Acoustic Dampening

Acoustic Dampening is the reduction of audible consequence within a defined volume, distinguished from the elimination of sound altogether by the fact that dampened sound is understood to persist in some reduced or deferred form. The distinction is not ornamental. Under the Twelfth Concordance, a volume in which sound has been dampened remains liable to audit, whereas a volume in which sound has been nullified does not. Practitioners have argued the point for four centuries.

Dampening is administered principally by the Acoustic Dampening Guild, a principal subsidiary body of the Acoustic Harmonization Guild and historically the certifying authority for dampening equipment. Its theoretical framework is supplied by the Guild of Harmonic Theorists, which maintains that all dampening is an act of deferral rather than deletion. The practical consequence of this position — that dampened sound must eventually be released somewhere — is the subject of Ordinance 707 and remains the most litigated question in the field.

Early practice and the Acoustic Dampening Guild

The earliest recorded dampening on the Tower's lower catalogued floors was performed by hanging Acoustic Dampening Socks at aperture margins, a technique associated with the Acoustic Dampening Guild in its administrative period. The socks, the emergent output of the Silentium pedis network, were at first undifferentiated by size; the Guild's certification schedule of 1187 introduced the nine sock grades still in use, of which grade IV and above may be hung in a reading room without a witnessing clerk present.

The Guild's early records describe dampening as a form of housekeeping, and its clerks were paid by the aperture rather than by the hour. This arrangement ended after the Winter of the Long Corridor, when a dampening party on a single storey of the north stack remained at work for fifty-one days and submitted a claim for four thousand apertures, three of which were later found to be the same aperture viewed from different landings.

Supersession and the Bureau

The Bureau of Resonance Dampening superseded the dampening efforts of the Acoustic Dampening Guild by instrument of 1344, though the Guild retained its certification functions and its jurisdiction over containment protocols for acoustic latency. The two bodies have not reconciled. The Guild holds a standing grievance against the Bureau concerning requisition of Silentium Resin during an Anharmonic Intrusion on Floor 611, in which the Bureau drew on Guild stock without a countersigned docket and returned the tins empty. The Bureau's position, stated in its own recension of the incident, is that the tins were never full.

The Guild nevertheless collaborates with the OML on the materialization of auditory figures, and jointly funds the position of Acoustic Liaison with two other bodies, an office whose incumbent is required to be present at every dampening of grade VI or above but whose duties at those dampenings are not recorded in any Concordance.

Apparatus

Modern dampening relies on three principal instruments. The Resonance Containment Amp Acoustic Nullification performs nullification proper and is therefore outside the scope of this article except insofar as it is frequently mistaken for a dampening device. The Harmonic Suppression Plate performs bounded dampening at fixed frequencies and is the standard fitting for stairwells. The Stair Dampening Counterweight Mlpm V 22 is a mechanical deferral device, weighted to hold dampened resonance until the stair is unoccupied, and is responsible for the low tone reported by visitors to Floor 707 shortly before closing.

Resin-impregnated socks remain in use where plates cannot be fitted. Socks are replaced at the close of each quarter, and none may be taken home.

The measurement dispute

There is no agreed figure for the efficacy of a dampening installation. The Acoustic Dampening Guild measures in deferred amplitude, expressed as the ratio of sound retained to sound released over a standard interval. The Bureau of Resonance Dampening measures in aperture attenuation, a figure derived from the number of margins treated and the grade of treatment applied. The two scales are not convertible, and both offices maintain that the other's figures are descriptive rather than normative.

"A volume may be reported as fully dampened on one schedule and as undampened on the other, and both reports may be correct. This is not an inconsistency. It is the state of the art."

— Seventh Concordance, Annex 4

The Guild of Harmonic Theorists has proposed a third scale, deferred release, which no one uses. Its secretary has continued to submit it annually since 1402.

Notable installations

The Cabinet of Echoes is the most cited dampening installation in the Tower, though its dampening is incidental to its function and its fittings have not been inspected since 1466. Floor 707 carries a full aperture schedule under Ordinance 707, including the north reading room, where the schedule is enforced by two clerks who check the sock grade at each aperture before opening and record the release at closing. The Third Spire resonance core is dampened by counterweight only, a decision taken after the plate failure of 1449 and never revisited.

Related practices include general dampening, Resonance Dampening, Contextual Dampening and the broader Dampening Protocols; the Acoustic Weavers' Guild disputes sock certification with the Acoustic Dampening Guild, a dispute now in its third century. Readers are reminded that a dampened room is not a silent room, and that conversation in a dampened room carries further than conversation in an untreated one.