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151 A p p e n d i x G This appendix provides guidance on key elements within the PA system specification that relate to speech intelligibility. Design Components 1. Terminal buildings. The terminals are classed as an assembly occupancy and shall meet the requirements of the IBC, the International Fire Code and the National Fire Alarm and Signaling Code (NFPA 72), as adopted by the Authority. The following are identified as functional areas in the terminals: a. Gate hold areas b. Concourse c. Ticket halls d. Baggage claim e. Back of house 2. Airport operations center. 3. Emergency operations center. 4. Nonterminal buildings. 5. Evacuation/mass notification/public address (EVAC/MN/PA) system includes: a. Announcement control system hardware in terminal main communications rooms and airport operations center b. Backup, or lifeline, announcement control system hardware in secondary terminal main communications rooms c. Message servers in specified terminal main communications rooms d. Digital amplifier mainframes and amplifier cards in terminal communications rooms e. Ambient noise collectors in specified communications rooms f. Ambient noise sensors and associated wiring in loudspeaker zones g. Loudspeakers and associated wiring in PA h. Microphone stations and associated data cabling i. Rack-mounted microphone stations in specified communications rooms j. PA system vendor software k. Flight announcement system and courtesy announcement system software l. Other work and accessories required for a complete and operational system 6. The EVAC/MN/PA system collects, manages, and distributes high-quality audible informa- tion to specific areas throughout the terminal buildings. The system has been specifically designed to intelligibly reproduce live, prerecorded, or assembled voice messages. The system is a fully network-based digital system and analyzes the ambient sound level in specified zones to adjust the distributed sound level in the zone accordingly. Sample PA System Specification Relevant to Speech
152 improving intelligibility of Airport Terminal public Address Systems National Fire Alarm and Signaling Code (NFPA 72) The EVAC/MN/PA system shall be capable of performing Emergency Voice Evacuation announcements and Emergency Mass Notification messages in compliance with NFPA 72 and any changes, additions, or upgrades to the system shall be fully compliant as well. Programming All hardware and software requirements for EVAC/MN/PA system functionality shall be coor- dinated with the Authority. This includes, but is not limited to, network connectivity, paging priorities, digital message assembly, system access, microphone paging, and paging station button functionality and screens. Digital Message Distribution Operation 1. Each message processed by the EVAC/MN/PA system must be intelligible at destination areas. 2. Messages must be coordinated such that dissimilar messages will not be distributed within an area at any given time. No message shall be lost because of coordination or priority pre- emption unless such message is no longer timely. 3. Any background music distributed over the EVAC/MN/PA system must be muted for all page messages within the area affected by the page messages. Background music should be muted during the night. 4. Priority is assigned such that the emergency paging function immediately cancels all other audio announcements or messages in the affected zones. Local paging functions have a higher priority than background music and recorded messages in the local paging zone. Recorded messages override background music in all zones. Digital Message Assembly 1. Standard or repetitive messages are studio-recorded voices assembled from digital audio files stored in the system audio library. Assembled messages form complete phrases capable of distribution without real-time operator input. 2. The EVAC/MN/PA system can record, store, and play back permanent messages. Message âtakesâ are stored in nonvolatile memory. 3. Two types of permanent messages are provided: Standard messages and Assembled messages. 4. Standard messages include: a. Public service announcements b. Regulatory announcements c. Other institutional messages required by the Authority 5. Standard messages are assignable to any zone or zones. 6. Assembled messages include: a. Flight boarding announcements b. Flight arrival and bag claim announcements c. Gate change announcements d. Delayed flight or cancelled flight announcements 7. Digital audio library: The digital message files shall contain CD-quality (minimum 44.1 kHz 16 bit), fixed and variable digitized message files that can be prepared by a professional announcer and supplied and arranged in data tables as follows: â¢ Bag claim lookup table â¢ Gate hold room lookup table â¢ Fixed message table
