Performance Assessment of BDS-2/BDS-3/GPS/Galileo Attitude Determination Based on the Single-Differenced Model with Common-Clock Receivers

Global navigation satellite system (GNSS)-based attitude determination has been widely applied in a variety of fields due to its high precision, no error accumulation, low power consumption, and low cost. Recently, the emergence of common-clock receivers and construction of GNSS systems have brought new opportunities for high-precision GNSS-based attitude determination. In this contribution, we focus on evaluating the performance of the BeiDou regional navigation satellite system (BDS-2)/BeiDou global navigation satellite system (BDS-3)/Global Positioning System (GPS)/Galileo navigation satellite system (Galileo) attitude determination based on the single-differenced (SD) model with a common-clock receiver. We first investigate the time-varying characteristics of BDS-2/BDS-3/GPS/Galileo line bias (LB) with two different types of common-clock receivers. The results have confirmed that both the phase and code LBs are relatively stable in the time domain once the receivers have started. However, the phase LB is expected to change to an arbitrary value after each restart of the common-clock receivers. For the first time, it is also found that the phase LBs of overlapping frequencies shared by different GNSS systems are identical. Then, we primarily evaluated the performance of BDS-2/BDS-3/GPS/Galileo precise relative positioning and attitude determination based on the SD model with a common-clock receiver, using a static dataset collected at Wuhan. Experimental results demonstrated that, compared with the double-differenced (DD) model, the SD model can deliver a comparable root–mean–square (RMS) error of yaw but a significantly smaller RMS error of pitch, whether for BDS-2, BDS-3, GPS, or Galileo alone or a combination of them. The improvements of pitch accuracy are approximately 20.8–47.5% and 40.7–57.5% with single- and dual-frequency observations, respectively. Additionally, BDS-3 can deliver relatively superior positioning and attitude accuracy with respect to GPS and Galileo, due to its better geometry. The three-dimensional positioning and attitude (including yaw and pitch) accuracy for both the DD and SD models can be remarkably improved by the BDS-2, BDS-3, GPS, and Galileo combination with respect to a single system alone.

Precise Underwater Gliders Pitch Control with the Presence of the Pycnocline

Glider-based mobile currents observations are gaining increasing research attention. However, the quality of such observations is directly related to the pitch accuracy of the glider. As a buoyancy-driven robot, the glider will be strongly disturbed during the passage through the pycnocline. The pycnocline refers to the oceanic phenomenon where the density of the seawater changes abruptly with respect to depth. The presence of the pycnocline influences the pitch of the glider and consequently affects the quality of the observed currents data. In this work, we propose an actuator constrained active disturbance rejection controller (ACADRC) to improve the accuracy of the pitch angle control when gliders move across the pycnocline. For this purpose, the dynamical model of the glider is first derived. Then, the longitudinal plane motion model of the glider considering the density variation is analyzed. Based on that, we discuss three typical types of pycnocline encountered during glider profiling, which are the pycnocline, the inverted pycnocline and the multiple pycnocline. To alleviate the low accuracy of bang-bang control and proportion integration differentiation control, and furthermore, to mitigate the disturbance of pitch by sudden density changes, we propose the actuator constrained active disturbance rejection controller in conjunction with specific glider pitch actuator hardware constraints. Simulation results show that the proposed method has significant improvement in pitch control accuracy over the comparison methods.

The Effects of a Multimodal Music Program on Young Children’s Facial Expressions During Controlled Singing Tasks

Understanding children’s emotional perceptions of creative tasks can contribute to the optimal design of music programs. Little is known of how young children perceive vocal tasks, and whether music training changes their emotional perceptions. This research examined children’s facial expressions while performing vocal imitation and improvisation tasks before and after music training. Young children ( N=79) aged four to six years were randomly assigned to a multimodal music program, Lego training, or a no-treatment control group. Their facial expressions while performing the tasks were analyzed, and learning outcomes were assessed by measuring participants’ pitch accuracy and improvisation skills at pre-and post-training. The results yielded no significant differences among the groups’ facial expressions. There was, however, a significant main effect of time such that participants showed more Surprise while performing vocal improvisation tasks. While participants in the multimodal music program scored higher on measures of pitch accuracy and improvisation skill, it may be necessary to increase the duration of early childhood music programs to reduce their feelings of apprehension when performing vocal improvisation tasks.

