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)
2) Change in floor level helps to reduce effective open areas between high-noise space (stage/dance floor) and seating areas.
3) Area for live or amplified music is separated from the main bar area by shielding with fin walls and/or bulkhead details. This can limit buildup of noise in areas where staff spend the majority of their time.
4) High-backed banked or booth seating is upholstered to provide absorption. This can be taken up to ceiling height. Remaining seating is also upholstered, to provide further absorption within the main bar area.
5) Bar is located as far as possible from high-noise area around stage/dance floor. There is no direct line of sight between bar and high-noise area. Mobile staff such as glass collectors, servers, or security staff can then be put on rotating shifts so their exposure to high-noise areas is limited.
6) Double door entrance lobby provided, to control noise break-out (see Figure 13.2 for further details).
Nightclubs should not be located within buildings that are structurally connected to any noise-sensitive location (e.g., dwellings).
Bars can be located within buildings that are structurally connected to noise-sensitive locations (e.g., dwellings) if there is no desire to provide live music or karaoke. Where dwellings are directly above, careful consideration should be given to whether the location is suitable depending on the anticipated style of bar. Even in a bar with no music there should still be an acceptance that separating partitions will have to be upgraded.
When controlling noise from a bar to an adjoining dwelling, it is likely that acoustic treatments of separating floors, separating walls, external walls, and load-bearing elements (columns, beams, flanking walls) will be required.
As a general rule of thumb, designers should expect the need to independently line all structural elements such as wall, floors, columns, and beams. This normally takes the form of metal or timber framing systems with multiple plasterboard linings. It is preferable that the core structural elements are specified as heavy mass constructions (concrete floors, high-density block walls).
For bars which are to have significant live or amplified music, glazing designs should allow for significantly heavy double glazing systems (e.g., twin layers of laminated glass) along with additional secondary glazing systems.
Glazing designs should allow for cavity depths between double glazing and secondary glazing units of at least 8 in/200mm. Such systems should be fixed glazing with compressible rubberized seals, with an allowance for the windows to be operable for cleaning purposes.
Acoustically absorptive reveals between double and secondary glazing units should be considered. This can be achieved by lining the reveals with mineral fiber ceiling tiles.
Ventilation systems are likely to be required, and provision should be made for significant attenuation works. This is likely to require acoustically lined ducts of 3–6 ft (1–2 m) in length, along with cowls to direct ventilation outlets and inlets away from noise-sensitive locations.
Acoustic lobbies to entrances and exits should be incorporated in order to reduce noise break-out, as detailed in Figure 13.2.
External walls to the lobby should be either a twin leaf, high-density masonry construction or masonry with an independent inner stud system lined with multiple high-density plasterboard linings.
It is preferable to design the lobby so that it is within the main curtilage of the building. Concrete roof constructions provide the best performance where an entrance lobby extends from the main curtilage of the building. Pitched roof systems with mineral fiber materials packed within the cavities and multiple high-density plasterboard linings can also be effective. Comments on roof structures are given in Chapter 4.
Doors should be oriented so that, even when both are open, there is no clear line of sight from inside to outside.
Doors should be fitted with self-closing mechanisms.
Ideally the lobby should be sufficiently deep so that one door can fully close before the second door is opened.
Doors should be either solid core timber or metal lined doors. Minimum performance levels of STC/Rw 35 dB should be considered for both doors, including any glazing set within the door.
The lobby should be lined with acoustically absorptive materials in order to reduce noise buildup. Wall-mounted fabric panels, acoustically absorptive ceiling tiles, and heavy wearing carpets should be considered.
Providing a good acoustic environment should be based on customer preference, but it can often be dictated by staff preferences or organizational preferences. It is assumed that in nightclubs customers prefer to be in an environment with loud bass-intensive music, while in local bars the preference may be for a quiet environment in which to chat. However, preferences may vary from customer to customer or from one night to another. The following should be considered in the design of bars and nightclubs.
The provision of quieter areas should be allowed for in any bar or nightclub, particularly where there is a desire to appeal to as wide a demographic as possible.
Avoiding the placement of loudspeakers near the bar area so that customers can easily give drinks/food orders, thereby improving customer service and efficiency.
Louder or quieter areas can be achieved by zoning amplified music systems, or through separating activities as shown in Figure 13.1.
Entrance lobbies to nightclubs are an effective way of controlling noise break-out, but they can also help building a sense of anticipation for customers as music levels increase when they approach the main club area.
Where there is a design preference for smooth surface finishes, consideration should be given to creating rooms of non-standard shapes, i.e., avoid simple square or rectangular rooms.
