Acoustic Index Research Articles

High-pass filters do not consistently strengthen associations between acoustic indices and avian species richness

High-pass sound filters are a common form of audio manipulation that attenuates or removes low frequency sounds from audio recordings. While high-pass filters are used to reduce anthropogenic noise, there is limited guidance on their optimal application and their effects on acoustic indices—numerical values derived from passive acoustic monitoring (PAM) recordings to summarize acoustic information. Here, we investigated the effects of three high-pass filter treatments (482 Hz, 1 kHz, and 2 kHz) on eight commonly implemented acoustic indices and one less-commonly used convolutional neural network metric. Specifically, we used simulated soundscapes with three levels of traffic noise interference and then applied the filter treatments to field recordings collected throughout Illinois, USA during May 2022–July 2023 and derived acoustic indices to further understand these effects. Our analysis revealed that interactions between acoustic filtering and vehicular noise pollution have diverse effects on the nine acoustic indices, both in simulated soundscapes and empirical PAM recordings. In general, a 1 kHz or 2 kHz filter was necessary in order to produce significant changes in acoustic index values. However, none of the applied filtering treatments consistently strengthened correlations between the examined acoustic indices and avian species richness. The Acoustic Complexity Index (ACI), Acoustic Richness Index (AR), and CityBioNet (CB) demonstrated greater resistance to biologically non-informative changes caused by filter implementation, with CB showing a notably higher correlation with species richness compared to the other examined indices. Our findings suggest that ACI, AR, and CB may be better suited to studies of avian species richness in soundscapes with high levels of anthropogenic noise. Future research is needed to establish best practices for acoustic filtering, understand the behavior of acoustic indices under various environmental contexts, and explore alternative methodologies for avian monitoring in human-modified contexts.

Update of Vocal Fold Shortening With Retrodisplacement of Anterior Commissure for Voice Feminization.

To assess the efficacy and long-term durability of the enhanced technique of Type II Vocal Fold Shortening and Retrodisplacement of the Anterior Commissure (VFSRAC) for voice feminization compared with the preceding Type I method. A retrospective analysis encompassed 506 patients drawn from a cohort of 1025 MtF transgender women who underwent VFSRAC between 2003 and 2021. The study period included cases from 2015 to 2021, during which the Type II update technique was implemented, involving a modification to the suture technique. Subjective and perceptual evaluations, aerodynamic and acoustic assessments, real-time pitch analysis, and videostroboscopic reviews were conducted pre- and postoperatively in the MtF transgender women cohort. Comparative statistical analyses were performed to discern differences between the earlier Type I method (2003-2014) and the more recent Type II method (2015-2021). The preoperative mean speech fundamental frequency (sF0) for Type II VFSRAC was 134.5 Hz. Postoperatively, the mean sF0 increased to 196.7 Hz, 212.3 Hz, and 207.5 Hz at 3 months, 6 months, and beyond 1 year, respectively, exceeding outcomes observed with the Type I method. Postoperative subjective and objective assessments indicated an augmentation in voice femininity. Acoustic and aerodynamic indices were within the normal range, and the regularity of the vocal fold mucosal wave was preserved within normal parameters. These results suggest that patients achieved a natural phonation pattern after surgery. The application of our updated type II VFSRAC has demonstrated feasibility and consistently yielded favorable results for individuals desiring a naturally feminine voice. 3 Laryngoscope, 134:5054-5061, 2024.

Acoustic indices enable the discrimination of temperate forest types and better predict differences in bird species composition than in bird species richness

Acoustic indices enable the discrimination of temperate forest types and better predict differences in bird species composition than in bird species richness

EcoSound-web: an open-source, online platform for ecoacoustics.

Passive acoustic monitoring of soundscapes and biodiversity produces vast amounts of audio recordings, but the management and analyses of these raw data present technical challenges. A multitude of software solutions exist, but none can fulfil all purposes required for the management, processing, navigation, and analysis of acoustic data. The field of ecoacoustics needs a software tool that is free, evolving, and accessible. We take a step in that direction and present ecoSound-web: an open-source, online platform for ecoacoustics designed and built by ecologists and software engineers. ecoSound-web can be used for storing, re-sampling, organising, analysing, and sharing soundscape recording or metadata projects. Specifically, it allows manual annotation of soniferous animals and soundscape components, automatic annotation with deep-learning models for all birds and for UK bat species, peer-reviewing annotations, analysing audio in time and frequency dimensions, computing alpha acoustic indices, and providing reference sound libraries for different taxa. We present ecoSound-web's structure and features, and describe its operation for typical use cases such as sampling bird and bat communities, using a primate call library, and the analysis of soundscape components and acoustic indices. ecoSound-web is available from: https://github.com/ecomontec/ecoSound-web.

The acoustic complexity index (ACI): theoretical foundations, applied perspectives and semantics

The acoustic complexity index (ACI) is a commonly used metric in ecoacoustics, demonstrating reliability across diverse environments and ecological conditions. However, this index requires specific procedures to be applied correctly. Based on the Canberra metric, the ACI is an unsupervised metric formulated to extract information from fast Fourier transform (FFT) sonic matrices. The ACI measures contiguous differences in acoustic energy of each frequency bin along temporal steps (ACItf) and a temporal interval along the frequency bins (ACIft). Aggregating data after an FFT with a clumping procedure allows for better scaling of sonic signals before computing the ACI. A filter must be applied to reduce the effects of nonenvironmental signals produced by microphone electrical noise . Due to the singularity of the index for values of 0, ACI requires ad hoc procedures to exclude element pairs for which one of the elements is equal to 0 from the comparisons. The spectral and temporal sonic signatures are vectors obtained from the sequence of ACItf and ACIft values, respectively. The comparison between sonic signatures using the chord distance index returns spectral and temporal sonic dissimilarities, allowing the evaluation of sonic patterns at different temporal and spatial resolutions. Sonic variability, sonic evenness, and the effective number of frequency bins are further derivative metrics that help interpret sonic heterogeneity by distinguishing the temporal and spatial heterogeneity of sonoscapes. Moreover, this paper proposes changing the terminology of ‘acoustic complexity index' to ‘sonic heterogeneity index.'

Unsupervised selection of acoustic indices: An experimental comparison for characterizing unlabeled audio recordings from sub-Andean forest soundscapes

We present an experimental comparison of applying six unsupervised (i.e. not relying on class labels) and almost parameterless feature selection methods for ranking acoustic indices. The study is aimed at guiding the practitioner in choosing appropriate acoustic indices when, in absence of class labels, a small but meaningful number of features to characterize soundscapes is desired. Forty acoustic indices were considered, which correspond to seventeen temporal, spectral and soundscape features, along with their basic statistics. Three publicly available soundscape datasets, registered in a sub-Andean forest, were used for the experiments; moreover, several subsets were considered according to the different times of the day. Results reveal that the Acoustic Evenness Index is the most important one in terms of representational power according to the six considered selection criteria, followed by the Acoustic Complexity Index when conditions are relaxed to examine features ranked among the top-five. Besides, the Bioacoustic Index, the Acoustic Diversity Index and the Root Mean Square Energy stand out as important features when characterizing days in their separated parts.

Soundscapes in Urban Green Spaces of a Megacity Across an Urban–Rural Gradient: A Case Study of Shanghai

Urban soundscapes are valuable indicators of urban biodiversity and ecosystem health. This study investigated the spatial and temporal characteristics of soundscapes in megacity green spaces and their relationship with the urban environment. An acoustic index was formulated and calculated using long-term data from Shanghai’s urban green spaces. The results show a significant increase in the acoustic index during spring and summer, peaking during these periods, while a decrease was observed from December to February, dominated by abiotic sounds. Diurnal variations indicate a rapid increase in the acoustic index at sunrise, reflecting heightened avian activity during the dawn chorus. Human interference in the urban center limited acoustic activity, whereas the outer suburbs, with their more natural environments, supported greater acoustic richness.

Continuous measurement of red wood ant (Formica rufa) outdoor behaviour using passive acoustic monitoring

Ants serve as ecosystem engineers that maintain important ecological processes within forests. Given their ecological importance, it is a clear scientific shortcoming that we lack non-invasive methods to survey their behaviour inside common opaque habitats such as mounds, litter, and soil. In this study, we assess if acoustic signals from red wood ant (Formica rufa) mounds are useful to infer temporal changes in ant activity within forested ecosystems. We found that acoustic indices used previously as a proxy for soil fauna in soil ecological studies (Acoustic Complexity Index, Bioacoustic Index) can indeed separate sounds generated by the ant's daily routines (biophony) from other forest sounds. Yet, we also show that these indices are problematic proxies for soil diversity as they increase not only due to an increased number of species but also due to an increased number of the same species. Acoustic measures that incorporated the strength of acoustic signals, Average Power Density (APD) and Peak Power Density (PPD) also increased with increasing ant abundance and constituted the conceptually best proxy for ant activity. For example, the PPD could i) track diurnal changes in Formica rufa activity with a high temporal resolution (minutes) and ii) detect altered behavioural responses to temperature changes. We conclude that microphones detecting biophony can provide high-resolution information about in situ ant behaviours in forested ecosystems. Thus, passive acoustics monitoring offers a promising avenue as a non-invasive monitoring tool for soil macrofauna studies.

Comparative Study of Two Semi-Occluded Vocal Tract Protocols: A Randomized Clinical Trial.

Semi-occluded vocal tract exercises (SOVTEs) are widely used as a therapeutic tool to create flow resistance in the upper airway. The current study was a randomized controlled clinical trial to establish the efficacy of two SOVTE protocols, flow-resistant tube (FRT) and Lessac-Madsen Resonant Voice Therapy (LMRVT). Exploratory investigations included a noninferiority analysis of FRT to the widely adopted therapy protocol (LMRVT), as well as examining the dosing required to improve acoustic measures and subjective ratings. Sixty-seven participants with voice disorder were randomized into one of five groups: 4-week FRT (n = 14), 8-week FRT (n = 19), 4-week LMRVT (n = 15), 8-week LMRVT (n = 5), and control (n = 14). Voice Handicap Index (VHI) and Vocal Fatigue Index scores were collected pre- and posttreatment. Acoustic analysis using the Acoustic Voice Quality Index was completed. We compared VHI between controls and 8-week FRT and LMRVT, adjusting for pre-VHI using linear regression. We examined the efficacy of 4-week protocols relative to controls and conducted a noninferiority comparison of FRT (4 and 8 weeks) to LMRVT (4 and 8 weeks) using 5- and 10-point margins. Finally, we compared the 4- versus 8-week sessions for both therapies. A statistically significant reduction of VHI in both 8-week FRT relative to controls (-10.60, 95% CI [-19.80, -1.40], p = .025) and 8-week LMRVT (-15.74, 95% CI [-29.40, -2.08], p = .025) was found. We also found an improvement in 4-week FRT relative to controls (-10.11, 95% CI [-20.03, -0.20], p = .046), but the 4-week LMRVT result was not statistically significant (p = .057). FRT was found to be noninferior to LMRVT in terms of VHI using a 10-point margin (FRT - LMRVT: 0.69, 95% CI [-5.76, 7.15], p = .01), but not using a 5-point margin (p = .054). There were no statistically significant differences in VHI scores between 4- and 8-week sessions for either therapy. Both FRT and LMRVT improved VHI scores relative to controls. FRT was noninferior to LMRVT in terms of VHI scores. There were no statistically significant differences in VHI scores between 4- and 8-week therapy sessions.

Validation of the Acoustic Voice Quality Index Version 03.01 in Turkish

ObjectivesThe aim of this study was to validate the Acoustic Voice Quality Index (AVQI) version 3.01 in the Turkish-speaking population. Materials and methodsConcatenated voice samples of the sustained vowel [a:] and continuous speech were collected from 127 dysphonic and 128 normophonic participants. The auditory-perceptual evaluation was performed by five experienced raters using the Grade parameter of the GRBAS scale. Rater reliability, concurrent validity, diagnostic accuracy, and differences between normophonic and dysphonic groups were analyzed for the AVQI version 3.01. ResultsThe number of syllables for the standardized reading text with the concatenation of the voiced parts lasting around 3 seconds (mean=3.84s) was 36. The ICC values of intra-rater reliability of G scores of five raters were excellent (mean ICC=0.934), and of inter-rater reliability they varied between moderate and excellent (mean ICC=0.786). AVQIv3 demonstrated a high diagnostic accuracy with AUC = 0.906 in identifying disrupted versus normal voice quality. With sensitivity of 80% and specificity of 94%, AVQIv3 = 2.345 was the cut-off point that differentiated most accurately between normophonic and dysphonic voices in Turkish. ConclusionAVQIv3 is an ecologically valid tool for objective differentiation between dysphonic and normal voices in the Turkish language.

Enhancing Acoustic Data Mobilization: A User-Friendly Data Platform for the Asian Soundscape Monitoring Network

Passive Acoustic Monitoring (PAM) has emerged as a crucial tool in monitoring efforts to track environmental changes and evaluate conservation measures in response to the biodiversity crisis (Sugai et al. 2018). PAM now offers long-term and continuous insights into biodiversity, using acoustic indices correlating with biodiversity and deep-learning tools to aid in the detection and identification of animal sounds (Sueur et al. 2014, Kahl et al. 2021, Wu et al. 2022). However, managing and mobilizing original recordings remains challenging due to their large size and lack of structure, hindering broader applications of these valuable data. Established in 2014 by Academia Sinica and Taiwan Forestry Research Institute, the Asian Soundscape Monitoring Network has amassed over 20 million minutes of audible and ultrasonic recordings from diverse landscapes, including forests, wetlands, urban parks and farmlands across Malaysia, Thailand, Taiwan and Vietnam. To enhance data mobilization and utilization, we developed a user-friendly data platform enabling browsing, searching, visualization, exploration and retrieval of the original recordings (Fig. 1), as well as derived data such as acoustic indices and species occurrences, and associated weather records (Fig. 2) The platform also allows users to visualize the temporal dynamics of the soundscape and identify acoustic events at monitoring sites by examining long-term spectrograms and time series of acoustic indices (Fig. 3). Detailed information about the monitoring sites and recorder deployment is provided. Each recording is tagged with a Creative Commons license, and a unique Archival Resource Key is assigned to every data retrieval for persistent identification, facilitating data reuse. Additionally, recordings containing human voices are identified and restricted to protect privacy. Our aim with this data platform is to streamline the mobilization of acoustic data, foster diverse applications, and enhance the overall value of the data.

Acoustic Analysis of Spatiotemporal Variability in Children With Childhood Apraxia of Speech.

The purpose of this study was to investigate acoustic spatiotemporal variability in children with childhood apraxia of speech (CAS) compared to children with typical development (TD). Increased spatiotemporal variability in children with CAS relative to nonapraxic peers has been documented in multiple kinematic studies. To date, few studies have investigated spatiotemporal variability in CAS using an acoustic signal. Data were drawn from 10 children with CAS and 10 children with TD, ranging in age from 5;0 to 11;2 (years;months), who participated in an online study. All children with CAS had a verified diagnosis and showed at least five CAS features across at least two tasks, independently confirmed by two speech-language pathologists with expertise in CAS. Children repeated the sentences "Buy Bobby a puppy" (BBAP) and "Mom pets the puppy" (MPP) 10 times each. The acoustic spatiotemporal index (STI), calculated from the amplitude envelope, was used to investigate acoustic spatiotemporal variability. Using a regression analysis, we analyzed group differences in STI values while controlling for age and gender. Children with CAS did not produce enough usable tokens of BBAP to analyze. MPP revealed significantly higher acoustic STI values in children with CAS compared to children with TD. No significant effects were observed for age or gender. Acoustic data collected online without the use of specialized equipment yielded high-quality audio data from which amplitude envelope tracing could be reliably accomplished. This study adds to a growing body of empirical data indicating that children with CAS produce speech with more variable spatiotemporal control compared to children with TD. In addition to producing more variable speech, children with CAS were less consistently able to form productions free of phonetic errors. These findings also demonstrate the feasibility of using remote data collection to investigate acoustic spatiotemporal variability, which allows for the recruitment of larger samples of low-incidence populations. https://doi.org/10.23641/asha.26814883.

Associations between acoustic indices and the evaluation of the urban soundscape according to ISO 12913

The development of high-quality acoustic environments (AE) is crucial for the transformation of cities into sustainable and health-promoting places. In recent years, the soundscape approach (ISO 12913) has gained attention for quantifying the AE using a standardised questionnaire for soundwalk participants. This way, several qualities of the AE can be analysed. However, soundwalks are costly and limited to a select number of sites. To scale up the assessment of the urban AE, the use of acoustic indices, which could reflect different qualities of a soundscape, represents a promising approach. Therefore, we present an analyses of the association between acoustic indices and affective soundscape qualities. We use soundscape data from the Be-MoVe project in Essen, Germany. In total, 35 soundwalks with 143 participations were conducted and data were collected from 858 questionnaires for 22 listening stations, each with a three-minute audio recording. These recordings are used to calculate ecoacoustic indices and complex network measures based on frequency correlation matrices, as these have shown promising results in previous studies. We present results from descriptive statistics as well as multi-level regression analyses modelling the relationship between self-rated affective qualities of AE and acoustic indices, taking into account spatial variability between different urban locations.

