The Bay Area Rapid Transit (BART) is often criticized for its loudness. According to measurements made in 2010, the noise reaches up to 100 decibels, enough to cause permanent hearing loss in the long term. This is why you should always wear earplugs on the BART, which can decrease the volume by up to 30 or so decibels, making it tolerable and harmless.
And while pointing out that BART gets really loud is indeed important, I would claim that there is something even more important to note. Namely, that BART is not merely loud, but it is also distinctly dissonant. Talking only about the stretch that goes from Millbrae to Embarcadero, an analysis I conducted reveals that the single worst period of dissonance happens on the ride from Glen Park to Balboa Park (at around the 20 second mark after one starts). If you are curious to hear it, you can check it out for yourself here. That said, I do not recommend listening to that track on repeat for any length of time, as it may have a strong mood-diminishing effect.
Most analyses of sound quality only deal with loudness, or at most, perceived loudness. But whether a sound is dissonant or not matters a lot too, in terms of how unpleasant (and perhaps how damaging) it is:
Ultimately, dissonance might be much more important than loudness, insofar as it tracks the degree to which environmental sound directly impacts quality of life. Thus, in addition to metrics that track how loud cities are, it might be a good addition to our sound contamination measurements to incorporate a sort of “dissonance index” into our calculations.
Andres goes on to discuss consonance & dissonance in the larger context of our research:
At the Qualia Research Institute we have pointed that the connection between dissonance and valence may not be incidental. In particular, we suggest that it falls out as a possible implication of the Symmetry Theory of Valence (STV). … We believe that Valence Structuralism and in particular the Symmetry Theory of Valence are powerful explanatory frameworks that can tie together a wide range of disparate phenomena concerning good and bad feelings. And if true, then for every unpleasant experience we may have, a reasonable thing to ask might be: in what way is this dissonant? For example: Depression may be a sort of whole-body low-frequency dissonance (similar to, but different in texture, to nausea). Anxiety, on the other hand, along with irritation and anger, might be a manifestation of high-frequency dissonance.
Likewise, whenever a good or pleasant feeling is found, a reasonable question to ask is: in what ways is this consonant? Let’s think about the three kinds of euphoria uncovered in State-Space of Drug Effects. Fast euphoria (stimulants, exercise, anticipation, etc.) might be what high-frequency consonance feels like. Slow euphoria (relaxation, opioids, etc.) might be what low-frequency consonance feels like. And what about spiritual euphoria (what you get by thinking about philosophy, tripping, and taking dissociatives)? Well, however trippy this may sound, it might well be that this is a sort of fractal consonance, in which multiple representations of various spatio-temporal resolutions become interlocked in a pleasant dance (which may, or may not, allow you to process information more efficiently).
Now what about noise? Here is where we place all of the blunting agents. The general explanation for why anti-depressants of the SSRI variety tend to blunt feelings might be because their very mechanism of action is to increase neuronal noise and thus reduce the signal-to-noise ratio. Crying, orgasm, joy, and ragegasms all share the quality of being highly symmetric harmonic states, and SSRIs having a generalized effect of adding noise to one’s neuronal environment would be expected to diminish the intensity (and textural orderliness) of each of these states. We also know that SSRIs are often capable of reducing the subjective intensity of tinnitus (and presumably the awfulness of BART sounds), which makes sense in this framework.
I find this idea– that we can explain the affective profile of any psychoactive drug through an analysis of how it changes a person’s “neuroacoustics“, and specifically how it affects their consonance/dissonance/noise balance — very exciting.