Thomas R. Horrall

Partition system for open plan office spaces

The partition system disclosed herein incorporates apparatus for generating a speech masking acoustic field. Respective speakers are mounted near the bottom of each of a plurality of partition panel segments defining each work space and are aimed horizontally. These speakers are driven by respective signals which are subjectively incoherent as to frequencies of interest in the masking spectrum, thereby to provide a sound field without perceptible discontinuities.

Multichannel masking sound generator

In the masking sound source disclosed herein, easily adjustable but matching acoustic energy spectrums are obtained from different channels by providing, for each channel, a plurality of bandpass filters, each of which is provided with a respective gain-controlled amplifier for selectively adjusting the respective signal level. The bandpass characteristics of each filter are matched to the corresponding filter in each other channel and a common control signal is applied to the respective gain-controlled amplifiers. The filtered and level-adjusted signals for each channel are then summed and applied to respective power amplifiers suitable for energizing loudspeakers. Accordingly, the frequency spectrum applied to all loud speakers will be the same even though the signals applied may be incoherently related within the spectrum.

The open office privacy calculator: A value engineering tool for acoustic professionals

Open‐plan spaces consistently challenge architects and acoustic consultants to achieve reasonable speech privacy and low inter‐office distraction. This paper presents a computerized tool to optimize design decisions, maximizing speech privacy while minimizing design effort and implementation cost. Speech privacy can be estimated through real‐time calculation of the Speech Privacy Index (SPI) at a grid of points in a given simulated open office plan. The Open Office Privacy Calculator graphically shows how much workers in that open office would be distracted by any single speaking person and the impact of office environmental parameters on the level of distraction. The tool provides a direct graphical link between design decisions, cost, and acoustic performance for partition height, ceiling height, ceiling type, and the addition of sound masking. Further, this tool introduces the Distraction Index (DI), a measure of how many adjacent office talkers that a given office worker can routinely be distracted by...

The role of sound masking treatment in the value engineering of office designs

In the design and planning of office spaces, sound masking systems are often considered optional because of an owner/occupier requirement due to an understanding that can create a more pleasing and private acoustic environment or are required to provide adequate speech privacy. Installations are rarely considered on the basis of project value engineering or return on investment. In this paper, the authors argue that sound masking systems should in fact be considered as another important cost component of the office design, and evaluated along with ceiling tile, private office wall construction and workstation design for their mutual impact on the project budget, as well as on their contribution to acoustical performance. The authors provide typical project data to demonstrate masking systems typically result in overall project cost savings.

Performance comparison of above ceiling and through ceiling sound masking systems

Sound masking systems are an important tool for providing speech privacy in offices and similar spaces. These systems typically use an array of loudspeakers radiating masking sound above an acoustical tile ceiling. The ceiling acts to diffuse the sound laterally in order to minimize localization on loudspeakers by the listeners below. The diffusion also helps keep the speech‐to‐noise ratio relatively uniform spatially, which may help minimize variations in privacy conditions. Unfortunately, the ceiling material, the plenum, and the space below are rarely homogeneous acoustically. There are usually openings in the ceiling for HVAC return air and lighting fixture ventilation, and different parts of the ceiling often use a variety of materials and elevations for aesthetic reasons. Large ducts and structural elements may compartmentalize the plenum. These variations pose substantial acoustical challenges for the designer and additional costs for the owner, not all of which can be satisfactorily resolved. Reco...

Instrumentation for measuring speech privacy in rooms

Federal legislation pertaining to oral privacy in healthcare and financial services industries has increased the need for a convenient and economical way to document speech privacy conditions in offices, medical examination rooms, and certain other workspaces. This legislation is embodied in the Health Insurance Portability and Accountability Act (HIPAA) and Gramm‐Leach‐Bliley Act (GLBA). Both laws require that reasonable measures be put in place to safeguard the oral privacy of patients and clients. While techniques for privacy documentation are known within the acoustical consulting community, it is unlikely that community alone has the capacity to provide the surveys needed to evaluate acoustical conditions and demonstrate compliance with the legislation. A portable computer with integrated soundboard and a suitable amplified loudspeaker and test microphone are all that are needed to perform in situ measurements of articulation index or other accepted indices of speech privacy. Along with modest traini...

Acoustical and planning considerations for home theater and multichannel music playback systems

Optimum multichannel sound playback in the home environment requires different room acoustical characteristics than traditional two channel playback. In particular, room surfaces should be acoustically more absorptive in order to avoid masking of later arriving reflections encoded in the software, and the availability of more than two channel playback permits such room design while preserving and enhancing the listener’s sense of immersion in the sound field. Newer recorded five and six channel transmission systems employing a dedicated low‐frequency effects channel require careful consideration of the type and placement of low‐frequency loudspeakers. The optimum location and directional and other characteristics of loudspeakers intended for existing home theater audio formats are often considered different than those for music playback, but multichannel transmission formats for both video and music‐only playback may impact these requirements. Layout requirements of the room, including screen size and pla...

Cost effective variable acoustics for multipurpose halls: 51 Walden Street.

51 Walden Street is a small multipurpose hall in Concord, Massachussets that serves for drama, symphony orchestra, concert band, and various other performance and rehearsal activities. As in many halls designed for a wide range of uses, limited passive variable acoustic provisions had been implemented with qualified success. However, recent measurements of the resulting acoustical conditions indicated that better acoustics required considerably more variability than possible using these simple techniques, which included varying the amount and positioning of sound absorption and reflecting surfaces within the hall. More complex passive variability, such as varying the room volume, was judged as not feasible because of the obvious architectural and cost limitations typically faced by community arts organizations. An experiment was carried out using a novel digitally controlled electroacoustic system to vary selected acoustical parameters, including reverberation time, early decay time, and clarity. Working ...

Acoustics of the new Filene Center, Wolf Trap Farm Park for the Performing Arts

To replace the original Filene Center that was destroyed by fire, a new structure was designed and built in a scant 2 years (1982–84). Like its predecessor, the 3800‐seat covered house, with an additional 3000 seats on the lawn beyond, serves as a summer home for the National Symphony Orchestra and caters to many other forms of artistic production. Under a mandate to rebuild the structure as it had been, the acoustical options were limited. Known problems such as discrete echoes off the high ceiling were eliminated. Stage acoustics were greatly improved by incorporating a totally new shell. Most significantly, the center was equipped with state‐of‐the‐art sound systems, including a sophisticated enhancement system that covers the under‐balcony areas. The principal acoustical characteristics of the center are discussed and the sound systems, their purpose, and their operational parameters described.

Acoustical design considerations for two air‐supported structures

This paper presents information on the acoustical design of the Hubert H. Humphrey Metrodome in Minneapolis, Minnesota and the Dalhousie University Athletics Complex (Dalplex) in Halifax, Nova Scotia. The Hubert H. Humphrey Metrodome seats up to 63 000 people under an air‐supported fabric roof. Major concerns that are discussed were reverberation control and the design of a system of loudspeaker clusters that are suspended from the roof membrane and maintain proper orientation when the structure is moved by changes in wind loading. The main feature of Dalplex, which is located in a residential neighborhood, is a 300 ft by 240 ft stainless steel air‐supported roof over the field house and running track. This 116‐in.‐thick stainless steel membrane presented some unique acoustical problems that had to be addressed, including control of reverberation in the fieldhouse, reduction of the noise of rain on the metal roof to acceptable levels, and reduction of crowd noise transmitted through the roof to nearby hou...