Hearing loop spill explained
Hearing loops create a magnetic field that is fairly consistent within the loop but reduces the further away from the loop you get. Outside of a simple rectangular loop an audible signal as far as 4 times the width of the room away from the loop can be heard, shown in Figure 1 below. This unnecessary or unwanted magnetic field is known as spill or overspill. The field created also emanates vertically by approximately the same distance, as shown in Figure 2. If another loop system is used within this ‘spill’ area the systems will interfere with each other.
Hearing loop spill needs to be considered in many environments where hearing loops are useful, for example in adjacent classrooms and lecture theatres, cinemas or where there is a performance area for electrical instruments.
The solution is usually to use a low spill array, or a cancellation loop. These loop solutions are a little more complex than a simple perimeter loop, but are used widely in theatres, educational establishments, cinemas and conference centres around the world. The dramatic improvement in performance can be seen in Figure 3 below.
Spill control is especially important to prevent the magnetic field generated by the loop from causing interference to electric guitars, dynamic microphones and some other electrical equipment. If your venue includes a performance stage or is used for live music, spill control will be required to isolate an area by using either a cancellation loop or Low Spill MultiLoop™ design.
Ampetronic was the first company to develop array systems and continues to lead the industry in design of array systems for a wide range of environments. Our highly skilled and experienced Support team use our proprietary design and analysis tools to produce installation drawings tailored for your application to ensure that spill is not an issue for you and your loop systems.
Fig.1 – Perimeter loop
Fig.2 – Perimeter loop vertical plot
Fig.3 – Ultra-low spill array
Fig.5 – Cancellation loop