Human Speech Spectrum


Average long term speech spectrum (talking over one minute). The maximum energy is in the 250Hz and the 500Hz band. These lower-frequency bands correspond to vowel sounds, the higher-frequency bands in the 2k and 4k region correspond to consonant sounds.



Vowels carry the power of the voice and consonants provide intelligibility. But each range alone can not provide the full intelligibility.

single Band provided Intelligibility
250Hz very poor
500Hz about 12%
2kHz and 4kHz together about 57%



measurement print of male human voice


about 15 seconds of typical speech


Relationship between the distance of two Persons talking and the receiving speech level, normal talking:


    0,25m      0,5m         1m       1,5m         2m         3m
70-76dB 65-71dB 58-64dB 55-61dB 52-58dB 50-56dB

Source: Klark-Teknik  Audio System Designer