Studying environment sounds using transfer entropy: Application to an urban park in the city of Milan, Italy

Sounds in large cities are usually characterized by multi-source overlaying components. This makes environment sound quality difficult to interpret, thus requiring different investigation approaches. This is the case of urban parks where the coexistence of anthropogenic and biophonic sound sources makes the evaluation of the local soundscape quality challenging. In this context, we applied the transfer entropy measure to extract additional information with respect to the more classical approach of eco-acoustics. The case study refers to the Parco Nord of Milan, Italy, for which classical soundscape analysis is already available. We used sound recordings (3.5h long each) taken over an area of approximately 20 hectares using 16 sensors. We calculated the classical eco-acoustic indices and studied the transfer entropy among all sites. The considered time series corresponded to three representative eco-acoustic indices (Acoustic Diversity Index, ADI, Acoustic Complexity Index, ACI and Dynamic Spectral Centroid, DSC calculated for all the 16 sites with 1-minute time resolution) obtained after a principal components analysis. A preliminary interpretation of the results is provided by selecting a representative index from one principal component and by comparing its behavior with a previous standard soundscape analysis performed by the authors for the same index and area.

Noise monitoring in primary schools: comparisons between different time-dependent parameters for acoustic performance evaluation

The A-weighted equivalent sound level is commonly used to describe or regulate environmental noise over a defined time interval. Although it is very convenient and easy to compare noise limits or requirements, it does not provide summary information on how noise evolves. On the other hand, the detailed analysis of the history of the measurements over time is too burdensome in the case of long-term monitoring. As part of a large study that aims to investigate the effects of noise on the cognitive abilities of primary school children, long-term unattended monitoring was carried out using low-cost instrumentation based on smartphone apps and calibrated external microphones. From the data obtained, acoustic indices and parameters were calculated, which allowed the assessment of the time-dependent noise exposure of the students based on the type of activity carried out in class. This analysis can be useful for validating the acoustic design requirements in schools.

Effect of cross-frequency correlation on the auralization of acoustic scintillation in outdoor sounds

Outdoor sound propagation is modified by random fluctuations in the acoustic refractive index due to atmospheric turbulence. This phenomenon, known as acoustic scintillation, results in fluctuations in the amplitude and phase as well as reduced spatial coherence of the sound waves. Recently, a physics-based model was proposed to construct time domain realizations of the amplitude and phase fluctuations for application in the auralization of outdoor sound sources. The approach assumed the frequency-dependent fluctuations, considered in separate 1/n octave frequency bands, are either fully correlated or fully decorrelated. This paper extends the method by including specific model-based cross-frequency correlation in the fluctuations. The approach is first presented, followed by examples of applications and a subjective evaluation of auralized samples with and without cross-frequency correlation.

Characterization of the acoustic attenuation index of perforated plasterboard ceilings and lining wall and comparison with an empirical model

Perforated plasterboards are known for their absorption performance. Measurements of the sound reduction index R is realized with these boards. Two configurations is tested in laboratory, one configuration of a perforated plasterboard ceiling suspended on concrete floor and a second configuration of perforated plasterboard lining wall fixed on 16cm concrete wall. Following this characterization, a semi-empirical model to estimate the attenuation index is proposed. The perforated board is simulated by considering an heterogeneous board of gypsum and holes related by the perforation rate. The prediction model is compared with the measurement with a good accuracy. Finally, after extrapolations of sound reduction index is proposed for other perforation rates.

Railway noise monitoring - a tool to analyse in detail the evolution of noise over time during a rolling stock renewal period

As part of the commissioning of a rail freight project, a noise monitoring system was set up to track the increase in rail freight traffic and to monitor noise over time. Noise monitoring is done by continuous measurement stations, an analysis of the classic noise exposure indexes LAeq,6-22h and LAeq,22-6h is realized, completed by an analysis of several event acoustic indexes, with a distinction between the different traffic types (Freight, regional trains). In addition, the European Regulation EU 2019/774 on the application of the technical specification for interoperability relating to the subsystem 'rolling stock - noise' to the existing freight wagons, obliges the circulation of less noisy freight trains on certain itineraries called "Quieter routes" from 8/12/2024. The projected benefit will not be limited to the nearby residents of these routes but will, by indirect consequence, enable a gradual acoustic gain on all the French rail freight routes, due to the retrofit or renewal of the existing rolling stock. The goal of the noise monitoring system is also to quantify the acoustic gains from the indirect effects of this new regulation.

