Speech intelligibility enhancement by early reflections
Early reflections in a room can improve speech intelligibility for normal-hearing listeners, because the auditory system integrates them with the direct sound which results in an increased speech level. The present study investigated the underlying mechanisms involved in early re ection processing. Monaural and binaural speech intelligibility tests were performed with 9 normal- hearing listeners in a loudspeaker-based virtual auditory environment where the amplitude of the direct sound and the early reflections could be varied independently. The re ection pattern was taken from a classroom simulated with the room acoustic software Odeon [Odeon (2008)]. The Danish sentence test Dantale II [Wagener, Int. J. Aud. 42, 10-17 (2003)] was used. The sentences were presented from the loudspeaker at 0° azimuth and speech intelligibility was measured with a diffuse speech shaped noise (SSN). Different signal-to-noise ratios were obtained by changing either the direct sound level or the early reflection level of the speech signal. Increased early reflection levels improved speech intelligibility but the effect was smaller than for increased direct sound levels. No binaural processing of early reflections other than a summation of the signals at the two ears could be observed for the diffuse SSN interferer.
Cremer L., and Müller, H. A. (1982). Principles and applications of room acoustics Vol. 1 Section III. 2.2, (Applied Science Publishers, London).
Favrot, S., and Buchholz, J. B. (2009). “Validation of a loudspeaker-based room auralisation system using speech intelligibility measures,” 126th convention of the Audio Eng. Soc., Munich.
Hagerman, B. (1982). “Sentences for testing speech intelligibility in noise,” Scand. Aud. 11, 79-87.
ISO (2004). ISO 389-8. “Acoustics – Reference zero for the calibration of audiometric equipment – Part 8. Reference equivalent threshold sound pressure levels for pure tones and circumaural earphones,” International Standardization Organization, Geneva, Switzerland.
Latham, H. G. (1979). “Signal-to-noise ratio for speech-intelligibility – Auditorium acoustics design index,” Appl. Acoust. 12, 253-320.
Lochner, J. P. A., and Burger, J. F. (1958). “The subjective masking of short time delayed echoes by their primary sounds and their contribution to the intelligibility of speech,” Acustica 8, l-10.
Lochner, J. P. A., and Burger, J. F. (1964). “Influence of reflections on auditorium acoustics,” J. Sound Vibrat. 1, 426-454.
Nabelek, A. K., and Robinette, L. (1978). “Influence of precedence effect on word identification by normally hearing and hearing-impaired subjects,” J. Acoust. Soc. Am. 63, 187-194.
Odeon Room Acoustic Software (2008). Version 9.1.
Parizet, E., and Polack, J. D. (1992). “The influence of an early reflection upon speech-intelligibility in the presence of a background-noise,” Acustica 77, 21-30.
Pavlovic, C. V. (1987). “Derivation of primary parameters and procedures for use in speech-intelligibility predictions,” J. Acoust. Soc. Am. 82, 413-422.
Pollack, I. (1948). “Monaural and binaural threshold sensitivity for tones and for white noise,” J. Acoust. Soc. Am. 20, 52-57.
Soulodre, G. A., Popplewell, N., and Bradley, J. S. (1989). “Combined effects of early reflections and background-noise on speech-intelligibility,” J. Sound Vibrat. 135, 123-133.
Thiele, R. (1953). “Richtungsverteilung und Zeitfolge der Schallrueckwuerfe in Raeumen,” Acustica 3, 291–302.
Wagener, K., (2003). “Design, optimization and evaluation of a Danish sentence test in noise,” Int. J. Aud. 42, 10-17.
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