This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards(NIS)according to the related international standards.The evaluation aims at examining ...This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards(NIS)according to the related international standards.The evaluation aims at examining the room performance and exploring its effectiveness in the frequency range from 125 Hz to 10000 Hz according to the international standard requirements.The room,which was designed and built several years ago,is an irregular rectangular shape free from diffusers.Its volume is about 158.84 m^(3),which meets the requirement of the ISO 354 standard Lmax<1.9V^(1/3).Cut-off frequencies of one and one-third octave are 63 Hz and 100 Hz respectively;however Schroder frequency is 400 Hz.Calculations of cut-off frequency and modal density showed adequate modes that give acceptable uniformity starting comfortably from frequency of 125 Hz.The room has a reverberation time that is suitable for its size over the frequency range of interest.The room sound absorption surface area and its sound absorption coefficient satisfy the criteria given in ISO 3741 and ISO 354.There is an accepted diffuse sound field inside the room due to the standard deviation of measured sound level,which is less than 1.5 dB over all the frequency range.The only exception was 125 Hz which may be due to a lack of diffusivity of the sound field at this frequency.The evaluation proves that the NIS reverberation room is in full agreement with the international standards,which in turns qualifies the room to host measurements inside without concerns.展开更多
This study examines the effect of speech level on intelligibility in different reverberation conditions, and explores the potential of loudness-based reverberation parameters proposed by Lee et al. [J. Acoust. Soc. Am...This study examines the effect of speech level on intelligibility in different reverberation conditions, and explores the potential of loudness-based reverberation parameters proposed by Lee et al. [J. Acoust. Soc. Am., 131(2), 1194-1205 (2012)] to explain the effect of speech level on intelligibility in various reverberation conditions. Listening experiments were performed with three speech levels (LAeq of 55 dB, 65 dB and 75 dB) and three reverberation conditions (T20 of 1.0 s, 1.9 s and 4.0 s), and subjects listened to speech stimuli through headphones. Collected subjective data were compared with two conventional speech intelligibility parameters (Speech Intelligibility Index and Speech Transmission Index) and two loudness-based reverberation parameters (EDTN and TN). Results reveal that the effect of speech level on intelligibility changes with a room’s reverberation conditions, and that increased level results in reduced intelligibility in highly reverberant conditions. EDTN and TN explain this finding better than do STI and SII, because they consider many psychoacoustic phenomena important for the modeling of the effect of speech level varying with reverberation.展开更多
文摘This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards(NIS)according to the related international standards.The evaluation aims at examining the room performance and exploring its effectiveness in the frequency range from 125 Hz to 10000 Hz according to the international standard requirements.The room,which was designed and built several years ago,is an irregular rectangular shape free from diffusers.Its volume is about 158.84 m^(3),which meets the requirement of the ISO 354 standard Lmax<1.9V^(1/3).Cut-off frequencies of one and one-third octave are 63 Hz and 100 Hz respectively;however Schroder frequency is 400 Hz.Calculations of cut-off frequency and modal density showed adequate modes that give acceptable uniformity starting comfortably from frequency of 125 Hz.The room has a reverberation time that is suitable for its size over the frequency range of interest.The room sound absorption surface area and its sound absorption coefficient satisfy the criteria given in ISO 3741 and ISO 354.There is an accepted diffuse sound field inside the room due to the standard deviation of measured sound level,which is less than 1.5 dB over all the frequency range.The only exception was 125 Hz which may be due to a lack of diffusivity of the sound field at this frequency.The evaluation proves that the NIS reverberation room is in full agreement with the international standards,which in turns qualifies the room to host measurements inside without concerns.
文摘This study examines the effect of speech level on intelligibility in different reverberation conditions, and explores the potential of loudness-based reverberation parameters proposed by Lee et al. [J. Acoust. Soc. Am., 131(2), 1194-1205 (2012)] to explain the effect of speech level on intelligibility in various reverberation conditions. Listening experiments were performed with three speech levels (LAeq of 55 dB, 65 dB and 75 dB) and three reverberation conditions (T20 of 1.0 s, 1.9 s and 4.0 s), and subjects listened to speech stimuli through headphones. Collected subjective data were compared with two conventional speech intelligibility parameters (Speech Intelligibility Index and Speech Transmission Index) and two loudness-based reverberation parameters (EDTN and TN). Results reveal that the effect of speech level on intelligibility changes with a room’s reverberation conditions, and that increased level results in reduced intelligibility in highly reverberant conditions. EDTN and TN explain this finding better than do STI and SII, because they consider many psychoacoustic phenomena important for the modeling of the effect of speech level varying with reverberation.
