Acoustic Index Research Articles

Smartphone-Based Voice Wellness Index Application for Dysphonia Screening and Assessment: Development and Reliability.

This study aimed to develop a Voice Wellness Index (VWI) application combining the acoustic voice quality index (AVQI) and glottal function index (GFI) data and to evaluate its reliability in quantitative voice assessment and normal versus pathological voice differentiation. Cross-sectional study. A total of 135 adult participants (86 patients with voice disorders and 49 patients with normal voices) were included in this study. Five iOS and Android smartphones with the "Voice Wellness Index" app installed were used to estimate VWI. The VWI data obtained using smartphones were compared with VWI measurements computed from voice recordings collected from a reference studio microphone. The diagnostic efficacy of VWI in differentiating between normal and disordered voices was assessed using receiver operating characteristics (ROC). With a Cronbach's alpha of 0.972 and an ICC of 0.972 (0.964-0.979), the VWI scores of the individual smartphones demonstrated remarkable inter-smartphone agreement and reliability. The VWI data obtained from different smartphones and a studio microphone showed nearly perfect direct linear correlations (r=0.993-0.998). Depending on the individual smartphone device used, the cutoff scores of VWI related to differentiating between normal and pathological voice groups were calculated as 5.6-6.0 with the best balance between sensitivity (94.10-95.15%) and specificity (93.68-95.72%), The diagnostic accuracy was excellent in all cases, with an area under the curve (AUC) of 0.970-0.974. The "Voice Wellness Index" application is an accurate and reliable tool for voice quality measurement and normal versus pathological voice screening and has considerable potential to be used by healthcare professionals and patients for voice assessment.

Effects of a Straw Phonation on Acoustic and Self-Reported Measures of Adolescent Female Singers: A Pilot Study

ABSTRACT Characteristics of adolescent female voice change include breathiness, inconsistent pitch, “cracks,” abrupt register transitions, vocal range changes, and decreased stamina. Researchers have found that semi-occluded vocal tract exercises (e.g. straw phonation) can assist with such difficulties with other varied populations, facilitating glottal closure, decreasing breathiness, and encouraging easier voicing. Therefore, the purpose of this investigation was to measure the effects of straw phonation (experimental) compared to “ah” vowel (control) warm-ups on acoustic and self-reported measures of seventh-grade female-identifying singers. We calculated each participant’s Acoustic Voice Quality Index (AVQI) prior to and after a 4–5-minute straw phonation (n = 6) or unoccluded “ah” vowel (n = 6) warm-up. Results indicated robust improvement in AVQI scores after both warm-ups, with a trend toward more acoustic improvement after straw phonation (5 improved, M = 0.48, compared to 4, M = 0.35). All participants self-reported that their respective voicing helped them to be more warmed up, but the effect was statistically much larger in the straw group (7.23 to 5.00, 10-point scale). Some participants self-reported that straw phonation was more effective than their typical warm-up. These results may indicate more robust benefits from straw phonation, which could facilitate increased motivation during a difficult transition.

Soundscapes and deep learning enable tracking biodiversity recovery in tropical forests

Tropical forest recovery is fundamental to addressing the intertwined climate and biodiversity loss crises. While regenerating trees sequester carbon relatively quickly, the pace of biodiversity recovery remains contentious. Here, we use bioacoustics and metabarcoding to measure forest recovery post-agriculture in a global biodiversity hotspot in Ecuador. We show that the community composition, and not species richness, of vocalizing vertebrates identified by experts reflects the restoration gradient. Two automated measures – an acoustic index model and a bird community composition derived from an independently developed Convolutional Neural Network - correlated well with restoration (adj-R² = 0.62 and 0.69, respectively). Importantly, both measures reflected composition of non-vocalizing nocturnal insects identified via metabarcoding. We show that such automated monitoring tools, based on new technologies, can effectively monitor the success of forest recovery, using robust and reproducible data.

Linking ecoacoustic indices to psychoacoustic perception of the urban acoustic environment

Research about human perception of the acoustic environment is dominated by the use of sound pressure levels (SPL) or proprietary psychoacoustic indicators, limiting the link between sound and perception to only these two approaches. The aim of this study is to make connections between soundscape perception descriptors and ecoacoustic indices so that a perceptual dimension of ecoacoustic indices is ascertained. The study employs a laboratory experiment where 309 participants were exposed to sound and imagery from nine different urban land uses (n = 2,781) according to the soundscape protocol DIN ISO 12913-2. Spearman’s correlation and ordinal logistic regression are used to analyze the relationship between continuous numeric ecoacoustic indices and Likert scale psychoacoustic perception outcomes. We find that the predictors median amplitude (M), acoustic richness (AR), number of peaks (NP), and acoustic evenness index (AEI) have significant correlations (r > 0.5: p ≤ 0.05) and effect sizes (β ≥ 0.1) for the psychoacoustic outcomes perceived affective quality (PAQ) of calm, pleasant, chaotic, annoying, and soundscape identifiers (SSI) traffic sounds and natural sounds. We find that between 59.4 % and 81.9 % of the variation within dependent SSI and PAQ variables is explained by ecoacoustic indices based on Nagelkerke’s R-Squared values. High M and AR values are indicators for sound environments with high median or consistent amplitude, such as traffic noise, and high NP and AEI values are indicators for high fidelity sound environments with natural sounds or human beings that may be perceived as calm or pleasant. We conclude that combinations of M, AR, NP, and AEI as composite indicators contribute to understanding nine of the 14 psychoacoustic perception outcomes in DIN ISO 12913-2.

Al2O3/GeO2/P2O5/F-Doped Silica Large-Mode-Area Optical Fibers for High-Power Single-Frequency Radiation Delivery

A new design of a passive optical fiber waveguide with a large mode area (LMA) and strong stimulated Brillouin scattering (SBS) suppression is proposed. The fiber core consists of two parts: a central one, doped with Al2O3 and GeO2, and a peripheral one, doped with P2O5 and F. The doping profiles form a gradient-increasing profile of the acoustic refractive index, which effectively implements the acoustic multimode SBS suppression method. Measurements of the SBS gain spectrum and SBS threshold power were carried out, showing an increase in the SBS threshold of no less than 11 dB compared to a conventional uniformly doped passive LMA fiber.

Discovering ecoacoustic codes in beehives: First evidence and perspectives

The sounds present inside a beehive originate from the overlap of honeybee buzzes with external sounds. They reveal patterns that support the hypothesis that the sonic context of the beehive may be utilized by honeybees as a source of ecoacoustic codes for communication and the coordination of social activity. Patterns were observed in a data series of acoustic files sampled at a frequency of 48 kHz during the period May–July 2023 in a beehive of Apis mellifera ligustica (Spinola, 1806). The acoustic information was extracted using the acoustic complexity index (ACItf) algorithm applied to a fast Fourier transform matrix. Data series, aggregated in 1368 min × 512 frequency bins × 61 days, were tentatively classified according to three temporal classes of aggregation (eight, six, and four clusters, respectively) using the hierarchical K-means clustering algorithm. The clusters obtained at these three resolutions were considered potential ecoacoustic codes (PECs) belonging to each minute of the data series.The number of discontinuities along the 24-h PEC sequence, the coefficient of variation of the number of PECs at daily and seasonal scales, and the PEC sample entropy confirmed a patterned distribution of PECs across the 24 h, modulated at a monthly scale. A significant correlation was found between these indices and the daily average wind speed, and temperature. Honeybee buzz is an informative medium used by honeybees to develop survival strategies.

The soundscape method and eco-acoustic indicators in the analysis of the acoustic environment of the mountain national parks in Poland and Sweden

Soundscape is one of the essential environmental elements affecting people’s experience in nature spaces. In the complex mechanism of landscape and soundscape perception, the acoustic characteristics of the environment are the primary influencing factor. The aim of the paper is the analysis of soundscape of two mountain national parks—Tatra National Park (TNP) in Poland and Sarek National Park (SNP) in Sweden. The first park is very frequently visited by tourists (around 4 million tourists a year) while the second park has an attendance of around a few thousand tourists. The paper presents the results of the analysis of acoustic measurements and ambisonic recordings made in the Koscieliska Valley (TNP) and the Rapa Valey (SNP, Swedish: Rapadalen) using classical method and the soundscape method. In addition, psychoacoustic parameters and soundecology indicators such as loudness, sharpness or roughness, ACI (acoustic complexity index), NDSI (normalized difference soundscape index), BIO (bioacoustic index), ADI (acoustic diversity index), and AEI (acoustic evenness index) were calculated.

What is the Effect of CPAP Treatment With Humidifier on Vocal Quality?

Evaluate vocal quality in patients with OSA before and after continuous use of CPAP with a humidifier using subjective patient perception and clinical assessment. The hypothesis was that CPAP treatment with a humidifier would benefit voice quality. Randomized, sham-controlled, blinded clinical trial. Forty-three natal males with obstructive sleep apnea for whom CPAP treatment was recommended following polysomnography were randomized into two therapy groups: CPAP and Sham-CPAP. Participants completed questionnaires on voice use, a voice self-assessment with the ten-item vocal handicap index (VHI-10), and complementary questionnaires: the Epworth sleepiness scale (ESS), Pittsburgh sleep quality index (PSQI), reflux symptoms index (LPRSI) and oral dryness visual analog scale (DRY). Their voices were recorded at three different times: before CPAP therapy, and after 3 and 6 months of continuous CPAP use. The acoustic voice quality index (AVQI), and an auditory-perceptual judgment (APJ) were also applied before and after the CPAP and Sham treatments. After 6 months of treatment, the CPAP group presented improvements in their sleep patterns; however, no statistically significant differences were observed between the groups in respect of the results of the voice-related questionnaires, the AVQI values, and the APJ of the voice quality. All of the participants had some degree of vocal deviation at baseline. CPAP therapy with a humidifier did not improve vocal quality as evaluated by the clinician or patient self-assessment. However, it did not have any significant negative effects on voice quality, so can be considered safe to use in male OSA patients.

Underwater soundscape observations and associated demersal fish movement during a seismic airgun survey in coastal Oregon

Sound is a crucial aspect of the underwater environment for fishes—various species use sound to communicate, identify predators, navigate, and many other activities needed for survival in their habitat. In the summer of 2021, a seismic survey passed nearby Southern Oregon to map the Cascadia Subduction Zone using an array of airguns. To evaluate the effect of the seismic survey on the behavior of demersal fish, acoustic pressure and particle motion measurements were collected within a marine protected area, accompanied by tagging of two rockfish species, Black Rockfish (Sebastes melanops) and China Rockfish (S. nebulosus). Acoustic measurements were obtained using a vector sensor array, deployed in 25 m deep water. It was found that while cumulative sound exposure levels were dominated by wind noise, other metrics such as peak sound pressure, kurtosis, acoustic complexity index, crest factor and acoustic entropy showed clear signals associated with the seismic survey. Animal behavior and spatial use by the two rockfish species were also evaluated. Overall, results indicate that there are slight differences in movement and spatial use during times of seismic survey noise presence, but observed differences are reduced after only a few days.

A frequency-dependent acoustic diversity index: A revision to a classic acoustic index for soundscape ecological research

In recent years, passive acoustic monitoring (PAM) has been widely applied in the field of soundscape ecology. Meanwhile, acoustic indices, as an important tool for rapid biodiversity assessment (RBA), have also attracted increasing attention. However, considerable evidence demonstrates that existing acoustic indices are susceptible to noise, which poses a challenge for wider applications of acoustic indices. In this work, we firstly provide insights into how noise affects the widely used acoustic diversity index (ADI), revealing that the global threshold scheme (i.e., −50 dBFS for all time–frequency bins) to generate the binary spectrogram (spectrogram containing time–frequency bins denoted as ‘1′ with power above the threshold and ‘0′ below) is the key factor that makes ADI sensitive to noise. To address this problem, we propose a revised ADI version named frequency-dependent acoustic diversity index (FADI), which employs a new threshold scheme to reduce noise impacts on its values. Specifically, considering that the noise floor along frequency axis usually varies in practice, i.e., a colored noise rather than a white noise exists in field recordings, floating thresholds adapted to the noise level at each frequency bin were employed and further incorporated with the global threshold of ADI. Controlled computational experiments using field recordings were conducted where manipulated noise levels were introduced as different signal-to-noise ratios (SNR). It was shown that the proposed FADI was significantly robust to noise within a much wider SNR range as compared with ADI. Furthermore, a singular example using a real-world recording also verified its effectiveness and highlighted the promising potential of FADI in applications of PAM.

Acoustic communities in an environmental gradient from native to urban areas in Central Brazil

AbstractAs urban areas expand due to increasing human populations, natural habitats are diminishing in quantity and quality. We conducted a study to examine the response of diurnal acoustic communities along a gradient of environments, ranging from native to dense urban areas. We hypothesized that acoustic indices would decline with urbanization, transitioning from natural and rural areas to urban environments. We conducted the research in and around Brasília, Central Brazil. We deployed 24 digital recorders in native, rural, low‐density and high‐density urban areas. We employed five commonly used acoustic indices (ADI, ACI, NDSI, H and BI) to characterize the acoustic communities and represent the existing biodiversity numerically. We initially compared the index values across different land use types using a non‐parametric rank sum test. Subsequently, we selected eight landscape metrics and performed a principal component analysis to summarize the surrounding matrix at each sampling point. We then employed generalized linear models to determine if the acoustic indices exhibited the anticipated variations. The results indicated significant variations in all indices among the different land use types, indicating their responsiveness to distinct acoustic communities and environmental characteristics. ADI, H and NDSI exhibited declining values from native to urban areas, while ACI and BI displayed the opposite trend. These findings underscore the influence of landscape structure on acoustic indices. Consequently, we concluded that adopting appropriate landscape planning, mainly through integrating natural and urban areas, could help preserve biodiversity in tropical urban regions.

Changes in the acoustic structure of Australian bird communities along a habitat complexity gradient

Abstract Avian vocalizations have evolved in response to a variety of abiotic and biotic selective pressures. While there is some support for signal convergence in similar habitats that are attributed to adaptation to the acoustic properties of the environment (the “acoustic adaptation hypothesis,” AAH), there is also evidence for character displacement as a result of competition for signal space among coexisting species (the “acoustic niche partitioning hypothesis”). We explored the acoustic space of avian assemblages distributed along six different habitat types (from herbaceous habitats to warm rainforests) in southeastern Queensland, Australia. We employed three acoustic diversity indices (acoustic richness, evenness, and divergence) to characterize the signal space. In addition, we quantified the phylogenetic and morphological structure (in terms of both body mass and beak size) of each community. Acoustic parameters showed a moderately low phylogenetic signal, indicating labile evolution. Although we did not find meaningful differences in acoustic diversity indices among habitat categories, there was a significant relationship between the regularity component (evenness) and vegetation height, indicating that acoustic signals are more evenly distributed in dense habitats. After accounting for differences in species richness, the volume of acoustic space (i.e., acoustic richness) decreased as the level of phylogenetic and morphological resemblance among species in a given community increased. Additionally, we found a significantly negative relationship between acoustic divergence and divergence in body mass indicating that the less different species are in their body mass, the more different their songs are likely to be. This implies the existence of acoustic niche partitioning at a community level. Overall, while we found mixed support for the AAH, our results suggest that community-level effects may play a role in structuring acoustic signals within avian communities in this region. This study shows that signal diversity estimated by diversity metrics of community ecology based on basic acoustic parameters can provide additional insight into the structure of animal vocalizations.

Sonotopes reveal dynamic spatio-temporal patterns in a rural landscape of Northern Italy

A sonotope is characterized as a sonic patch that forms a hierarchical link between a finer, local scaled acoustic community and the coarser landscape scaled sonoscape. Unfortunately, the concept of sonotopes has yet to be empirically supported. We tested the hypothesis that a spatially explicit sample of sonic information from a heterogeneous landscape would exhibit spatially unique sonotopes with distinct spatio-temporal patterns and acoustic communities. We used the Acoustic Complexity Index (ACItf) to analyze sonic information (WAV) gathered from an array of 10 sound recorders deployed within a lattice of 10, 4-ha hexagonal sample sites distributed evenly throughout a 48-ha undivided heterogeneous landscape in Northern Italy. We examined the temporal patterns of sonic activity (ACItf) between seasons (March – July and August – November 2021) and across five astronomical periods of a 24-h day (Night I, Morning Twilight, Day, Evening Twilight, and Night II). We used cluster analyses to identify sonotopes from groupings of similar ACItf values for each sample site and visualized the spatial arrangements of sonotopes throughout our study area between seasons and among astronomical periods. Sonic activity from bird biophonies increased in March – July during the Day but in August – November greater sonic activity shifted to crepuscular and nocturnal periods with the biophonies from crickets. Sonotopes exhibited spatially unique, dynamic arrangements of patch size and placement depending on the season and astronomical period. We discuss how acoustic communities and continuous geophonies play a role in the arrangement of sonotopes and their relation to the sonoscape.

To Bag or Not to Bag? How AudioMoth-Based Passive Acoustic Monitoring Is Impacted by Protective Coverings

Bare board AudioMoth recorders offer a low-cost, open-source solution to passive acoustic monitoring (PAM) but need protecting in an enclosure. We were concerned that the choice of enclosure may alter the spectral characteristics of recordings. We focus on polythene bags as the simplest enclosure and assess how their use affects acoustic metrics. Using an anechoic chamber, a series of pure sinusoidal tones from 100 Hz to 20 kHz were recorded on 10 AudioMoth devices and a calibrated Class 1 sound level meter. The recordings were made on bare board AudioMoth devices, as well as after covering them with different bags. Linear phase finite impulse response filters were designed to replicate the frequency response functions between the incident pressure wave and the recorded signals. We applied these filters to ~1000 sound recordings to assess the effects of the AudioMoth and the bags on 19 acoustic metrics. While bare board AudioMoth showed very consistent spectral responses with accentuation in the higher frequencies, bag enclosures led to significant and erratic attenuation inconsistent between frequencies. Few acoustic metrics were insensitive to this uncertainty, rendering index comparisons unreliable. Biases due to enclosures on PAM devices may need to be considered when choosing appropriate acoustic indices for ecological studies. Archived recordings without adequate metadata may potentially produce biased acoustic index values and should be treated cautiously.

Psychometric features of Acoustic Voice Quality Index, version 03.01, in Persian language

ABSTRACT The goal of this study was to investigate the psychometric features of the Acoustic Voice Quality Index, in Persian, as an objective and multi-parameter tool for evaluating the overall voice quality. Three hundred and ten Persian-speaking individuals, 155 with various types and severity of dysphonia, and 155 healthy individuals, performed two tasks: reading a phonetically balanced text and a sustained vowel /a/. Voice recordings were made. Perceptual evaluation with the G score of the GRBAS scale was completed by five raters, and intra-rater reliability and inter-rater reliability were calculated. The Acoustic Voice Quality Index was calculated with standard syllables corresponding to 3 s of voiced speech and 3 s of vowels. Concurrent validity, construct validity, test–retest reliability, and diagnostic accuracy of the AVQI were analyzed. The results suggest that the number of syllables corresponding to 3 s of voiced speech was 23. Perceptual evaluation demonstrated excellent intra-rater and inter-rater reliability. The AVQI demonstrated a strong correlation with perceptual evaluation (rs = 0.877, P < 0.001), as well as high construct validity. In addition, the index had very good test–retest reliability (icc = 0.992). The cut-off point of the index was 3.62 in Persian. The area under the ROC curve was 0.815, indicating that the index had the ability to differentiate between dysphonic and non-dysphonic voices. And it can be stated that the AVQI 03.01 is a reliable objective tool for distinguishing dysphonic from non-dysphonic voice in Persian that can be utilized in clinical and research settings.

Modified subtotal laryngectomy with formation of a tracheopharyngeal shunt for locally advanced cancer of the larynx and hypopharynx

Aim. To study the effectiveness of modified subtotal laryngectomy with the formation of a tracheopharyngeal shunt in patients with locally advanced cancer of the larynx and laryngopharynx.Materials and methods. We conducted a cohort study on the use of combined treatment (surgical and radiation/ polychemotherapy) in 25 patients: 24 men, 1 woman; median age – 56 years. The subtotal laryngectomy technique that we developed and used included the preservation of one arytenoid cartilage, the posterior third of the vocal fold, and the recurrent nerve on the side not affected by the tumor. We studied postoperative complications, the length and diameter of the tracheopharyngeal shunt, the functioning of the arytenoid cartilage, the frequency of voice recovery and its quality, and overall and relapse-free survival.Results. In the postoperative period, 8 (32%) patients developed a pharyngocutaneous fistula; tracheal stenosis after tracheostomy was observed in 8 (32%) cases. The length of the tracheopharyngeal shunt varied from 16.4 to 25.6 mm, in all cases its course was tortuous, the diameter of the preserved part of the vocal fold varied from 1.1 to 1.5 mm. 24 (96%) patients demonstrated the functioning of the arytenoid cartilage and its work as a valve. Voice function recovered in 24 (96%) patients. Fundamental frequency was 155.3 ± 20.9 Hz, maximum phonation time of the vowel “A” – 3.5 ± 1.0 s, duration of pauses in phrase – 0.24 ± 0.03 s, speech rate – 99.8 ± 8.4 words/ min, number of words in phrase 6.5 ± 0.3. The average value of the Acoustic Voice Quality Index was 6.74, which indicates dysphonia (for the Russian language, the threshold value for dysphonia is 4.86), but this did not interfere with patients’ communication at home and on the phone. Overall and relapse-free survival at 1, 2, and 3 years were 100%, 89%, 78% and 86%, 78%, 72%, respectively.Conclusion. The method of operation proposed by us contributes to the restoration of voice function in the majority of patients with oncological outcomes comparable to total laryngectomy.

Is myocardial fibrosis appropriately assessed by calibrated and 2D strain derived integrated backscatter?

AimsIncreased collagen content of the myocardium modifies tissue reflectivity and integrated backscatter (IBS) indexes are suggested as markers of myocardial fibrosis (MF). We sought to assess the correlation between calibrated (c) IBS and bidimensional (2D) strain derived IBS with left ventricular (LV) MF in patients with severe aortic stenosis (AS).Methods and resultsWe made a prospective observational cohort study including 157 patients with severe AS referred for surgical aortic valve replacement (AVR), with complete preoperative transthoracic echocardiography, cardiac magnetic resonance (CMR) and endomyocardial biopsy (EMB) obtained from the anterior basal septum at the time of surgery. Two groups of 30 patients were specifically evaluated, with and without late gadolinium enhancement (LGE) at CMR. IBS was obtained at QRS peak from both parasternal long axis (PLAX) and apical-three-chamber (AP3C) views and measured in decibels (dB). Whole-cardiac cycle IBS at basal anterior septum was obtained from 2D longitudinal strain. Correlation analysis of reflectivity indexes was performed with global and segmental (anterior basal septum) values of native T1 and extracellular volume (ECV), and EMB collagen volume fraction (CVF) (Masson´s Trichrome). IBS values were compared in both group of patients (LGE + vs. LGE –). 60 patients (74 [36–74] years, 45% male) with high gradient (mean gradient: 63 ± 20mmHg), normal flow (45 ± 10mL/m2) AS and preserved left ventricular ejection fraction (60 ± 9%) were included. Basal septum cIBS was − 17.45 (–31.2–10.95) and − 9.17 ± 9.45dB from PLAX and A3C views, respectively. No significant correlations were found between IBS and both non-invasive CMR tissue characterization and CVF: median MF of 9.7(2.1–79.9)%. Acoustic indexes were not significantly different according to the presence of pre-operative LGE.ConclusionIn this group of patients with classical severe AS, IBS reflectivity indexes are of no added value to discriminate the presence of MF.Graphical

Using acoustic indices in ecology: Guidance on study design, analyses and interpretation

Abstract The rise of passive acoustic monitoring and the rapid growth in large audio datasets is driving the development of analysis methods that allow ecological inferences to be drawn from acoustic data. Acoustic indices are currently one of the most widely applied tools in ecoacoustics. These numerical summaries of the sound energy contained in digital audio recordings are relatively straightforward and fast to calculate but can be challenging to interpret. Misapplication and misinterpretation have produced conflicting results and led some to question their value. To encourage better use of acoustic indices, we provide nine points of guidance to support good study design, analysis and interpretation. We offer practical recommendations for the use of acoustic indices in the study of both whole soundscapes and individual taxa and species, and point to emerging trends in ecoacoustic analysis. In particular, we highlight the critical importance of understanding the links between soundscape patterns and acoustic indices. Acoustic indices can offer insights into the state of organisms, populations, and ecosystems, complementing other ecological research techniques. Judicious selection, appropriate application and thorough interpretation of existing indices is vital to bolster robust developments in ecoacoustics for biodiversity monitoring, conservation and future research.

Can acoustic indices reflect the characteristics of public recreational behavioral in urban green spaces?

Acoustic indicators serve as an effective means of assessing the quality of urban green space soundscape. The informative, easy accessibility and non-invasive nature of acoustic monitoring renders it an excellent tool for studying the interaction among the natural environment, wildlife, and human activities. Urban green space is essential in the urban ecosystem and constitutes the primary location for public outdoor recreation. However, the existing methods for monitoring public recreational behavior, such as on-site observation, drone observation, or questionnaire interviews, require significant labor or professional expertise. All of these methods have their limitations, so there is still much to be researched in the acoustic indices and recreational behavior. As a result, the potential for using acoustic characteristics to monitor public recreational behavior remains underexplored. To address this gap, this study investigates the potential of 5 widely used acoustic indices and acoustic intensity for monitoring public recreational behavior: Acoustic Complexity Index (ACI), Acoustic Diversity Index (ADI), Acoustic Richness (AR), Normalized Difference Soundscape Index (NDSI), and Power Spectral Density (PSD). Data were collected from 35 monitoring points in urban green spaces during the opening hours (6:00–22:00) to analyze the relationship between these indices and public recreational behavior. The findings indicate that (1) ACI, ADI, and AR daily exhibited multi-peak daily variation characteristics similar to those of public recreational behavior, displaying a “W” shape, while NDSI exhibits opposite variation characteristics; (2) the spatial variation characteristics of ACI, ADI, and AR change in response to the green space, and these changes align with public recreational behavior; (3) the correlation analysis and generalized linear mixed model construction further demonstrate that acoustic indices are effective in capturing the dynamic activities of visitor behavior; and (4) PSD undergoes significant temporal dynamic changes along the frequency gradient, with different frequency intervals reflecting the activity information of different recreational behaviors. In conclusion, this research highlights the effectiveness of using acoustic indices to analyze both the spatial and temporal variation characteristics of public recreational behavior in urban green spaces. The results can provide valuable data support for the enhancement and renovation of urban green spaces.

Test-Retest Reliability of the Acoustic Voice Quality Index and the Acoustic Breathiness Index

The acoustic voice quality index (AVQI) and the acoustic breathiness index (ABI) are two validated measurements for the objective-acoustic assessment of voice quality. The aim of this study was to evaluate the relative and absolute reliability of AVQI and ABI as well as detect the natural variability of vocally-healthy voices. Totally, 39 vocally-healthy participants received weekly an AVQI- and ABI measurement using the freeware VOXplot over a period of 3 weeks. This study is a within-subject design to assess significant differences between the test and retest measurements (test and mean of two retests) of AVQI and ABI with the paired sample t test and to investigate the reliability of these two acoustic parameters with the intraclass correlation coefficient (ICC), Bland-Altman plot, and the minimal detectable change (MDC). No significant differences between the test-retest measurements of AVQI and ABI were revealed (all P-values>0.05). The relative reliability of AVQI and ABI showed good results (eg, ICC=0.81, and ICC=0.92, respectively). Absolute reliability measured with the MDC yielded a test-retest value of 0.78 and 0.66 for the AVQI and ABI, respectively. Deviations within this range may be due to natural variations of the voice (random bias). AVQI and ABI revealed high-reliability results in a test-retest measurement of vocally-healthy participants.