®Gypsum board backed with insulation on GI metal framework for the peripheries and fixing services like grills, lights, smoke detectors etc. Further Gypsum based Gyptone Quattro 41 boards with approx 16% open area(total perforated area) were used at the ceiling which were additionally backed with acoustic insulation to achieve the desired parameters of reverberation time. Additionally, 180 degree rotatable wings were provided on the stage with 12.5 mm Fireline gypsum board over the metal tubular framework. The ceilings of the technical areas like Green Rooms, Control room were done with High NRC ceiling tiles over a powder coated GI based T grid system.
As it is evident that every inch of the hall has been thoroughly worked upon, this auditorium finds its place among one of the most iconic buildings in New Delhi.