Combining Perceptual Metrics

Consumer Survey

We conducted an online survey of earplug consumers to determine the relative importance of three dimensions: target loudness reduction, sound quality, and own-voice occlusion.

55 respondents were recruited using the comments section of HearingTracker YouTube videos evaluating earplugs. The survey used a constant-sum task in which users assigned relative importances that summed to 100.

Table 1. Relative importances of perceptual dimensions. Values reflect average (s.d.) importance rankings across 55 earplug consumers.

Dimension	Rated Importance
The loudness of my environment is quieter when wearing earplugs	47.8 (19.9)
The tone of my environment sounds natural when wearing earplugs	37.1 (16.8)
The sound of my own voice is not boomy when wearing earplugs	15.1 (11.9)

Loudness reduction was rated as most important, closely followed by sound quality, and occlusion was a distant third. Due to its low rated importance and measurement complexity, we decided to omit occlusion for this generation of evaluation.

SoundScore Computation

The average rated importances were used as weights to create the combined metric:

Component	Weight
Loudness Reduction	0.56
Sound Quality	0.44

\text{SoundScore} = \frac{(w_{\text{loud}} \cdot s_{\text{loud}} + w_{\text{qual}} \cdot s_{\text{qual}})}{\text{max observed}} \times 5

The resulting score is the earplug's SoundScore on a scale from 0 to 5 where 5 is best.

SoundGrade and Expert Choice Award

SoundGrade

We further simplify the SoundScore to a letter-grade SoundGrade. Letter grades are both easier to understand and more aligned with our intent to focus consumers on large differences between devices rather than small ones.

Table 2. SoundScore to SoundGrade mapping.

SoundScore	SoundGrade
4.0--5.0	A
3.0--3.9	B
2.0--2.9	C
1.0--1.9	D
0.0--0.9	F

For earplugs that allow for multiple levels of attenuation, the device's overall SoundScore and SoundGrade are the maximum value as measured across all practical levels.

Expert Choice Award

Any earplug that achieves a SoundGrade of "A" wins the HearAdvisor Expert Choice award. This award recognizes earplugs that achieve a best-in-class balance between loudness reduction and sound quality.