Bandwidth Changes Research Articles

Regulation Enforcement

This paper compares the effectiveness of two mechanisms of regulation enforcement: (1) the frequency of inspections and (2) penalties for violations. Threat effects of increased penalties and inspection rates, rather than corrective effects upon receiving an inspection or penalty, are the focus of analysis. Mining industry data from 2004–2009 are used to analyze the responses of mines to separate increases in inspections and citation penalties regarding regulations of safety standards. Mines did not improve safety in response to increased penalties at the ex-ante inspecting rates; however, mines significantly reduced accidents under increased inspections when implemented at those higher penalty rates. The identification strategy results in a local average treatment effect that implies increasing inspection rates from current levels would likely increase social welfare. Results are shown to be robust to bandwidth changes and model specification. The interpretation of the estimated local effect in the context of selection is analyzed. Robustness checks regarding selection exploit staffing changes and restrict to similar samples of treated and non-treated mines, justifying that results are representative.

Thermo-Optical and Structural Studies of Iodine-Doped Polymer: Fullerene Blend Films, Used in Photovoltaic Structures.

Optical and structural properties of a blend thin film of (1:1 wt.) of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) doped with iodine (I2) and then exposed to a stepwise heating were reported and compared with the properties of doped P3HT films. The UV-Vis(T) absorption measurements were performed in situ during annealing runs, at the precisely defined temperatures, in a range of 20–210 °C. It was demonstrated that this new method allows one to observe the changes of absorption spectra, connected with the iodine release and other structural processes upon annealing. In addition, the thermally-induced changes of the exciton bandwidth (W) and the absorption edge parameters, i.e., the energy gap (EG) and the Urbach energy (EU) were discussed in the context of different length of conjugation and the structural disorder in polymers and blends films. During annealing, several stages were distinguished and related to the following processes as: the iodine escape and an increase in P3HT crystallinity, the orderly stacking of polymer chains, the thermally inducted structural defects and the phase separation caused by an aggregation of PCBM in the polymer matrix. Moreover, the detailed X-ray diffraction studies, performed for P3HT and P3HT:PCBM films, before and after doping and then after their thermal treatment, allowed us to consider the structural changes of polymer and blend films. The effect of iodine content and the annealing process on the bulk heterojunction (BHJ) solar cells parameters was checked, by the impedance spectroscopy (IS) measurements and the J-V characteristics registration. All of the investigated P3HT:PCBM blend films showed the photovoltaic effect; the increase in power conversion efficiency (PCE) upon iodine doping was demonstrated.

Market-oriented reform and land use efficiency: Evidence from a regression discontinuity design

This paper explores the causal effect of market-oriented reform on land use efficiency, by taking a fuzzy regression discontinuity (RD) design based on China’s land market reform. The reform in this paper refers to the event that the central government strictly directed city governments to choose market-oriented methods in transferring industrial land since July 1, 2007. Such an institutional background leads to a discontinuity where the probability of land transferred through market-oriented methods significantly jumped up after July 1. The RD results show that market does have a positive impact on land use efficiency, which is indicated by the shortened land development period, relaxing of the constraint on floor area ratio, and superior companies being screened out to become land buyers. These effects are not only statistically significant and economically sizable, but also keep robust facing multiple changes of bandwidth, alternate of the database, and deletion of special samples. However, we also find the positive effect of market is conditional on government-enterprise relationships. If we compare land whose buyers are companies with a close relationship with governments, market will neither increase the intensity of land use nor make superior companies stand out. This paper contributes to the literature on the efficiency of market for two aspects: (1) by using a novel RD design we identify the causal effect of market-oriented reform on land use efficiency; (2) by uncovering the conditional effect of market we prove the limitation of market in a transitional economy, where other factors like networks, political forces still play an important role.

Locally weighted regression with different kernel smoothers for software effort estimation

• Locally Weighted Regression method provides an efficient solution to learn from local effort data. • A comprehensive experiment with 1080 Locally Weighted Regression variants has been constructed. • It has been fount that Uniform kernel functions cannot outperform non-uniform kernel functions. • Kernel type, polynomial degrees and bandwidth parameters do not produce a definite effect on estimation accuracy. • Locally Weighted Regression with Triweight or Triangle kernel outperform other complex kernels. Estimating software effort has been a largely unsolved problem for decades. One of the main reasons that hinders building accurate estimation models is the often heterogeneous nature of software data with a complex structure. Typically, building effort estimation models from local data tend to be more accurate than using the entire data. Previous studies have focused on the use of clustering techniques and decision trees to generate local and coherent data that can help in building local prediction models. However, these approaches may fall short in some aspect due to limitations in finding optimal clusters and processing noisy data. In this paper we used a more sophisticated locality approach that can mitigate these shortcomings that is Locally Weighted Regression (LWR). This method provides an efficient solution to learn from local data by building an estimation model that combines multiple local regression models in k -nearest-neighbor based model. The main factor affecting the accuracy of this method is the choice of the kernel function used to derive the weights for local regression models. This paper investigates the effects of choosing different kernels on the performance of Locally Weighted Regression of a software effort estimation problem. After comprehensive experiments with 7 datasets, 10 kernels, 3 polynomial degrees and 4 bandwidth values with a total of 840 Locally Weighted Regression variants, we found that: 1) Uniform kernel functions cannot outperform non-uniform kernel functions, and 2) kernel type, polynomial degrees and bandwidth parameters have no specific effect on the estimation accuracy. In other words, no change in bandwidth or degree values occurred with a significant difference in kernel rankings. In short, Locally Weighted Regression methods with Triweight or Triangle kernel can perform better than more complex kernels. Hence, we encourage non-uniform kernel methods as smoother function with wide bandwidth and small polynomial degree.