Where there is a preference for simple square or rectangular rooms, consideration should be given to well-distributed absorptive finishes, e.g., wall panels, ceiling-mounted absorption, or carpets.
13.3.3 Restaurants, cafés, and kitchens
Noise break-out issues associated with cafés and restaurants are generally associated with noise from kitchens, mechanical ventilation, and air extract. Noise levels within areas used for customers to eat are usually sufficiently low to not cause a problem when protecting staff hearing. The issue of customer comfort is associated with the provision of an environment which has sufficient high background noise levels to give a sense of privacy for each group of diners and the avoidance of high-noise events that may cause distraction.
When considering noise break-out from kitchens, the following good practice is recommended:
Impact sounds (chopping, footfall, etc.) are a particular issue. Locating kitchens above noise-sensitive locations should be avoided, i.e., do not place commercial kitchens above dwellings, hotel bedrooms, treatment rooms, offices, or meeting rooms.
Design of good noise control to ventilation and air extract systems is imperative. The NR/NC requirements stated in Appendix B provide a guide on adequate control levels, both within kitchens and for surrounding rooms and building types.
There should be an allowance in any mechanical system design for the inclusion of acoustic treatments such as attenuated duct work, resilient mounts, and acoustic louvers. This is a specialist design area, so it should be subcontracted to an appropriate contractor.
Locate fridge/freezer units, ovens, burners, and benchtop electrical equipment away from any adjoining wall between a kitchen and a noise-sensitive location (e.g., dwellings, hotel bedrooms).
The location of external waste and recycling areas should be as far from any noise-sensitive location as possible. It is generally good practice to screen these areas, so there is no direct line of sight to any noise-sensitive location.
It is good practice to separate kitchens from dining areas with partitions that provide a minimum insulation value of STC/Rw 50 dB.
In instances where there is a desire to be able to view the kitchen from the dining area, limit the open area of any viewing aperture, avoid floor-to-ceiling openings, consider partial or complete screening of any opening with double glazed units, and locate noisy equipment (ovens, burners, benchtop electrical equipment) as far from the viewing aperture as possible.
Providing corridors to separate direct access from a kitchen to a dining area should be considered to reduce noise break-out during serving.
When considering noise control within restaurant or café dining areas, the following guidelines are suggested:
Diners in restaurants and cafés tend to assume an environment that will be suitable for speech communication without interruption from other diners or other noise sources. Guidelines on suitable ambient noise levels and reverberation times are given in Appendix B.
Where there is a preference for hard floor finishes (timber, laminate, concrete, tile), it should be accepted that noise levels will quickly build up. This can be offset with the use of upholstered seating and soft furnishings, wall-mounted absorptive panels, and even tablecloths.
Areas of hard flooring around bars, serving stations and self-service cutlery/condiment stations should have rubber matting placed over the floor in order to reduce noise from any dropped glasses, dishes, or cutlery.
Background music in areas where reverberation times are higher can be appropriate dependent on the style of restaurant being created (e.g., rock-oriented cafés where people expect louder music).
Where noise control levels of NC/NR 35 or below are set within a room, systems should have a maximum supply air velocity of 5 ft/s (1.5 m/s) and a maximum return velocity of 6.5 ft/s (2m/s). This would be akin to ventilation to a restaurant area.
Where noise control levels of NC/NR 40 or below are set within a room, systems should have a maximum supply air velocity of 8 ft/s (2.5 m/s) and a maximum return velocity of 10 ft/s (3m/s). This would be akin to ventilation to a café.
Placing cowls or absorptive wall and ceiling linings around coffee/espresso machines can help reduce steam jet and banging noise. However, it should be recognized that this noise is associated with cafés and fresh coffee, so it is not always preferable to completely eliminate this noise. For restaurants or fine dining, these machines should be located well away from the diners. For cafés they should be visible and include the recommended treatments.
1.3.5 Cinema
Cinema design is a highly specialized area of acoustics and it is always considered best practice to engage the services of an acoustician on such projects. The following sets out current design guidelines on achieving shell stage design.
In order to control external noise, it is recommended that cinemas are not constructed in locations where maximum external noise levels regularly exceed LAmax(s) 80 dB.
Minimum façade insulation levels of STC/Rw 45 dB should be achieved. See Figure 13.4 for details on possible specifications.
Guidelines on permissible ambient noise levels, mechanical noise levels, and reverberation times are given in Appendix B, along with guidelines on suitable door specifications.
External walls and roof constructions are likely to require lining with an acoustically shielded construction, as shown in Figure 13.3.
