Legal Writing

Octaves and Decibels

By Maeve Maddox

A reader asks:

Can you inform on the usage of . . . octave and decible?  I am of the opinion, that octave deals with human voice and decible deals with noise. 

Both words, octave and decibel are terms of measurement. Octave derives from the Latin word for ?eight? and decibel incorporates the Latin word for ?ten.? The words can be used in various contexts. I?ll just address the uses suggested by the question.

The words bel and decibel are units of measurement of sound intensity. A bel is

A unit, equivalent to ten decibels used in the comparison of two levels of power in an electrical communication circuit.

A decibel (db) is one tenth of a bel.

?Bel? is a shortening of the name of inventor Alexander Graham Bell (1847-1922). A bel is

A unit, equivalent to ten decibels, used in the comparison of two levels of power in an electrical communication circuit.

An octave in the musical sense is an interval embracing eight notes of the diatonic scale. Think of the Do-re-me song in Sound of Music.

Doe- a deer, a female deer
Ray- a drop of golden sun
Me- a name i call myself
Far- a long long way to run
Sew- a needle pulling thread
La- a note to follow so
Tea- a drink with jam and bread
That will bring us back to do oh oh oh

The normal speaking range of the human voice is about 20-50 decibels. Sounds that go above that range become annoying, for example a vacuum cleaner (70 db). Noise becomes painful at 120 db. Sounds above 132 db lead to permanent hearing damage and eardrum rupture.

In answer to the question, decibel refers to sound, pleasant or unpleasant, whether it originates in the vocal cords or elsewhere.

NOTE: Although both the OED and Merriam-Webster give db as the abbreviation for decibel, I’ve been informed by a technical writer that the standard abbreviation is dB.
Sources:
Gale Encyclopedia of Medicine.
Mosby’s Medical Dictionary,
Oxford English Dictionary
Online Etymology Dictionary

Full post as published by Daily Writing Tips on February 04, 2010 (boomark / email).