Listening height for seated and standing listeners

A telecoil picks up the loop's field where it is: in the listener's hearing aid or implant processor, at head height. The field from a floor loop is not the same at 1.2 m as at 1.7 m, and it can be very different on a raised tier or a balcony. So a loop is planned, and later measured, where listeners' heads will be.

Key points

• Plan and measure at head height. The usual figures are 1.2 m (about 4 ft) for seated listeners and 1.7 m (about 5 ft 7 in) for standing listeners.
• Height changes the field most near the loop wire and in small rooms. In the middle of a large room, seated and standing listeners get nearly the same level.
• Rooms used both ways are checked at both heights, and the weaker or less even result sets the design.
• On tiers and balconies, what counts is the distance from the loop to the head. Keep it even, or give the raised area its own loop.
• With a loop in the ceiling, standing listeners are closer to the wire than seated ones.

Why height matters

A loop's field is strongest near the wire and weakens with distance. Most telecoils pick up the vertical part of the field while the listener's head is upright. Inside a floor loop, that vertical field is fairly even across the middle of the room but changes quickly near the wire: directly above the wire it falls away, and a little way inside it peaks. As a rule of thumb, the strongest band sits roughly one listening height in from the wire.

Raising the listening plane lowers the field, smooths the edge peak and moves the strong band further from the wire. A field map drawn at the wrong height can look better or worse than what a listener actually hears.

Worked example (synthetic): Community Hall, a 10 m × 10 m perimeter loop on the floor, one turn, no metal loss, same current throughout. All worked figures on this page come from a simple model of the wire's field (the Biot-Savart law), and real rooms differ. Field along the center line, in dB relative to the room center at seated height:

At the center, standing listeners get about 0.6 dB less than seated ones; near the wire the gap grows to about 3 dB. Room size matters too. With the same kind of loop, the center drops by about 2.3 dB from seated to standing height in a 4 m × 5 m meeting room, 0.6 dB in the 10 m hall and 0.15 dB in a 20 m × 20 m room. In a small loop the head is far away compared with the loop's size, so height counts for more.

Seated and standing heights

IEC 60118-4 applies its field-strength targets to the space where listeners' heads will be, which it calls the useful magnetic field volume, rather than to a flat area. Measurement points are chosen by where listeners will be and how high their heads are, and the usual heights are 1.2 m for seated and 1.7 m for standing listeners. For the targets themselves, see IEC 60118-4 field strength: 400 mA/m and ±3 dB explained.

• Fixed seating (pews, theater seats, lecture rows): plan at 1.2 m.
• Standing areas (foyers, ticket halls): plan at 1.7 m.
• Mixed use (seated talks one night, a standing reception the next): check both and design to the weaker or less even result. With a floor loop that is usually standing height near the wire.
• Lower listeners, such as young children on small chairs: check a lower plane as well. Closer to a floor loop, the field is stronger and its edge peak sharper.

In Hearing Loop Designer, listening height is a Basic-mode input, with presets for seated (1.2 m), standing (1.7 m) and a lower 0.8 m plane, or a height you set. The heat map, cross-section, 3D view and reports all show the field at that height, so you can switch between seated and standing and see which one sets the design. See the field-strength features.

Tiered seating, stages and balconies

Tiers. On a raked floor each head is still 1.2 m above its own row, but its distance from the loop grows if the loop stays at the lowest level.

Worked example (synthetic): a 12 m × 15 m lecture room, flat for the first 5 m, with risers climbing 1.5 m over the back 10 m. Along the center aisle, at 1.2 m above each row:

• Loop flat on the slab under the risers: about 8 dB between the strongest and weakest seat, with the back row weakest.
• Loop laid on the risers, following the rake: about 4 dB across the same seats.

Following the floor keeps the head-to-loop distance close to constant. Where the route can't follow the floor, split the seating into areas by level and plan each at its own listening plane. The step-by-step design method shows where this fits.

Stages. Decide whether the stage is a listening area. A choir loft in a 300-seat sanctuary may need coverage; if so, plan at the stage floor plus seated or standing height. If not, keep the field off the stage where you can, because instrument pickups and some stage equipment can pick up the loop. That is an overspill question: see Hearing loop overspill.

Balconies. Worked example (synthetic): a 300-seat sanctuary with an 18 m × 24 m main-floor loop and a balcony 6 m deep, its floor 4 m up. Seated balcony listeners are 5.2 m above the main loop, which gives them about −2.4 dB at the front row and −7.6 dB at the back on the center line, relative to the main-floor center at seated height. Side seats are lower still. Treat the balcony as its own listening area, usually with its own loop. That loop's field also reaches the seats underneath, where it overlaps the main loop's. Connect the two loops so their fields add: connected the other way, they can cancel at the balcony. The seats underneath get both fields and can end up too strong, so plan for them and measure them when commissioning. Balconies often hold steel, so allow for metal loss.

Loops in the ceiling or the floor below

Ceiling loops. With the loop overhead, standing heads are closer to the wire. Put Community Hall's loop in a 3 m ceiling and a seated head is 1.8 m below it, a standing head 1.3 m, so standing listeners get slightly more. High ceilings cost level and evenness: in a 6 m ceiling the same loop needs a little over twice the current (about 6.7 dB more) for the same center field at seated height, and seats 0.6 m in from the corners fall about 9 dB below the center. A ceiling loop also sends its field upward, so check what is on the floor above.

The floor below. Fixing the loop to the ceiling of the room below is a common route when the floor finish can't be lifted. Add the slab and void depth to the listening height: with the loop 0.4 m below the finished floor, a seated head is 1.6 m from the wire, which costs about 0.5 dB at the center of Community Hall. The bigger question is the slab itself: reinforcing steel or a steel deck causes metal loss, which weakens the field and the high frequencies most.

Measuring at the right height when commissioning

The design is a prediction; installed performance is confirmed by commissioning. Measure where the design said heads would be:

• Use the design heights, from the floor the listener is on, and both heights where the room is used both ways.
• Hold the probe vertical, as a telecoil sits in an upright head. A stand or marked pole keeps the height consistent across the grid.
• Measure background magnetic noise at the same heights, with the loop off.
• Include the hard positions: seats nearest the wire, the back row of a tier, the balcony and the seats under its edge.
• Write the heights in the commissioning record next to the readings.

More in Commissioning a hearing loop.

Common questions

Is listening height measured from the floor or from the loop?

From the floor the listener is on. The field, though, depends on the distance from the loop to the head, so on tiers, balconies and stages, or with a loop in the ceiling or under the slab, work out that distance as well.

Should a room used for seated and standing events be planned at 1.2 m or 1.7 m?

Both. With a floor loop, standing height usually gives the lower field near the wire, and seated height the bigger edge peak. Plan so both heights reach the targets, then commission at both.

Does a higher listening height mean a bigger driver?

Sometimes. In the middle of a large room, seated and standing differ by a fraction of a dB. In a small room or under a high ceiling, distance costs real level: about 2.3 dB in the 4 m × 5 m example and 6.7 dB in the 6 m ceiling example. More level means more current and more drive voltage. See Sizing a hearing loop driver.