Voice Evacuation for Manchester Airport Terminal One. Paul Malpas, MIOA.

Introduction Manchester has by far the busiest UK airport outside London, with nearly three times as many passengers in 1996 as Glasgow or Birmingham (see Table 1). Terminal One has been developed to increase this capacity by 25% and to provide an extra 25 retail outlets. AIRPORT TERMINAL PASSENGERS London (Heathrow) 55,722,800 London (Gatwick) 24,106,100 Manchester 14,484,700 Glasgow 5,471,600 Birmingham 5,352,500 London (Stansted) 4,811,400 Table 1 UK's busiest airports, 1996 Early in the project, Architects Nicholas Grimshaw & Partners, Engineers Ove Arup & Partners and Contractor Bovis-Lehrer McGovan took office together on site with the client, Manchester Airport plc. This large team set about designing, engineering and constructing the massive transformation of the departures area of Terminal One. Included in this work was the upgrading and extending of emergency systems in this area, including the Voice Alarm (VA) evacuation system. Arup Acoustics were asked to give electroacoustic design input to the loudspeaker layouts and to specify the systems. This account describes a number of design issues concerned with VA design in airports and relates them to the work at Manchester Airport involving Arup Acoustics (AAc) and the Manchester office of Ove Arup & Partners (OAP). In the first section, airports are described in general to set the context to the project and to highlight a number of aspects of VA design in terminal buildings. Following that is an overview of the total works and a summary of the starting point for the VA design. After that, two sections explain the functional and electroacoustic design methods respectively. To illustrate the account of the electroacoustic design, some example spaces have been chosen to examine the loudspeaker layout options considered, the chosen design solutions and the resulting installed performances. An Introduction to Airport Terminals It is important to bear in mind that the main function of airport terminal building design is to facilitate passenger movement in large numbers. An appreciation of this point is a great help in digesting the complexities of the plans, and in identifying the spaces for special electoacoustics attention. Figure 1 illustrates the principal passenger routes of a typical, international and domestic airport terminal. Fig 1. Principal passenger flow routes through a generic international/domestic airport terminal. With consideration to evacuation systems, airport terminals can be characterised as follows:- They are usually very large buildings containing voluminous spaces. Periodic expansion often complicates the layout and passenger routes. They often have very large numbers of occupants. Most occupants are unfamiliar with the layout of the buildings. Evacuation planning must avoid the possibility of security breaches and must address all safety issues. The building form and compartmentation is derived principally from passenger flow. Some specific terminology is involved and a glossary of terms is included at the end of this article. Building Works and Building Layout Before design work began in 1995, Terminal one consisted of T1 International and T1 Domestic. T1 International contained most of the accommodation and has now been extended, remodelled and refurbished to create Terminal One Central (T1C). Work included the extension by 17m of the 120m main frontage onto the apron, the addition of a new airside lounge to the west and remodelling of most of the departure area. The new lounge connects to the first Harrods store in the UK outside London. The T1C contract covered around 20,000 m2 and was valued at £23 million. T1 Domestic had comprised a small combined arrivals and departures hall, some baggage sortation and the domestic Pier A. Under the separate Terminal One East (T1E) contract, Pier A became a flexible pier (domestic/international) and the terminal was extended to the east to create Terminal One British Airways – the combined domestic and international terminal for BA and its partner airlines. This £68 million project was opened in the summer of 1998, is the biggest BA operation outside London, and its first to be branded in the new British Airways 'World Image' livery. This part of the terminal alone has been designed to ultimately handle up to 6 million passengers per year and expects to be handling over 4.5 million passengers by 2001. As the family of airlines partnered by BA at Manchester has extended, the distinction between the parts of the terminals has become less clear to passengers, and there are already plans to rename Terminal One British Airways as Terminal Three. Figure 2 is a photograph of a model showing the extent of new and refurbished areas of T1C and T1E, Voice Alarm Systems – Works Overview The building is covered by two discrete systems: Terminal One Central and Terminal One East. Terminal One Central (T1C) was already covered by a PA system suitable for VA operation. VA had been installed in recently developed areas during subsequent chapters of the building's history. This system preceded recent VA and fire