Speech Transmission Index Research Articles

Pilot Cap Acoustic Transparency for Pediatric Amplification Devices

Consistent hearing device use in young children with hearing loss is challenging for families. A hearing aid accessory, called a pilot cap, is often recommended to families to help mitigate the issues around device retention. Although pilot caps are commonly suggested to families, there is sparse data available about how acoustically transparent they are when used with a hearing aid. The purpose of this study was to measure the acoustic transparency when a hearing aid functions under a pilot cap accessory. The Verifit 2 Hearing Aid Analyzer and the Speech Intelligibility Index (SII) were used to measure acoustic transparency related to access of aided speech. Measurements involved four hearing aids that are commonly fit on pediatric patients and four different commercially available pilot caps. SII data were collected at two intensity levels for four simulated sensorineural hearing losses (SNHLs). Response differences between acoustic measurements with a hearing aid plus a pilot cap compared with the hearing aid alone (control) were collected. A total of 80 SII measurements were made. There were 16 SII measurements of the hearing aid alone (control conditions) and 64 SII measurements with combinations of the hearing aids and pilot caps selected for this study. For each hearing aid, there was no significant difference between the SII measurements collected for the hearing aid alone and the hearing aid plus a pilot cap. Additionally, there was no significant difference between the different pilot caps used with each hearing aid tested. Pilot cap use with the four types of hearing aids in this study results in no significant differences in acoustic transparency compared with the control condition. The data in this study support the use of the pilot caps for hearing device retention in children with hearing loss. https://doi.org/10.23641/asha.22647217.

Investigation of the Effectiveness of the Chancel Availability and Geometry of Four Traditional Churches in Malaysia: Simulation Experiment

Two significant spaces define the soundscape of worship in a church: chancel and nave. The chancel is a space with the primary function of a sound source, where the preachers and choir are often seated during church services. Church design and layout have changed throughout history based on the functional needs of its target congregation. Some modern churches have omitted the chancel to fit contemporary design aesthetics. The main aim of this study is to investigate the relationship between the chancel and the acoustics performance of a church. Four churches with varying geometries of circular, polygonal, and rectangular chancels were selected for this study. Two simulations of varying chancel characteristics of chancel availability and chancel geometry were conducted. The recorded speech intelligibility index (STI) and reverberation time (RT) results indicate that chancel availability and geometry significantly affect churches’ acoustic performance. The simulation of the chancel availability mainly affected speech intelligibility, where the models with chancels recorded a higher STI than the models without chancels. In terms of chancel geometry, the results of the STI of the circular chancels were more encouraging than the polygonal and rectangular chancels.

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.

Assessment of speech intelligibility during different teaching activities in classrooms with and without acoustic treatment

There is limited data for assessing speech intelligibility in real classrooms with realistic occupied noise levels and teacher’s and students’ speech levels for different teaching activities in Turkish secondary school classrooms. This study investigates the effect of reverberation time (RT), occupied noise levels and signal-to-noise ratio (SNR) on speech transmission index (STI) in real classrooms for instruction and group work. Noise levels were measured and STI values were calculated in two secondary school classrooms with RT of 0.88 s and 2.73 s. During instruction situation, calculated mean STI values were 0.63 (classroom with acoustic treatment) and 0.29 (classroom without acoustic treatment) for normal voice effort and 0.65 (classroom with acoustic treatment) and 0.39 (classroom without acoustic treatment) for raised voice effort. During group work, STI values ranged from 0.50 to 0.74 in classroom with acoustic treatment and from 0.01 to 0.34 in classroom without any acoustic treatment. SNR of 15 dBA is only approached in classroom with acoustic treatment during instruction situation. The effect of increasing SNR on STI is prominent in the classroom without acoustic treatment which already has low SNR values. The present results show that the classroom with acoustic treatment will have good speech intelligibility for instruction with normal vocal effort and for group work with raised vocal effort at 3 m distance. However, the classroom with no acoustic treatment will have STI values in the range of bad and poor intelligibility. The present results confirm the impact of SNR and RT on speech intelligibility and shows that RT value of minimum 0.8 s is optimal to have good speech intelligibility in a secondary school classroom of approximately 250 m3 with a capacity of 18 students.

A Comparison of Acoustical Performance Between Traditional and Modern Church

Due to various worship approaches, churches' plans and designs have evolved over time.Intraditional churches, the chancel is where the preacher and choir are while the nave is where the audience is seated. The modern churches on the other hand usually follow the auditorium layout, where the chancel is replaced by a stage. The stage serves asa space for the musical worship and performances, other than preaching by the pastors. In acoustical terms, the chancel and the stage are known as the sound source and the audience is the sound receiver. It is essential to understand the relationship between the differences in the characteristics of traditional and modern churches and the impact on their acoustical performance.Two churches with different layout (cruciform and rectangular) from traditional and modern churches in Malaysia were selected to run a computer simulation using ODEON Room Acoustic Software. The results were then reviewed and analyzedin acoustical parameters: (i) Reverberation Time (RT) and (ii) Speech Transmission Index (STI). Smaller church scored better in STI thus it is better for speech driven worship service as while bigger church scored better in RT thus it is more ideal for musical worship. In addition, the existing materials found in modern churches improved the overall acoustical performances. In conclusion, the church acoustical performance is affected by factors like the volume, distance between the sound origin, receivers and the surrounding walls, total absorption area and types of surface material and its absorption coefficient.

THE ASSESSMENT OF ACOUSTICAL PERFORMANCE OF MOSQUES IN SHAH ALAM

A mosque is a place where Muslims conduct activities such as praying and listening to talks. Therefore, it is important for a mosque to have great acoustics quality as it influences the worshipper’s experience when praying or listening to Imam’s preaches. The acoustical evaluation in the mosque is rarely conducted and, in most cases, the development of good acoustic quality in the mosque is never considered at an early stage of design. In the present investigation, two large-volume mosques in Shah Alam were investigated: Section 7 Mosque (MS7) and Sultan Salahuddin Abdul Aziz Mosque (MSA). The objective of this study is to evaluate the acoustical characteristics of the mosque and its quality level. In addition, the speech intelligibility performance of each mosque was also determined using Speech Transmission Index (STI) and Rapid Transmission Index (RASTI). The experimental work found that the reverberation time of MSA has attained recommended values of reverberation time for that given size and volume while MS7 has slightly higher. The speech level attainment of both mosques is sufficient for worshippers to hear comfortably, but the background noise is high. Nevertheless, the signal-to-noise ratio (S/N ratio) indicates that both mosques have been able to obtain more than 15 dB(A) for improved speech intelligibility. The STI and RASTI prediction shows that MS7 has attained ‘fair’ and ‘bad’ ratings. In contrast, ‘poor’ and ‘bad’ ratings are achieved in the MSA.

Multicomponent Signal for Comparing Direct and Indirect Methods of Speech Transmission Index Measurement

When evaluating the intelligibility of speech distorted by noise and reverberation, direct or indirect methods of measuring the speech transmission index are used. However, it remains insufficiently studied how significantly differ the results of measurements obtained by direct and indirect methods. To find an answer to this question, the use of a multicomponent test signal consisting of four "elementary" signals separated by pauses is proposed in this paper. As "elementary" signals, it is proposed to use a maximum-length sequence, a speech shaped maximum-length sequence, a speech shaped stationary noise, and a speech shaped amplitude-modulated noise. Use of amplitude-modulated noise allows estimating speech transmission index by a direct method. Other "elementary" signals make it possible to estimate speech transmission index by two variants of indirect method. The proposed algorithms and corresponding computer programs were tested on trial signal models, while the consistency of the obtained results with the results of previous studies was revealed. The results of the signal models studies show that both considered variants of the indirect speech transmission index measurement method lead to underestimated results compared to the direct method. For one of the variants of the indirect method, the value of the estimate bias is 0.03–0.04, regardless of the interfering conditions. For another variant of the indirect method, the estimate bias varies from 0.01 to 0.18, depending on the interference conditions.

Assessment of speech intelligibility in scholar classrooms by measurements and prediction methods

According to Italian regulation, the Ministerial Decree of 11 October 2017 about Environmental Criteria, reference values for acoustic indoor quality descriptors in public buildings are imposed. Regarding school environments, indoor acoustic quality targets refer to reverberation time, clarity, and speech intelligibility, whose representative acoustic descriptor is the speech transmission index (STI). This paper presents pyeSTImate, a Python-based tool for speech transmission index prediction in lecture rooms. The tool returns fully simulated results from the dimensions and material characteristics of classrooms with parallelepiped geometry and without limitations in size. Extensive experiments have been conducted with different simulation methods, evaluating the accuracy by comparison with in situ measurements selected from primary, secondary, and university classrooms in school buildings of the Marche Region in Italy. The combination of simulated speech transmission indexes with a prediction method based on an artificial neural network has also been evaluated. The analysis of the performance demonstrates the computational robustness of the tool that enables its use for the analysis of existing rooms, as well as for the renovation and design of new spaces.

The effects of speech intelligibility on reading comprehension under task-switching behaviour in open-plan offices

Numerous investigations showed that speech noise is the most disturbing factor in work efficiency. Work efficiency decreases with speech intelligibility. The results of a recent study show that the effect of speech intelligibility on work efficiency is significantly correlated with the effect of speech intelligibility on reconcentration. To examine the effects of speech intelligibility on reading comprehension under task-switching behaviour, a total of 30 students were recruited to participate reading comprehension test, which is interrupted by a creative task. Task performance, psychology, and physiology indicators were carried out under eight experimental conditions with speech transmission index = 0.00, 0.17, 0.26, 0.36, 0.45, 0.52, 0.57, and 0.71. The experimental results showed that the task-switching behaviour had no evidence to support a significant impact on task performance for each speech intelligibility. However, task-switching behaviour significantly impacts participants’ fatigue and workload as the value of the speech transmission index increases.

Measurements of classroom acoustic conditions in which young neurodiverse persons learn in São Paulo and Nebraska

Autism is a set of complex neurobehavioral conditions that involve, among other characteristics, hypo/hypersensitive responses to any sensory input, usually referred to as sensory processing disorder. The most common sensory difference associated with autistic individuals is an over or under response to visuals, touch, smells, tastes, balance, and sounds when compared to neurotypical individuals. Among these, auditory sensitivity has a significant influence. Research studies to date have revealed that autistic individuals are highly susceptible to surrounding sounds, and show that certain noises, such as loud sounds, classroom bells, sirens, the radio or the TV, and traffic noise, may induce uncomfortable and distracting behavior. In this study, we investigated the acoustic environment of classrooms/facilities designed for a more inclusive education. A number of room acoustic descriptors, such as reverberation time (RT), speech clarity (C50), speech transmission index (STI), sound levels, and auditory strength (S/N ratio) were measured in this regard. The experimental measurements were performed in several rooms and facilities focusing on autistic individuals in Campinas, São Paulo, in Brazil and in Omaha, Nebraska, in the United States.

Age effect on students’ intelligibility listening to a teacher with a dysphonic voice

The purpose of this project is to assess the acoustical conditions in which optimal intelligibility and low listening effort can be achieved in real classrooms for elementary students, taking into consideration the effects of dysphonic voice and typical classroom noise. Speech intelligibility tests were performed in classrooms with 80 normal-hearing students (7–11 years old). The speech material was produced by a female actor using a normal voice quality and simulating a dysphonic voice. The stimuli were played by a Head and Torso Simulator. Child babble noise and classrooms with different reverberation times were used to obtain a Speech Transmission Index range from 0.2 to 0.7. The results showed a significant decrease in intelligibility when the speaker was dysphonic, in STI higher than 0.33. The rating of listening difficulty showed a significantly greater effort in perceiving the dysphonic voice. Younger children showed poorer performance and greater listening difficulty compared to older children when listening to the normal voice quality. Both groups were equally impacted when the voice was dysphonic. The results suggested that better acoustic conditions are needed for children to reach a good level of intelligibility and to reduce listening effort if the teacher is suffering from voice problems.

