Receivers

Receivers are a distinct class of auditory phenomena classified under Auditory Anomalies and governed by the stipulations of the Thirteenth and Forty-Second Concordances. They are defined as permanently silent Apertures which, by their inherent nature, capture and indefinitely retain specific sound events that have ceased to occur elsewhere in The Tower. The captured sound is not audible within the vicinity of the Receiver itself but can be accessed under strictly controlled conditions by Librarians of sufficient grade.

Physical Manifestation

Receivers most commonly manifest as smooth, non-reflective depressions in Permastone walls or floors, ranging from ten to fifty centimeters in diameter. Their edges are subtly defined, often detectable only by a change in temperature or a faint vibrational hum felt through direct tactile contact. A minority of documented Receivers take the form of architectural features such as hollow newel posts on disused stairwells or the interiors of certain types of silent bells. Each Receiver is inscribed upon discovery with a unique designation following the pattern of its floor number, the Greek letter rho (), and a sequential identifier (e.g., 714--09).

Acquisition and Retention

The mechanism of acquisition remains poorly understood. Concordance XIII, Annex C, states a Receiver "becomes attuned at the moment of a sound's final utterance within the jurisdiction of the Tower." This has been interpreted to mean a sound becomes eligible for reception only when it is no longer produced by its original source and has faded from all conventional echo cycles. Controversially, Concordance XLII, Clause 8, contradicts this, suggesting Receivers are proactive and may "precipitate the silence they later fill," implying they may cause the cessation of a sound to facilitate its collection. The prevailing administrative view, upheld by the Librarian-General’s Office, treats the former as doctrine for cataloguing purposes.

Retention is believed to be perfect and permanent. Once a sound event is received, it exists in a state of suspended auditory fidelity within the aperture. Notable archived examples include the exact pattern of drips from a melted Icicle of Duration on Floor 1,112 (“The Glacier Hall”), the closing cadence of the Last Chime of the Seventh Carillon, and the final sigh of Archivist-Provisional Aris, uttered upon completing her inventory of Floor 909 (“The Gallery of Unseen Faces”).

Access Protocol

Accessing the retained sound requires a sanctioned Auditory Resonance Drill, a brass device calibrated to the specific frequency of silence emitted by the target Receiver. The procedure, detailed in Appendix of Concordance XIII, must be witnessed by two Librarians of at least Third Grade. The drill is inserted into the center of the Receiver, and upon achieving resonance, the captured sound is played back once, at its original amplitude, directly into the listening horn of the drill. The sound is not broadcast into the surrounding environment. A transcription is made immediately following the playback, and both the transcription and the resonance calibration settings are filed with the Department of Acoustic Cartography. The original sound within the Receiver remains unchanged and can be re-accessed following the same protocol.

Taxonomic Disputes

The classification of Receivers is a point of ongoing scholarly contention. The School of Phenomenal Integrity argues they are merely a specialized type of Echo Well, differing only in their selectivity and access method. The rival Manifest Theory Consortium maintains Receivers are unique ontological entities—not containers for sound, but the preserved potential for a specific sound to be heard, making them more closely related to Conceptual Anchors than to physical apertures. This debate directly impacts resource allocation for their study and maintenance.

Notable Installations

• The Grand Receiver (Δ--01): Located on Floor 0 (The Atrium), this is the largest known Receiver, a disc of three meters in diameter set into the floor beneath the Central Index. It is believed to hold the sound of the Foundation Stone being laid, though access has been forbidden since the Seventh Amendment to Concordance XIII.
• The Whispering Column (442--17): A Receiver in the shape of a fluted column on Floor 442 (“The Scriptorium of Erased Words”). It retains the collective whisper of scribes correcting a single, monumental error in the First Concordance, a sound described in transcripts as "a rustling like leaves, followed by a profound, unified exhalation of dismay."
• Receiver-Complex Theta: A cluster of seventeen small Receivers on Floor 888, each capturing a discrete component of the ambient noise from the now-silent Clockwork Aviary. When accessed in sequence according to the complex schedule outlined in Ordinance 888.45., they recreate the full auditory environment of the Aviary for a duration of precisely 4 minutes and 33 seconds.