No interaction between fundamental-frequency differences and spectral region when perceiving speech in a speech background

Differences in fundamental frequency (F0) or pitch between competing voices facilitate our ability to segregate a target voice from interferers, thereby enhancing speech intelligibility. Although lower-numbered harmonics elicit a stronger and more accurate pitch sensation than higher-numbered harmonics, it is unclear whether the stronger pitch leads to an increased benefit of pitch differences when segregating competing talkers. To answer this question, sentence recognition was tested in young normal-hearing listeners in the presence of a single competing talker. The stimuli were presented in a broadband condition or were highpass or lowpass filtered to manipulate the pitch accuracy of the voicing, while maintaining roughly equal speech intelligibility in the highpass and lowpass regions. Performance was measured with average F0 differences (ΔF0) between the target and single-talker masker of 0, 2, and 4 semitones. Pitch discrimination abilities were also measured to confirm that the lowpass-filtered stimuli elicited greater pitch accuracy than the highpass-filtered stimuli. No interaction was found between filter type and ΔF0 in the sentence recognition task, suggesting little or no effect of harmonic rank or pitch accuracy on the ability to use F0 to segregate natural voices, even when the average ΔF0 is relatively small. The results suggest that listeners are able to obtain some benefit of pitch differences between competing voices, even when pitch salience and accuracy is low. The accuracy with which we are able to discriminate the pitch of a harmonic complex tone depends on the F0 and the harmonic numbers present. For F0s in the average range of speech (100–200 Hz), pitch discrimination is best (implying accurate F0 coding) when harmonics below about the 10th are present [6–10]. When these lower-numbered harmonics are present, pitch discrimination is also independent of the phase relationships between the harmonics, suggesting that these harmonics are spectrally resolved to some extent. In contrast, when only harmonics above the 10th are present in this range of F0s, pitch discrimination is poorer and is affected by the phase relationships between harmonics, suggesting that interactions occur between these spectrally unresolved harmonics [6–10]. Psychoacoustic studies of sound segregation have often been carried out with interleaved sequences of tones. Some of these studies have investigated segregation based on differences in pitch accuracy and have varied the accuracy by systematically varying whether resolved or only unresolved harmonics are present. Previous studies have found that stream segregation can occur with alternating sequences of tones, even if the tones consist only of unresolved harmonics [11–14]. However, the question of whether streaming is greater with resolved than unresolved harmonics has received mixed answers. In cases where the listeners’ task was to segregate the streams, some studies have shown little difference in streaming between conditions containing resolved or only unresolved harmonics [11, 15], whereas another study using a similar approach found significantly greater stream segregation when resolved harmonics were present than when only unresolved harmonics were present [12]. However, in situations where the task was either neutral or encouraged listeners to integrate the sequences into a single stream, the results have been consistent across studies in showing greater segregation for complex tones containing resolved harmonics than for tones containing only unresolved harmonics [13, 14]. These findings support the idea that pitch accuracy can affect our ability to segregate sounds. Less is known about the role of low-numbered harmonics in the context of segregating competing speech. Bird and Darwin [2] showed that lower harmonics dominate performance in a speech-segregation task based on F0 differences, but they did not test any conditions containing only high-numbered harmonics. Oxenham and Simonson [16] explored the effect of harmonic rank on speech intelligibility by comparing conditions where the target and single-talker masker had been lowpass (LP) or highpass (HP) filtered to either retain (LP-filtered) or remove (HP-filtered) the spectrally resolved components from the target and masker [16]. The LP and HP cutoff frequencies were selected to produce roughly equal performance in noise for both conditions. Surprisingly, performance in the LP and HP conditions improved by similar amounts when the noise masker was replaced by a single-talker masker with a different average F0, suggesting no clear benefit of having resolved harmonic components in the speech. However, that study only used relatively large values of average ΔF0 that according to recent F0 estimates were approximately 4 and 8 semitones (ST). Moreover, this study did not parametrically vary the ΔF0 between the target and masker. It may be that pitch accuracy is only relevant for more challenging conditions, i.e. for conditions with smaller average values of ΔF0. Thus, it remains unclear whether the effect of ΔF0 on performance is affected by the presence or absence of low-numbered, spectrally resolved harmonics. The aim of the present study was to determine whether there is an effect of spectral region, and hence pitch coding accuracy, on the ability of listeners to use average F0 differences between a target and an interfering talker to understand natural speech.

