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The psychology of acoustics

by Darren
acoustics-jnl13.4

Acoustical office design can have a profound effect on workers’ productivity and overall well-being.

An office building’s acoustic design can directly affect a company’s profitability, writes Karien Slabbert.

Case study: Why acoustics in offices matter
Anne van der Walt* works in an open-plan office. Although there are partitions between the various cubicles, sound travels from one end of the office to the next. Noise levels are high, as the environment is a fusion of people talking on phones, chatting, radios and ad hoc desk meetings. She often feels distracted, becomes irritated and frazzled, which influences her productivity – especially at the end of the day when concentration levels generally tend to dwindle. “I wish the office could be less noisy and that I don’t have to listen to the incessant chatter of loud colleagues, as this would help to control my stress levels,” she laments.
Research supports Van der Walt’s perception – and frustration – of an open-plan office with bad acoustics.
* Name changed

The United States General Services Administration recently published a comprehensive guide to acoustics in the workplace. In it, they state: “Office acoustics isa key contributor to work performance and well-being in the workplace.”

The guide further states: “Having speech privacy is necessary for confidential interactions and work processes. ‘Acoustical comfort’ is achieved when the workplace provides appropriate acoustical support for interaction, confidentiality and concentrative work.”

Undeniably commercial office buildings’ design must create an efficient, productive and healthy working environment. According to Sound Research Laboratories (SRL), a good acoustic building design plays a fundamental role in achieving this.

With commercial buildings time equals money – per hour billing, fixed-fee contracts and crucial targets. Companies cannot afford sick or underperforming staff. According to SRL, a building’s acoustic design (or lack thereof) directly affects the company’s profitability. It can also create a good or bad impression on clients. Moreover, a building with poor acoustics will struggle to get or maintain tenants. Undeniably, unacceptably high noise levels are distracting and often down-right irritating.

On the right wavelength
People are more productive in a pleasant working space. A good acoustic environment reduces stress by reducing the noise levels that invades one’s work space, as well as redirecting and mitigating existing noise frequencies. Common areas in commercial buildings play an important role in business. Atriums, food courts and walkways should all provide for clear intelligible communication.

According to SRL, acoustic absorption will help to ensure that a working space is not too echoic. Acoustic walls that surround private or noisy rooms will stop enough sound to keep conversations confidential, or to stop noisy activities in one room from disturbing adjacent areas.

Appropriate internal noise levels
The Green Building Council of South Africa (GBCSA) has devised a Green Star rating method for buildings. For acoustics there is the IEQ-12 rating that also applies to “as-built ratings”. This would apply to office, multi-unit residential and retail design, according to Mackenzie Hoy Consulting Engineers. The Green Star rating offers two credits for internal noise levels. The targets are based on South African National Standards (SANS) noise levels and recognise the fact that people are unable to work effectively if the environment is too noisy.

A bit of background noise is often helpful to improve privacy and make people more comfortable. The flipside also applies, as SANS 10103 states: “Where acoustic masking is employed, a rating level in excess of 45 dBA and a sound spectrum containing predominantly low frequencies could give rise to other problems, such as fatigue or a lack of concentration.”

Therefore, if an office is too quiet, staff members feel uncomfortable to do their jobs and enjoy less conversation privacy between rooms, while overly noisy spaces can hamper concentration and cause stress levels to spike, according to SRL. The mix needs to be just right.

The ABC of improving workplace acoustics:

  • A = Absorb (via drapes, carpets and ceiling tiles).
  • B = Block (via panels, walls, floors, ceilings and layout).
  • C = Cover-up (via sound masking).

Acoustics in buildings: key aspects

  • Inter-space noise control: Inside a building, typical sound paths include ceilings, room partitions, acoustic ceiling panels, doors, windows, flanking and ducting. Technical acoustic solutions depend on the noise source and the acoustic transmission path.
  • Interior space acoustics: Surfaces have sound-absorbing and -reflecting properties. Excessive reverberation time can lead to an overly noisy space.
  • External noise levels: The law regulates noise disturbance from neighbouring buildings. It is a criminal offence to create noise disturbance. This law is now enforced more stringently, according to SRL. Generators are often the main culprits, and accordingly need a noise impact assessment (NIA) to accompany the permission application.
  • Building envelope: Noise transmission from the building envelope (and vice versa) also plays a key role. Main noise paths include roofs, eaves, walls, windows and doors.
  • Glass: The sound control rating of glass is expressed as a weighted sound reduction index (Rw) measured in decibels (dB). Conventional laminated glass with a single normal strength (NS) vinyl interlayer is rated at 33dB. A high penetration-resistant (HPR) interlayer can improve the rating to 34dB.
  • Laminated safety glass is one way of controlling noise levels. A special vinyl interlayer offers better sound control than traditional polyvinyl butytal (PVB) interlayers. This product can be glazed into standard aluminium, wooden or specialist frames to control noise from a variety of sources, such as road traffic, music and busy, noise-ladened public areas.
  • Mechanical noise control: Noise and vibration from mechanical equipment, such as heating, ventilation and air-conditioning (HVAC) systems, can cause unwanted noise. Mechanical equipment can be spread out across a ceiling plenum in commercial spaces, causing localised “hot spots” that disrupt meetings. The equipment can be consolidated into rooms that, when not properly isolated from the adjacent spaces, can become noise epicentres for an entire floor.
  • Mechanical noise can also be in the form of vibration transmitted through a building’s structure. Non-isolated machinery can set in motion walls, floors, and ceilings, which can radiate noise into a room, sometimes far away from the actual vibration source. This is because a building’s structure can be a very efficient carrier of vibration. Proper vibration isolation is essential in eliminating structure-borne noise.  

The importance of noise control
According to HOK, a global design, architecture, engineering and planning firm, noise is an issue in most workplace environments. Interestingly it can enable or disable productivity, depending on individual preferences and the type of work being done. “The key is enabling people to control noise by providing access to a room with a door and acoustical separation when needed,” states the consultancy firm. Key aspects that boost productivity include:

  • Perceived noise (discernible by the average human ear) is typically higher in open office environments, but this depends on a space’s organisation, the materials and the nature of work being done.
  • When employees have a degree of control over the noise in their environment, they are less distracted by it.
  • Contrary to popular belief, noise interruptions during simple, mundane tasks can provide the stimulation needed to keep going. Interruptions during complex work, however, require a longer period of time to re-orient, and continued interruptions are likely to have negative effects on the mood, which reduces the motivation to resume work.

Full acknowledgement and thanks are given to Sound Research Laboratories South Africa, Acoustic News, www.gbcsa.org.za, www.hok.com and PG Glass for providing the information to write this article.

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