alarm design codes. The head-end (i.e. centrally located) equipment for the PA/VA in T1C had been upgraded previously by Audix Communications. This included fault monitoring and battery back-up in readiness for upgrading the loudspeaker layouts and cabling. The latest work at the terminal gave the opportunity to change the loudspeaker layouts in a large majority of spaces. AAc and OAP specified the loudspeaker types and locations by applying zoning requirements set by MAplc. Audix were awarded the contract to upgrade their own part of the central equipment to deal with the additional number of loudspeaker zones and loads. The overall electrical and mechanical services (E&M) contract went to ABB-Steward. The upgraded T1C system comprises 748 loudspeakers, 34 zones and 90 amplifiers of 8.5 kW total capacity. Terminal One East This area was predominantly new-build and was to operate almost independently of the remainder of Terminal One. Under a separate contract, the existing VA system was replaced by a new VA system, specified for the whole of T1E. This was facilitated by the fire compartmentation design. The airport specified all zoning requirements, operational microphones, pre-recorded messages and areas of coverage. AAc/OAP produced from this a full technical specification as part of the E&M contract documents, and Audix Communications was again awarded the contract, this time against one competitor. The new T1E system comprises the following equipment: Inputs: A total of 58 in number, made up of: 1 fire microphone 1 evacuation message 1 coded suspect packet alert 20 security, management and information desk microphones (including 5 in other terminals, connected via structured cabling) 23 gate microphones + 6 pier expansion inputs 2 pre-recorded announcements 3 further spare inputs 1 test message/test source input Outputs: A total of 41 in number, comprising 36 main loudspeaker zones 5 common evacuation stair loudspeaker zones (658 loudspeakers, 87 amplifiers, 6 kW total.) Equipment: 2 Input and routing racks; - pre-amplifiers. - matrix/controller (V32 and microprocessor controllers) - ambient noise sensing (ANS) controllers - equalisers - fault monitoring and reporting - fire alarm interface 4 power amplifier racks 1 battery & charger rack. Design Principles System Design In addition to the normal requirements of BS 5839 (Part 8 was released after award of the contract) and BS 7443 (now effectively BS EN 60849) together with the basic requirements of MAplc led to the T1C upgrade and to the new T1E system: VA zoning must relate directly to the evacuation plan, whereas PA zoning must be for operational purposes (i.e. paging areas). The resulting loudspeaker zones are based on the 'lowest common denominator' between the PA and VA requirements, including any essential rationalisation to avoid over-complication. Careful consideration must be given to emergency zone sizes and boundaries (evacuation is usually to the adjacent compartment, but many evacuation routes are on to the apron and unnecessary evacuations must be avoided for safety and port management reasons). The zone division must be kept simple to avoid the creation of many small loudspeaker zones. One of the most effective methods is to cover staff areas with conventional fire alarm sounders (perhaps 'pulsed' for alert). This principle is supported by the fact that airport staff are generally highly trained in safety issues, and there is less benefit of voice alarm over conventional tone than there is in public areas. It is usually not advisable to include a public alert stage as areas are so extensively linked (may cause unnecessary evacuations). Coded alerts or low flash rate beacons are sometimes used to warn staff of possible incidents. Tenanted areas (concessions, duty free shops, food court preparation areas, carriers' lounges etc.) must ultimately be covered by the system. The interface with the tenant's space can be made in a number of ways, including: Solution 1: The entire concourse is covered by overhead loudspeakers. Tenancies are constructed of part-height, open-top cabins. On commissioning of the tenancy, the individual loudspeakers above are PA-inhibited. Note that this solution provides some difficulties to the fire engineering (sprinklers, smoke extract) as the tenant cabins provide the major fire load on a concourse. Solution 2: Provide VA junction boxes (alongside junction box for the fire alarm detectors). Large areas of tenancies on a separate loudspeaker zone to adjacent non-tenanted areas, for protection and for separate PA requirements. This solution was applied at Manchester. Electroacoustic Design The mechanisms of achieving intelligibility in electroacoustics design is now well documented (1). In acoustical terms, intelligibility is a function of direct-to-reverberant ratio (D:R), signal-to-noise ratio (S:N, noise referring to occupational background noise levels) and Reverberation Time (RT). D:R is in turn a function of the loudspeaker types and locations, room geometry and RT. Figure 3. Figure 3 illustrates why loudspeaker layouts and room acoustic control are essential and interrelated considerations