Tuning a sound masking system

Tuning sets each sound masking zone to a target level and shapes its sound to a target spectrum, then checks with measurements across the zone that the result is even. It is the step that decides whether a masking system works and goes unnoticed, or is either useless or annoying, and it is the step most often rushed.

Why tuning matters

A masking controller produces a signal, but what reaches a listener's ear depends on the room: the depth of the ceiling plenum, the ceiling tiles, ductwork and lights in the way, furniture, carpet and glass. Two zones with identical equipment and settings will sound different. Tuning measures what is actually arriving in each zone and adjusts the system until it matches the design target.

The target has two parts. The overall level decides how much the background is raised. The spectrum, meaning how that sound is spread across low, middle and high frequencies, decides whether the sound covers speech and whether it sounds comfortable. A system at the right overall level with the wrong spectrum can still sound hissy or boomy and still let speech through. The principles are covered in how sound masking works.

Matching the target spectrum

The design sets a target curve for each zone: a level in each frequency band, usually falling gradually towards the high frequencies. The tuner measures the sound in each band and uses the controller's equaliser to raise or lower individual bands until the measured curve matches the target within the tolerance set in the design.

Before tuning starts

Tuning measures the room as people will use it, so the room has to be finished. If it changes significantly afterwards, the zone needs to be checked again.

• Ceilings complete, with all tiles, lights and diffusers in place.
• Furniture, screens and carpet installed, or as close to final as possible.
• HVAC running in its normal occupied mode, since its sound is part of the background.
• The space quiet of people and construction work, which usually means after hours.
• All speakers connected and working, with wiring checked against the zone plan.
• A calibrated sound level meter with one-third-octave band analysis, checked with its calibrator before and after the session.

The tuning process

Each zone is tuned on its own, starting with the masking off to capture the existing background. The sequence below repeats until the zone is on target.

1. Baseline. With masking off, measure the background at several points. Record the overall level and the spectrum, and note any noisy diffusers, equipment or lights. This shows how much masking the zone needs and where the HVAC is already doing some of the work.
2. Set the level. Turn the zone on and adjust its level until the measured overall level at a central reference point is close to the target.
3. Equalise. Measure the spectrum and adjust each band on the equaliser until the curve follows the target. Recheck the overall level, since equalising changes it.
4. Measure the grid. Measure at a grid of points across the zone at seated ear height, including points directly under speakers and between them. Record each reading.
5. Check evenness. Compare the readings. A wide spread means some areas have less privacy than others and people will notice the sound changing as they move. Find the cause before adjusting further.
6. Record and hand over. Save the controller settings and the measurement sheet, then start the ramp-up schedule.

Spaces that need extra care

Some areas rarely tune well on the first pass. Private offices are small, so a single speaker dominates and the reading depends heavily on where the meter stands; many designs leave offices lightly masked and put the effort into the corridor outside. Reception and waiting areas often have high ceilings, glass and hard floors, which colour the spectrum. Areas next to mechanical rooms, kitchens or busy entrances already have a higher background, so the zone level may need to be lower there than elsewhere. Open-ceiling spaces with downward-facing speakers need careful attention to speaker height, because people standing directly under a low speaker will notice it. Where paging shares the speakers, set the paging level separately after the masking is tuned and check that announcements are clear over the masking.

Checking evenness

Evenness is checked on plan. The tuner marks measurement points between and under speakers, then looks at the readings together rather than one at a time.

An outlier is a clue, not something to average away. A reading well above the rest may sit next to a noisy diffuser or a speaker installed facing the wrong way; a reading well below may be under a duct that blocks the speaker, or in an area where a speaker is not connected. Fix the cause, then remeasure.

Common complaints and their causes

Ramp-up and later changes

Most systems are brought up to their tuned level over a few weeks so occupants adjust without noticing. The schedule then reduces the level outside working hours. After that, the zone should be checked again whenever the space changes: new walls, a changed ceiling, a reconfigured furniture layout or a significant HVAC change. A short check against the original measurements is usually enough to tell whether retuning is needed. If privacy complaints persist after tuning, look at construction and layout before touching the level; our guide on speech privacy in open offices explains why.

What the tuning record should include

• A plan of each zone with speakers and numbered measurement points.
• The baseline readings with masking off.
• The target level and spectrum for each zone.
• Final readings at every point, overall and by frequency band.
• Controller settings: zone levels, equaliser settings, schedules and paging levels.
• Meter model, calibration check results and the date and conditions of the measurements.
• Any issues found and how they were resolved.

Treat it like the balancing report for an HVAC system, a record of how the system was set and why. Our guide to testing, adjusting and balancing describes the same discipline for air and water.

How ehZee can help

We tune new and existing masking systems zone by zone, investigate complaints with measurements rather than guesswork, and leave a record you can use when the space changes. See our sound masking systems service.

Common questions