Hoth noise is used to model indoor ambient noise when evaluating communications systems such as telephones. It is named after D.F. Hoth, who made the first systematic study of this. The official definition of Hoth noise is IEEE standard 269-2001 (revised from 269-1992), "Draft Standard Methods for Measuring Transmission Performance of Analog and Digital Telephone Sets, Handsets and Headsets."
The table below gives the spectral density of Hoth noise, adjusted in level to produce a reading of 50 dBA.
Freq (Hz) Spectral Bandwidth Total power in density 10 log_f each 1/3 octave band (dB SPL/Hz) (dB) (dB SPL) 100 32.4 13.5 45.9 125 30.9 14.7 45.5 160 29.1 15.7 44.9 200 27.6 16.5 44.1 250 26.0 17.6 43.6 315 24.4 18.7 43.1 400 22.7 19.7 42.3 500 21.1 20.6 41.7 630 19.5 21.7 41.2 800 17.8 22.7 40.4 1000 16.2 23.5 39.7 1250 14.6 24.7 39.3 1600 12.9 25.7 38.7 2000 11.3 26.5 37.8 2500 9.6 27.6 37.2 3150 7.8 28.7 36.5 4000 5.4 29.7 34.8 5000 2.6 30.6 33.2 6300 -1.3 31.7 30.4 8000 -6.6 32.7 26.0
The tolerance for each 1/3rd octave band is กำ3dB.