Acousticians, how do you calculate room volumes?

Acousticians give a lot of meaning to the acoustic volume of a space. Too large and the room can be too reverberant, not loud enough and the early reflections are inaudible. Too small and the room cannot develop enough reverberation and uncomfortably loud.

Get it wrong and the space will have a lifelong handicap. It is not easy to reduce volume, nor is it cheap to increase it later on. So checking the acoustic volume is one of the critical tasks one repeats throughout the design process.

Hand calculations on 2D drawings is the basics. But now days, I receive a 3D model of the hall before I get scaled 2D drawings. Thankfully 3D models have made this easier, but not necessarily faster. Closing a volume air-tight when its complex and inconsistently built is only for the patient amongst us.

So I’ve decided to automate the volume estimation from the 3D model, in Rhino, using some basic Grasshopper tricks. This seems to work fairly well. The accuracy is in par with other approaches and satisfies room acoustics requirements. But the true benefit is that it takes less than a minute and does not require any model manipulation. It can also be made more accurate by drawings sections at 250mm centers for example instead of every meter.

Acousticians, how do you calculate your complex volumes?

And you, how to you calculate your volumes?

World Theatre Day

Since the early 1960s, the World Theatre Day is internationally celebrated on the 27 March. On this occasion, I want to express gratitude to all the crews, staff, production, artists, roadies, cleaner, ushers and anyone involved in making the show go on.

Celebrating small and big stages for the last 20 years, here is a snapshot of my contribution to the performing arts across 4 different consultancy firms and 31 different drama theatres, 8 opera houses and 22 recital and concert halls.

Here looking for another 20 years…

… also wondering when is World Orchestra Day?

Real-time noise prediction for car races in Grasshopper.

I never thought I’d worry myself with traffic noise predictions. Performing arts centers are usually well enough insulated for this to be designed out. We typically focus more on ground vibrations from trams, underground and aircrafts.

But this situation is different. It is not a performing arts center. It is any tower, with an undefined geometry and height, to be built within a race track “loop”.

Traffic noise propagation is a well understood process. But the methods have been developed to protect buildings from the relentless and generally increasing traffic noise from public roads. Not much of the above fits particularly well to a loop with 20-25 high speed performance vehicles.

The basic assumption that a continuous flow of vehicles can be represented by a line source simply cannot be applied to a twisty car race track. Nor can a single number sound power level that ignores spectral character and is derived from vehicle counts (per 18hrs), average speed, proportion of trucks/buses and road surface.

Racing cars typically start together before spreading over the closed loop of the track. They have very distinctive sound spectral signatures (V8, V6, Supercars, motorbikes all sound different). And they travel at much higher speeds on a very special surface.

With these conditions, CoRTN just cannot be applied and one has to look at the PROs and CONs of the European or Nordic methods. These allow at least more detailed descriptions of the cars as noise sources. More precisely, as point sources moving along small segments of a road.

This is precisely what we have implemented in Grasshopper. The definition can take any geometry and location for the tower. The process is:

  • Divide the track into segments travelled for each car, given its own speed, within a 1 second interval
  • Calculate the attenuation of noise through the distance between each car and each facade of the tower.
  • Includes atmospherically conditions (worst case wind)
  • Includes ground attenuation
  • Includes shielding for the facade
  • Includes shielding from noise barriers on the side of the track
  • Does all the above in octave bands
  • Sums up the contribution of all cars for each facade element of the tower, for every 1 second period
  • Stores and trace this incident level as a noise logger would do
  • Extract Lmax, L10/L90 percentiles and Leq for the duration of the race.

The model does not include yet:

  • Road/tire noise component (I am not sure it is relevant for these surfaces and these noisy car/exhausts)
  • Engine breaks and drag noise
  • Speed variations along the track (constant speed regardless of twists and turns)
  • Variable trajectories for each car.

This has been fun! It has allowed us, not only to bet on the cars (randomly assigned speeds) but also to test famous race tracks and see which is the loudest.

Ready, steady, click!

Real-time motor racing noise prediction on a track with Grasshopper

    2022 wrap-up

    2022 was marked by the completion of projects for which I led the acoustic design and the start of several significant commissions for ARD!

