Acoustical Privacy Research Articles

Is the Noise of Overhead Neighbors Inescapable?

If you have ever lived in an apartment and had overhead neighbors, you have probably been anoyed by the noise they made just walking. This can be a problem even in luxury condominiums designed with acoustic privacy in mind. Now we know why.

Upgrading Acoustic Privacy

Looks at the meaning of “acoustic privacy”, and how the requirement varies with the task and the factors which control it; the open plan and cellular office environment – the essential factors which should be considered; how the “acoustic data” provided by developers and manufacturers, particularly those of partition suppliers, should be interpreted; what can be done to optimize the varied uses of conference and management areas to maintain confidentiality and audibility: some dos and don′ts of audio‐visual systems; and the common problems and the remedial action which can be taken.

Progress in environmental noise control.

Environmental noise, i.e., unwanted sound around and within the buildings in which people work and live, is an ubiquitous byproduct of mankind’s societal and technological development. Noise exposure of populations throughout the developing world gradually accelerated starting with the industrial revolution of the 19th century and increased dramatically with the population growth and introduction of new transportation and other sources during the 20th. In recent decades, people who sought the tranquility of suburban living were increasingly greeted with new industrial parks whose tenants also sought escape from decaying, no longer economically sound, urban locations. Even the return to regenerating city centers assures little relief from the noise of new highway, rail, and expanding airport developments or, for that matter, from noisy air conditioning equipment serving buildings nearby or from the sounds of one’s own building neighbors above, below, or next door. This paper reviews the last 40 or so years of what must be considered remarkable progress in dealing with the diverse challenges of environmental noise. In terms of the classical ‘‘systems’’ approach to noise control, the sources and transmission paths are now reasonably well developed and understood both in theory and in measurement. The effects of environmental sounds that ultimately reach the human receptors are less so, however. The continuing development of adequate criteria represents the significant remaining challenge in environmental noise control. This paper reviews some of the pioneering criteria developments for background noise and acoustical privacy in buildings and for community noise.

The significance of background sound in acoustical privacy for multifamily dwellings

Background sound is generally recognized as an important consideration in achieving acoustical privacy for open plan as well as enclosed offices. Too often in the design of multifamily structures little systematic attention is given to the background sound levels that will actually exist in the completed dwelling spaces and therefore the ultimate acoustical privacy that will be experienced by the occupants. A number of recent case histories have been examined in terms of the sound isolation rating (NIC or STC) and background sound level (dBA) versus satisfaction. This effort suggests criteria in terms of both STC and background sound levels are necessary to adequately predict occupant satisfaction.

Security by masking

By radiating the proper amount of masking noise into the space between the leaves of boundary walls of an area to be kept secure, both acoustical privacy and the audibility of masking noise that flows back into the secure area can be controlled at the same time. This letter provides design relations and suggestions for system configuration.

On-Site Acoustic Privacy Investigation and Corrective Design for a Large Training Center

On-Site Acoustic Privacy Investigation and Corrective Design for a Large Training Center

Acoustic privacy in condominium living

There were new demands for acoustical privacy by the condominium owners from the builders of condominiums as condominium living became popular in the 1970's. The condominium owner had different perspective about acoustical privacy than the short‐term apartment dweller. The builders were at a loss to understand why there were complaints in some instances even with the best that they could build. The construction improvements, however, are only possible to an economically feasible limit. The concept of background noise as a means of reducing annoyance due to intrusive noise is not well understood by architects and builders. There is a need for defining “comfortable” acoustical privacy in condominiums of which background noise is an integral part. A case is made for ensuring that the finished condominiums would have the background noise level that was built into the “comfortable” acoustical privacy analysis.

Acoustical privacy for closed office design—Part II

Sound attenuation was measured between two adjacent closed rooms sharing a common plenum area. The first part of this study [J. Acoust. Soc. Am. 64, SI, S149 (1978)] concentrated on sound transmission between rooms along a path through the ceiling and common plenum. A high STC wall limited the transmission of sound through the common partition. In this second part of the study, a partition with an STC of 36 was built in order to measure performance of each ceiling/partition assembly. Interzone attenuation measurements were conducted according to the PBS C.2 test method. These results were then compared with subjective responses to speech intelligibility for an elevated voice level in the presence of background masking sound. The results show a nearly constant signal to noise ratio that controls speech intelligibility. In addition, combinations of ceiling STC ratings, partition STC ratings, and masking sound levels are presented which provide signal to noise ratios that were subjectively judged to provide confidential speech privacy.

Noise impact in modern Hawaii

This paper presents an overview of noise impact considerations in modern Hawaii, emphasizing those which are different from most mainland situations. The favorable year‐round climate encourages outdoor recreation in public parks and the natural ventilation of residential and school buildings. However, this lack of closure often causes the noise from modern transportation systems to be excessive. Also, because of limited useable land, the high density of open housing often causes problems with acoustical privacy. Examples of the variation in freeway traffic noise with height in an “open” high‐rise building will be shown. The high background noise levels created by the tradewinds in certain tropical foliage will be cited and examples shown of use as an acceptable masking noise. Likewise, the use of surf noise in planning deluxe condominium complexes will be cited. Two unique transportation noise sources will be discussed: 24‐h sugar cane hauling operations and gas‐turbine‐powered interisland hydrofoils. Noi...