Establishing the Reliability and Validity of Web-based Singing Research

In this study, the robustness of an online tool for objectively assessing singing ability was examined by: (1) determining the internal consistency and test-retest reliability of the tool; (2) comparing the task performance of web-based participants (n = 285) with a group (n = 52) completing the tool in a controlled laboratory setting, and then determining the convergent validity between settings, and (3) comparing participants’ task performance with previous research using similar singing tasks and populations. Results indicated that the online singing tool exhibited high internal consistency (Cronbach’s alpha = .92), and moderate-to-high test-retest reliabilities (.65–.80) across an average 4.5-year-span. Task performance for web- and laboratory-based participants (n = 82) matched on age, sex, and music training were not significantly different. Moderate-to-large correlations (|r| =.31–.59) were found between self-rated singing ability and the various singing tasks, supporting convergent validity. Finally, task performance of the web-based sample was not significantly different to previously reported findings. Overall the findings support the robustness of the online tool for objectively measuring singing pitch accuracy beyond a controlled laboratory environment and its potential application in large-scale investigations of singing and music ability.

Musicians’ Earplugs: Do They Affect Performance or Listeners’ Perceptions?

BACKGROUND: Does wearing musicians’ earplugs while performing affect the quality of the performance? Can listeners perceive a difference in sound when musicians are performing with or without earplugs? The risk of hearing loss is a concern for musicians, but some are reluctant to wear hearing protection due to factors such as an inability to hear their own instrument properly and the possibility of decreased sound quality for listeners. OBJECTIVE: The purpose of this study was to determine the effect of musicians’ earplugs on instrumental pitch accuracy and the perception of tone quality, intonation, and dynamic contrast, as perceived by musicians and listeners. METHODS: Ten university studio faculty teachers were recorded performing single pitches and lyrical and technical passages, first without earplugs and then immediately after with earplugs. A sample of 8 studio faculty teachers and 88 undergraduate music education students completed a researcher-created music perception test of tone quality, intonation, and dynamic contrast. RESULTS: Objective analyses of the single pitch recordings made by faculty with and without earplugs indicate that pitch accuracy did not favor either condition consistently. Results from the perception test indicate that although both faculty and student listeners perceived some differences, the most frequent perception was that the audio pair was equal, and there was no clear difference between performing with and without earplugs in terms of tone quality, intonation, or dynamic contrast. CONCLUSION: These findings suggest that musicians should feel confident that wearing musicians’ earplugs while performing does not adversely affect pitch accuracy or listeners’ perceptions of their timbre and dynamic control.

The Bow

This chapter discusses how beginning bow balance exercises allow the mastery of the three fundamental bowings: martelé, détaché, and legato. Other related bowings that serve as an extension of these three fundamental bowings are provided as well. Preparation of the bow, the students’ path to earning their bows by demonstrating proper physical alignment and instrument posture, and games and beginning rote pieces that build strong bilateral playing motion are explained. Several activities are explored on how to develop pitch accuracy with the bow. In addition, the chapter discusses common bowing errors and offers solutions: how to maintain rhythmic precision, create a rich tone quality, and keep right-hand fingers loose and flexible.

Intermediate-Advanced Level

The chapter provides several exercises that aim to refine left-hand technique in the intermediate-advanced levels of string playing. These techniques include building better pitch accuracy, tuning double stops, executing trills, producing both natural and false harmonics, shifting, perfecting vibrato, and performing glissando. Right-hand bowing techniques that develop phrasing as well as various sound colors and advanced bowing styles are discussed. The author explains how incorporating western music history and theory concepts in rehearsals help students gain a deeper understanding about a piece’s purpose, musical form, harmonic structure, and rhythmic principles so that students can convey a powerful and emotional performance.