Mike Raley – mike.raley@ecoreintl.com
Ecore International
715 Fountain Avenue
Lancaster, PA 17601
Popular version of paper 1aAAa2
Presented Monday morning, December 7, 2020
179th ASA Meeting, Acoustics Virtually Everywhere
Hospitals are noisy places. The Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) surveys patients’ perception of their hospital care. Consistently, the quietness of the hospital is one of the lowest scores in the survey. If you have ever spent time in a hospital, that is likely no surprise.
What might be surprising is that a recent study by Bliefnick et al. showed that the acoustic metrics we typically use to evaluate noise in hospitals are not well-correlated with HCAHPS scores. Interestingly, they found that peak occurrence rates, how often a loud sound was above a certain threshold, were well-correlated with HCAHPS scores. In another recent study, Park et al. found that footsteps were a top five contributor to perceived loudness peaks, noise events that are significantly louder than the sound level before and after the event. Along with anecdotal evidence from healthcare designers, these two studies indicate that footsteps could contribute to a patient’s perception of quietness, and reducing noise from footsteps could improve that patient experience.
Test standard ASTM E3133 measures floor impact sound radiation in the space where the impact occurs. This differs from the common impact insulation class (IIC) standard (ASTM E492) that measures impact sound in the room below where the impacts occur.
Using ASTM E3133 we can compare floor impact sound levels for flooring common to hospitals, such as VCT and standard sheet vinyl, as well as specialty acoustical flooring like sheet vinyl fusion bonded to a rubber backing (Vinyl Rx).
Figure 2 shows that the Vinyl Rx can significantly reduce floor impact radiated sound, with a 13dB reduction in the overall sound level compared to VCT (a ~60% reduction in perceived loudness). The significant reduction in impact sound levels gives us an exciting indicator that specialty acoustical flooring has the potential to reduce predicted loudness peaks and improve the patient experience.
Unfortunately, there are some issues with the ASTM test method that limit its usefulness. In the course of testing to ASTM E3133, we uncovered substantial variation in the sound levels measured using two standard tapping machines from different manufacturers. The variation in tapping machines is evident even on a loud floor like concrete (see Figure 3).
The standard has provisions to account for the self-noise of the tapping machine, but those provisions do not correct the discrepancy between the two machines. Further investigation has shown that different flooring actually changes the self-noise of the tapping machine, so it cannot be easily accounted for.
While it may be possible to modify tapping machines to address the variation in self-noise, the most likely solution to the problem is a different impact source. Impact sources like golf balls, cue balls, and ball bearings can create consistent impacts without the self-noise issues of standard tapping machines. These objects are also readily available and easily transportable, so they lend themselves well to field measurements.