Reflective Surfaces for the Hearing of Speech and Music in an Anechoic Chamber

Abstract

Speech articulation tests in our anechoic chamber, with and without the benefit of three reflective surfaces (to be described) for reinforcing the speech, reveal that the percentage of typical speech words heard correctly is 93.3% with the reflectors and only 69.7% without them. The directional characteristics of speech around the head of the speaker were consistent with those for tones of different frequencies; thus, the sound-pressure level of a 13 oct band of speech, centered at 4000 Hz, dropped 14 dB when the speaker turned 180° away from the recording microphone. The results obtained in the anechoic room, without the reflectors, are consistent with those we obtained 40 years ago at a noise-free location on a dry lake bed. The results are demonstrated with data and tape recordings, which reveal qualitatively and quantitatively the beneficial effects of suitable reflectors. The effects of early reflections on the quality of music are also demonstrated by tape recordings. These effects may be as important as is optimal reverberation time.