Indirect systems, the more traditional and often cheaper approach, involve placing an array of speakers above the ceiling and aiming them at the deck at a particular angle. However, with overhead spaces as crammed as they are in modern facilities with cables, piping, ductwork and structure, indirect systems are often ruled out except, perhaps, for less congested areas of the hospital. A newer approach is direct sound masking, which uses a larger number of speaker devices set in the ceiling tiles themselves. This provides a more uniform level of background sounds in the spaces served, but requires the architect to coordinate ceiling speakers with other fixtures such as sprinkler heads, enunciators, lighting fixtures, and Wi-Fi antennas to avoid a cluttered look to the ceiling. The esthetic considerations here deserve a little more time in figuring out.
There are about 30 system choices available. Their design and performance can be evaluated using the ASTM E1130 Standard Test Method for Objective Measurement of Speech Privacy in Open Offices using Articulation Index. This standard provides hospitals the means for evaluating and documenting speech privacy conditions in open-plan areas. This documentation is useful in responding to JCAHO inspections questioning the adequacy of aural privacy in healthcare open-plan areas.
Dennis Paoletti, FASA, FAIA
Principal, Shen Milsom Wilke LLC, San Francisco
In which specific locations within a hospital are sound masking systems most commonly specified and for what purpose?
Any location that requires speech privacy is a candidate for sound masking, which helps to stabilize the background sound level in a space that is too quiet. Ironically, many spaces have become too quiet as a result of energy-efficient HVAC systems that slow down or turn off, and do not deliver air at sufficient velocity to generate background sound levels consistent with recommended noise criteria.
Potential spaces requiring sound masking may include: enclosed offices, open plan offices, and possibly patient rooms and conference rooms.
What are the pros and cons of different locations for sound masking systems?
Historically, sound masking loudspeakers have been located in a plenum space above a sound-absorbing ceiling. Other potential locations–for example, below a raised floor or exposed–are possible, but more challenging and can impact performance and cost in that the installation may require more loudspeakers, closer spacing, and special enclosures.
With regards to HIPAA compliance, how do you understand and interpret the requirement for “reasonable safeguards” to ensure speech privacy?
The original HIPAA authors were not aware that acoustical consultants could calculate and determine levels of speech privacy; hence, “reasonable safeguards” were introduced, which allowed for subjective, general conditions … whatever that may be. This included establishing “practical” methods, such as keeping specific/variable distances from those having conversations.
Because expensive real estate limits these distances, and most individuals do not understand the importance of background sound levels, achieving speech privacy cannot be ensured.
What type of noise do sound masking systems most commonly put out?