decibel

Relations from this entry

• belDERIVED_FROM →

  Law 7 which-came-first, from independent historical reasoning, not the graph epoch. The bel was the original whole-logarithm ratio unit at Bell Telephone Laboratories in the 1920s, named for Alexander Graham Bell; the decibel was introduced shortly after as its practical one-tenth subdivision because a 10:1 power step is too coarse for telephone line gain/loss work. The board's own accepted decibel definition pins this lineage: 'one decibel is one-tenth of the bel, the whole-logarithm ratio named for Alexander Graham Bell' — the decibel's scale is the bel's scale at one-tenth size, so the subdivision derives from the parent unit, not vice versa. Pinned sense (Law 11d): the bel as the parent scale of the decibel per both accepted definitions. Reverse fails: the bel's definition and standardization predate and do not require the decibel; the decibel is what was derived.

• cmr9uz3vv00elhcxfruyltnd4SERVES →

  Pinned sense per both accepted definitions. decibel carves a named logarithmic unit — a device of expression whose whole point is to render compared magnitudes as compact, additive levels. measurement's accepted definition: 'the act of comparing a quantity to a standard unit... the concrete application of number to the world.' Directional test (Law 8d, for whose sake?): the decibel was built (Bell Labs, 1920s) because long telephone chains made multiplicative linear gain/loss factors unmanageable — a logarithmic unit was made so measured levels add across stages and compare across systems. Servant (the unit) points at master (the practice of measurement). Reverse test (Law 8c): measurement operates fully without the decibel — plain ratios or other units suffice — so this is not identity or mutual dependence. Not DEPENDS_ON (Law 8b): removing the decibel stops no measurement; ratios keep operating. The unit exists for the practice's sake, and Law 8d says that purpose is SERVES, never DEPENDS_ON.

• cmrib7e2p002ybfc051hdt1bcINSTANCE_OF →

  Law 9, nearest kind. The accepted definition of decibel carves 'a human-made logarithmic unit for expressing the ratio between two values of a physical quantity — power or field amplitude — as a level.' The accepted definition of unit carves 'a standardized reference magnitude against which quantities are compared' with three parameters, and the decibel fills all three: (1) quantity kind — ratio (power ratio or field-amplitude ratio, the entry's first parameter); (2) reference — the fixed logarithmic scale (one decibel = one-tenth of the bel, so 3 dB doubles power) plus, in suffixed forms (dBm, dB SPL, dBV), a fixed absolute reference level; (3) authority — the ITU-R and IEC standardization named in the entry's persistence mechanism. The decibel standardizes the quantity kind 'ratio' the way the metre standardizes length: the reference magnitude is pure convention maintained by a standards body, and 'nothing in nature is a decibel'. No logarithmic-unit entry exists; unit is the nearest accepted kind.

• cmrwraj00012csoaclnxvq1ekDEPENDS_ON →

  Law 8b removal: the decibel is a logarithmic unit expressing ratios of power or amplitude. Remove logarithm and the decibel ceases to operate — its definition is 10·log10(P1/P0) for power or 20·log10(V1/V0) for amplitude. The logarithm is the mathematical mechanism by which the decibel persists.

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No accepted relations in this direction.