Frequency Contours Research Articles

Site correction of a high-frequency strong-ground-motion simulation based on an empirical transfer function

In this study, an empirical transfer function (ETF), which is the spectrum difference in Fourier amplitude spectra between observed strong ground motion and synthetic motion obtained by a stochastic point-source simulation technique, is constructed for the Taipei Basin, Taiwan. The basis stochastic point-source simulations can be treated as reference rock site conditions in order to consider site effects. The parameters of the stochastic point-source approach related to source and path effects are collected from previous well-verified studies. A database of shallow, small-magnitude earthquakes is selected to construct the ETFs so that the point-source approach for synthetic motions might be more widely applicable. The high-frequency synthetic motion obtained from the ETF procedure is site-corrected in the strong site-response area of the Taipei Basin. The site-response characteristics of the ETF show similar responses as in previous studies, which indicates that the base synthetic model is suitable for the reference rock conditions in the Taipei Basin. The dominant frequency contour corresponds to the shape of the bottom of the geological basement (the top of the Tertiary period), which is the Sungshan formation. Two clear high-amplification areas are identified in the deepest region of the Sungshan formation, as shown by an amplification contour of 0.5Hz. Meanwhile, a high-amplification area was shifted to the basin’s edge, as shown by an amplification contour of 2.0Hz. Three target earthquakes with different kinds of source conditions, including shallow small-magnitude events, shallow and relatively large-magnitude events, and deep small-magnitude events relative to the ETF database, are tested to verify site correction. The results indicate that ETF-based site correction is effective for shallow earthquakes, even those with higher magnitudes, but is not suitable for deep earthquakes. Finally, one of the most significant shallow large-magnitude earthquakes (the 1999 Chi-Chi earthquake in Taiwan) is verified in this study. A finite fault stochastic simulation technique is applied, owing to the complexity of the fault rupture process for the Chi-Chi earthquake, and the ETF-based site-correction function is multiplied to obtain a precise simulation of high-frequency (up to 10Hz) strong motions. The high-frequency prediction has good agreement in both time and frequency domain in this study, and the prediction level is the same as that predicted by the site-corrected ground motion prediction equation.

Improvement of a Cloud Microphysics Scheme for a Global Nonhydrostatic Model Using TRMM and a Satellite Simulator

Abstract The cloud and precipitation simulated by a global nonhydrostatic model with a 3.5-km horizontal resolution, the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), are evaluated using the Tropical Rainfall Measuring Mission (TRMM) and a satellite simulator. A previous study by Roh and Satoh evaluated the single-moment bulk microphysics and established the modified microphysics scheme for the specific tropical open ocean using a regional version of NICAM. In this study, the authors expanded the evaluation over the entire tropics and parts of the midlatitude areas (20°–36°S, 20°–36°N) using a joint histogram of the cloud-top temperature and precipitation echo-top heights and contoured frequency by altitude diagrams of the deep convective systems. The modified microphysics simulation improves the joint probability density functions of the cloud-top temperatures and precipitation cloud-top heights over not only the tropical ocean but also the land and midlatitude areas. Compared with the default microphysics simulation, the modified microphysics simulation shows a clearer distinction between the land and ocean in the tropics, which is related to the contrast between the shallow and the deep clouds. In addition, the two microphysics simulation methods were also compared over the tropics using joint histograms of the cloud-top and precipitation cloud-top heights on the basis of CloudSat measurements. It was found that the microphysics scheme that was modified for the tropical ocean displayed general cloud and precipitation improvements in the global domain over the tropics.

