Providing an acoustically balanced working environment benefits both employers and employees directly by significantly improving overall productivity. Unfortunately, it is often the least considered aspect in workspace design. The highest overhead and investment for most businesses is its staff. In order to capitalize on that investment, it is critical that employees are as productive as possible. That means an office environment with high speech privacy and less annoying by distractions.

Employees’ most productive time is spent trying to do quiet and focused work. Yet, employee surveys have shown that the number one facility issue is noise within the office environment with its associated distraction, stress, and loss of productivity. Not only is there an immediate and ongoing cost to the company, but also some employees may choose to seek a better work environment, further impacting corporate efficiency and generating unnecessary hiring and retraining costs.

There are three acoustical issues that must be addressed by employers who wish to be proactive: Ambient Sound Level, Speech Privacy, and Sound Transmission Paths.

First we will address ambient sound levels. Every office has a level of background ‘noise’ that is directly related to the type of work being performed. The most distracting and counter-productive sounds are those associated with overhearing other people’s conversations, mechanical systems, and intermittent sounds such as ringing telephones, photocopiers and other intrusive ‘noises’.

Speech privacy is the most critical issue in any office environment. If speech is indirectly intelligible to others, employees feel extremely restricted in their communications with colleagues within their own workspace and during their telephone conversations. Normal levels of speech should be unintelligible between closed offices and to others over 15 feet away in open areas.

Now let’s examine the sound transmission paths. There are four distinct paths by which sound is transmitted from source to receiver:

• The direct route that is unimpeded between a sound source and a receiver.
• The indirect path in which there is a material or structure between the sound source and the receiver but which lacks the density and/or mass to significantly reduce the sound energy.
• The reflected path when a sound reflects off hard surfaces, such as walls, windows, floors and ceilings, and is received by the receiver even though the source is not in the direct line of sight.
• And there is a diffracted path by which sound travels between source and receiver and goes around otherwise effective barriers in the direct path.

Knowing how sound travels, three basic remedial techniques can eliminate distracting noises and maximize speech privacy in office environments: Absorption, Blocking and Masking.

Reflected sound energy can be absorbed by introducing ‘soft’, porous surfaces. The liberal use of ceiling tiles with a high absorption coefficient, fabric covered furnishings, open area partitions and carpets will reduce the ambient sound level and speech intelligibility over distance.

Blocking with dense, heavy materials reflect the sound back towards the source and significantly reduce the amount of sound getting to the receiver. Hence, open area partitions require a dense, high mass material core with absorptive material on both sides and should be 5 1/2 feet in height to reduce the diffracted sound paths.

The third remedial technique, which is the introduction of low level / broadband sound in the work area, is an effective way to reduce speech intelligibility. This is achieved though Sound Masking, which generates a sound spectrum that broadly, covers speech frequencies and is contoured to the human ear’s sensitivity to sound. Hence, by rendering distracting conversations less intelligible, those directly involved in the conversation have a sense of privacy.

It is important to note that Sound Masking systems must be tuned after an installation, and re-tuned if and when an office area is reconfigured. A poorly tuned system not only fails to adequately reduce speech intelligibility but can actually become a source of annoyance in itself.

All three of the above noted materials and systems need to be considered in order to control the acoustic environment in the workplace. This is particularly important in ‘open landscape’ designs and where ‘closed’ office walls do not go fully up to the structural ceiling. The construction and height of area partitions, selection of acoustical ceiling tile, and the quality and flexibility of a Sound Masking system can mean the difference between success and failure in achieving an acoustically ‘friendly’ environment.

Sound Masking is an acoustical technique designed to reduce voice intelligibility, thereby increasing speech privacy. In order to achieve this, an electronically generated, broad-band noise spectrum is generated and introduced into the area of concern through speakers installed on a 15 foot grid pattern to ensure a consistent distribution of this masking sound throughout the area. These speakers are installed above the ceiling tiles in the plenum space, facing the structural ceiling above. The sound generated by the speakers is dispersed and reflected downward through the acoustic tiles, into the space below, by the structural ceiling. This sound energy path results in a homogeneous distribution of the masking sound spectrum throughout the open or closed office environment.

Sound Masking should be used in conjunction with high quality acoustic tiles, other absorptive elements and barrier components to maximize overall effectiveness. Sound Masking systems utilizing speakers mounted on walls, in partitions, in or under solid surfaced raised floors or facing downward through the acoustic tiles can be used in critical situations.