Acoustical privacy for closed office design

Tests were conducted to determine the degree of sound isolation between a closed two‐room pair of offices with a common ceiling and partition. Several ceilings were tested with a standard metal stud office partition with Fiberglas insulation and 1/2‐in. gypsum wallboard. Ceiling STC ratings for each system were compaired to SPP > 70 requirements, according to PBS C.1 and C.2, for speech privacy in closed plan offices. Subjective tests were also conducted with a background masking sound system to determine its effect on speech privacy between offices. The objective of this work was to determine if speech privacy can be obtained in adjacent closed offices without an STC > 40 ceiling board provided that an adequate masking sound system is installed.

Use of the Articulation Index to Evaluate Acoustical Privacy in the Open Office

Use of the Articulation Index to Evaluate Acoustical Privacy in the Open Office

Vibration induced masking noise

Very high acoustical gradients negate acoustical privacy in buildings which normally have acceptable transmission loss between units. This is particularly true of mountain condominium complexes which have entertainment areas in the same building. The vibro-mask system reduces the acoustic gradient by introducing masking noise into the quieter areas such as sleeping quarters. Acoustical transducers induce structural vibration which is in turn transmitted throughout the building with a reasonable degree of uniformity. Equalization of the input power spectrum is accomplished by electronic networks to obtain the desired masking sound spectrum.

Noise reduction analysis for a dispensary at a Naval Air Station

In order to determine the noise reduction requirements of exterior construction for a proposed dispensary building at a Naval Air Station, measurements were made of peak noise levels and spectra of various aircraft operations flying near and over the site. The results of these measurements were significantly different from levels calculated using the CNR methodology. The differences appear to be related to the manner in which training missions are flown at military bases. Reliance on CNR data alone for noise reduction analysis at military bases can be misleading. To aid the architect in design and layout of the building, a series of guidelines was proposed. These guidelines related background noise criteria, speech communication distances within different spaces, and degree of acoustical privacy desired. Four allowable levels of intrusive noise were established, relating to these evaluations. The resulting allowable intrusive noise and the measured exterior noise exposure were then used to determine the noise reduction requirements of the exterior construction. The architect's visual and technical responses to this analysis are presented.

Acoustical privacy in the landscaped office

Two landscaped offices were used for field studies of the acoustical isolation value of masking noise, absorptive ceilings and partial-height screens. The occupants of one of the offices were recruited for a subjective study of the relative acceptability of various masking noises. The study showed that this group consistently preferred less noise — a conclusion that contradicts some previous experience. Interviews indicated that the acceptability of masking noise is closely linked to the occupants' activities and the resulting need for privacy. Propagation measurements were made under a flat lay-in ceiling configuration to determine the effectiveness of screens, ceiling materials and ceiling baffles. The ceiling baffles were not found to be a practical means of ensuring a low ceiling reflection coefficient. The results of the measurements are analyzed in terms of changes in articulation index. Consideration of the area disturbed by a hypothetical speaker emphasizes the importance of small relative changes in articulation index caused by small changes in physical parameters.

Re-vision of the speech-privacy calculation.

The articulation index used in telephone communication, the listening equation for sonar, and the acoustical-privacy calculation of architectural acoustics are all founded on a computation of an excess of signal level over noise level just sufficient to permit some stated detectability. From this viewpoint, data compiled for “Speech Privacy in Buildings” by Cavanaugh, Farrell, Hirtle, and Watters [J. Acoust. Soc. Am. 34, 475–492 (1962)] have been reviewed for possible simplications in their procedure for estimating acoustical privacy. Interrelations are demonstrated among various current methods for rating noise and sound insulation, and a general equation for acoustical privacy is derived. As an example, for the case of “confidential” privacy, 200-ft2 floor area, and raised voice, satisfactory acoustical privacy is to be expected if D+NA = 85 dB, where D is the sound isolation between the rooms (the reduction of sound from one room to the next) as rated by a procedure like that for the sound-transmission class, and NA is the background-noise level in the receiving room measured with a sound-level meter on A-weighting.

Simulated Background Noise to Improve Acoustical Privacy in Buildings

In many existing buildings where the construction provides a low degree of sound isolation between rooms, complaints concerning a lack of acoustical privacy most frequently arise where the ambient-background-noise levels are low. In most cases, the adequate improvement of the construction is either impractical or too costly. An increase of the ambient-background-noise level, on the other hand, can often provide the desired improvement of privacy. Sometimes this can be achieved by modifying an existing ventilating system. Where this cannot be done, background noise duplicating the characteristics of ventilation-system diffusers and other types of air distribution devices can be simulated electronically and distributed by means of loudspeakers. The instrumentation and technique as used in a few recent building installations is described.