Though this example focuses solely

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Measuring the impact
Articulation Index (AI) tests conducted between two workstations illustrate the importance of keeping tolerance as low as possible and consistently meeting the specified sound masking curve throughout the facility.

In this example, two occupants sit approximately 4.7 m (15.5 ft) apart within an open plan. The partitions are 1.6 m (64 in.) in height and the ceiling tile is highly absorptive (Figure 1). However, without sound masking, the ambient level is only 40.6 dBA, and the listener can understand 85 percent of the other person’s conversation. When masking is applied, comprehension quickly declines. In fact, for each decibel of increase in masking volume, comprehension drops by an average of 10 percent. With the masking rcs data set to 48 dBA (i.e. the typical maximum level for comfort) with a narrow tolerance of ±0.5 dBA, the listener can understand just 14 to 25 percent. When a broader tolerance of ±2 dBA is applied, he or she can understand up to 59 percent—barely an improvement over the unmasked conditions (Figure 2).

on volume, variations in frequencies can similarly impact masking performance.

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Figure 2: Though a small amount of deviation is avoidable, the AI tests show too broad a tolerance (e.g. ±2 dBA) represents more than a 40 percent drop in sound masking performance. A tight tolerance of ±0.5 dBA ensures the masking effect is consistently experienced across the space.

Architectural evolution
The importance of spatial uniformity (i.e. achieving tight tuning tolerances throughout the space) is also emphasized by the evolution of sound masking architecture. Since the technology was first introduced in the 1960s, numerous advancements have been made in order to make tuning a more precise and efficient exercise.