WITHDRAWN: Informational masking and the effects of differences in fundamental frequency and fundamental-frequency contour on phonetic integration in a formant ensemble

WITHDRAWN: Informational masking and the effects of differences in fundamental frequency and fundamental-frequency contour on phonetic integration in a formant ensemble

Score-Informed Analysis of Tuning, Intonation, Pitch Modulation, and Dynamics in Jazz Solos

Both the collection and analysis of large music repertoires constitute major challenges within musicological disciplines such as jazz research. Automatic methods of music analysis based on audio signal processing have the potential to assist researchers and to accelerate the transcription and analysis of music recordings significantly. In this paper, we propose a framework for analyzing improvised monophonic solos in multi-instrumental jazz recordings with special focus on reed and brass instruments. The analysis algorithms rely on prior score-information, which is taken from high quality manual solo transcriptions. Following an initial solo and accompaniment source separation, we propose algorithms for tone-wise extraction of fundamental frequency and intensity contours. Based on this fine-grained representation of recorded jazz solos, we perform several exploratory experiments motivated by questions relating to jazz research in order to analyze the use of expressive stylistic devices such as intonation, pitch modulation, and dynamics in jazz solos. The results show that a score-informed audio analysis of jazz recordings can provide valuable insights into the individual stylistic characteristics of jazz musicians.

Ictal EEG classification based on amplitude and frequency contours of IMFs

Electroencephalogram (EEG) signal serves is a powerful tool in epilepsy detection. This study decomposes intrinsic mode functions (IMFs) into amplitude envelope and frequency functions on a time-scale basis using the analytic function of Hilbert transform. IMFs results from the empirical mode decomposition of EEG signals. Features such as energy and entropy parameters were calculated from the amplitude contour of each IMF. Other features, such as interquartile range, mean absolute deviation and standard deviation are also computed for their instantaneous frequencies. Discriminative features were extracted using a large database to classify healthy and ictal EEG signals. Normal EEG segments were differentiated from the seizure attack in individual IMF features, multiple features with individual IMF, and individual features with multiple IMFs. Discriminating capability of three Cases was tested. (i) Artificial neural network and (ii) adaptive neuro-fuzzy inference system classification were used to identify EEG segments with seizure attacks. ANOVA was used to analyze statistical performance. Energy and entropy-based features of instantaneous amplitude and standard deviation of instantaneous frequency of IMF2 and IMF1 have 100% accuracy, sensitivity, and specificity. Good performance with a single feature that represents information of the whole data was obtained. The result involved less complicated computation than other time–frequency analysis techniques.

Interpretation of the extent of hydraulic fracturing for rockburst prevention using microseismic monitoring data

As the mining depths increase, an increasing number of deep coal mines in China encounter frequent intense rockburst problems. Conventional destress measures, employed effectively in shallow mines to reduce rockburst risk, are not suitable to deep coal mines because they are labor-intensive and time-consuming and hence are costly. Hydraulic fracturing in coal seams before mining a particular area has been considered as an effective destressing method for rockburst prevention. This paper focuses on using microseismic data to evaluate the extent of hydraulic fracturing in coal seams. To that purpose, innovative methods are proposed to process and interpret microseismic monitoring data. The proposed methods consist of an improved HHT method for signal filtering, an improved time-window energy eigenvalue method for first arrival picking, and a four-channel combined algorithm for seismic source location determination. Using the elaborate signal processing and interpretation methods, high-precision source locations of microseismic events recorded in a field hydraulic fracturing test at Huafeng Coal Mine are obtained. Microseismic event frequency and energy contours are plotted to characterize the fracture development and propagation process. The interpretation method was successfully applied in the coal seam hydraulic fracturing tests. Direct field observation and stress monitoring were also conducted to verify the results by the microseismic data interpretation method. Compared with conventional monitoring techniques such as stress monitoring and direct field observation, microseismic monitoring can cover a large monitoring volume with a high response sensitivity and it can capture the spatial-temporal fracture evolution process easily. It provides a practical approach to quantify the extent of hydraulic fracturing in coal seams for rockburst prevention.

Error patterns in fundamental frequency contours of L2 Mandarin utterances by Cantonese and English learners

Error patterns in fundamental frequency contours of L2 Mandarin utterances by Cantonese and English learners

Ultratransparent Media and Transformation Optics with Shifted Spatial Dispersions.