    New paper: ICA2022 – Machine Learning experimentation for Performing Arts


    Designs that do not provide good projection and support for all areas of the stage result in an imbalance of the orchestral sound or noticeable variations depending on where the performer stands. Several years ago, the author et al presented on the importance of whole stage imaging. In this paper, we focus on how a design can be assessed for its capacity to support all sections of the orchestra on stage, from the point of view of the listener. Most simulation packages start with the source definition in a 3-dimensional space. We suggest that the whole stage imaging requires the analysis to be carried out from the listener’s point of view. The paper first explores ways by which the whole-stage imaging can be represented, introducing a new visual tool that carries out the analysis for all possible source positions in real-time at once. We then present a deterministic (but tedious) approach to quantify the results. Finally, the same analysis is carried out using different
    machine-learning processes that attempts at quantifying the whole-stage imaging. It inform,s in a visual way, the imbalance between orchestra sections while facilitating communication with the project architects.

    Keywords: Performing Arts, Ray-Tracing, Whole-Stage, Machine Learning

    New AECOM paper! ANC 2022 – Engineering approach to auralisation in architectural acoustics.


    Auralisation is to the ears what visualisation is to the eyes. Auralisation is not a new tool. It has long been used for stakeholder engagement and to support design decision. However, it is mostly associated with high-end projects, detailed 3D simulations and even more expensive equipment set precisely in purposely fitted rooms. In this paper, the authors argue that auralisation does not need to be hyper realistic to become an extremely useful tool for stakeholder engagement and design guidance. The authors will present a simplified approach to auralisation, based on standard day-to-day engineering calculations, to cater a wider range of projects and stakeholders. Examples will be given on recent typical acoustic projects including construction noise ingress in a civic building and the building acoustic design of a healthcare facility.

    Keywords: auralisation, convolution, building acoustics, engineering approach

    “Pitch perfect acoustics” at HKUST-SHAW Auditorium

    This article, review of a concert at the HKUST-SHAW Auditorium, nearly one year after it opened praises the musicians. But it has also a few good words about Thomas’s acoustic design.

    The hall’s acoustics allowed every detail of the music to be heard”. Photo: HKUST

    Update on Tianhan Grand Theatre, China

    Back in April, we shared photos of a scaffolded theatre with no finishes and filled with concrete, dust and steel. Today, we are happy to share a photographic update.

    The plastic over seats is a sign that dusty works are finishing up soon
    Inspections and the final touch are always both exciting and stressful activities toward the end of the construction phase.

    Ethiopian National Theatre Project, Addis Ababa

    ENTP in Addis Ababa (render)

    ARD is excited to join Kling Consult, BWKI GmbH, t2o Engineers and ADDIS MEBRATU Consulting Architects and Engineers for the design and construction of the 2nd largest theatre in Africa: the Ethiopian National Theatre Project.

    Update Tianhan Grand Theater, China

    Naturally ventilated, this 1200-seat grand theatre is under construction. From a simple but acoustically optimised design…

    Rendered interior showing the louvres for natural ventilation on side walls

    … to reality:

    Construction progress, inside view
    Orchestra pit floor mechanism in place.

    Shenzhen Baoan Cultural District Performing Arts Center

    One of the few projects for which I had acoustic design responsibility before leaving Hong Kong has finally opened. It is nice to see the results and an architecture team proud of the project. Well done to my ex-colleagues there for seeing it through.

    The Shenzhen Baoan Cultural District Performing Arts Center is a 28,000m2 facility by the water, part of a larger complex including a museum and library.

    It includes a 1500-seat opera house and a 600-seat multipurpose hall. The main hall is quite functional and designed to accommodate opera and ballet but also a wide range of contemporary Chinese performances. The diffusion on the wall is fully integrated into the architectural finish.

    (c) Zhang Chao Studio
    (c) Zhang Chao Studio

    The multipurpose hall is a blackbox with an architectural presence. Able to go flat floor for banquets and tiered on both sides of a fashion catwalk. Its ceiling is technical, the upper white walls project sound for concert and speech events, the lower walls and rear wall are absorptive to accommodate a flexible sound system configurations.

    (c) Zhang Chao Studio

    Now it is in the hands of artists and I wish them all the best in turning these two venues into a creative and successful new house in Shenzhen.

    Read more here: