Short Reverberation Time Research Articles

Reverberation Time in Traditional Courtyard Yue Opera Theatres

The development of traditional Chinese theatres is closely related to the development of traditional Chinese opera. The acoustic quality of the theatre plays a crucial role in the performance effect of Chinese opera. As one of the five major traditional Chinese opera genres, Yue opera has a significant number of existing traditional theatres in the Shaoxing area. This study conducted on-site measurements of the reverberation time in traditional courtyard Yue opera theatres. The results indicate that the mid-frequency EDT values in the main viewing areas range from 0.6 to 0.7 s, and T30 is around 0.7 s. Furthermore, aiming to investigate the optimal reverberation time for Yue opera performance spaces and the factors influencing preferences, subjective experiments using auralization technology and a paired comparison method were conducted. The results show that the optimal reverberation time for Yue opera performance spaces is around 0.8 s. There was no difference in the optimal reverberation time between the ordinary group and the experienced group, but the ordinary group tended to show a higher preference for shorter reverberation times. Compared to singing clips, recitation clips obtained higher preference scores for short reverberation times, indicating that audiences require higher clarity when listening to recitations.

The sound of silence: children’s own perspectives on their hearing and listening in classrooms with different acoustic conditions

In this study, we investigated primary school children’s perspectives on their hearing and listening in classrooms with different acoustic quality levels. The sample included 213 children. The children completed a self-report questionnaire rating how well they could hear and listen in various situations in classrooms with two different acoustic conditions: Poor acoustic quality (long reverberation time [Long RT]) versus Adequate acoustic quality (short reverberation time [Short RT]) equipped with a sound-absorbing system. The results showed that auditory perception in the two conditions depends on the child’s age, with only fourth- and fifth-grade children reporting benefits from classroom acoustic correction. Our study provides preliminary results on children’s perspectives regarding their hearing and listening experiences during school learning, drawing out the implications for the design and implementation of school metacognitive interventions aimed at improving children’s and teachers’ awareness of motivational-affective, regulative, and environmental aspects favoring listening at school.

Estimating the characteristic vibrations of a sound field in a room using coefficient of variation in the power spectrum of a decay-cancelled impulse response

Estimating the characteristic vibration distribution of a room sound field is difficult because the half-power bandwidth of the characteristic vibrations broadens due to room impulse response decay. Therefore, a coefficient of variation in a power spectrum of a decay-cancelled impulse response is proposed for estimating the characteristic vibrations of a room sound field. In the decay-cancelled impulse response, only the decay of the impulse response is cancelled. Cancelling the decay narrows the half-power bandwidth, thus enabling a clearer estimation of the characteristic vibration even in a sound field with a short reverberation time. In this study, sound fields with different characteristic vibration distributions were numerically simulated to investigate whether the coefficient of variation could estimate their difference.

Objective Assessment of Binaural Benefit from Acoustical Treatment in Real Primary School Classrooms.

Providing students with an adequate acoustic environment is crucial for ensuring speech intelligibility in primary school classrooms. Two main approaches to control acoustics in educational facilities consist of reducing background noise and late reverberation. Prediction models for speech intelligibility have been developed and implemented to evaluate the effects of these approaches. In this study, two versions of the Binaural Speech Intelligibility Model (BSIM) were used to predict speech intelligibility in realistic spatial configurations of speakers and listeners, considering binaural aspects. Both versions shared the same binaural processing and speech intelligibility backend processes but differed in the pre-processing of the speech signal. An Italian primary school classroom was characterized in terms of acoustics before (reverberation, T20 = 1.6 ± 0.1 s) and after (T20 = 0.6 ± 0.1 s) an acoustical treatment to compare BSIM predictions to well-established room acoustic measures. With shorter reverberation time, speech clarity and definition improved, as well as speech recognition thresholds (SRTs) (by up to ~6 dB), particularly when the noise source was close to the receiver and an energetic masker was present. Conversely, longer reverberation times resulted (i) in poorer SRTs (by ~11 dB on average) and (ii) in an almost non-existent spatial release from masking at an angle (SRM).

Effects of speech intelligibility and reverberation time on the serial recall task in Chinese open-plan offices: A laboratory study

Speech intelligibility is an essential index for evaluating acoustic performance in open-plan offices. Both speech-to-noise ratio (SNR) and reverberation time (RT) are critical parameters for determining the Speech Transmission Index (STI). STI is an important parameter for the objective prediction of speech intelligibility. Many studies explored the effects of speech intelligibility on work performance and acoustic environmental perceptions in open-plan offices by changing the SNR to obtain various STI conditions. However, few studies research how RT affects speech intelligibility and then influences work performance and perceptions of acoustic environments in open-plan offices. This study conducted a laboratory experiment to identify the changing trends of work performance and acoustic environment perceptions with the increase in STI under different RT conditions and to explore how room RT affects work performance and perceptions of the acoustic environment under the same STI condition. The acoustic conditions tested in this study varied in speech intelligibility (STI of 0.21, 0.42, and 0.61) and reverberation time (RT of 0.4 s and 1.4 s). The main outcome of this study is that occupants have less mental workload, faster task completion speed, and higher acoustic adaptability in a long RT environment compared to a short RT environment at an STI of 0.42. Furthermore, the data show a decreased work performance and an increased speech disturbance with the increase in STI in the short RT environment, while that trend was not observed in the long RT environment. The effects of STI conditions on occupants may differ by gender and noise sensitivity.

An investigation of classroom sound levels as a function of class size

It is generally acknowledged that students with special hearing and communication needs should be taught in classrooms with relatively short reverberation times. There has been a great deal of research into the effect of room acoustics on the signal-to-noise ratio experienced by pupils. There is, however, much less research into the effect of class size on ambient noise levels during lessons, and hence on the signal-to-noise ratio and on absolute sound levels in classrooms. These absolute levels are important because many students with special needs are sensitive to high noise levels, either for psycho-acoustic reasons or because of the limited dynamic range of cochlear implants and other assistive devices. In his work as an expert witness on acoustics for Special Education Needs and Disabilities Tribunals, the author has measured in-lesson sound levels for different types of teaching and learning activity in many schools throughout England. He has analysed these to investigate the correlation, when corrected for acoustic factors, between class size and sound levels generated by teachers and pupils, and to consider whether there is a typical class size at which an effect analogous to the Lombard Effect occurs. From this the author draws conclusions as to the acoustic justification for teaching pupils with special hearing and communication needs in smaller classes.

Incremental use of FFT as a solution for low BT-product reverberation time measurements

The limitations in performance of band-pass filters to accurately process rapid decaying signals in lower frequency bands is an obstacle for some measurements within building acoustics. For instance, it would be beneficial to be able to accurately measure reverberation times down to the 20 Hz one-third octave band for impact sound in timber buildings. Here, it is tested whether calculations with FFT with small incremental steps may be a way to achieve discrete frequency time signals with faster performance than traditional band-pass filters. The tests show that incremental FFT gives accurate estimations of the reverberation time corresponding down to 0.1 s at 20 Hz with a spectral resolution of 2 Hz. Using the one-third octave limits it is possible to form approximate one-third octave band results. It is seen that accurate estimations of reverberation time are achievable for BT⩾0.5 (T=0.1 seconds for the 20 Hz one-third octave band) and possibly even lower, if the dynamic range in the interrupted noise signal is sufficient. The higher one-third octave results show to work as well. A disadvantage with the method is that during short reverberation times (0.1 s) there is a severe spectral leakage to the side bands. Also, the method requires higher dynamic range decay signals compared to band-pass filtered signals. If a one-third octave resolution is requested, a dynamic range of 50 dB or greater is preferable. With a coarse resolution of e.g., 10 Hz and having no averaging into one-third octave bands, it is possible to measure short reverberation times (0.1 s) with signals having close to the same dynamic range used in classical band-pass filtered reverberation time measurements.