By using pure dielectric photonic crystals, we demonstrate the realization of ultratransparent media, which allow near 100% transmission of light for all incident angles and create aberration-free virtual images. The ultratransparency effect is well explained by spatially dispersive effective medium theory for photonic crystals, and verified by both simulations and proof-of-principle microwave experiments. Designed with shifted elliptical equal frequency contours, such ultratransparent media not only provide a low-loss and feasible platform for transformation optics devices at optical frequencies, but also enable new freedom for phase manipulation beyond the local medium framework.

On the seasonal variation of various types of precipitation over global tropical ocean region: A perspective from TRMM measurements

The radar reflectivity and precipitation rate from Precipitation Radar (PR) onboard Tropical Rainfall Measuring Mission (TRMM) are obtained over the global tropical regions (35°S–35°N) during the period from 2007 to 2012, combined with coincident vertical velocity at 400 hPa ( ω 400 hPa), relative humidity at 850 hPa (RH850 hPa) and lower tropospheric stability (LTS) from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. First of all, the seasonal and spatial distribution of meteorological factors, including ω 400hPa, RH850 hPa, and LTS, together with rain rate are investigated. Next, four typical Regions of Interest (ROIs) and their individual seasons (i.e., favorable and non-favorable seasons for rainfall) are identified for further analysis by determining whether there exist most pronounced seasonal differences observed in ω 400 hPa. Meanwhile, rainy area, and rainfall of three precipitation types (i.e., shallow, stratus, and convection precipitation regimes) over the ROIs has been calculated. The three dimensional structures of individual precipitating system are analyzed, based on normalized contoured frequency by altitude diagram (NCFAD) and other statistical methods. Finally, with a focus on convection precipitation system, we give a quantitative description of the response of precipitation vertical structure to meteorological factors. Namely, how the rain echo top height (RTH), echo top height with reflectivity of 30 dBZ (ZTH30 dBZ), and reflectivity center of gravity (ZCOG) vary with ω 400 hPa, RH850 hPa, and LTS. In particular, (1) high rain rate dominates over intertropical convergence zone, which is characterized by strong updraft, sufficient moisture, and low LTS, showing the average rain rate is negatively associated with ω 400 hPa at both temporal and spatial scales. That is to say, lower ω 400hPa comes with more intensive rain rate. (2) The meteorological factors, along with average rain rate, exhibit appreciable seasonal variation. To be specific, negative (positive) ω 400 hPa anomalies is mostly found over the northern (southern) hemisphere in summer and autumn, as opposed to the patterns found in winter and spring. (3) In terms of the area with rainfall, the stratiform precipitating system accounts for more than 50% of the total area under investigation, followed by the convective precipitating system (about 30%), and the shallow precipitating system (less than 20%). In contrast, convective precipitating system, among others, takes the lead (about 65%) in contributing to the accumulated rainfall amount in the ROIs studied, followed by stratiform precipitating system (about 25%), and the shallow precipitating system (about 10%). (4) In the season with relatively higher ω 400 hPa, both rainy area and accumulated rainfall amount for all three types of precipitation show a increasing trend, irrespective of ROI. By comparison, rain rate and its vertical structures show large discrepancy, i.e., the intensity of convective precipitation system in favorable season tends to systematically increase as compared with that in non-favorable season. (5) The bulk precipitation system parameters used to describe convective precipitating system, including RTH, ZTH30 dBZ, and ZCOG, are observed to be elevated sharply with increasing ω 400 hPa and RH850 hPa. The same holds for the increasing LTS but with a smaller magnitude in the elevated height. This implies that ω 400 hPa and RH850 hPa most likely play a dominant role in dictating the vertical development of convection.

