If you couple the psychological real effect in increasing sensitivity to sound at night with a more silent environment and generally no house heavy appliances working passed some late hours, less electrical disturbance in the neighborhood it does not need a Darpa research to feel a better acoustic experience in part resulting from decrease in the noise floor and more auditory sense relaxation ...😋
When i was doing my critical set of acoustics experiments for more than one year straight each day i waited in the evening late to verify the results and confirmed them or not,...Day listenings was not enough reliable...
By the way we do not remember sound details quality in a conscious way pass a very very short time. But my body remember it and remind it of some improvement or the opposite in the form of feelings when listenings...To experience this we must be totally relax with music we know completely well.. ..if it was not true i would have been unable to tune 100 resonators by ears mechanically . ( it was an acoustic puzzle because location matter)
By the way i never planned to do that, i make it one by one set of three without even knowing that it was a planned experiment at all i only go behind each small improvement and corrections ...More fun than buying and we learn how to hear...
Then the improvement of acoustics parameters perception in the late evening is real ...