What is Sound Masking?

Sound masking is the introduction of a specifically-tailored audio source (frequency/signal) into an occupied office/building environment that creates and/or increases speech privacy.

In open offices, incorporation of sound masking decreases the distance where conversations may be clearly understood, thereby reducing distractions and increasing privacy for building occupants. This is accomplished by reducing the talker's 'signal-to-noise ratio' as experienced by the listener, (i.e. 'covering' speech of another occupant with a masking signal at the listener's location). 

Sound masking signals (produced by emitters and loudspeakers) are placed throughout a space where occupants are present that should not be distracted or where listeners are not intended to hear nearby conversations. Installing sound masking only near a talker has no effect on interrupting their speech intelligibility to others. 

In enclosed spaces, sound masking is typically incorporated both inside and outside of the enclosed space to maintain speech privacy. Sound masking signals placed outside of the enclosed space will prohibit in-room conversations from being overheard by building occupants passing near the space. Placing sound masking inside a room promotes speech privacy by “protecting” conversations taking place in the adjoining spaces (such as a private office).

Successful Deployment

For a sound masking deployment to be successful, little to no variation in the sound masking signal should be detected throughout a given space. Uniform distribution of sound masking is critical to occupant comfort, acceptance, as well as speech privacy performance. Even distribution of sound masking is predicated on consistent and adequate emitter/loudspeaker placement throughout a space with coverage over the entire physical space, or 'wall-to-wall' coverage. 'Gaps' in sound masking coverage will be noticeable and distracting to a building occupant. 

Additionally, proper sound-level adjustment will dictate project success in terms of occupant acceptance and comfort levels. It is critical that sound masking be installed when a space is unoccupied and calibrated to the proper sound levels prior to allowing occupants access to a space. This applies to both new and existing facilities. Improper adjustment and installation during occupation will be distracting to occupants and greatly hinder acceptance by those occupants. 

Qt X features 'soft start' capabilities, which is a calendar-based time period where levels may be attenuated at first occupancy and increased gradually over time to the final sound masking level. This soft start feature slowly acclimates occupants to sound masking and should always be used in spaces which are occupied with no sound masking installed.  

Installation & Configuration

The Qt X sound masking platform provides a vast array of functional approaches to deploying sound masking.

Direct field sound masking places sound masking emitters/loudspeakers in the “direct field” (downward facing directed at listeners,) allowing the sound masking signal to be delivered unimpeded by building architecture/finishes. The Qt X platform utilizes predetermined/optimized sound masking spectrums based on which the type of direct field sound masking emitter is connected to the control processor (emitter type selectable in Web UI/Qt X software).

Indirect sound masking (upward firing directed away from listeners) commonly places loudspeakers above ceiling finishes using the structural deck to disperse sound evenly. This indirect approach is commonly referred to as “in-plenum,” and requires that sound masking signal adjustment (equalization) be made within the Qt X software by a qualified technician to compensate for the loss of signal through the ceiling materials.

Qt X controller models are available which support both direct and indirect loudspeaker/emitter deployments. Models may be used in conjunction with one another to create a complete sound masking system to meet the needs of the architectural conditions in a facility.

The number of loudspeaker/emitters required and their respective spacing is based on a variety of architectural conditions:

• mounting heights 

• type of device serving masking 

• air plenum depth

• architectural finishes 

Design Team services should be used prior to deployment to ensure the proper number of devices and correct sound masking distribution method is deployed. Installation should not be attempted without a verified layout and wiring schematic, as each project/area will have unique requirements which should be considered as part of the design criteria.

Zones & Sound Masking Levels

Depending on the type of space and its intended use, target sound masking levels may vary from area to area throughout a facility. Multiple controller outputs as well as multiple controllers may serve zones of sound masking, which simplifies user controls and adjustments. Outputs may be adjusted independently to compensate for emitter/loudspeaker mounting heights and architectural conditions present.

Each zone of Qt X sound masking may serve specific architectural spaces and include background music and/or paging signals (when used with supported emitter/loudspeakers) by using external audio sources. Typical sound level targets to create effective / comfortable sound masking for common office environments are as follows.

A-weighted sound masking levels in dB SPL as measured 4ft (1.2m) above finished floor using a calibrated sound pressure level meter. (Class 1 SPL Meter / Microphone recommended)

In cases where sound masking levels exceed the above recommendations, occupant acceptance will diminish greatly and may lead to complaints, especially in extremely quiet environments. This may result in dissatisfaction with the sound masked environment and a request by staff to lower sound masking levels. This would ultimately reduce the effectiveness of the system. For this reason, each zone of a Qt X sound masking system should be calibrated and adjusted precisely upon installation using calibrated measurement equipment by the qualified installer.

Post-Deployment

Adjustments

Once sound masking levels are optimized for a space, the levels should be maintained indefinitely. Even slight changes in level may be noticed by building occupants when they occur. Sound masking may be adjusted in small increments over a longer period of time at specific times of day using scheduling functionality. Reducing a sound masking levels at night (under conditions of little to no building occupancy) may be beneficial for security staff to detect intrusion.

Scheduling

Qt X provides daily scheduling functionality which allows attenuation of the sound masking levels at specific hours of the day to meet reduced masking level needs. This scheduling functionality includes a “ramp duration time,” which gradually adjusts levels during the scheduled timeframe. A gradual change in sound masking level reduces the potential that building occupants will notice and become distracted by changes. The table below indicates the recommended ramp duration time based on desired sound masking attenuation: