THE CONSIDERATION OF ACOUSTIC DESIGN in commercial buildings is often overlooked; yet, in commercial environments such as cinemas, it is one of the key design features. This is because the people who operate cinemas know that being able to hear the film is almost as important as being able to see it. In essence they have a product which they hope to show off in as favorable manner as possible. The publication Sound Business by Julian Treasure, and the creation of the international organization the Audio Branding Academy, are clear indicators that businesses are beginning to use sound as a means to enhance their sales as well as the perception of their products. This can have direct links to the built environment and it should be the aim of any designer to either provide a space that is as acoustically neutral as possible to allow a business to add their own identity, or tailor a space for the specific needs of a business and its customers.
Behind this new area of acoustic design there are also the key requirements of providing suitable working environments for staff, avoiding disturbance to neighboring properties, and meeting the expectations of the end user. As this can be a particularly complex subject area, this chapter will set out some of the more basic design rules and cover a selection of the most common commercial environments.
13.2.1 Defining the acoustic environment
The level of acoustic performance for a commercial space will be dependent upon four key design factors:
2) The comfort and wellbeing of staff – the most obvious being control of excessive noise levels to avoid hearing loss, but there can also be correlations between staff productivity and inappropriate noise environments.
3) The noise impact on existing neighbors – noise created by commercial activities is not uncommon and can be a significant part of any design work required to show compliance with national and local requirements that protect existing amenity.
4) The expectations of the end user – this can often differ considerably from the basic expected requirement; for example, a room may be designed as a space in which to eat, but the end user may also expect it to be a suitable place to talk or listen to live music.
The first three design factors are normally set as part of any design brief to ensure that minimum statutory requirements are achieved or a basic level of comfort is provided.
The final key design factor is often achieved as a result of luck or chance, but it is probably reasonable to assume that in most situations the aim is to create an environment in which there is a sense of privacy without isolation. For example, people tend to feel comfortable in cafés/restaurants where they can easily hear and understand the people they are talking to but do not want to be overheard or understood by other groups in the room. Similarly, people tend to prefer retail environments where there is a sufficiently diffuse and constant background noise level so that they do not feel they are under scrutiny by other shoppers or shop assistants, but not so noisy that they are distracted or discouraged from extended browsing. Of course, there are obvious exceptions to these rules but these tend to be integral to the type of client that a business is trying to attract. Some retailers purposefully create a sound environment akin to a loud bar or disco to attract young shoppers and exclude older shoppers, while some bars set playlist policies for music and style to define themselves a place for people with a particular taste.
13.2.2 Specification targets
Appendix B details minimum ambient noise, mechanical noise, and reverberation time requirements for a range of commercial spaces. There is limited guidance on the control of sound transmission in commercial spaces, with the exception of cinema design; however, Chapter 14 outlines the requirements for hotels and can provide a good starting point for other commercial developments (e.g., bars/clubs). Any consideration of the control of sound insulation should also look to the guidance given in Section 6.4 regarding perceived levels of sound insulation.
The following provides an outline for where sound insulation should be considered:
Any room which is created as a treatment space (such as within a day spa) should provide a good level of speech privacy between it and any other room (around STC/Rw 45–50 dB). Where the treatment is medical in nature (e.g., dentists, optometrists), these levels should be increased to insulation levels comparable with those detailed for healthcare environments (see Chapter 8).
Locating rooms with lots of bass-intensive noise (e.g., amplified music) close to rooms which are for more intimate activities (e.g., dining) will require high levels of sound insulation (around STC/Rw 55–60 dB). Note that total control of noise is not guaranteed.
High-end retail environments or places where customers will be discussing significant sums of money or personal details (jewelry shops, car showrooms, banks) should allow for withdrawn rooms which provide high levels of confidentiality (STC/Rw 50 dB min).
Partitions separating general retail space or retail units (e.g., open-fronted shops within a mall or within a department store) should provide minimum insulation values of STC/Rw 45 dB. Levels of STC/Rw 50–55 dB should be seen as a minimum for entirely separate retail units which open out into the street (e.g., strip mall).
Note: These insulation requirements can be reduced in environments where background noise levels are kept artificially high (e.g., music or noise masking), although the use of such noise may not always be appropriate for the commercial setting.
THE FOLLOWING SECTION HAS BEEN SET OUT with topic headings based on particular commercial/retail environments. As this is a wide topic area, each building type cannot be discussed in detail, so only key points have been included.
13.3.1 Outdoor eating/drinking areas
The primary concern with outdoor space is the impact of noise from these spaces on surrounding noise-sensitive locations, with a secondary concern regarding the comfort of the users.
In order to minimize noise impact from outdoor eating and drinking areas, where they are overlooked by noise-sensitive locations (e.g., dwellings), as well as improve user comfort, the following advice is offered:
Avoid placing such areas within 65 ft (20 m) of any dwelling.
Where such areas are affiliated to noisy commercial activities (such as bars or nightclubs with high levels of amplified music), ensure that there is significant separation between noisy internal areas and the external space. Access via long corridors or multiple doors between such areas is recommended.
Provide seating layouts of two to four people per table. Avoid large group seating arrangements, particularly for spaces used at nighttime. Smaller groupings usually mean people will interact more quietly.
Orient seating layouts so that as many users as possible face away from any noise-sensitive location.
High-backed seating or seating with overhead canopies can be used to create intimate pockets and reduce overall noise levels.
Avoiding the provision of seats in outdoor smoking areas has been seen as a means to limit noise, however it can have the opposite effect of encouraging people to congregate in larger groups. Providing limited seating for outdoor smoking areas can limit the formation of larger groups.
Where possible, provide screening between an outdoor seating area and a noise-sensitive location. Ideally an acoustic barrier (e.g., a fence or wall) with minimum height of 6 ft (1.8 m) in close proximity to the outdoor seating area can be effective, but even visual screening can help to limit the perception of noise on nearby residents.
Where weather conditions allow, soft cushioning to seating should be encouraged.
Locating external seating areas in enclosed courtyards can result in significant disturbance where noise-sensitive locations overlook a courtyard, and should be avoided.
The introduction of vegetation (grass, shrubs, wall-climbing plants) can go some way to provide acoustic absorption within courtyard space, but performance will be limited.
Amplified music in such areas should be avoided. If it is to be used, it should be seen as a background source. The use of small loudspeakers set in multiple locations is preferable to fewer, larger loudspeakers.
Management of such spaces is key, and careful consideration should be given to the need for external eating or drinking areas which are to be used after 9:00PM.
13.3.2 Bars and nightclubs
There are three key areas for consideration when dealing with acoustics in bars and nightclubs:
a) protecting the hearing of the employees
b) ensuring the control of noise break-out to noise-sensitive locations around the bar or club
c) creating a good environment for the users.
Noise levels in some bars and nightclubs can exceed guidance levels issued for the protection of hearing (see Table 3.1). In some instances the approach taken by governments is that when people choose to enter such environments they do so at their own risk, but for employees the element of choice is removed and so it is incumbent upon the owners to ensure protection. This can often only be achieved through limiting shift patterns for key workers; however, there are some good guidance methods that should be adopted as part of general design. Figure 13.1 shows a proposed layout for a bar with provision for live or amplified music.
1) Grid represents location of loudspeaker system over small dance floor for use with DJ. It is now possible to specify flat-panel speakers and/or directional speaker systems to reduce noise build up across the space.
13.1 Possible bar/club layout for controlling high noise levels (adapted from HSE, 2008)