The Science of Sound: Where Audio, Acoustics, and Architecture Meet

In today's multimedia world, how a room sounds is a big factor in how the architectural design is viewed. Concert halls that are too reverberant are lambasted, boardrooms that sound like echo chambers on conference calls are avoided, restaurants that inhibit conversation are shunned, and retail outlets that emit unpleasant atmospherics are often empty.

Typically, good acoustics will go unappreciated but poor acoustics may contribute to a client's commercial demise. In these instances, the architect cannot reasonably be held responsible for the commercial failure or the poor sound. There are ways, however, that architects can pre-empt the challenges ahead.

Drilling into the Science of Sound
A big challenge is recognizing what "good" sound is. Although clearly subjective - people know good sound when they hear it - science can provide a basis for understanding. The behavior of sound waves in enclosed spaces can be problematic, especially if things such as room use, number of people, and materials have not been considered in advance. For example, low-frequency sound waves are long and, depending on room size, can easily become modal. This condition can manifest itself in the form of standing waves, which interfere with an audio system's attempt to produce quality sound. Knowing this in advance can help in planning room use and materials. If it's clear that standing waves will become a problem, then it is possible to adjust room materials to include more low- frequency absorptive material or slightly change room configuration (such as parallel walls) to preclude the presence of standing waves.

In addition to accurate frequency measurement, another important metric is sound pressure level, or SPL, which is a measure of intensity and indicates how loud the audio system is going to be in that space. SPL is usually measured in db (0db SPL is the low end of the human hearing threshold; 140db represents the level at which there is hearing damage; 70 is about normal conversation level).

Matt Czyzewski¹, vice president of technical operations at an international provider of professional installed audio electronics, notes the importance of understanding a room's use early in the design process:

"It is important to know that SPL is a relative measurement depending on how an audio system will be laid out in a room and the proximity of the people to the sound source, the measure of intensity will only represent that particular point in space," says Czyzewski. "For instance, in an auditorium, you may not want SPL variance to be more than 3db from front to back, meaning the room design and the audio system design need to provide even coverage."

Therefore, frequency measurement, SPL measurement, and numerous other details need to be quantified to ensure precision in a room's design. What is important, and how do you get it done? There are many software tools available in the marketplace to measure and analyze a room design's sonic behavior, but using them doesn't ensure proper design. Czyzewski states that the behavior of sound in a room can be premodeled. "In software you can build the room and model it with carpet and windows and any other surfaces and materials you might have in the esign. Then you can find out how the room behaves without a sound system, discovering where reflections and roblem spots are likely to arise due to design and materials. Then, if you put in a sound system, you understand here the best location is for the equipment to get the best coverage in the room."

With this process, an architect may discover certain pockets of the room don't perform well, allowing him or her to alter features such as walls or materials before moving to the next stage.

Another useful measurement is the RT60, or reverb time, which indicates how the room reacts to sound being resent and where speakers can be placed to minimize the room's anomalies. To be sure, there will be anomalies, as no room is perfect, but understanding the RT60 allows acousticians to choose certain types of speakers over others, place speakers higher or lower, or move them front to back in the room to get the best reverb time possible.

Acoustic Design as an Element of Early-stage Architectural Design
It behooves designers to include audio planning in the early stages of architectural design for budgetary reasons and to ensure successful implementation. If analysis is completed prior to committing to design and materials, it becomes easier and less costly to make changes to the space.

Cory Covington², a senior designer at an architectural firm, suggests considering acoustics early on but understanding what level of involvement is needed beforehand. "There are a lot of positives to including acoustic design early," Covington says, "but be sure exactly what you need. If it's an event space or restaurant where music and audio systems will be important, then you may need an acoustical consultant, which will bring up the cost of the design but likely save you money long-term. Those early decisions will affect construction, materials, and even design choices if you need to use different materials or shapes to accommodate acoustical issues."

Beyond room design and proper acoustical planning, materials are important, which means striking a balance between aesthetic and acoustical impact. Each choice of materials for walls, carpet, and even chairs will have a different absorption coefficient that changes over the entire frequency range. Hard materials and flat, straight surfaces can be difficult to handle acoustically, so a combination of absorptive and reflective materials is often the best solution. And don't forget that people are absorptive, too. It's important to consider how many people will typically be in the space.

There is no easy answer to this challenge, says Covington. "It becomes a trade-off," he says. "Because of this, it's important to involve the client and tell them if they want certain materials, they should be aware of the effects that choice will have on the sound. If you keep the communication going and work through the situation, you can usually find the solution."

Once the issue of materials is solved, it is important to be clear on the building/room application. What is the likely size of the audience? What will be the likely furniture layout and materials, typical traffic flow, and the actual application in the space? If the seating space is fully occupied a few times a year, then consider that when designing the acoustic signature of the room.

