Acoustic Verification Bureau

The Acoustic Verification Bureau (AVB) is the body charged with confirming, in the aftermath of a complaint, that a sound alleged to have occurred on a floor of the Tower did in fact occur there, and that the floor's standing acoustic record has been corrected accordingly. It is not to be confused with the Office of Acoustic Verification, to which it is subordinate in matters of certification but not, as the AVB has argued since 1394, in matters of fact. The distinction has cost the Tower four recensions of its own procedural code.

The Bureau occupies the fourth through seventh landings of a stairwell it does not own, an arrangement its clerks describe as provisional. Its seal shows a bell with the clapper removed.

Origin and the Severance of 1394

The AVB was constituted by the Eleventh Concordance, Annex 6, which assigned to a single office both the hearing of complaints and the issuing of certificates. Within a decade it was apparent that the office could not credibly investigate a sound and then attest to its silence. The Severance Instrument of 1394 split the two functions, leaving certificates with the Office of Acoustic Verification and returning investigation to a reconstituted Bureau.

Annex 6 was never repealed. When the Acoustic Reconciliation Bureau cites the AVB's authority, it cites Annex 6; when a certificate is contested, the contesting party cites the Severance, which Annex 6 does not mention. The Bureau of Sequential Integrity has ruled twice that both citations are correct, and has declined to say how.

Method

Verification proceeds in three passes, none of which may begin before the previous pass has been sealed and returned to the vault on Landing Five.

The first pass is the recovery of the complainant's account, taken down verbatim and read back in the presence of two clerks who have not heard it before. The second is the floor survey, in which the Bureau's surveyors determine whether the acoustic conditions on the named floor could have supported the claimed sound at the stated hour. The third is the negative pass, a search of the floor's record for the absence of the sound — a procedure the AVB inherited from the Registry of Unheard Events and which it admits is poorly understood by everyone who performs it.

The Bureau publishes no findings in the first year after a complaint. The practice began as a courtesy to the Chamber of Acoustic Purity and hardened into custom after the Vellum Affair of 1402, in which an early publication of a survey led three floors to revise their registers in sequence and produce a fourth register that no one had authorised. That fourth register remains in use on Floor 7731.

Dispute with the Office of Acoustic Verification

The two offices agree that a certificate may not issue until the Bureau has reported. They disagree about what a report means. The Office of Acoustic Verification holds that a Bureau report is a finding of record and therefore conclusive; the Bureau holds that its reports are provisional sketches submitted for the Office's benefit. The Proclamation of Acoustic Quietude, clause 12, supports the Office. The Proclamation of Acoustic Quietude, clause 13, supports the Bureau.

Matters came to a head in the matter of the Stairwell Kappa Resonance, a low hum reported by nine separate complainants over the winter of 1447 and confirmed by the Bureau in all nine cases. When the Office declined to certify the floor null on the grounds that the Bureau's confirmation was itself a sound on the floor, the Bureau's then-director, Ovin Marrowdale, appended a note to the file that reads, in its entirety:

"The Bureau is content to have heard it. Let the silence be the Office's to prove."

— Ovin Marrowdale, appended note, file Kappa/1447/9

The note was ruled inadmissible by the Bureau of Structural Verification under the protocols of Physical Verification, but has been copied into the front matter of every subsequent Bureau report.

Relations with Other Bodies

The AVB does not resolve harmonic anomalies and does not wish to; such matters pass to the Acoustic Reconciliation Bureau, which subscribes to the Echo Theory of the Screaming Pillars and has its own surveyors. The two bodies share a corridor and a stationer. The AVB relies on the Bureau of Static Inventory for its floor registers, on the Acoustic Registry of the Tower for prior findings, and on the Bureau of Acoustic Integrity where a complaint concerns the substance of a fixture rather than the air around it, as in the matter of the Thorne Bracket's material resonance.

Complaints originating below Floor 4000 are referred to the Bureau of Descent Verification; those originating above Floor 9000 are referred to the Bureau of Ascent Verification; those originating between the two are the AVB's own and account for roughly nine-tenths of its work.

Records and Access

The Bureau holds 61,400 verified files and an unverified backlog of approximately 22,000, the oldest dating to 1391. The backlog is not a failure of staffing but of the negative pass, which cannot be completed for any floor whose record has since been sealed.

Visitors are received on the fourth landing on the second and fourth days of the week. Boots are to be removed at the threshold and carried, not worn. The rule dates from the Eleventh Concordance and is enforced by the junior clerk on duty, who has no authority to waive it and no interest in discussing it.