Loudspeaker System Design for Airports: Ensuring Everyone Gets the Message

Air travel, whether for business or leisure, is a big part of most people’s lives. According to the International Civil Aviation Organization, more than four billion passengers travel through airports around the world every year. Airports can vary in size from small landing strips to large international hubs that serve more than 250,000 people in a single day.

Navigating an airport can be stressful and chaotic. Travelers need to clearly and quickly understand where to go and when—in unfamiliar places, and often in unfamiliar languages.

Audio announcements are an effective method of conveying critical and timely information to passengers. Because airports are reverberant, crowded, noisy environments, well-designed loudspeaker systems are paramount to making sure communications run smoothly.

Designing a loudspeaker system for an airport is no simple task. Airports are small cities in their own right, and every airport is unique, with unique design challenges. This overview outlines the most important considerations for building and delivering complete, consistent audio coverage with high speech intelligibility while meeting the unique acoustic and architectural challenges of every space.


To go even more in-depth on this topic, including a sample airport project outlining key airport applications and loudspeaker solutions, check out our JBL Loudspeaker System Design Webinar and Design Guide.


Coming in Loud and Clear
For a message to be effective, it must be clear and easy to understand. Airports are often large, open structures with highly reflective surfaces, including glass walls and hard, polished floors. These cavernous spaces are conducive to both high noise levels and long reverberation times, which pose significant challenges to sound system designers.

Factors that influence speech intelligibility include:

  • Clarity of the original signal
  • Direct-to-reverberant ratio (D/R)
  • Signal-to-noise ratio (S/N)
  • Signal path bandwidth
  • Sound pressure levels and system distortion

Let’s take a closer look at the direct-to-reverberant ratio, which is a function of the interaction of a loudspeaker and its environment.

When a loudspeaker transmits sound into a space, the sound that arrives straight from the speaker to the listener’s ear is called direct sound. As sound travels in an enclosed space, it reflects off boundaries such as ceilings, windows, hard furniture and floor tiles. This sound that bounces around the space and arrives back at the listener’s ear is reverberant sound, or reverberation. Providing clear messages means optimizing the space’s direct-to-reverberant ratio—maximizing direct sound and minimizing the number of reflections.

Another critical consideration: Can the PA system provide adequate sound pressure level to ensure the announcement overcomes the background noise in the environment? For airports, an ideal signal-to-noise ratio target is in the 12-15 dB range.

 

Optimizing the Speech Transmission Index
The Speech Transmission Index is an objective intelligibility measurement that describes how comprehensible speech will be in given conditions.

Learn more about the STI Index in our ‘Loudspeaker System Design for Airports’ design guide.

STI—measured from 0 to 1—takes into account the effects of both reverberation and background noise. STI values between 0.44 and 0.6 represent fair or average intelligibility; values above 0.6 represent good speech intelligibility, and values above 0.76 are considered excellent. Values below 0.44 represent poor speech intelligibility, and values below .36 are unacceptable.

When designing a PA system, it’s important to ensure that STI values meet the specifications required for a given project, as well as standards defined by local ordinances. In most cases, an STI value of 0.5 or greater is required for public spaces like airports. (STI can be measured in the field with a handheld STIPA meter.)

When a loudspeaker transmits sound into a space, the sound that arrives straight from the speaker to the listener’s ear is called direct sound.

It’s important to remember that many airport visitors hear announcements in their second or third language. Research has shown that for messaging to be effective, STIs need to be higher when addressing non-native listeners than native listeners.

 

Methods for improving STI include:

  • Adding acoustic absorption: Interior design that integrates soft, absorptive materials can help reduce reverberation. Unfortunately, the sound system designer doesn’t often have control over this process.
  • Focusing coverage with directional loudspeakers: Speakers with narrow dispersion patterns can improve STI by directing sound away from reflective surfaces to reduce reverberation.
  • Orienting loudspeakers close to listeners: Reducing the distance from the speaker to the listener maximizes direct sound and minimizes reflected sound.
  • Maximizing the quality of the original signal: To take full advantage of good room acoustics, a well-designed sound system, and low background noise, announcements must be of high quality. Training airport announcers on proper microphone technique can dramatically improve the intelligibility of live announcements.