Often, nailing down these challenges means working with an acoustical consultant. Again, communication may be the most valuable tool in the kit. Says Covington, "It's critical to communicate the issues up-front with a consultant regarding client desires and the architect's goals and work with them on things like materials, design, and timing to help make everything work."

In the end, with the architect at the helm, just about everyone should have input into the project. Notes Covington, "The intent comes from the architect and the client but then all the subcontractors, construction, mechanical, electrical, plumbing, and acoustical consultant need to review the job to make necessary adjustments to preclude sound problems from cropping up."

Audio System Design as Part of Stage Two Architectural Design
Most goals can be achieved at stage two unless there are major issues. At stage two, people are often reluctant to change things. This leads back to the fundamental wisdom of dealing with audio system and acoustical issues as early as possible.

An audio system is more than speakers, amps, microphones, and processors. All electrical components comprise the audio system. It includes everything down to cable. Consider how important it is to have a way to pull cable that won't affect the carefully planned aesthetics. No one wants to tear out walls or dig trenches in the floor to put in conduit after the fact. Also remember that the room itself, including the furniture and other material, is part of the audio system.

Jonathan Shor³ is the director of technology at an AV systems design and integration firm, which handled audio design and integration at the Frank Gehry-designed IAC building in New York City. Shor had to deal with special requests in its main lobby as well as the boardroom.

"The boardroom was a challenge," Shor states, "because they didn't want typical ceiling speakers, and the ceiling was an important architectural element that couldn't be touched except to spray with absorptive material. We created separate program audio from the telecommunications system. The program audio is for a rear-projection screen on a wall, and we inserted left/right speakers there. That system handles videoconferencing, DVD playback, PowerPoint presentations, and other program material."

The work didn't stop there: The boardroom table became a piece of audiovisual equipment. McCann professionals built small, oval-shaped speakers and mics into the table. They had to find a speaker that worked in close proximity to the mic without feedback and then fit the mics, speakers, as well as flip-up video monitors, into the table.

Even more intriguing, a self-powered subwoofer was built into the pedestal. The audio system includes processing for microphone inputs and outputs to amplifiers and mixers and a DSP engine for handling crossover, delay, and EQ that allows the system to adapt and match the room response.

Defining a Good System
Reviewing the basics of an audio system begs the question of what to look for in a system. This is one of the paradoxes of fitting an audio system into an architectural design. Sometimes high-end, professionally designed and installed audio systems can be difficult for users to operate. On the other hand, lowend systems can have low sound quality and inferior technology that breaks down or quickly becomes obsolete, costing, in retrospect, more in the long run.

Whatever the approach, in the end what defines a good system is when the end-user can walk in, hit a switch, and have it perform the way it was designed to work. If people cannot use it, then even with high-end specs and fancy consultants, it is effectively a useless system. The key concepts here are transparent performance, ease of use, scalability, and support.

With a good audio system in place, how can one measure return on investment? In certain cases, it's quite simple. For example, in a performance venue or a building that hosts ticketed events, sales will indicate whether or not the investment was sound. Likewise, to some extent, an important part of the success of a restaurant, beyond the food, is the rest of the sensory experience. If the restaurant is constantly busy, then ROI can be realized. Elsewhere, like commercial space, it can be hard to judge, but there are ways, says Czyzewski. "If you don't have to readdress the audio system every 3 years as a result of complaints or breakdowns, then you've done your work properly, but you can really only measure that success by the satisfaction of the users."

Other Considerations
Of course, there is a sign-off process to the completion of any project, but when it comes to audio, how can you determine if the end result sounds good, and who should be involved in that evaluation? Ironically, owners are often left out of this process because they have designated a go-to person to oversee the project. Yet, they should still be included at various points along the way, including final evaluation, so they know what the approach of the design team was and how that has come to fruition. It's always good to have the owner's voice involved at all stages, even debating what equipment to choose and what price levels to include for that equipment.

In the end, that speaks to communication, as stated previously. Therefore, to ensure a successful marriage of audio, acoustics, and architectural design, given the demands of today's multimedia world, it is better to assemble a wellconceived design team, keep the lines of communication open, and follow the guidelines outlined here.

Tim Wetmore ([email protected]) is a writer and commentator based in New York City. A former editorial director of Pro Sound News, Systems Contractor News, and EQ Magazine, Wetmore has been published in an array of technology and business publications and is also an accomplished video producer.

Kevin Jacobson ([email protected]) is international training manager at Biamp Systems. Based out of Biamp's headquarters in Beaverton, OR, Jacobson is responsible for providing technical and product application support to Biamp customers throughout the world. Jacobson has extensive experience as a systems engineer in a range of network, software support, user training, and technical support applications. Prior to Biamp, he worked as a professional technician for the Oregon Department of Transportation, where he designed and implemented front-end-user interfaces and assisted administration with troubleshooting network and technical issues.

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