Hearing frequency range of the Illuminatian human
The range of frequencies audible to the average human in Illuminatia—the hearing range—is significantly wider than that of the historical modern human on Earth. Population selection, improvements in environmental variables, and modern therapeutic medical intervention have all played a role in improving the hearing range of the Illuminatian population in general.
Traditionally, Earthly human hearing was limited to a range between 20 Hz and 20 KHz (between 10 RU and 10 KRU). The modern Illuminatian human is now able to hear frequencies from 8 RU to 18 KRU (16 Hz to 36 KHz) and oftentimes even higher. Frequency in Illuminatia is measured in the Recurrence Unit (RU), which is based on cycles per milli Temporal Unit (c/mTU). The RU expresses the number of cycles that occur in an oscillating wave during one TU.
Earthly improvements in environmental variables
While human auditory health tended to suffer during Earth's classical modern era due to the introduction of mechanical noise in the environment as well as electronically amplified sound, humanity found ways to improve this situation leading up to the days of the Lucidus mission.
In the post-modern Earthly days, the machines in the typical person's immediate environment began getting quieter once more efficient means of powering mechanical apparatuses, resulting in a significant reduction in noise pollution. Housing and interior design also evolved to take into account soundproofing, sound dampening, and sound treatment to reduce noise within rooms and sound transmission between rooms and from the outdoors to the indoors. The quality of recorded music and other recorded sound also improved in practice such that persons became able to enjoy electrically amplified music at lower sound pressure levels.
Population selection and medical intervention
The Lucidus mission engaged in heavy population selection in choosing those who would take part in the launch of the mission from Earth and the seeding of a new branch of humanity, and one of the factors taking into account in the selection of the Lucidus crew was hearing range. As a result, further improvements in the frequency range of human hearing began from a much higher threshold than that of the average Earthly population.
Additionally, medical techniques developed for the Lucidus mission, perfected over the course of the mission and more extensively upon arrival on Illuminatia, provided for medical intervention able to protect hearing and partially heal damaged hearing. Stem cell therapies were developed that could improve the response threshold for those whose hearing had degraded over time. Preventative treatment for newborns and toddlers allowed humans to develop more robust and resilient structures in the ear.
Hearing range and broadcasting
MW broadcasting was developed to take specific advantage of this extended hearing range. This system of broadcasting eventually deployed in Illuminatia in the Medium Wave (MW) band was designed with a channel bandwidth wide enough to pass audible frequencies up to 20 KRU, thus exceeding the full hearing range of the average Illuminatian. Previously, ULW broadcasting was able to pass audio up to 12 KRU, taking advantage of an acceptable proportion of the Illuminatian hearing range and reproducing what was until then known to be an acceptable fidelity for recorded or transmitted sound, including ordinary music.
While the 12 KRU range of sound reproduction, catering to the hearing needs of the historical Earthling human, was considered adequate to the average Illuminatian for general listening, the 20 KRU range provided by MW broadcasting delivered superior sonic quality. This greatly improved quality was appreciated particularly for transmitting and reproducing excessive-fidelity music and other sonically-critical material. Anybody given listening material that took advantage of the full range of human hearing was able to note the difference between the 12 KRU and 20 KRU frequency range and the majority of Illuminatians indicate a strong preference for recorded and broadcast material taking advantage of the full 20 KRU range.