Effect of speaker orientation on speech intelligibility in an automotive environment

In addition to background noise, binaural effect, and the acoustic boundary conditions of a given space, speech intelligibility (SI) is affected by the source/speaker directivity or orientation, the latter of which has not been researched in small enclosed spaces, such as an automobile. Thus, this study aims to investigate the effect of speaker orientation on SI in automobiles, using both the speech transmission index (STI) and subjective experiments. Given the limited variation range for the orientation of rear-row speakers in an actual scenario, only the situation for front-row speakers was considered in this study. An artificial mouth was regarded as the speaker, which is placed at the driver’s seat. Binaural room impulse responses were measured for different listener locations and speaker orientations in an automobile and a listening room with negligible reflections. Subsequently, STIs were calculated and subjective speech reception thresholds (SRTs) in Mandarin Chinese were evaluated for the different listener locations and speaker orientations. The result shows that the SI in the listening room considerably decreases when the speaker orientation deviates from the listener due to the speaker directivity, with a best-ear STI (SRT) variation of up to 0.24 (7.4 dB). In comparison with the result in the listening room, early reflections improve SI in the automobile by a best-ear STI (SRT) increase (decrease) of up to 0.3 (7.7 dB). The speaker deviating from the listener signifies that the early reflections in the automobile afford a higher SI improvement. Thus, the variation range of SI with various speaker orientations in the automobile was greatly reduced compared with that in the listening room, with a best-ear STI (SRT) variation of no more than 0.1 (2.7 dB). Overall, the speaker orientation mostly does not affect SI except when the speaker is facing the listener due to rich early reflections inside an automobile. Moreover, the comparison between the subjective and objective results shows that the best-ear STI can well express the variation in the SRT in the automobile under various speaker orientations. This study bridges the gap in the research of SI considering various speaker orientations in an automotive environment and helps understand the combined effect of various factors on SI under the special acoustic condition in an automobile.

Objective and subjective assessment of the speech intelligibility in rooms with an Active Acoustic Enhancement Systems

Speech Transmission Index (STI), apart from the Reverberation Time (RT), remains an important parameter used for the speech intelligibility assessment indoors. As the Active Acoustic Enhancement Systems (AAES) are getting more and more commonly used, it was verified how such systems affect speech perception. In accordance with the 3382-1 and 3382-2 regulations, objective parameters were measured in two enclosures with the AAES. The RT values varied from 0.91 to 1.61 [s] for the hall in Mińsk Mazowiecki and from 0.75 to 1.52 [s] in Puławy. The STI values varied from 0.57 to 0.64 in Mińsk Mazowiecki and 0.64 to 0.69 in Puławy. Despite the significant differences in the RT values, STI coefficients remained almost unchanged. The listening test was designed to verify if the subjectively assessed intelligibility would confirm the objective measurements' results. 50-element nonsense words (logatome) lists were used for in-situ experiments and, in the second part, binaural laboratory arrangement. Both parts involved over 120 listeners. Three scenes were selected: without AAES and two different AAES setups. In summary, subjective measurements' results were compared with the obtained STI, RT and Clarity (C50, C80) values to prove their importance in indoors speech intelligibility evaluation.

A prediction model of speech transmission index based on reverberation time in non-native linguistic context

High speech intelligibility is an essential requirement for classrooms, especially in relation to non-native students. Speech transmission index (STI) was proved as the most relevant acoustic parameter to assess speech intelligibility. In this paper, twenty-seven classrooms for non-native teaching purposes were selected for investigation. Physical acoustic measurements were conducted in these classrooms and numerical simulation verification was determined by ODEON version 16. The relationships between STI values and RT values were fitted based on non-linear curve fitting regression models. In this paper, three primary forms of non-linear curve fitting regression models were employed for predicting curves. A logarithmic function was selected as the basic regression equation to describe the effects of RT values on STI values. The results showed that STI values increase with the decrease of RT values for all age groups. From the verified results, it was possible to propose the predictive equation that presents the best accuracy in predicting the experimental data for non-native teaching purposes. The impact of different age groups and linguistic environment on STI were discussed. The prediction model is expected to estimate STI values by using RT values during the early design stage in a non-native linguistic context.

Objective evaluation of multipurpose enclosures equipped with active acoustic enhancement systems

Research on optimal acoustic parameter values that have been carried out for recent decades and the necessity to provide different acoustic solutions to events of a different type led to construction of rooms with variable acoustic conditions. Nowadays, active acoustic enhancement systems (AAES) become more and more popular. Application of such systems allows adjustments of acoustic parameters required for particular performance. This paper presents results from measurements of objective parameters of multipurpose enclosures equipped with AAES. Investigated halls are located in Poland in the following cities: Łańcut, Mińsk Mazowiecki, Puławy, Wieluń and were intentionally built or renovated as multipurpose rooms. All of those halls were equipped with Yamaha AFC version 3 system. The measurements were performed according to ISO338-1/2 standards. In total 13 active acoustic system settings (presets) were analyzed to investigate their influence namely Reverberation Time (RT), Early Decay Time (EDT), , Initial Time Delay Gap (ITDG), Center Time (Ts), Clarity (C80, C50), Definition (D50), Interaural Cross Correlation (IACC) and Speech Transmission Index (STI). The analysis of the obtained results showed that it is possible to obtain the appropriate acoustic conditions with acoustic parameters values set in the suggested range for a given event using active acoustic systems.

The effects of workstation arrangements on the acoustical performance of the architecture design studios.

Architecture design studios spaces needs special treatment for its acoustical environment. Interaction, communication, meetings, and various activities could influence concentration, which in turn, affects other aspects as quality of the architectural concepts and creation level. Workstation arrangement could consider as one of the elements which can improve the design studio acoustical conditions. In this paper, we evaluate the impact of 5 types of workstation arrangement with two different partitions heights (1.10m and 1.60m). The measurements were conducted in the College of Architecture, Imam Abdulrahman Bin Faisal University, KSA. Speech Transmission Index, STI in the nearest workstation, Distraction distance rD, privacy distance rP, A-weighted background noise level Lp, A, B and A-weighted SPL of speech at 4 meters Lp,A,S,4m have been measured according to ISO 3382-3. We found that U-shaped workstation arrangement can improve the acoustical environment the design studio. Furthermore, good results were observed using 1.60m partition height for all types of arrangements.

Quantifying Access to Speech in Children with Hearing Loss: The Influence of the Work of Pat Stelmachowicz on Measures of Audibility.

This article reviews the research of Pat Stelmachowicz on traditional and novel measures for quantifying speech audibility (i.e., pure-tone average [PTA], the articulation/audibility index [AI], the speech intelligibility index, and auditory dosage) as predictors of speech perception and language outcomes in children. We discuss the limitations of using audiometric PTA as a predictor of perceptual outcomes in children and how Pat's research shed light on the importance of measures that characterize high-frequency audibility. We also discuss the AI, Pat's work on the calculation of the AI as a hearing aid outcome measure, and how this work led to the application of the speech intelligibility index as a clinically utilized measure of unaided and aided audibility. Finally, we describe a novel measure of audibility-auditory dosage-that was developed based on Pat's work on audibility and hearing aid use for children who are hard of hearing.

Investigating the Potential of Transparent Parallel-Arranged Micro-Perforated Panels (MPPs) as Sound Absorbers in Classrooms.

Acoustic deficiencies due to lack of absorption in indoor spaces may sometime render significant buildings unfit for their purpose, especially the ones used as speech auditoria. This study investigates the potential of designing wideband acoustic absorbers composed of parallel-arranged micro-perforated panels (MPPs), known as efficient absorbers that do not need any other fibrous/porous material to have a high absorptive performance. It aims to integrate architectural trends such as transparency and the use of raw materials with acoustical constraints to ensure optimal indoor acoustic conditions. It proposes a structure composed of four parallel-arranged MPPs, which have been theoretically modelled using the electrical Equivalent Circuit Model (ECM) and implemented on an acrylic prototype using recent techniques such as CNC machining tools. The resulting samples are experimentally analysed for their absorption efficiency through the ISO-10534-2 method in an impedance tube. The results show that the prediction model and the experimental data are in good agreement. Afterward, the investigation focuses on applying the most absorptive MPP structure in a classroom without acoustic treatment through numerical simulations in ODEON 16 Acoustics Software. When the proposed material is installed as a wall panel, the results show an improvement toward optimum values in Reverberation Time (RT30) and Speech Transmission Index (STI).

Hearing Thresholds, Speech Recognition, and Audibility as Indicators for Modifying Intervention in Children With Hearing Aids.

The purpose of this study was to determine if traditional audiologic measures (e.g., pure-tone average, speech recognition) and audibility-based measures predict risk for spoken language delay in children who are hard of hearing (CHH) who use hearing aids (HAs). Audibility-based measures included the Speech Intelligibility Index (SII), HA use, and auditory dosage, a measure of auditory access that weighs each child's unaided and aided audibility by the average hours of HA use per day. The authors also sought to estimate values of these measures at which CHH would be at greater risk for delayed outcomes compared with a group of children with typical hearing (CTH) matched for age and socioeconomic status, potentially signaling a need to make changes to a child's hearing technology or intervention plan. The authors compared spoken language outcomes of 182 CHH and 78 CTH and evaluated relationships between language and audiologic measures (e.g., aided SII) in CHH using generalized additive models. They used these models to identify values associated with falling below CTH (by > 1.5 SDs from the mean) on language assessments, putting CHH at risk for language delay. Risk for language delay was associated with aided speech recognition in noise performance (<59% phonemes correct, 95% confidence interval [55%, 62%]), aided Speech Intelligibility Index (SII < 0.61, 95% confidence internal [.53,.68]), and auditory dosage (dosage < 6.0, 95% confidence internal [5.3, 6.7]) in CHH. The level of speech recognition in quiet, unaided pure-tone average, and unaided SII that placed children at risk for language delay could not be determined due to imprecise estimates with broad confidence intervals. Results support using aided SII, aided speech recognition in noise measures, and auditory dosage as tools to facilitate clinical decision-making, such as deciding whether changes to a child's hearing technology are warranted. Values identified in this article can complement other metrics (e.g., unaided hearing thresholds, aided speech recognition testing, language assessment) when considering changes to intervention, such as adding language supports, making HA adjustments, or referring for cochlear implant candidacy evaluation.

Proposal of a Simplified Tool for Early Acoustics Design Stage of Classrooms in Compliance with Speech Intelligibility Thresholds

The speech intelligibility properties of classrooms greatly influence the learning process of students. Proper acoustics can promote the inclusion of foreign students and children with learning or hearing impairments. While awareness of the topic is increasing, there is still no parameter that can describe all aspects of speech transmission inside a room. This complicates the design of classrooms and requires designers to have extensive knowledge of theory and experience. In the scientific and technical literature, there is a lack of predictive tools, easy to use by designers, which can guide the choices in the early design stages in order to move towards technical solutions able to ensure adequate levels of speech intelligibility. For this reason, in this paper, the most relevant speech intelligibility parameters found in the literature were collected and discussed. Among these, the Clarity index and Speech Transmission Index were singled out as the most effective ones, whose prediction can be made with relatively simple methods. They were then analyzed through their prediction formulas, and a tool was proposed to allow an easy estimation of the minimum total equivalent sound absorption area needed in a classroom. This tool greatly simplifies the early acoustics design stage, allowing the intelligibility of speech within a classroom to be increased without requiring much theoretical effort on the part of the designers.