Architectural improvements to increase reverberation and reduce flutter echo in two music rehearsal rooms

New music rehearsal rooms at a small college suffered from flutter echo and very short reverberation times. The architecture of these rooms included visually elegant designs which the college wanted to retain if feasible. We coordinated with the college, the architect, and a wood worker to develop concept ideas for improvement which would be cost effective and retain the elegant architectural. By using finite difference time domain (FDTD) simulation and mock-up listening tests, we evaluated the acoustic properties of these concept options. After completion of these tests and simulations, a design was implemented in each room based on acoustic performance and visual impact. We will present measurement results pre- and post-renovation, along with our methodology used for the FDTD analysis and mockup testing.

Primary school children’s verbal working memory performances in classrooms with different acoustic conditions

Verbal working memory plays a crucial role in supporting the learning process over the school years. In this study, we investigated the role of the acoustic conditions of school classrooms, specifically reverberation time and babble noise, on second-graders’ verbal working memory. A sample of twenty-five second-graders was administered a validated verbal working memory task in two different acoustic conditions, with a time frame of 1 month: Poor acoustic quality (long reverberation time [Long RT] and babble) versus Adequate acoustic quality (short reverberation time [Short RT] and babble). Results showed that the same children were able to remember fewer words and less accurately on the task in a classroom with longer reverberation time and babble compared to one with shorter reverberation time and babble. Moreover, children omitted more words in the recall task in the Poor acoustic quality condition than in the Adequate acoustic quality condition. The results suggested that primary school children’s verbal working memory processing is sensitive to variations in the classroom acoustic conditions. These findings offer a research contribution about the importance of adopting a contextual view on cognitive development and insights for the implementation of school interventions in terms of metacognitive work on learning to listen and classroom design. • Primary school children’s verbal working memory processing is sensitive to variations in the classroom acoustic conditions. • Results provide support of adopting contextual view on cognitive functioning and development.

Intelligent passive room acoustic technology to satisfy acoustic design standards in classrooms

PurposeInformed by acoustic design standards, the built environments are designed with single reverberation times (RTs), a trade-off between long and short RTs needed for different space functions. The novel intelligent passive room acoustic technology (IPRAT) has the potential to revolutionise room acoustics, thus, it is imperative to analyse and quantify its effect. IPRAT achieves real-time room acoustic improvement by integrating passive variable acoustic technology (PVAT) and acoustic scene classification (ASC). This paper aims to compare IPRAT simulation results with the AS/NZS 2107:2016 Australian/New Zealand recommended design acoustic standards.Design/methodology/approachIn this paper 20 classroom environments are virtually configured for the simulation, multiplying 5 classrooms with 4 aural situations typical to New Zealand classrooms. The acoustic parameters RT, sound clarity (C50) and sound strength (G) are considered and analysed in the simulation. These parameters can be used to determine the effects of improved acoustics for both teacher vocal relief and student comprehension. The IPRAT was assumed to vary RT and was represented in the simulation by six different absorption coefficient spectrums.FindingsThe optimised acoustic parameters were derived from relationships between C50, RT and G. These relationships and optimal RTs contribute a unique database to literature. IPRAT’s advantages were discerned from a comparison of “current,” “attainable” and “optimised” acoustic parameters.Originality/valueBy quantifying the effect of IPRAT, it is understood that IPRAT has the potential to satisfy the key recommendations of professional industry standards (for New Zealand namely; AS/NZS 2107:2016 recommended design acoustic standards).

A Slight Increase in Reverberation Time in the Classroom Affects Performance and Behavioral Listening Effort.

The purpose of this study was to investigate the effect of a small change in reverberation time (from 0.57 to 0.69 s) in a classroom on children's performance and listening effort. Aiming for ecological listening conditions, the change in reverberation time was combined with the presence or absence of classroom noise. In three academic tasks, the study examined whether the effect of reverberation was modulated by the presence of noise and depended on the children's age. A total of 302 children (aged 11-13 years, grades 6-8) with normal hearing participated in the study. Three typical tasks of daily classroom activities (speech perception, sentence comprehension, and mental calculation) were administered to groups of children in two listening conditions (quiet and classroom noise). The experiment was conducted inside real classrooms, where reverberation time was controlled. The outcomes considered were task accuracy and response times (RTs), the latter taken as a behavioral proxy for listening effort. Participants were also assessed on reading comprehension and math fluency. To investigate the impact of noise and/or reverberation, these two scores were entered in the statistical model to control for individual child's general academic abilities. While the longer reverberation time did not significantly affect accuracy or RTs under the quiet condition, it had several effects when in combination with classroom noise, depending on the task measured. A significant drop in accuracy with a longer reverberation time emerged for the speech perception task, but only for the grade 6 children. The effect on accuracy of a longer reverberation time was nonsignificant for sentence comprehension (always at ceiling), and depended on the children's age in the mental calculation task. RTs were longer for moderate than for short reverberation times in the speech perception and sentence comprehension tasks, while there was no significant effect of the different reverberation times on RTs in the mental calculation task. The results indicate small, but statistically significant, effects of a small change in reverberation time on listening effort as well as accuracy for children aged 11 to 13 performing typical tasks of daily classroom activities. Thus, the results extend previous findings in adults to children as well. The findings also contribute to a better understanding of the practical implications and importance of optimal ranges of reverberation time in classrooms. A comparison with previous studies underscored the importance of early reflections as well as reverberation times in classrooms.

Factors Affecting Auditory Estimates of Virtual Room Size: Effects of Stimulus, Level, and Reverberation.

When vision is unavailable, auditory level and reverberation cues provide important spatial information regarding the environment, such as the size of a room. We investigated how room-size estimates were affected by stimulus type, level, and reverberation. In Experiment 1, 15 blindfolded participants estimated room size after performing a distance bisection task in virtual rooms that were either anechoic (with level cues only) or reverberant (with level and reverberation cues) with a relatively short reverberation time of T60 = 400 milliseconds. Speech, noise, or clicks were presented at distances between 1.9 and 7.1 m. The reverberant room was judged to be significantly larger than the anechoic room (p < .05) for all stimuli. In Experiment 2, only the reverberant room was used and the overall level of all sounds was equalized, so only reverberation cues were available. Ten blindfolded participants took part. Room-size estimates were significantly larger for speech than for clicks or noise. The results show that when level and reverberation cues are present, reverberation increases judged room size. Even relatively weak reverberation cues provide room-size information, which could potentially be used by blind or visually impaired individuals encountering novel rooms.

Directional sound field decay analysis in coupled spaces

Multi-exponential energy decays—showing a distinct curvature in the measured decay curve—are a well known phenomenon in coupled spaces if both spaces exhibit different reverberation times due to their specific absorption characteristics or volumes. Recently, Berzborn et al. (2019) investigated directional energy decay curves—calculated from a plane wave decomposition of the sound field—as an analysis framework for the angular distribution of energy during the decay process in reverberation rooms. In this contribution, we investigate the directional characteristics of the energy decay in two rooms connected by a door. Spherical microphone array measurements at two different receiver positions and coupling areas were performed. Results indicate a distinct anisotropic energy decay in the room with the shorter reverberation time, showing a decreased isotropy in the late decay process compared to the early part.

An Archaeoacoustics Analysis of Cistercian Architecture: The Case of the Beaulieu Abbey

The Cistercian order is of acoustic interest because previous research has hypothesized that Cistercian architectural structures were designed for longer reverberation times in order to reinforce Gregorian chants. The presented study focused on an archaeoacacoustics analysis of the Cistercian Beaulieu Abbey (Hampshire, England, UK), using Geometrical Acoustics (GA) to recreate and investigate the acoustical properties of the original structure. To construct an acoustic model of the Abbey, the building’s dimensions and layout were retrieved from published archaeology research and comparison with equivalent structures. Absorption and scattering coefficients were assigned to emulate the original room surface materials’ acoustics properties. CATT-Acoustics was then used to perform the acoustics analysis of the simplified building structure. Shorter reverberation time (RTs) was generally observed at higher frequencies for all the simulated scenarios. Low speech intelligibility index (STI) and speech clarity (C50) values were observed across Abbey’s nave section. Despite limitations given by the impossibility to calibrate the model according to in situ measurements conducted in the original structure, the simulated acoustics performance suggested how the Abbey could have been designed to promote sacral music and chants, rather than preserve high speech intelligibility.

Acoustic simulation of J.S. Bach’s Thomaskirche in 1723 and 1539

This paper investigates an early acoustical theory of Hope Bagenal about the Leipzig Thomaskirche, where J.S. Bach composed and conducted from 1723 to 1750. Bagenal predicted that the church had a shorter reverberation time than previously in Bach’s time as a result of the Lutheran alterations to the space in the 16th century. This study uses on-site measurements to calibrate a geometric acoustical model of the current church. The calibrated model is then altered to account for the state of the church in 1723 and 1539. Simulations predict that the empty church in 1723 had a T30 value nearly one second lower than today, while the empty church in 1539 was much more reverberant than today. However, when the fully occupied church is simulated across all time periods, the difference in T30 is much smaller, with values at 1 kHz ranging from 2.7s in 1539, 2.5s in the present day, and 2.3s in 1723. These empirical data are crucial for understanding the historical setting of Bach’s music as heard by its original congregation and by its composer.

The impact of sound field amplification systems on speech perception of pupils with and without language disorders in natural conditions

The purpose of the study was to investigate in natural conditions the impact of sound field amplification systems (SFAS) on the perception of monosyllabic nonsense words in first to fourth-grade students with and without language disorders in classrooms with different acoustics.One hundred forty-five monolingual primary school pupils were included in the study. Two study groups were formed: pupils with typical language development (TD) (n = 145) and pupils with developmental language disorders (LD) (n = 72). Acoustic measurements were made in twelve classrooms with different reverberation time. Monosyllabic nonsense words perception tests, presented by an examiner, were carried out in classrooms with and without SFAS.The number of errors in the test carried out with SFAS in different acoustic conditions reduced in pupils of Grade 1 with TD (Z = –2.273, p = .023; Z = –1.965, p = .049) and with LD (Z = –2.410, p = .016; Z = –2.156, p = .031). The SFAS installed in large classrooms with long reverberation time significantly increased the number of errors in nonsense monosyllables perception (rS = 0.361, p < .01, rS = 0.229, p < .01). The mean number of errors in children with LD was higher than in children with TD in monosyllabic nonsense words tests carried out with and without SFAS (U = 3194, p < .001; U = 3518.5, p < .001).First-grade students benefit from sound field amplification in perception of monosyllabic nonsense words regardless of classrooms acoustics, and irrespective of the level of language development. The positive effect of SFAS on nonsense word perception was not observed in pupils of Grade 2, 3, and 4 of primary school. Classroom acoustics affects the expected positive impact of SFAS for children older than first graders. Amplification increases speech perception and decreases the number of errors in the reproduction of monosyllabic nonsense words in classrooms with short reverberation time.

Пороговая длительность звуковых сигналов для оценки приближения и удаления их источника в норме и при сенсоневральной тугоухости 2–3-й степени

The study of temporal characteristics of spatial hearing was carried out in 10 patients aged 68–83 years with sensorineural hearing loss (SNHL) (hearing loss 41–62 dB) using the method of constant stimuli and moving sound image modeling in a room with short reverberation time. Patients had no acute celebrovascular accidents, traumatic brain injuries and myocardial infarctions in their medical history. The moving sound images were created by linear variation of the amplitude of wideband noise burst sequences in the frequency range of 0.2–8 kHz, which were presented from two loudspeakers. According to the individual data obtained in the patients with SNHL of the 2nd -3rd degree, the threshold signal duration required for reliable determination of approaching and receding moving sound images varied within 300–800 ms. The average duration threshold in the group of SNHL patients was 400 ms, while in subjects with normal hearing it was 150 ms. Therefore, SNHL patients need more time for correct detection of the sound image motion direction than the subjects with normal hearing. These changes in perception may be due to the combined effect of the change in supra-threshold sound coding and the failure of the high-frequency binaural mechanism as a result of the hearing thresholds decrease.

Speech Perception in Classroom Acoustics by Children With Hearing Loss and Wearing Hearing Aids.

PurposeThe classroom acoustic standard ANSI/ASA S12.60-2010/Part 1 requires a reverberation time (RT) for children with hearing impairment of 0.3 s, shorter than its requirement of 0.6 s for children with typical hearing. While preliminary data from conference proceedings support this new RT requirement of 0.3 s, peer-reviewed data that support 0.3-s RT are not available on those wearing hearing aids. To help address this, this article compares speech perception performance by children with hearing aids in RTs, including those specified in the ANSI/ASA-2010 standard. A related clinical issue is whether assessments of speech perception conducted in near-anechoic sound booths, which may overestimate performance in reverberant classrooms, may now provide a more reliable estimate when the child is in a classroom with a short RT of 0.3 s. To address this, this study compared speech perception by children with hearing aids in a sound booth to listening in 0.3-s RT.MethodParticipants listened in classroom RTs of 0.3, 0.6, and 0.9 s and in a near-anechoic sound booth. All conditions also included a 21-dB range of speech-to-noise ratios (SNRs) to further represent classroom listening environments. Performance measures using the Bamford–Kowal–Bench Speech-in-Noise (BKB-SIN) test were 50% correct word recognition across these acoustic conditions, with supplementary analyses of percent correct.ResultsEach reduction in RT from 0.9 to 0.6 to 0.3 s significantly benefited the children's perception of speech. Scores obtained in a sound booth were significantly better than those measured in 0.3-s RT.ConclusionThese results support the acoustic standard of 0.3-s RT for children with hearing impairment in learning spaces ≤ 283 m3, as specified in ANSI/ASA S12.60-2010/Part 1. Additionally, speech perception testing in a sound booth did not predict accurately listening ability in a classroom with 0.3-s RT.Supplemental Material https://doi.org/10.23641/asha.11356487

Second language vocabulary level is related to benefits for second language listening comprehension under lower reverberation time conditions

ABSTRACTThe acoustic qualities of a room can have a deleterious effect on the quality of speech signals. The acoustic measurement of reverberation time (RT) has shown to impact second language (L2) speech comprehension positively when lower due to release from spectral and temporal masking effects as well as top-down processing factors. This auralization experiment investigated the benefits of better L2 vocabulary and executive function (updating) skills during L2 listening comprehension tests under shorter versus longer RT conditions (0.3 and 0.9 s). 57 bilingual university students undertook L2 vocabulary, number updating and L2 listening comprehension tests. After splitting groups into high/low vocabulary and updating groups, a mixed ANOVA was conducted. The high number updating group showed no significant differences or interactions in L2 listening comprehension than the lower number updating group across RT conditions. The high vocabulary group had 22% better L2 listening comprehension than the low vocabulary group in long RT, and 9% better in short RT. A significant benefit in L2 listening comprehension due to release from reverberation was only evident in the high vocabulary group. Results indicate that the benefit of good room acoustics for listening comprehension is greatest for those with better language (vocabulary) ability.

An investigation of acoustical environments in the elderly care facilities

62 rooms including living rooms, common rooms and dining rooms in 11 elderly care facilities had been measured, and some objective acoustical parameters in these rooms were measured such as background noise level (BNL) and reverberation time (RT). The range of BNL in 62 rooms was from 26.8 dBA to 67.2 dBA, and the mean BNL was 41.3 dBA and the standard deviation (SD) was 10.1 dBA. In these rooms, the averaged BNL in the living rooms was lower than those in the common rooms and the dining rooms, while the dining rooms had the highest averaged BNL. The RT in 500–4000 Hz octave bands, early-to-late sound ratio (C50) in 500–4000 Hz octave bands and speech transmission index (STI) in these rooms were 0.36–1.86 s, −4.48 to 9.67 dB and 0.47–0.81, respectively. Their mean values were 0.94 s, 1.73 dB and 0.64, and the SD were 0.40 s, 3.09 dB and 0.09, respectively. For all these measured rooms, the living room had a relatively short RT with a good speech intelligibility, while the dining room had a long RT with a fair speech intelligibility. To provide the elderly people with a good speech communication environment, some sound absorption and insulation treatment measures should be taken for the long RT and high BNL in the rooms of the elderly care facilities to reduce the BNL and RT and improve the speech intelligibility in these rooms.