Increased bird sound diversity in vineyards enhances visitors' tour experience

Abstract Biodiversity is rapidly declining, reducing the quantity and quality of human interactions with nature and constraining its contribution to human health and well‐being. Natural sounds are a key component of our experience of nature, but biodiversity losses are reflected in soundscapes, which are becoming less diverse and quieter. We characterised the soundscapes across 21 English vineyards using acoustic indices and related them to bird species richness and abundance. We found that higher bird species richness, but not abundance, led to more diverse and louder soundscapes, as reflected in higher values of Acoustic Complexity Index (ACI), Bioacoustic Index (BIO) and Normalised Difference Soundscape Index (NDSI), and lower values of Acoustic Entropy Index (H). Secondly, at three of the study vineyards that run vineyard tours, we measured visitors' experience of the tour in terms of sound enjoyment, soundscape connectedness and tour satisfaction and related these to ambient and experimentally enhanced soundscapes, where we used playback recordings of five additional birdsongs to increase the soundscapes' complexity and volume. Under ambient conditions, respondents' (n = 107) experience was significantly higher at sites with soundscapes that had higher ACI and BIO values, and lower H, Acoustic Diversity Index (ADI) and NDSI values, indicating a positive effect of more diverse and louder soundscapes. Natural sounds formed an important part of the tour experience at these sites, making visitors feel more present and connected to nature. Under experimental soundscape enhancement, respondents (n = 79) reported hearing significantly more bird species during the tour, and they reported significantly higher scores for sound enjoyment, soundscape connectedness and tour satisfaction than under ambient conditions. This effect was stronger in visitors who engaged more in pro‐environmental behaviours, such as purchasing organic foods. Our study demonstrates (i) the direct contribution of aural modes to our experience of nature and (ii) that the delivery of biodiversity conservation measures aimed at supporting bird diversity could simultaneously enhance the experience and well‐being benefits of spending time in nature. Natural soundscapes should therefore be recognised and valued as natural capital, and their protection should be incorporated into conservation planning and policy. Read the free Plain Language Summary for this article on the Journal blog.

A Multiparametric Acoustic and Self-Perceptual Measure of Laryngeal Hydrations in Speech-Language Pathologists: A Preliminary Longitudinal Investigation

PurposeSpeech-language pathologists (SLPs) work with individuals with communication disorders. Their work can strain their voice, resulting in dysphonia, adversely affecting their career and quality of life. Laryngeal hydration can prevent vocal damage and improve vocal performance in SLPs. However, there is limited research on the effects of laryngeal hydration in SLPs using longitudinal studies. Hence, the present study aims to assess the longitudinal impact of laryngeal hydration in SLPs using multiparametric acoustic and self-perceptual measures. MethodThe research method lasted for six consecutive days, with each day lasting 2-3 hours for each participant. Ten SLPs, aged 18-30 years, were recruited. On alternate days, laryngeal hydration treatment (Systemic, surface, and combined hydration) was given while participants performed vocal loading tasks. Pre- and post-recordings of the Acoustic Voice Quality Index (AVQI) and its consistent parameters (CPPs, HNR, shimmer%, shimmer local, LTAS slope, LTAS Tilt) and self-perceptual measures [Perceived Phonatory Effort (PPE), Perceived Vocal Tiredness (PVT)] were taken. Kruskal-Wallis Test and the Wilcoxon Signed Rank Test were used to assess vocal changes in SLPs with laryngeal hydration. ResultsNo significant differences in overall AVQI scores were found between pre and post-tests for all types of laryngeal hydration treatment. However, there was a significant increase in CPPs and the LTAS slope for combined hydration and a decrease in HNR with an increase in shimmer local for systemic hydration in the post-test compared to the pre-test. Only systemic hydration in the post-test showed a rise in PPE and PVT compared to the pre-test, compared to surface and combined hydration. ConclusionVoice outcome measures of the present study demonstrated the immediate beneficial effects of surface hydration and combined hydration in SLPs by preserving voice quality during vocal loading. Systemic hydration had less of an immediate impact on voice quality. This study suggests empirical evidence for laryngeal hydration, which can enhance vocal performance and preserve voice quality in SLPs.