The production of Norwegian tones by multilingual non-native speakers

Aim and objectives/purpose/research questions: The aim of this study is to examine the extent to which multilingual second language (L2) speakers of Norwegian manage to produce lexical pitch accents (L*H¯ or H*LH¯) as expected in natural spontaneous speech. Using native speech as a reference, we analyse realizations of multilingual speakers whose respective dominant languages are Lingala, a lexical tone language, and Swahili, a non-tonal language with fixed stress, and hypothesize that this difference might be reflected in the speakers’ competence in the East Norwegian tone system. Design/methodology/approach: We examined a corpus of spontaneous speech produced by eight L2 speakers and two native speakers of East Norwegian. Acoustic analysis was performed to collect fundamental frequency (f0) contours of 60 accentual phrases per speaker. Data and analysis: For LH and HLH tonal patterns, measuring points were defined for quantitative evaluation of f0 values. Relevant aspects investigated were (a) pattern consistency, (b) f0 dynamic range and (c) rate of f0 change. Pattern consistency data were statistically evaluated using chi-square testing. The dynamic range and rate of f0 change data were explored through to linear mixed effects models. Findings/conclusions: We found no really substantial differences between the speaker groups in the parameters we examined, neither between the L2 speakers and the Norwegian natives nor between the Lingala and Swahili speakers. Originality and significance/implications: This study is a contribution to the scarcely explored area of L2 acquisition of tones. It is concerned with languages that have received little or no attention in the field: Norwegian, Lingala and Swahili. Participants are multilinguals who have extensive language learning experience. Further, the study is based on a corpus of spontaneous speech.

Informational masking and the effects of differences in fundamental frequency and fundamental-frequency contour on phonetic integration in a formant ensemble

This study explored the effects on speech intelligibility of across-formant differences in fundamental frequency (ΔF0) and F0 contour. Sentence-length speech analogues were presented dichotically (left = F1+F3; right = F2), either alone or—because competition usually reveals grouping cues most clearly—accompanied in the left ear by a competitor for F2 (F2C) that listeners must reject to optimize recognition. F2C was created by inverting the F2 frequency contour. In experiment 1, all left-ear formants shared the same constant F0 and ΔF0F2 was 0 or ±4 semitones. In experiment 2, all left-ear formants shared the natural F0 contour and that for F2 was natural, constant, exaggerated, or inverted. Adding F2C lowered keyword scores, presumably because of informational masking. The results for experiment 1 were complicated by effects associated with the direction of ΔF0F2; this problem was avoided in experiment 2 because all four F0 contours had the same geometric mean frequency. When the target formants were presented alone, scores were relatively high and did not depend on the F0F2 contour. F2C impact was greater when F2 had a different F0 contour from the other formants. This effect was a direct consequence of the associated ΔF0; the F0F2 contour per se did not influence competitor impact.

Automated tracking of dolphin whistles using Gaussian mixture probability hypothesis density filters.

This work considers automated multi target tracking of odontocete whistle contours. An adaptation of the Gaussian mixture probability hypothesis density (GM-PHD) filter is described and applied to the acoustic recordings from six odontocete species. From the raw data, spectral peaks are first identified and then the GM-PHD filter is used to simultaneously track the whistles' frequency contours. Overall over 9000 whistles are tracked with a precision of 85% and recall of 71.8%. The proposed filter is shown to track whistles precisely (with mean deviation of 104 Hz, about one frequency bin, from the annotated whistle path) and 80% coverage. The filter is computationally efficient, suitable for real-time implementation, and is widely applicable to different odontocete species.

Discrimination of frequency modulated sweeps by mice.

Mice often produce ultrasonic vocalizations (USVs) that sweep upwards in frequency from around 60 to around 80 kHz and downwards in frequency from 80 to 60 kHz. Whether or not these USVs are used for communication purposes is still unknown. Here, mice were trained and tested using operant conditioning procedures and positive reinforcement to discriminate between synthetic upsweeps and downsweeps. The stimuli varied in bandwidth, duration, and direction of sweep. The mice performed significantly worse when discriminating between background and test stimuli when the stimuli all occupied the same bandwidths. Further, the mice's discrimination performance became much worse for stimuli that had durations similar to those natural vocalizations of the mice. Sweeps composed of different frequency ranges and longer durations had improved discrimination. These results collected using artificial stimuli created to mimic natural USVs indicate that the bandwidth of the vocalizations may be much more important for communication than the frequency contours of the vocalizations.

