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TL v66n3: Directional Speakers
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Using Directional Speakers in an Academic Library



Academic libraries have long been regarded as places of quiet and solitude. Their commonly-held image is one of students working alone at long tables or isolated in study carrels as librarians walk through the building with glasses on the bridges of their noses, shushing anyone who dares to get loud. While this view of college and university libraries may still exist in some places, it is becoming increasingly rare as widespread shifts in user attitudes and expectations about acceptable levels of noise change the almost iconic belief that libraries are supposed to be silent.

Advances in communications technology are one of the primary contributors to ambient noise in most environments, including libraries. As far back as 1981, Luyben, Cohen, Conger, and Gration discussed concerns with rising library noise levels, mentioning several previous studies on the topic of noise reduction in libraries (Luyben, Cohen, Conger, & Gration, 1981). In addition to the sound of fax machines, printers and photocopiers, the 1990’s introduced cellular phone usage and its accompanying noise. Increasing prevalence of cell phone usage generated the idea of creating policies concerning the use of such devices in libraries (Rogers, 1999).

Since that time, the connectivity brought about by communications advances has caused libraries to include features to foster, enhance, and support collaboration to an even greater extent. Now, libraries often contain coffee shops, restaurants, group study areas, rows of computers, makerspaces, and other features that create, and even encourage, movement, conversation, and interaction. Users have come to expect these new features in the modern library. These expectations have led to an interesting challenge for libraries: balancing contemporary features which by their nature create noise, with the traditional expectation that a library is a quiet and calm place. Yelinek and Bressler (2013) addressed this challenge in a review that not only looked at the impact of louder environments in libraries, but also outlined various approaches libraries have taken to accommodate changing noise levels. These approaches include the creation of noise-free areas, using furniture types that tend to encourage or discourage library user interactions based on noise requirements, and developing various policies for noise regulation.

The challenge to balance these conflicting needs is especially difficult for smaller libraries which have less space available for creating separate spaces for both quiet and noise. When one of the authors worked in a small one-room library at Weill Cornell Medical College in Qatar (WCMC-Q) several years ago, librarians had to develop a noise policy due to frequent complaints about sound levels. With this policy, the library’s administration created an enforced quiet zone in the library. While the policy was in place, library users frequently expressed frustration that they could not perform activities that require elevated sound levels in the library, such as group study sessions. These complaints led administration to change the noise policy to allow elevated sound levels during certain times. Because the library was a single room, there was little opportunity to provide an environment that could satisfy the needs of all library users. The inability to maintain satisfactory sound levels in the library led to a number of discussions among librarians regarding tools that could assist in managing noise. 

One of the more interesting ideas that arose from these conversations was the possibility of using speakers that focused sound in a targeted location to provide information to library users without creating disturbances outside the intended area. These speakers are referred to as parametric, or directional, speakers. Since the 1960’s, engineers have been able to create speakers that modulate the sound wave frequencies to move in a linear direction. These arrays were initially only usable underwater. By the early 1980’s, however, several researchers had created speakers that were able to focus sound into a targeted location in the air by using ultrasonic waves (Schneider, 1998, p. 40). Unfortunately, at the time discussions were being held at WCMC-Q, the technology for these speakers had not progressed to a point where directional speakers were a practical option. 

More recently, librarians at Austin Peay State University’s Woodward Library investigated using parametric speakers as a way to deliver information. The Woodward Library is a three-story building that contains a number of rooms on each floor for various activities, such as group study or viewing videos. However, the main floor of the library consists of a large open space and has a great deal of activity. Noise from a coffee shop on this floor, commotion at the Access Services Desk, and the general tumult of library users entering and exiting the library all combine to create elevated sound levels in an area that also contains the majority of the library’s public use computers. In this environment, it is difficult to provide information about the library and its resources without adding further disturbances. As is the case with many libraries, the Woodward Library attempts to provide an atmosphere that is conducive to learning and study, while also meeting the information needs of its users through modalities that are neither static nor quiet. 

When libraries are already becoming noisier by virtue of having noise-producing features as mentioned before, the question becomes how to balance the sound inevitably created in a modern library with the need for calm and quiet study space. Parametric speakers offer a potential solution to this conundrum. In recent years, the capabilities of these speakers has improved and their cost has decreased. These sound systems are now able to focus the direction of sound waves in order to broadcast audio to precise locations. When listeners are even a few inches removed from the focal point of the sound waves, they should find the sound level significantly reduced. Using parametric speakers strategically throughout a library will not eliminate undesirable noise altogether, but these devices may provide libraries with an ability to provide multimedia information while not creating additional disturbances.