in achieving sufficient speech intelligibility. For a given space there will be a maximum reverberation time (RT) beyond which no practicable loudspeaker layout will be able to achieve the speech intelligibility criteria set. On the other hand Figure 3 also shows that over-restriction of the scope for loudspeaker layout design (eg architectural constraints) may result in unachievable room acoustic requirements. Between these extremes, there is a balance to be struck between the loudspeaker layout design and the amount of acoustic control required. The procedure for evaluating a proposed loudspeaker layout for a given space involves a sequence of steps: The range and distribution of direct sound pressure levels from the loudspeakers is calculated. The applicable room volume and the number of loudspeakers needed to cover it is estimated. The reverberation time of the existing space is predicted and from that the reverberant level in the space, allowing for loudspeakers in connected spaces. A design signal-to-noise ratio is set, and the corresponding background noise level limit for the space obtained by subtracting this ratio from the total sound level (i.e. direct + reverberant) at the quietest location. The range and distribution of %ALcons is calculated from the Peutz equation (1) and converted to Speech Transmission Index (STI) by the Farrell-Becker equation (1). The required reverberation time is then adjusted in the calculation until the STI range meets the design criteria. The result is the design RT for the given loudspeaker layout in the given space. Example Applications The Spaces The electroacoustic design in the following three spaces is discussed in some detail: Arrivals corridor: an example where electroacoustic design is a simple issue. BA International Lounge: an example of solutions sensitive to practical loudspeaker locations. BA Check-In-Hall: an example of solutions in voluminous spaces. Arrivals Corridor Dimensions: 120m long x 10m wide x 2.4m high Finishes: Carpet (hard-wearing), perforated ceiling tiles, seating. This corridor is an example of the kind of spaces where the elctroacoustic design is typically a simple issue. This kind of space can be characterised as follows:- room height < 5 m; RT1 = 1s or less; loudspeaker layouts have sufficient architectural scope to allow efficient coverage of listener areas only; background noise not > 75 dB(A) for periods of 30s or more. Note that any distraction from the ideal conditions may require a lower RT to achieve the required intelligibility. Such conditions might include: loudspeakers not evenly spaced for consistent direct sound level loudspeakers not directed squarely onto listener plane unusual room proportions high noise levels, eg signal-to-noise ratio less than 15 dB, noise levels typically greater than 70 dB(A); rooms with significant inter-connection/coupling to adjacent spaces. Ceiling loudspeakers (100mm cone diameter) were spaced every 4.5m. The resulting speech intelligibility was rated at 0.65 STI (as measured by the RASI method, S:N>25 dB). BA International Lounge Figure 4. Dimensions: Main room – 30m diameter, 4.5m high. Rotunda – 19m diameter, 10m high, see Figure 4. Finishes: Carpet (hard wearing), perforated ceiling tiles (at 4.5m only), seating This room required special attention to the electroacoustic design, partly because of its size, but mainly because of the preference against placing loudspeakers in the high level ceiling of the rotunda. The rotunda is too wide to serve with ceiling loudspeakers at the circumference, and ceiling or cabinet loudspeakers overhead in the rotunda could not be easily accommodated. The main design questions were: Could a lateral solution work, using the structural columns on the circumference of the rotunda? Would the requirements for acoustic control be practicably achievable, particularly compared to an overhead solution? Two outline loudspeaker designs were assessed in terms of the longest RT that would be acceptable and compatible with the speech intelligibility criteria (Figure 4). In this space, the design was set at STI 0.45, to be achieved at 15 dB S:N. Analysis showed that the two solutions required a similar RT (lateral: 1.6s, overhead: 1.5s). As the difference was small, the lateral (and preferred) solution was specified. Four pairs of medium length (4 drivers) column loudspeakers were placed on each of the four structural columns. The mid-frequency RT measured in the space was 1.5s, with 1.45s at 2 kHz. The measured STI range was 0.51 - 0.58 with a S:N ratio greater than 25 dB and 0.48 – 0.53 with a S:N ratio fixed at 15 dB in the RASTI meter. BA Check-In Hall Figure 5. Dimensions 50m long x 13.5 wide (main space) x 12m high, overall width 23.5m, see Figures 5 & 6. Finishes: Terrazzo floor, perforated ceiling tiles This space is the largest in the whole of the Terminal One extension. It required special attention to the electroacoustic design because of the practical limits on RT control for such a large volume. Any additional areas of absorption required would constitute significant cost and architectural integration issues. The main design questions were: How much acoustic absorption would be needed? How would the balance between acoustic control and loudspeaker layouts be best struck? Again, two outline loudspeaker designs were assessed: overhead (ceiling) and lateral (Figure 5). The assessments were made in terms of the maximum tolerable RT to achieve the intelligibility criteria, set as 0.45 at 15 dB S:N for this space. The analysis clearly showed that the lateral solution required significantly less acoustic control (2.0s RT) than an overhead solution (1.6s RT). The lower figure of 1.6s for the overhead solution was theoretically achievable, but left little margin for unexpected acoustic effects, which are known to crop up in unusually large spaces. An overhead solution could not therefore be proposed with sufficient confidence in its success. A column loudspeaker solution was specified – units selected were of medium length with 4 drivers. They were located in pairs, spaced at 13m x 13m at a height of 3.5m and angled down at around 15 degrees. The measured (i.e. apparent) RT in this space was discovered to be dependent on the distance between source and receiver. At measurement locations close to the source (i.e. around 10m), the result was 1.6s at mid-frequencies. However, at longer distances, this rose to around 2.0s. To a listener, some loudspeakers would be close and some further away, and so it is not clear which apparent RT would apply to the expected intelligibility of the space. This aspect of electroacoustic design for extra-large spaces would benefit from further research and collection of experiences. In this case, the success of the design is borne by the intelligibility of speech through the system in the space. The measured STI range was 0.49 – 0.74 with a S:N ratio > 25 dB and 0.49 – 0.63 with a S:N ratio fixed at 15 dB in the RASTI meter. The success of the visual integration can be seen from Figure 6. Figure 6. Images and Sounds Further photographs of the building and the installation can be seen at: www.arup.com/acoustics/AAc-_News.htm. Audio recordings of the system performance can also be down loaded from this site. Conclusions Airports have much in common with most public buildings, except for matters of scale and complexity. An understanding of how an airport operates helps break down the complexity. Airport PA/VA systems will require unusually high numbers of inputs and outputs, and so some rationalisation of loudspeaker zones may be desirable to avoid over-complication. Often, the majority of spaces within an airport can be applied with a characteristic electroacoustic solution. These spaces can be quickly identified on inspection of the plans and sections. Acoustically difficult and architecturally featured spaces need identifying, for special electroacoustic consideration. The implications of a loudspeaker design on the room acoustic design must be fully considered, to ensure an overall solution. Speech intelligibility modelling methods have shown sufficient precision to influence good design decisions and have given confidence in the specified designs that has been borne out in a successful solution. Extremely large spaces still hold some design challenges, and if further precision is needed, these are spaces that warrant principle research efforts. Reference (1) Davis & Davis, Sound System Engineering, second edition); Paul Malpas MIOA is with Arup Acoustics, St. Giles Hall, Pound Hill, Cambridge. Glossary of Airport Terminology Landside/Airside Outgoing passengers have 'gone airside' once they have passed through outbound security. Incoming passengers have 'gone landside' once they have passed through customs. The Landside/Airside boundary has international significance and has relevance in the layout of the building and the design of the PA/VA. Landside Concourse Area where passengers and well-wishers can spend time before the passengers go airside. Also known as public concourse. Airside Concourse Lounge for use by all passengers awaiting flights, usually opening onto duty-free shopping, food courts etc. Also known as the Retail Hall. Uncleared Passengers Passengers who have landed but have not yet been cleared through in-bound control. Airbridge The covered walkway to the aircraft. The far end is manoeuvrable by an operator to get a position on the aircraft. SAT Stand Access Tower, the fixed part of the access to the aircraft, usually including stairs between arrivals and departures levels, and security controlled doors. May also provide access to the Apron. Apron The airside exterior of the terminal building. Passengers may cross the apron to board an aircraft via a stairway. CIP Commercially Important Persons Pier An extension of the terminal that comprises arrivals and departures corridors (usually stacked above each other), gate desks and corresponding stand access. Flexible Pier A pier that can be configured for use as either a domestic pier or an international pier, by the careful arrangement of doors and secure routes. Opening and/or closing of a small number of doors linked to the security system is all that is usually needed to switch uses.

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