Floor slabs to projection rooms should ideally be concrete slab constructions with a minimum weight of 300 kg/m2 and a maximum permitted dead load deflection of ¼ in (5 mm).
For new developments, partitions which separate cinema auditoriums from adjoining commercial activities are likely to require additional acoustic treatments (e.g., suspended ceiling treatments where bars are located below auditorium), particularly where amplified music is expected within the adjoining commercial space.
For new developments, it is also anticipated that any mechanical room or noisy equipment associated with an adjoining commercial activity will need to be located well away from any auditorium.
Service penetrations which pass through auditorium walls should be avoided completely.
Where service penetrations through auditorium floors are unavoidable, they should be independently lined with triple layers of high-density plasterboard and lagged with mineral fiber insulation along their entire length.
Raked seating and floor finishes to auditoriums should be isolated from the structural floor and separating walls. The preference is for concrete slab or screed constructions set on resilient isolation layers.
Ensure that escalators and lifts/elevators do not share a common wall with the cinema auditorium.
Table 13.1 outlines minimum insulation levels for good shell stage cinema design.
Figure 13.3 is a suitable separating wall detail showing appropriate detailing for the wall head and wall foot.
Include a break in the roof liner tray.
Allow for a deflection head detail at wall head sealed with a flexible gypsum-based caulk.
Suspended ceiling details are required and should include mineral fiber quilt with minimum three layers of high-density plasterboard. Where boards meet wall, seal any gap with a flexible gypsum-based caulk.
Table 13.1 Cinema partitions, performance guidelines (pre-owner’s fit-out/shell stage)
Partition | Minimum STC/Rw | Comment |
Auditorium to auditorium | 72 | Any wall/floor used should also be able to achieve a minimum reduction of 45 dB at 63 Hz |
Auditorium to concession | 62 | Concession includes any food serving, bar, or corridor around an auditorium |
Auditorium to projection room | 60 | It is assumed that, due to the need for an aperture in the projection room wall, this could not be tested on site |
Projection room to concession | 57 | Concession includes any food serving, bar, or corridor around an auditorium |
Auditorium to store/escape stairs | 52 | Including under-croft below raked seating |
Auditorium to staff areas/bathrooms | 57 | It is preferable to locate toilets away from auditorium areas |
Auditorium to adjoining commercial activities (restaurant/bar) | 72 | Any wall/floor used should also be able to achieve a minimum reduction of 45 dB at 63 Hz |
Stud work and plasterboard to be set on a resilient layer. This can be a bituminous-based felt or a closed cell foam material.
Floating concrete screed details are advised. Screed is laid over a high-performance resilient mount capable of providing acoustic isolation under high loads.
Screed and permanent shuttering isolated from separating wall with an isolation strip.
Separating wall lined either side with minimum four layers high-density board, preferably of varying thicknesses, and twin layers of mineral fiber quilt within the cavity. Mineral fiber may require stapling into position to avoid sagging in the cavity, or to be fitted on a supporting net or chicken wire.
13.3 Cinema wall detail, auditorium to auditorium
Figure 13.4 shows a suitable detail for controlling flanking noise at the external façade. Here it is assumed that the external leaf of the external wall is masonry but a cladding system would also be acceptable.
Locate expansion joint to inner external leaf of masonry behind separating wall detail to break the continuous line of the block work. The gap should be filled with a flexible water-resistant seal.
Where the plasterboard to the wall that separates the auditorium meets the external wall, any gaps should be made good with a flexible gypsum-based caulk.
The inner leaf of the external wall should be lined with an independent stud frame, set a minimum of 5/12 in (10 mm) from the block work wall. A minimum cavity depth of 4 in (100 mm) should be provided.
13.4 External wall detail for cinemas, auditorium to outside
The plasterboard lining to the external wall should be minimum three layers of high-density plasterboard.
A layer of high-density mineral fiber quilt should be placed within the cavity created by the external wall lining. Mineral fiber may require stapling into position to avoid sagging in the cavity, or be fitted on a supporting net or chicken wire.
DEFRA (2005) Guidance on the control of odour and noise from commercial kitchen exhaust systems. London: DEFRA/HMSO.
HSE (2005) Controlling noise at work, the control of noise at work regulations 2005. London: Health and Safety Executive/HSE Books.
HSE (2008) Sound advice. Control of noise at work in music and entertainment. London: Health and Safety Executive/HSE Books.
Lothian, S. (2008) Smoking outdoors and noise survey. Edinburgh: Edinburgh Napier University.
RICS (2012) SKA rating scheme. London: RICS.