Why Acoustical Problems Occur
When acoustical problems occur in new buildings, ie: Acoustics results not meeting expectations, the reason is very often that the acoustics consultant was not involved sufficiently early on in the project. Early involvement of the acoustics consultant can be a critical determinant of a project’s success, particularly in projects whose acoustical performance is central to the building’s function.
The earliest stages of project development include decisions of great acoustical impact to the project – project budget, site selection, building massing, and locations of key spaces within the building. These decisions are often difficult or impossible to revise later, and may place the project in the difficult position of raising money for design features that might have been avoided with earlier advice from the acoustics consultant.
Those planning a building sometimes assume that the acoustics input can arrive in Design Development or Construction Document Phases. While this may be true for some projects, those projects whose success requires high acoustical performance benefit greatly from the acoustics consultant’s involvement during the initial Programming, Budgeting, Conceptual Planning and Schematic Design phases of the project. Without this early involvement, delayed acoustical input necessarily takes the form of retro-fixes to deal with acoustical issues, invariably adding cost to the project.
By no means should it be assumed that concert halls and opera houses are the only acoustics critical buildings. An acoustically-critical facility can serve the performing or visual arts, residential, office, retail, laboratory, healthcare, education, sports, or multi-purpose uses.
See our project portfolio for real world examples of such facilities.
With all such facilities, both new buildings and renovations, the collaboration from the earliest moment possible among the owner, users, architect, theatre consultant and acoustics consultant is critical to achieving a quality facility at the lowest possible cost.
Key decisions that have acoustical implications in all buildings include:
- Program Preparation
- Site of the building or parts of building
- Locations of specific rooms within the building to achieve sound isolation without excessive cost of construction (materials & techniques)
- Planning of mechanical and electrical systems and the space they use.
These factors affect the quality of acoustics in any acoustically-critical building project. I will discuss two examples of buildings for the performing arts, which have been the major focus of my work.
A Real World Example
In one instance, the acoustics consultant’s guidance on site selection for a major concert hall was able to save the project $2 million Canadian (in 1997 dollars!). The goal was to locate the concert hall near a light rail subway without the need for elaborate building or track isolation. Carefully planned site vibration measurements suggested that the hall be positioned 350 feet from the subway tracks with a separation between the concert hall and its lobby. The architect managed this by first creating a plaza between the ground level subway entry and the lobby. The structural engineer, the mechanical engineer and the acoustics consultant worked together to separate the lobby structure from the concert hall structure itself. Because of the long cold winters in this city, a subterranean walkway was constructed below the paved area to allow patrons to enter the lobby from the subway station and adjacent underground auto parking facility.
The building, while visually and functionally one building, is in fact two structurally separate buildings connected with acoustic joints. This allowed the basement of the lobby building to contain mechanical and electrical equipment for both the lobby and concert hall buildings without subjecting the concert hall to noise and vibration. A third structurally separate building, adjoining the backstage end of the concert hall, contains office and dressing room accommodations for performers and artistic staff, with a basement mechanical room serving these spaces and the rehearsal room. This allowed the concert hall and rehearsal hall to be built in structures with no machines to create noise and vibration. The concert hall and the rehearsal hall were likewise structurally separated from one another using acoustic joints, to prevent transmission of sound and vibration between the two critical listening spaces.
Had this major concert hall been cited and positioned by a design team before the acoustics consultant was retained and working, substantial design work, and therefore design fees, would have been expended before the owner and design team were aware that the subway-related noise was an issue. If that had happened, the owner would have been faced with a decision to spend almost 2 million dollars Canadian to isolate their building, or ask the team to redesign the building to take advantage of greater distance from the tracks. Of course this redesign would have be costly, in both time and money.
The subway line was not the only potential noise exposure for this concert hall. It is also situated under the flight path that served a nearby airport. Knowing this also allowed the acoustics consultant to recommend the constructions to ameliorate aircraft noise from above. Awareness of the aircraft noise issue up front allowed the consultant to recommend an appropriate roof slab, ceiling slab and sound-absorptive attic space to control the noise. A collaboration with the design team and contractor resulted in a single step wall construction that allowed for sufficient space and absorbing material, and could easily be accommodated with two-wythe cast-in-place concrete walls. The early collaboration between engineers, construction manager and acoustics consultants allowed the design to achieve the critical goal of silence in the concert hall at the least possible cost and construction time.
The Bottom Line
Early retention of an acoustics consultant need not be costly to the project, and it can result in an excellent project while saving construction cost. The cost can be as minimal as attendance at one early meeting and a brief letter report; or in more complex cases it might involve site measurements and several meetings to fully understand the conditions.
On another project, the owner had chosen a site for their concert hall before assembling a design team. The site was on an important street in a central city location. It was also adjacent a subway line – quite an old subway line that did not have the benefit of track vibration isolation. There also was insufficient space on this urban site to position the critical spaces sufficiently far from the tracks to reduce the vibration from subway trains. The only choice was to isolate the new concert hall building on natural rubber pads at the cost of about 2 million dollars US.
The client was understandably reluctant to spend this money. The decision to build the landmark facility on this site had been made sufficiently long before as to make changing it difficult and embarrassing. However, changing the budget was also difficult for the owner. The acoustics consultant asked if they would consider any other sites without subways adjacent. The owner’s project director was willing to consider several other sites, intending to bring them back to the board of the organization for consideration. Some sites were visited, lists of pros and cons made and evaluated. The board decided to build on their long dreamt of site, and raise their publicly-announced budget by 2 million US. Had potential sites been vetted beforehand, perhaps an alternative, less expensive, solution could have been realized.
Whether a concert hall or an amenity gym in a research lab, the design of acoustically-sensitive buildings benefits when the disciplines have the chance to work collaboratively. Engaging an acoustical consultant at the outset of a project is a critical step toward creating a holistic team. Such a team actively turns constraints into elegant solutions, rather than reactively fixing problems that may have been foreseen. As the cost of labor and materials continues to rise globally, so too does the value of thoughtful decision making during programming and design.