Cambridge Sound

Why Do You Need Sound Masking?
Because noise distractions are driving your employees crazy
Because the constant interruptions are making your employees less productive and losing you money 
Because sensitive data is being communicated and overheard in your work environment and you are legally bound to protect it.
Most offices today feature more open spaces and smaller, and often shared, workstations.  Less sound absorptive materials are being used such as lower or non-existent partitions, hard or glass surfaces, and thinner walls and doors. This creates acoustical challenges that negatively impact workplace satisfaction, productivity, and speech privacy.
Where is Sound Masking used?
Corporate: Open office, private office ,conference rooms       
Healthcare: Patient rooms, waiting areas, reception areas 
Hospitality: Guest rooms, lobby areas, spas
Government and Law: Secured facilities, courtrooms, law offices
Technology:: Engineering labs, co-share spaces, design studios
Finance: Call centers, retail banks, board rooms
Education: Research laboratories student centers, libraries
Venues:  Houses of worship, conference centers, airport lounges
What is Sound Masking?
Sound masking is the “cover” portion of the equation. Sound masking is the addition of an unobtrusive background sound, similar to airflow, to reduce the intelligibility of human speech and reduce distractions. The resulting environment leads to greater productivity and increased privacy and comfort.
What is Speech Privacy?
Simply put, speech privacy is the inability of an unintentional listener to understand another person’s conversation. So, people with a lack of speech privacy are overhearing lots of conversations that they shouldn’t be, which is, understandably, quite annoying to employees.
When we look at acoustical related complaints of office workers, we find that most complaints center around the idea that others can hear our conversations, or that we can hear others’ conversations (a lack of speech privacy).  Rarely is the problem that there is simply too much noise in the environment.
As an example, many people have no problem working in a coffee shop or other public place, but once they are in an office, the expectation of speech privacy is very different, and indeed the reality of speech privacy is very different as well.  In the office, we are able to understand every word that our neighbors are yelling into their speakerphone, but in the coffee shop it didn’t seem to matter.
So when we define speech privacy, there must be an element of intelligibility.  It is not practical to eliminate all conversational sounds in a workplace, but it is certainly not impossible to significantly reduce intelligible speech throughout a workplace.
What is the difference between sound masking and white noise?
white noise vs sound maskingSound masking is often misunderstood as white noise. White noise is irritating when it is amplified, sounding similar to a loud AM radio static. Sound masking is different than white noise because it is band limited to only overlap with the frequencies of human speech. By matching the frequencies of human speech, sound masking is specifically engineered to mask conversations for greater speech privacy and productivity. White noise, includes all frequencies at equal energy and can be distracting and annoying. Sound masking is more comfortable acoustically, as only the frequency spectrum needed to increase privacy and minimize distraction are produced.
Why not just get a white noise machine?
white noise like a fanWhite noise machines are localizable.  This means that you can tell where the sound is coming from. Just like a fan, your ears can spot a white noise machine and it thus becomes distracting in of itself. A sound masking system is a more immersive experience as the sound is everywhere. When properly tuned and installed, sound masking should fade into the background. There should not be any gaps in sound masking as you walk throughout the office and a constant sound field should be produced whether you are sitting or standing.
How can sound masking provide an immersive experience?
Sound masking should be installed with great a detailed installation plan, accounting for every light fixture, wall, and even the material of your ceiling. This is achieved by appropriate spacing of sound masking speakers (emitters) and adjusting the intensity of the sound masking. Direct field sound masking aims the sound masking downwards, so in plenum obstructions do not interfere with the sound masking. This is a newer approach to sound masking for maximum uniformity. Networked sound masking is another way to have precisely engineered sound masking. Networked sound masking system enables individual speaker level control, meaning you can adjust each speaker to blend into the room.


