Human Speech Spectrum
Average long term speech spectrum (talkin 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% |
A real measurement print of male human voice:
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
