The Effects of Noise, Early and Late Reflections on Speech Intelligibility

In this paper, an assessment of the combined effects of the noise, early and late reflections on speech (monosyllables of consonance-vowel-consonance type) intelligibility for binaural listening mode was made. Test signals were synthesized in two ways. In the first case, the noisy monosyllables (signal-to-noise ratio was varied from -15 dB to +5 dB) was filtered by two-channel room impulse responses for distances varied from 2 m to 10 m from the sound source in the middle size auditorium. In the second case, the room impulse responses were cut after 50 ms and used for filtering the same noised monosyllables. Filtered monosyllables were listened through headphones and entered into the computer using the keyboard. The results of testing showed that monosyllables intelligibility is the highest for 2 m distance and is the lowest in the middle of the room. A slight increase in speech intelligibility at the back wall can be explained by the combined action of direct sound and early reflections. The decrease in speech intelligibility in the middle of the room can be further explained by a decrease in the quality of the speech signal.