A CloudSat Perspective on the Cloud Climatology and Its Association with Aerosol Perturbations in the Vertical over Eastern China

Abstract Many efforts have been taken to investigate aerosol–cloud interactions from space, but only a few studies have examined the response of vertical cloud structure to aerosol perturbations. Three-dimensional cloud climatologies of eight different cloud types identified from the CloudSat level-2 cloud product during the warm season (May–September) in 2008–10 over eastern China were first generated and analyzed. Using visibility as a proxy for cloud condensation nuclei, in combination with satellite-observed radar reflectivity, normalized contoured frequency by altitude diagrams of the differences in cloud radar reflectivity Z profiles under polluted and clean conditions were constructed. For shallow cumulus clouds (shallow Cu) Z tends to be inhibited, and it is enhanced in the upper layers for deep cumulus (deep Cu), nimbostratus (Ns), and deep convective clouds (DCC) under polluted conditions. Overall, analyses of the modified center of gravity (MCOG) and cloud-top height (CTH) also point to a similar aerosol effect, except for the nonsignificant changes in MCOGs and CTHs in deep Cu. The impacts of environmental factors such as lower-tropospheric stability and vertical velocity are also discussed for these types of clouds. Although consistent aerosol-induced elevations in MCOGs and CTHs for Ns and DCC clouds are observed, the effect of meteorology cannot be completely ruled out, which merits further analysis.

Untangling the time-course of viewpoint-(in) dependence of face perception: a parametric ERP study

The syntactic and prosodic information needed for auditory language comprehension is intertwined within the speech signal. Previous studies seeking to isolate automatic syntactic processes have reported an early left anterior negativity (ELAN) between 100 and 200 ms elicited by syntactic phrase structure violations. Although prosody was already well controlled in these studies, a change in the fundamental frequency (F0) contour occurred together with the syntactic violation. The present magnetoencephalography study aimed to disentangle the influence of these two superimposed processes. Responses elicited by a syntactic phrase structure violation were compared to responses elicited by a prosodically incongruent change in the sentence's F0 contour in order to estimate the contribution of a prosodic incongruency to the ELAN effect. While both violations elicited stronger superior temporal cortex activation than correct sentences in a 110–160 ms time window, the syntax violation effect was larger than the prosody violation effect and showed a left hemispheric bias which was absent for the prosodic violation. Furthermore, only syntactically incorrect sentences elicited an additional very early effect in a preceding time window. Thus, the syntax violation effect found in the current and also in previous studies cannot be attributed to the detection of an unexpected prosodic contour, but rather reflects difficulties in local phrase structure building.

Across-formant integration and speech intelligibility: Effects of acoustic source properties in the presence and absence of a contralateral interferer.

The role of source properties in across-formant integration was explored using three-formant (F1+F2+F3) analogues of natural sentences (targets). In experiment 1, F1+F3 were harmonic analogues (H1+H3) generated using a monotonous buzz source and second-order resonators; in experiment 2, F1+F3 were tonal analogues (T1+T3). F2 could take either form (H2 or T2). Target formants were always presented monaurally; the receiving ear was assigned randomly on each trial. In some conditions, only the target was present; in others, a competitor for F2 (F2C) was presented contralaterally. Buzz-excited or tonal competitors were created using the time-reversed frequency and amplitude contours of F2. Listeners must reject F2C to optimize keyword recognition. Whether or not a competitor was present, there was no effect of source mismatch between F1+F3 and F2. The impact of adding F2C was modest when it was tonal but large when it was harmonic, irrespective of whether F2C matched F1+F3. This pattern was maintained when harmonic and tonal counterparts were loudness-matched (experiment 3). Source type and competition, rather than acoustic similarity, governed the phonetic contribution of a formant. Contrary to earlier research using dichotic targets, requiring across-ear integration to optimize intelligibility, H2C was an equally effective informational masker for H2 as for T2.