Sample pA System Specification Relevant to Speech 153 Fixed message files may also be standalone non-assembled messages such as security messages and parking warnings. Performance Requirements Audio Specifications â¢ Frequency response Â±0.5 dB at 20 Hz to 20 kHz. â¢ Test: Measure the electrical power output of each power amplifier at normal gain setting at 50; 1,000; and 12,000 Hz. The maximum variation in power output at these frequencies must not exceed Â±0.5 dB. â¢ Total harmonic distortion (THD) <.05 percent at rated amplifier output 20 Hz to 20 kHz. â¢ Distortion test: Measure distortion at normal gain settings and rated power. Feed signals at frequencies of 50; 200; 400; 1,000; 3,000; 8,000; and 12,000 Hz into each preamp channel and measure the distortion in the power amplifier output. The maximum distortion at any frequency is 3 percent total harmonics. â¢ Noise referenced to input -120 dBu 20 Hz to 20 kHz. â¢ Signal-to-noise ratio (SNR) >90 dB. â¢ Maximum latencyâ11.9 milliseconds from communications station to power amplifiers through three network switches. System Equalization The system shall provide for frequency response equalization for each loudspeaker zone out- put. Filter types shall allow notch, high pass, or low pass. Filters shall have a Q range of 0.055 to 33. Provide nine filters for each zone output. Ambient Noise Analysis and Control The systems shall include the capability to automatically adjust the volume levels in each zone, based on changes in the ambient noise levels in those zones. 1. Each zone that includes a sensor within its boundaries shall have automatic control. 2. The system shall automatically null announcement or program material for that zone to prevent ârun-awayâ or inaccurate volume tracking and shall provide smooth unobtrusive control. 3. Software shall allow for set up of the following parameters: â¢ Automatic, slaved to an automatic channel, or fixed modes â¢ Configuration of one to four sensors for control of a zone and control of multiple zones from one or more grouped sensors â¢ Control of threshold, maximum gain allowed and scaling ratio. 4. Software shall provide for â¢ Real-time monitoring of sensor levels â¢ Program levels â¢ Output levels â¢ Gain changes. 5. System shall provide for automatic setup of zones using the integrated system messaging. System Design Requirements General â¢ All installations must be coordinated with the appropriate department of the Authority. â¢ The EVAC/MN/PA system design and all modifications shall comply with all requirements of the State and Authority.
154 improving intelligibility of Airport Terminal public Address Systems â¢ The EVAC/MN/PA system shall comply with the requirements of the National Fire Alarm and Signaling Code (NFPA 72), the Authorityâs Inspection Authorities, and the Manufacturerâs instructions. â¢ Audio modeling using an approved simulation software is required to predict the intelligibil- ity of the space, based on architectural features and materials interacting with loudspeakers and their placement. Loudspeaker Design Requirements â¢ Each physical loudspeaker/amplifier zone shall consist of a discrete contiguous space with a common function (e.g., each gate hold room, concourse circulation adjacent to each gate hold room, airline ticketing lobby, baggage claim area, security checkpoint, concessions, and operations office). Areas with different functions shall not be combined in the same physical loudspeaker/amplifier zone. â¢ The loudspeakers for each loudspeaker/amplifier circuit shall be consistent within the circuit. â¢ Loudspeaker spacing shall be based on ceiling heights and ceiling materials and the type of space the zone encompasses. Loudspeakers shall be tapped and balanced with amplifier settings so that announcements are intelligible. â¢ Each physical loudspeaker/amplifier zone that will have varying amounts of ambient noise shall have at least one ambient noise sensor, and zones shall be evaluated for more than one ambient noise sensor based on size. Ambient noise sensors shall be mounted such that they are closer to sources of ambient noise than to EVAC/MN/PA system loudspeakers. Acceptance Testing/Commissioning Operational Test Perform an operational system test to verify conformance of the system to the Specifications. Perform tests that include originating program material distribution; page material distribution; message distribution coordination; zone distribution selection; message assembly; system super- visory, alarm, and monitoring functions; ambient noise control functionality; and paging opera- tor workstation features. Observe sound reproduction for proper volume levels and freedom from noise. All zones affected by the project shall be included in the test. Intelligibility Test Perform intelligibility tests in compliance with NFPA 72 Chapters 18 and 24 and the require- ments of this Facility. Acoustic Coverage Test Feed pink noise into the system using octaves centered at 4,000 and 500 Hz. Use a sound level meter, with octave band filters, to measure the level at approximately 40-foot spacing intervals in each zone. For spaces with seated audiences, the maximum permissible variation in level is Â±2 dB and the levels between locations in the same zone and between locations in adjacent zones must not vary more than Â±3 dB. The documentation of tests, measurements, and adjustments performed shall include a list of personnel and the list of certified test equipment used and shall be in compliance with NFPA 72. All information recorded from all testing shall be shown on the as-built documents.