Acoustics and Sound Masking Systems

An Integrated Product Solution
to Increase Privacy and Productivity

Noise is best described as unwanted sound. Unwanted sounds can be health and safety hazard by increasing stress levels and impairing communication and concentration. In the office, noise is a productivity issue as much as it is a safety issue. The office environment should be a relatively quiet place to work. Recent research suggests acoustics can have a large impact on occupant performance and productivity and is often the major complaint of building occupants.

Office Noise: A Productivity Killer

Since 1996, the Center for the Built Environment (CBE) at Berkeley has been conducting a comprehensive study project called Acoustical Analysis in Office Environments. The CBE mined survey data to investigate occupant satisfaction in a variety of office settings. As of 2007, this study has included more than 8,000 respondents in 66 different surveys. This study found that in occupants’ self-rated job performance, 60% of workers think acoustics interfere with their ability to get their job done. Acoustical satisfaction has typically recieved low scores in CBE’s Post Occupancy Evaluation (POE) surveys. View chart from study.

Unwanted noise affects productivity.

Unwanted noise affects productivity.

Acoustics are an important attribute of commercial office building design. Fixing an acoustic problem after construction is costly and architects and designers are being held accountable for acoustic issues. Studies have shown that noise is probably the most prevalent annoyance source in offices, and that noise can lead to increased stress for occupants. Speech privacy may be an even more important effect than noise. Yet acoustics in most cases do not receive the level of design attention as thermal, ventilation and other architectural and engineering considerations.

Controlling Noise in the Office

Noise controls are the first line of defense against excessive noise exposure in the office. The use of these controls should aim to reduce the hazardous exposure and minimize distractions that dampen productivity. With the reduction of even a few decibels, the hazard to hearing is reduced, communication is improved, and noise-related annoyance is reduced. ALUR Walls & Sound Masking reduce worker exposure to noise in a workplace both by reducing the transmission of sound and by masking the sounds that do transmit.

Understanding STC Ratings

Sound Transmission Class (STC) is a measurement of the decibel reduction in noise a material/partition can provide, abbreviated ‘dB’. The human ear perceives a 10dB reduction in sound as roughly reducing the volume by half. For example, a sound reduction from 50dB to 40dB seems half as loud. This is an important fact to keep in mind when considering office acoustical design.

Ratings and Privacy

  • STC 25 – Normal speech is easily understood
  • STC 30 – Normal speech audible but unintelligible
  • STC 35 – Loud speech audible & understandable
  • STC 38 – Normal speech inaudible
  • STC 38 – Loud speech audible but not understandable
  • STC 40 – Loud speech audible but unintelligible
  • STC 45 – Loud speech barely audible
  • STC 50 – Shouting barely audible
  • STC 55 – Shouting not audible

STC Ratings for some typical office walls and partitions

  • ½" Tempered Glass – STC 36
  • ½" Laminated Glass – STC 38
  • 4" Drywall (5/8" each side) – STC 35-39
  • ALUR Dividing Wall – STC 44-52

Numbers Sometimes Lie

STC ratings are measured in specially constructed acoustical chambers under optimum conditions. real-world field conditions, such as lack of adequate sealing, back-to-back electrical boxes and flanking paths can diminish acoustical performance. The as-built ‘field-STC’ (FSTC) is usually much lower than the laboratory-measured STC. For example, a drywall with an STC rating of 35, which has a hole of only 0.001% of the total wall area, is reduced to an effective STC of almost 30. This may sound like a small reduction, but consider the fact that a ±10 change in STC rating is twice (or half) as loud.

Sound Making: A Comprehensive Approach

The bottom line is that poor acoustics can ruin a good office design even if the walls aren’t the problem. Unacceptable noise levels can result in discomfort and lost productivity. Adding sound masking is an important component to maintaining acceptable noise levels in an office environment. ALUR sound masking products work together with ALUR walls to provide a comprehensive acoustical solution. ALUR sound masking products are HIPA and GBLA compliant, offering uniform, non disturbing sound throughout the office. ALUR sound masking products mask targeted frequencies, enhancing privacy and reducing complaints.

More Information

Find out more about the benefits of adding ALUR sound masking products to your office environment.

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ALUR Sound Masking System

Adding sound masking is an important component to maintaining acceptable noise levels in an office environment.

Adding sound masking is an important
component to maintaining acceptable noise levels in an office environment.

System Components


ALUR sound masking systems feature a control unit with digital sound generator, tone controls and amplifier. The control unit powers up to 25 speakers (6,000 sq ft) and is UL and FCC certified. Units have integrated volume, bass and treble control knobs and come standard with a 110/240V external power supply.

Plenum speakers typically mount in the space between the drop ceiling and the hard ceiling. They feature directional mounts enabling the speaker to be pointed in any direction. Plenum speakers have a 5" driver in sealed enclosure and five settings for quick adjustment.

Open ceiling speakers are ideal for offices that do not have a drop tile ceiling grid. The speaker, terminal and switch are hidden. Open ceiling speakers also have a 5" driver in sealed enclosure and five settings for quick adjustment.

Reducing the Radius of Distraction

ALUR sound masking has been found to reduce the radius of distraction in an open office plan from 40' to 15'.


Test Conditions

  • Workstation Dimensions: 7'x7'
  • Ceiling Height: 9'
  • Ceiling SAA: 0.6
  • Panel Height: 5'
  • Panel STC rating: 20
  • Masking: 45 dBA
  • Background noise: 37 dBA