Effects of Semantic Context and Fundamental Frequency Contours on Mandarin Speech Recognition by Second Language Learners.

Speech recognition by second language (L2) learners in optimal and suboptimal conditions has been examined extensively with English as the target language in most previous studies. This study extended existing experimental protocols (Wang et al., 2013) to investigate Mandarin speech recognition by Japanese learners of Mandarin at two different levels (elementary vs. intermediate) of proficiency. The overall results showed that in addition to L2 proficiency, semantic context, F0 contours, and listening condition all affected the recognition performance on the Mandarin sentences. However, the effects of semantic context and F0 contours on L2 speech recognition diverged to some extent. Specifically, there was significant modulation effect of listening condition on semantic context, indicating that L2 learners made use of semantic context less efficiently in the interfering background than in quiet. In contrast, no significant modulation effect of listening condition on F0 contours was found. Furthermore, there was significant interaction between semantic context and F0 contours, indicating that semantic context becomes more important for L2 speech recognition when F0 information is degraded. None of these effects were found to be modulated by L2 proficiency. The discrepancy in the effects of semantic context and F0 contours on L2 speech recognition in the interfering background might be related to differences in processing capacities required by the two types of information in adverse listening conditions.

Microphysical processes and hydrometeor distributions associated with thunderstorms over India: WRF (cloud-resolving) simulations and validations using TRMM

Thunderstorms are one of the disastrous weather events that affect various parts of the Indian region during the pre-monsoon summer months of March–April–May (MAM). Keeping this societal impact in account, this paper has documented the vertical distribution of cloud microphysical properties and dynamical fields associated with number of thunderstorms over different thunderstorm-prone regions of India. The main objective of this study was to bring out the spatial heterogeneity in the structure of thunderstorms during MAM. In spite of being such an important weather system, the present-day skill of forecasting such systems is particularly poor. This as such prompts us to ponder whether any existing microphysical scheme is able to capture the inherent heterogeneous structure of thunderstorms over different parts of India. To find an answer to this question, the regions are divided based on pre-monsoon lightning distribution obtained from the tropical rainfall measuring mission lightning imaging sensor data. Keeping this observation in background, cloud-resolving simulations are performed using the Weather Research and Forecasting-Advanced Research Weather Model (version 3.2) along with three explicit microphysical schemes for a number of thunderstorm cases those occurred over five different regions of India. The composite structure of all thunderstorms simulated over a region is compared with observation to identify the systematic model bias. It is clearly brought out that the Thompson scheme with the present form is not able to capture different phases of thunderstorms over different parts of the country. However, WDM6 and Morrison are able to capture some of the features reasonably well, along with some degree of uncertainty. The inner structure of thunderstorms is very well brought out by contour frequency altitude diagram. This study therefore provides a framework and a basis of further modifications of WDM6 and Morrison for improving the model forecast for thunderstorms over the Indian region.

Detection of Sentence Boundaries in Polish Based on Acoustic Cues

Abstract In this article the authors investigated and presented the experiments on the sentence boundaries annotation from Polish speech using acoustic cues as a source of information. The main result of the investigation is an algorithm for detection of the syntactic boundaries appearing in the places of punctuation marks. In the first stage, the algorithm detects pauses and divides a speech signal into segments. In the second stage, it verifies the configuration of acoustic features and puts hypotheses of the positions of punctuation marks. Classification is performed with parameters describing phone duration and energy, speaking rate, fundamental frequency contours and frequency bands. The best results were achieved for Naive Bayes classifier. The efficiency of the algorithm is 52% precision and 98% recall. Another significant outcome of the research is statistical models of acoustic cues correlated with punctuation in spoken Polish.

Establishing rainfall frequency contour lines as thresholds for rainfall-induced landslides in Tegucigalpa, Honduras, 1980–2005

Establishing Rainfall Frequency Contour Lines as thresholds for rainfall-induced landslides in Tegucigalpa, Honduras