According to Holosonics, a company that sells directional sound systems, these parametric speakers have been used in a number of highly-regarded institutions with a large volume of visitors, such as the Boston Museum of Science, the Field Museum of Chicago, the Harvard Peabody Museum, the Yale Art Gallery, the New York Public Library, and the Smithsonian (Holosonics). In each of these venues, audio systems featuring parametric speakers are being used to broadcast localized sound without disturbing people outside of target areas, even when these areas are within larger open spaces. Unfortunately, there is no impartial information that discusses how well these systems work or whether there is any evidence of value added to the institutions that utilize them. However, being able to focus audio precisely has the potential of allowing multiple displays which provide narratives to verbally explain in greater detail what the user is viewing. Woodward Library purchased a parametric speaker system to test the viability of using this technology in an environment that attempts to balance a traditionally quiet environment with current needs and expectations that are noisier. Thus, this article attempts to examine the potential uses of parametric speakers, as well as the possible applications of directional sound systems. We also hope that it will start deliberations among librarians and information professionals on how this technology can be used in libraries to add value to library services.

Literature Review

We searched for relevant literature in databases that specifically index library topics, as well as databases that include literature for professions that also would benefit from this type of technology, such as museums and art galleries. Our search identified only one article that addressed the topic of using parametric speakers in any type of display. Kondo, Terada, and Kano (2012) state that parametric speakers are “ideal for presenting guide audio in museums.” The authors discuss how these speakers allow guided audio tours to broadcast for multiple displays without overlapping with each other. However, the article’s main focus is the technical aspects of getting the sound quality to work properly in these audio systems (Kondo et al., 2012). A dearth of information about using parametric speakers in quiet environments meant that the Woodward Library would have to invent approaches for finding the right speakers, planning their usage, and evaluating their added value. 

Purchasing and Testing a Directional Sound System

Because there was no information in the literature that provided suggestions for specific parametric speakers, we used Google to search for companies that sell these audio systems. A number of entries resulted from a search using the term “parametric speakers.” In the first three pages of results, Soundlazer, Hypersound, Dakota Audio, and the aforementioned Holosonics were the four main companies that appeared. Each of these companies have sound systems that could potentially be used in a library, but only Soundlazer and Holosonics have product menus that list speaker options and prices. The other two companies, Dakota Audio and Hypersound, show product specifications for their speakers, but do not make them available for direct purchase. Customers who have an interest in these products have to turn to any of a number of design companies who provide quotes for complete audio-related projects, which would then include the use of these speakers. A second search using the term “laser speakers” yielded many of the same results, but also included a company called Browning Innovations. This company requires the buyer to contact them for further information about the audio systems they sell. The purpose of this search was to look for an inexpensive sound system that the Woodward Library could easily purchase to test the potential uses of a parametric sound system in a library. Both Soundlazer and Holosonics make their sound systems available for online purchase. The Woodward Library selected a less expensive parametric speaker starter kit from Soundlazer. The kit consisted of an audio cable, a power adapter, the speaker array, and a built-in amplifier (see Figure 1).

Figure 1. Parametric speakers system in Woodward LibraryFigure 1. The system as it has been set up in the Woodward Library. The parametric speaker is circled in green.

Once the speaker system kit arrived, we initially tested it in a home environment using a laptop. When testing it in this setting, we could hear sound reflecting off a number of surfaces, including a sofa, the ceiling, a table, and other furnishings. However, when the speaker was in the correct position, the sound seemed to be coming from directly inside the listener’s head. A smaller environment contains a number of obstacles that make using a product like this more difficult, so the real test was to try it in the library where there was more open space. In the Woodward Library, we attached the speaker system to a television that could broadcast a news channel. After we installed the speaker, we increased the volume on the television to allow the sound to broadcast. The sound quality within the speaker’s target area was excellent, and when listeners moved outside of the focal area by even a few inches, they could not hear the television. One drawback we discovered when testing this particular speaker was that the back of the amplifiers heated up quickly, creating some concern that the speakers might overheat if used for an extended period of time.  However, because we purchased the system in order to test noise levels when using this relatively new technology, it was more important to us to determine if the speaker system added potentially disruptive noise to the library rather than to fully evaluate every aspect of the system. After testing this system, we decided that because the speaker was able to broadcast without creating noise outside of a certain location, the test was a success. Woodward Library staff were encouraged by these results to investigate other potential locations in the library where speakers like this could be utilized.

How to Measure and Compare Usage

Without substantial information available in scholarly journals regarding parametric speakers, there are no impartial experience-based guidelines for measuring the value added to a library. This lack of implementation and usage guidance may make it necessary to be creative in the way the impact of these products are measured. For example, one evaluation might involve setting up multiple displays in the library with proximity-sensitive counters that only record a count after a library patron spends more than a predetermined amount of time in front of the display. Findings from a study of this nature could gauge of the level of interest in displays that include audio. Using Google to search the phrase “proximity sensor counter library” produced a variety of results, including irrelevant results such as sensors created by individuals who were selling products on eBay, sensors that detected metals, and “how-to” guides that explained how to make a people counter using infrared technology. A few larger companies offer these type of products and sell primarily to libraries; however, the sensors are too expensive to justify purchasing for testing. These measuring tools may be something to consider in the future, if the price of sensors decreases.

How Other Institutions Use these Systems

Other institutions in the same region as the Woodward Library use parametric audio systems, including the Nashville Public Library. As patrons walk into the library, they can sit in the lobby area and watch a live television program. The sound being broadcast is directed into the area of the sofas. The specificity of focusing sound through the use of directional speakers allows library guests to watch television without disturbing other library users. In this case, the placement of the speakers is a determining factor in creating a small target area of undetectable sound. This speaker application is an example of the potential application of this technology that not only can be replicated by the Woodward Library, but could also be set up in other libraries.

Another example of how libraries could potentially use these speakers can be seen in a Clarksville, Tennessee, city-sponsored park. Fort Defiance Civil War Park and Interpretive Center includes displays of life-size photographs of Clarksville natives whose memories capture the Civil War era experience. As visitors walk near these displays, they trigger a proximity sensor that automatically starts playing a relevant audio recording. Parametric speakers add a dynamic component to these displays by creating a sense that the person in the photograph is speaking directly to the visitor. Unfortunately, the room’s dimensions and composition allow sound waves to reverberate, and when multiple displays are activated at once, the overlapping audio creates confusion for the visitor. This unintentional result from the use of parametric speakers shows that understanding the distance required between multiple displays is an important consideration not only in the speakers' implementation, but, most importantly, in their effectiveness. Complications such as this show that sound displays can prove to be as much a distraction as an enhancement and should be tested thoroughly in the environment in which they will be used.


At Austin Peay State University, the Woodward Library conducted a test of parametric speakers offered by Soundlazer. For this test, the speaker array was arranged to broadcast live television to a targeted area, and library personnel were asked to listen for extraneous noise outside of the specified location. As was observed with a similar arrangement at the Nashville Public Library, there was no discernable increase in noise levels. Successful tests of speaker arrays demonstrate the ability to broadcast sound from live programming, which allows the library to keep patrons current on various events, including news, campus events, sports, or other television programs.

In the future, the Woodward Library will most likely attempt to use parametric speakers to provide sound for displays in a way that is similar to their usage at Fort Defiance Interpretive Center. At present, the library has a number of glass display cases which are often in use. Display themes may include “books that were made into movies,” “Civil War literature and memorabilia,” or “a celebration of scholarship.” By using directional speakers in tandem with these displays, we expect the library will attract increased patron interest. As mentioned previously, having multiple displays allows the library to find ways to measure the value added to the exhibits by gauging user interest when comparing displays both with and without audio enhancement.

With so little information available on how these speaker systems are being used in academic environments and cultural institutions, brainstorming sessions with library professionals are vital to the process of implementing, planning, and evaluating parametric speakers. At the Woodward Library, these sessions produced a number of ideas, such as using the speakers in the library’s main entrance. By installing these speakers in the library’s foyer, users walking into the library could be provided with information regarding library hours or events. Additionally, any other announcements could be broadcast without creating a disturbance inside the building. Librarians also discussed the possibility of installing monitors that display tutorials for library services and resources. These monitors would then be equipped with directional speakers to add an audio component to the information. Arrangements such as these can be located near the busy computer resources without creating further disturbances. 

Although libraries have traditionally been places of quiet solitude, changes in library environments coupled with evolving patron attitudes toward noise have increased sound levels in most libraries. To combat this trend, new technologies such as parametric speakers will be needed to ensure scholars have a peaceful venue to work. Ideas such as the ones in this article demonstrate that there are a number of possible uses for parametric speakers, and as libraries begin to find new uses for these audio systems, they are likely to become more prevalent in libraries. Directional sound technology offers a number of possibilities for providing audio-enhanced resources in environments that are traditionally expected to provide a calm atmosphere for quiet contemplation.


Holosonics. "Audio Spotlight - History." Retrieved from

Kondo, K., Terada, T., & Kano, F. (2012). Speech intelligibility of guide audio with parametric loudspeakers. Noise Control Engineering Journal, 60(5), 548-558.

Luyben, P. D., Cohen, L., Conger, R., & Gration, S. U. (1981). Reducing noise in a college library. College & Research Libraries, 42(5), 470-481.

Rogers, M. (1999). Communication overload. Library Journal, 124(12), 66-67.

Schneider, D. (1998). In the audio spotlight. Scientific American, 279(4), 40-41.

Yelinek, K., & Bressler, D. (2013). The perfect storm: A review of the literature on increased noise levels in academic libraries. College & Undergraduate Libraries, 20(1), 40-51.



Christopher Ross Bowron, Emerging Technologies Librarian at Austin Peay State University, can be reached at

Kebede H. Wordofa, Coordinator of Technology and Resources at Austin Peay State University, can be reached at


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