The JBL Control 16C/T Two-Way 6.5″ Coaxial Ceiling Loudspeaker is an ideal ceiling speaker for airport installations.

CHOOSING LOUDSPEAKERS
When designing a PA system for an airport, it’s important to start with a clear understanding of the project and sound reinforcement objectives. To choose the right loudspeakers for each application, consider the following factors:

  • The system must meet required specifications, including:
    • SPL requirements
    • Frequency response
    • Directivity
    • Coverage
    • Signal-to-noise ratio
    • STI requirements
  • The system must meet applicable local standards and codes. For example:
    • If the PA system also needs to function as an emergency voice alarm system, additional standards and codes of practice may apply.
    • Standards may vary from country to country—always consult local standards and codes before designing the system.
  • It’s important to understand the architecture of the space and to know which solutions will be acceptable to the architect, interior designer, and other airport stakeholders. Considerations include:
    • Which types of loudspeakers will be the most effective?
    • Which speakers will match the look and feel of the space?

At King Abdulaziz International Airport (KAIA) in Jeddah, Saudia Arabia, pictured and noted are several JBL Pendant Speakers, ensuring the utmost announcement clarity throughout the terminal.

JBL Airport Loudspeaker System Solutions
JBL offers a wide range of speakers and software tools that can be used to design system solutions for various applications, ceiling heights, architectural styles, and room acoustics. Common speakers for airports include:

  • Pendant loudspeakers: Ideal for areas with ceilings that are too high for ceiling speakers to be effective.
  • Ceiling loudspeakers: A great choice for terminal pier applications, these speakers integrate unobtrusively into ceilings and provide excellent consistent coverage when properly distributed.
  • Column loudspeakers: These tall, slender speakers provide throw and directivity while blending into the architecture of the space. JBL Intellivox active and passive directivity-controlled column arrays and CBT passive directivity controlled systems give designers a wide palette of tools to cover every application and space.
  • Surface-mounted loudspeakers: These are ideal for retail, restaurants, infills, and other targeted solutions.
  • Outdoor-rated loudspeakers: Rugged, IP-rated loudspeakers are well-suited for all-weather applications, including curbside and transit areas.

Optimizing System Design and Prediction With JBL DDA Software
JBL’s DDA (Digital Directivity Analysis) software is a powerful, intuitive Windows application for accurately predicting the acoustic performance of loudspeaker systems in open or closed spaces. Using DDA, the radiation pattern of JBL Intellivox loudspeaker arrays can be controlled and tailored to the shape and the acoustics of the space.

Other design features include 3D acoustic room modeling, direct sound simulation, and statistical prediction of acoustic parameters. DDA also generates FIR output filters, which can be uploaded to supported DDS-controlled loudspeaker arrays using JBL WinControl software.

Take a Deeper Dive
Want to explore loudspeaker system design for airports even further? Download our free Design Guide or view our Video Webinar to discover more products and tips and walk through a sample project that demonstrates the design process for a typical large airport.

courtesy: aucklandairport.co.nz

Real-World Airport System Design Case Studies

  • Van Don International Airport, Vietnam“We decided to use HARMAN’s audio equipment to provide superb speech intelligibility and audio coverage at the airport. We set up JBL open-back ceiling speakers coupled with pattern control speakers to deliver maximum clarity across the airport.”
  • Auckland International Airport, New Zealand“Waddell used EASE AURA acoustic modeling software to determine that only two JBL DC280 loudspeakers would be needed to provide clear, intelligible coverage of the new baggage claim area.”
  • Explore our complete library of JBL Transportation and Tunnel case studies.

INTERESTED IN TALKING FURTHER? WE’RE HERE TO HELP
Ready to kick off your airport AV or other installation? Contact your local JBL application engineer or HARMAN representative for detailed product information, advice and support and if you’re not sure where to start, no problem, just submit this form and we’ll have someone email you to answer your questions and help you get going.

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