In order to realize the best results from your investment, Sound Masking Systems should be designed, installed, fine-tuned and maintained by those who specialize in noise and vibration control. Where overall office acoustics is a major issue and concern, the cost of an Acoustical Consultant is a worthwhile investment as they can not only look at all aspects of the space but can recommend the reputable specialist suppliers of acoustic tiles, partitions, barriers and masking systems. If sound masking is the only aspect that you are considering, the following provides a solid outline and approach to getting an effective and quality system:

First Things First

• Meet with the Sound Masking Professional and become familiar with the variety of systems available (avoid those who only have a single , ‘one-size-fits-all’ system to offer)
• Have a floor plan available (auto-cad or hard copy)
• Prepare a list of information about your facility.

• When possible take the consultant on a tour of your facility
• Make your expectations clear and be sure to understand the limitations
• Once the furnishings are installed you will need to organize a completely quiet time within the area where the sound masking is installed so the system can be properly tuned

Combinations and Possibilities

There is a sound masking system to meet every acoustical requirement!!

• One to Eight Speaker – 2 zone Mini-Mask-8 ohm systems (with Decora design cover plate). All system components are installed in the wall or mounted on a wall. (225 – 2000 square feet)
• 8 - 30 Speakers– 2 zone Mini-Mask 70 volt systems (with Decora design cover plate). All system components are installed in the wall or mounted on a wall. (2000 - 6750 square feet)
• 30 Plus Speakers – Centralized Digital Sound Masking/Paging/Music systems. 4/8 environmental zones to however many zones required. Single, multi-floor and full building projects.

Once we understand:
your facility,
your requirements,
your expectations and
your budget we can design
your customized Sound Masking System.

Sound Masking Systems are manufactured in many shapes and sizes. While some are very basic, others are highly sophisticated and technically advanced with many specialized features. Regardless of which system is selected or specified, its prime function is to render speech unintelligible over distance, so that a degree of inter-personal privacy is attained. It has also been found to reduce one’s awareness of distracting noises; hence concentration and work related effectiveness are increased.

Obviously, every situation and existing physical space is different. However, whether it is specified to introduce speech privacy in a Doctor’s small reception area or for a large, multi-floor space with a variety of environmental features, the system must be equally effective. This explains why there is a variety of different Sound Masking Systems available and also why particular systems are selected and/or specified.

Question

What are the basic requirements that are ABSOLUTELY necessary to ensure the successful introduction of Sound Masking in a defined area?

• The area must meet internationally accepted standards (ie: ASHRAE) in terms of the ambient, unoccupied sound levels
• Use of RANDOM Pink Noise generation
• A speaker layout indicating zoning of the masking system according to each acoustical environment
• 1/3 Octave equalization for each zone of masking
• Separate channels of amplification for each masking zone
• Volume control down to 225 square feet
• Reliable and correctly located speakers
• A Class “A” 1/3 or ‘real time’ sound level meter for tuning each environmental zone independently
• A trained specialist to tune the masking system(s) with the Class “A” sound level meter
• Defined specification(s) for a Sound Masking spectrum that is suitable for each of the diverse acoustical environment(s) that may be encountered. Such as:

Trained Acoustic Specialist

The person who tunes the Sound Masking must be trained to use the Class “A” specialized sound meter. They must be aware of:

• The acoustic environment of each zone
• The dB by frequency and dBA levels of an area before the pink noise is generated in the space
• Ambient background sound levels that are too high (i.e.: masking would be hard to tune properly)
• The masking spectrum best suited to the space, if not pre-specified

The specialist must be capable of:

• Measuring sound pressure levels by 1/3 octave frequencies
• Reading dBA levels
• Sensing the development of a spectrum
• Adjusting the levels on the equalizer so a specific masking spectrum develops correctly
• Customizing a masking spectrum to better suite a zone
• Judging if suggested dBA levels are too low or too high for an area
• Testing the level of speech privacy once the masking spectrum is developed
• Sensing the comfort level the occupants will experience

Be Aware

Tuning a sound masking system WELL is the most significant aspect of the project.

1. The masking system purchased must have the components that allow proper tuning.
2. Volume control alone, does “NOT” replace an EQ for proper tuning.
3. A system pre-tuned at the factory does not allow for speech privacy in all acoustic environments.
4. Sound Masking cannot be tuned with the human ear or a simple sound level meter. A high quality sound meter owned and operated correctly by a trained specialist is a significant feature to be considered when choosing a system.

The Truth

1. A remotely tuned (tuning from a different building or space without someone being in the sound masking space) Sound Masking System has yet to be developed.
2. Every system must be tuned with a sound meter that measures the sound levels generated through the speakers. The person tuning must stand within the zone in order to read the proper measurements and re-measure each time adjustments are made on the equalizer. Once the proper spectrum has been developed, small volume adjustments can help to reach the exact dBA level for maximum speech privacy.