Vertical and Adjacent Crosstalk of Induction Loop Systems in NUS COM4

The NUS School of Computing is proud to introduce their new facility, the 5-storey COM4 building, where student of NUS’ School of Computing can utilise for various uses from discussions, to learning and teaching labs. The School of Computing has decided to cater their facility to be as inclusive as possible which has accessibility, including Hearing Enhancement Systems to be implement within the rooms throughout the building.


Hearing Enhancement Systems or Induction loop systems have become an integral part of ensuring accessibility and inclusivity for individuals with hearing impairments. These systems use magnetic fields to transmit sound directly to hearing aids or cochlear implants, enabling users to hear clearly in public spaces, such as theatres, lecture halls, and conference rooms. However, to ensure optimal performance, it is crucial to understand two important concepts related to induction loop systems: vertical and adjacent crosstalk or Overspill. In this article, we will delve into these concepts and explore their significance in creating a seamless listening experience for all.


What is Vertical Overspill?


Vertical overspill refers to the dispersion of the magnetic field generated by an induction loop system above and below the intended coverage area. It occurs when the magnetic field extends beyond the desired boundaries, leading to signal leakage and potential interference with other induction loop systems that are located above and below. Vertical overspill can cause problems in multi-story buildings or venues with multiple floors or rooms situated above and below each other. To mitigate vertical overspill, the installation of induction loop systems should involve careful consideration of the venue's structure and acoustics and in this case, the induction loops can be found above the false ceiling.


Factors affecting Vertical Overspill


Factors such as the height of the loop, the presence of metal structures or obstacles, and the layout of adjacent rooms or floors can impact the extent of vertical overspill. By using appropriate loop designs, like a low spill multiloop, it is possible to limit the magnetic field's vertical dispersion, focusing the signal within the desired listening area and minimizing interference with other spaces.


Challenges in installing Induction Loops in Ceilings


The standard location in installing Induction Loops would be either on or in the floor. However, there are special circumstances in which resorting to installations of induction loops in the ceilings would be a requirement to overcome the vertical overspilling of signals between rooms that are above and below each other.


The challenges faced when installing of ceiling loops are;

  1. Height of ceiling – during installation and future troubleshooting if required, the induction loops will be at heights of at least 2.5 meters which requires ladder access.
  2. Access and Space Constraints – Dependent on the overall height of the room, access to ceilings would require the usage of ladders and following that, when working with false ceilings, the presence of the aluminum grids reduce the accessibility and space that installers have.
  3. Material of Ceiling – metal grids of false ceilings can have an impact to the overall performance of the induction loop due to Metal Loss, hence proper planning is required for an effective effect.
  4. Presence of other services in ceilings – other services will also be housed in the space above the false ceiling, hence, proper coordination between contractors is crucial to ensure that there is sufficient space to install the induction loop systems.


Achieving IEC 60188-4 Compliance for Induction Loops in Ceilings


In NUS COM4’s context, the induction loops are installed at 3.3 meters from the floor which is quite a distance that requires a higher rating loop driver to be able to generate the signal down to the listening height which is at seated position. On top of that, the performance of the induction loop is further hindered by Metal Loss that is due to the aluminium grids that hold up the ceiling boards.


To overcome these challenges, the highest rated amplifiers were proposed to check the requirements to comply to the IEC 60118-4 standards for induction loops that were installed in the ceilings.


What is Adjacent Overspill?


Adjacent overspill refers to the spreading of the magnetic field beyond the intended coverage area horizontally. It occurs when the magnetic field extends into neighbouring areas, potentially causing overlapping signals and reducing clarity. Adjacent overspill is particularly relevant in environments where multiple induction loop systems are installed side by side or in close proximity.


To address adjacent overspill, proper planning and design are crucial. The spacing between adjacent induction loop systems should be carefully determined to avoid interference. Additionally, advanced signal processing techniques can be employed to reduce crosstalk and enhance the separation of adjacent systems.


Importance of Minimizing Overspill


Minimizing both vertical and adjacent overspill is vital to ensure a high-quality listening experience for individuals using hearing aids or cochlear implants. Excessive overspill can lead to sound distortion, reduced speech intelligibility, and confusion, thereby defeating the purpose of installing an induction loop system. By understanding and addressing these issues during the system's design and installation phase, venue owners and specialists can maximize the system's effectiveness and provide equal access to audio information for all individuals.




Vertical and adjacent overspill are crucial considerations when implementing induction loop systems. To achieve optimal performance and user satisfaction, it is essential to carefully design and install the system while taking into account factors such as building structure, room layout, and neighbouring systems. By minimizing overspill through appropriate loop design, spacing, and signal processing techniques, venues can provide seamless access to audio information for individuals with hearing impairments, promoting inclusivity and enhancing the overall experience for all attendees.

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