Speech Privacy Systems: Above Or in Ceiling?
Direct field speech privacy and sound masking systems are displacing conventional systems with loudspeakers mounted in the plenum. This paper discusses the relative advantages of the two systems.
A recent survey of workers by the National Research Council of Canada clearly demonstrates that office workers in a typical open plan environment are satisfied with their office acoustics only if the ambient background sound is in the range of 45 dBA-47 dBA. If sound levels are below this range, intruding speech sound from adjacent offices and circulation areas is sufficiently distracting that most workers find it difficult to easily concentrate on their work. If levels exceed 47 dBA, the ambient sound itself is judged obtrusive and unpleasant to many workers. Only if ambient sound from the heating and ventilating system is fortuitously of the correct loudness, correct spectrum (frequency distribution), steady throughout the day, and uniform spatially throughout the office, can the user be provided background sound from mechanical sources within this very narrow range. This is rarely possible, largely because HVAC engineers usually design office mechanical systems to provide typical operating sound levels at least 5–10 dBA below this range to assure that they do not exceed 47 dBA under the highest anticipated heat loads and air velocities. Other factors leading to insufficient ambient sound from the mechanical system design are the inability to reliably predict initial HVAC operating noise levels precisely and to design for both even sound and air distribution, and the normal slow decline of several decibels in sound output as filters age.
Electronic sound masking systems are a particularly cost effective way of assuring that background sound is maintained within acceptable limits. The cost of a masking system is normally a small fraction of the cost of any architectural changes that might be contemplated to significantly improve speech privacy. In most cases, sound masking is considerably more effective than any architectural noise control treatment, although both may be required in certain cases, depending on existing room surface treatments and furniture configuration.
A typical sound masking system using loudspeakers above the suspended acoustical ceiling is easily adjustable to provide the correct frequency distribution and precise operating level of ambient sound, but only if considered on an average basis throughout the space. Achieving adequate spatial uniformity of ambient sound is a serious challenge faced by masking system designers, and one that few are able to provide consistently using loudspeakers above the ceiling.
Even a 3 dB variation from one workspace to another can have a dramatic effect on speech privacy, yet the performance of most systems varies by more than that, particularly because the sound attenuation characteristics of typical ceiling and plenum materials and openings varies substantially from point to point. Masking sound originating from the loudspeakers above the ceiling is attenuated differently at different locations within the space, accounting for this variation.
Theoretically there are some measures that can be taken to mitigate the problem, such as providing each loudspeaker with a volume control, using many more loudspeakers, and providing sound attenuating “boots” at each opening in the ceiling: realistically these measures are rarely employed because of the resulting costs. More commonly, the provider will claim that a wider spread in masking sound level is acceptable, if the issue is addressed at all. The unfortunate result is that the system is either operated at a level that causes annoyance to many users, or conversely that it is operated at a lower level that fails to provide good privacy throughout the office.
In contrast to the uniformity of sound required in the open office, people working in closed offices normally require about 6 dB less ambient sound than those in open offices. In fact there are usually serious complaints if the closed area sound level is the same as that considered optimum in the open space. Unfortunately a common type of office construction is to omit a separating wall in the plenum between the open and closed spaces, ie there is a common return air plenum for both. While this construction has good reasons from a mechanical system economy standpoint, it also results in about the same ambient sound level in both offices if the speech privacy system is installed in the common plenum. Unwanted sound intended for the open area bleeds through to the closed area. In fact, due to normal reverberant buildup in the small room, the sound level normally increases above that in the open office, unless mitigating measures are taken, such as installing costly barriers in the plenum or a different ceiling material in the closed offices with higher acoustical isolation (NRC Rating). Otherwise, even measures such as installing different zones or volume controls on the closed office system will prove largely ineffective because it is the sound serving the open area that controls what is heard in the closed offices.
Recently several manufacturers have introduced a type of ceiling mounted system that is able to provide much better uniformity of masking sound throughout the typical open plan office. These systems use loudspeakers which radiate sound directly into the occupied space below, rather than into the above-ceiling plenum. Their principal advantage is that the non-uniformity caused by HVAC openings in the ceiling or ventilation slots in lighting fixtures, or by building structural elements, fireproofing, and large ducts or other mechanical components in the plenum no longer have any significant effect on the spatial distribution of masking sound. The system designer can assure very uniform coverage simply by providing a well-defined and simple layout of masking loudspeakers, without a precise knowledge or consideration of above ceiling building elements.
These systems also assure that the frequency distribution of sound is optimum because there are no significant frequency-dependent acoustical attenuators between the loudspeakers and users: hence their overall description as direct field or in-ceiling systems. To the user this means that the system is able to provide effective masking at considerably lower sound level and potential for annoyance, and that the acoustical effectiveness is maintained throughout the building. The in ceiling system also completely avoids the problem of inability to obtain different ambient sound levels in open and closed offices because there is no bleed in the plenum from one area to the other. Because of these acoustical advantages as well as economic factors, direct field systems have gained increased acceptance in the marketplace.
Thomas R. Horrall, FASA



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