Sonic Plunger

The Sonic Plunger is a hand-operated acoustic implement consisting of a rubberised suction cup mounted on a rigid shaft, used throughout The Tower to displace standing resonance from enclosed volumes. Unlike the Aural Dampeners, which absorb sound at the point of contact, a sonic plunger does not silence a cavity; it moves the cavity's accumulated resonance elsewhere, generally downward, and generally into a floor that has not consented to receive it. The instrument is catalogued under Floor 1,412, though the catalogue note adds that the floor in question has never been located and that the entry was filed on the strength of a delivery receipt.

Sonic plungers are issued only against signature and are numbered individually on the shaft. Ninety-one percent of those issued are returned. The remainder are recorded as "retained in service" and are not chased.

Origin and the Kettle Dispute

The implement enters the record in the Fifth Concordance, Annex 9, which permits the "mechanical urging of trapped resonance toward an aperture of lower occupancy." The phrase was drafted by Clerk Adela Voss-Marn, whose own notes describe the operation less loftily. "We had a kettle-shaped problem on the fourth landing," she wrote in her working ledger for the winter of that year, "and I pushed at it the way one pushes at a drain, and it went down the stairwell, and it stayed down."

Voss-Marn's method was disputed for eleven years by the Department of Acoustic Cartography, which objected that resonance displaced by suction could not be charted, since it left no trace at either the point of origin or the point of arrival. The objection was eventually withdrawn after the Cartographers conceded, in a marginal note of unusual frankness, that "the unresolvable disposition is itself a datum."

Method and the Cadence Index

A plunge is performed in three movements: seating, compression, and release. The cup is seated at the nodal point of the standing wave, compressed until the seal registers a pressure of not less than four units on the Ephemeral Gradients scale, and released at a rate the operator judges appropriate. An operator who judges incorrectly will hear the resonance return within the hour, usually louder.

The Seventh Cadre later quantified the release rate as a subsidiary term of the Cadence Index, assigning each completed plunge a displacement value between 0.4 and 9.2 sa.u. Values above 8.0 require the operator to hold active Certification in Abrupt Sonic Trauma Preparedness, a requirement introduced after the bleed field of Floor 770 expanded eight metres past its demarcation during an unsupervised plunge in the following spring. The Cabinet of the Plunger, which regulates the instrument, maintains that the expansion was coincidental.

The Contradiction of the Third and Fifth Concordances

Scholarship is divided on whether the instrument may be used against a catalogued subject. The Third Concordance, Annex 2, forbids the application of suction "to any sound which has been entered in the register," on the grounds that a registered sound has a place and that a place may not be pumped. The Fifth Concordance, at Annex 9, permits it without qualification.

"Where the two instruments disagree, the elder governs; where they agree, neither is read."

— Marginalia of Librarian Orst, cited in the recension notes to the Third Concordance

In practice the question is settled by the Axiom of Sonic Precedent: a sound that has been plunged once may be plunged again, and a sound that has not been plunged acquires the right to be left alone only after it has been catalogued twice. See also the discussion of related precedents under Doctrine of Sonic Palimpsests, which treats the layering left behind a displaced resonance at some length.

Floor 333 and the Winter Incident

The most cited cautionary case is the winter of the year the reading room on Floor 333 was found to contain a resonance at 41 cycles that could not be attributed to any source, any occupant, or any object in the room. A plunger team was dispatched under the authority of the Manual of Auditory Demarcation and displaced the resonance in a single afternoon of work.

The resonance arrived, intact, one floor below, in the office of the registrar, where it settled into the shape of a hum and has remained since. The registrar's successive petitions for removal have been refused on the basis of Determination 188, which distinguishes a primary sonic event from its resultant echo and holds that the latter, once established at a new address, is a different sound and beyond the reach of the original order. The hum is now listed in the register as an Architectural Echo of the third class, and the registrar has been asked to stop mentioning it in correspondence.

Administration and Practical Notes

Sonic plungers are held by the Phonological Archivists and may be signed out at the instrument desk on Floor 6 by personnel in good standing. Cups are replaced annually; shafts are not. Plunges are logged in the register with time, volume, and displacement value, and the log is reviewed each quarter by the Department of Ambiance Amp Inclemency.

The following inventory is typical of a desk issue as recorded for a single working week:

• Plungers issued: 9
• Plunges logged: 41
• Displacements exceeding 8.0 sa.u.: 2 (Certification verified for both)
• Plungers returned: 8
• Plungers retained in service: 1 (shaft no. 17, last seen on the stair between Floors 400 and 401)

The instrument should not be used on a resonance while it is being read to. This restriction derives from an incident in the Acoustic Cataloguing annexe and was described at the time as self-evident.