Impact of winding parameters on the fiber bandwidth in the cylindrical area of a hydrogen pressure vessel for generating a digital twin

AbstractThe wet winding process is an established manufacturing technology for the production of rotationally symmetrical components made of fiber‐reinforced plastic (FRP), such as type‐IV hydrogen pressure vessels. In this process, the FRP laminate is produced by continuously depositing an impregnated fiber band on the winding core in a winding pattern adapted to the component stress. Despite a long history of the process, there are shortcomings in the understanding of the process, without which further optimization in terms of cost and material efficiency will reach its limits in the future. Currently, the fiber band is assumed to have a constant rectangular cross‐section in most simulations, which neglects manufacturing influences such as fiber spreading. The investigations carried out aim to extend the process understanding by a realistic description of the fiber bandwidth when deposited on the winding core. The investigations show that the fiber spreading, as well as the absolute fiber bandwidth, depend on the resin loading and the fiber band tension, independent of the winding pattern in the cylindrical area of a pressure vessel shaped winding core. In addition, the fiber bandwidth changes by 15%–20% during circumferential winding, depending on the machine movement.

3D Flexible Frequency Selective Surface with Stable Electromagnetic Transmission Properties

AbstractFrequency selective surfaces (FSS) that can be tightly laminated to complex nondevelopable surfaces have a wide range of applications in many engineering areas. This paper presents a 3D flexible FSS prepared by mechanically guided 3D assembly, capable of being conformally adhered to complex surfaces, while maintaining stable frequency selective properties as well as transmission performance. The stretching strain applied to the prestrained ecoflex substrate can precisely tune and control the buckled 3D metal structures, which leads to the stretchability of the flexible FSS, introduces the increase of the inductance inside the metal cells, and expands the metal gap resulting in a reduction of the capacitance between the unit cells. The mutual correlation of capacitance and inductance ensures in the mechanism that the FSS transmission characteristics will not be significantly affected by the applied strain, as verified by calculations using the equivalent circuit method. Both the results obtained by the experiments and simulations indicate that the resonant frequency of the 3D flexible FSS is 5.7 GHz and the bandwidth at −10 dB is 0.94 GHz, while the resonant frequency shift will not exceed 0.45 Hz, and −10 dB bandwidth change will not exceed 0.32 GHz with applied strain of 17.8% in the ecoflex substrate. At the same time, the 3D flexible FSS maintains stable transmission performance for oblique incidence, with only 0.5 GHz frequency shift at 45° incidence. This stretchable flexible FSS with stable electromagnetic (EM) properties may find potential applications in EM shielding and spatial filtering due to its high flexibility, ready applicability, and cost‐effectiveness.

Assessing Human Feedback Parameters for Disturbance-Rejection

Electromyography (EMG) interfaces are a promising alternative to traditional manual interfaces such as joysticks, mice, and touchscreens for applications such as prosthetics, rehabilitation, and human-computer interaction. McRuer's crossover model has been extensively studied to determine the impacts of dynamical systems on humans using manual interfaces; however, the same analysis has not been conducted with EMG interfaces or more complex dynamical systems. In this paper, we establish and assess changes in human parameters (gain and delay) and bandwidth for manual (joystick) and EMG interfaces when humans are tasked with controlling a first- and second-order dynamical system. We performed a secondary data analysis to estimate the human parameters for 11 participants by performing least-squares fitting on the error between empirical estimates (calculated from measured signals and system dynamics at specific frequencies) and parameterized models (developed from the McRuer's gain-margin crossover model). EMG delay was smaller than the manual delay for the first-order system and EMG delay was smaller with the first-order system than the second-order system. EMG bandwidth was also larger than the manual bandwidth for both first- and second-order systems. These results suggest that using an EMG interface improves the user's reaction time in a first-order system, and the EMG interface increases the bandwidth that the user can control for both first- and second-order systems compared to a manual interface. Understanding the differences in delays and bandwidth based on interfaces and system dynamics is useful for designing multimodal interfaces or for complex systems where the human delay or bandwidth is important.

Implementation of P4-Based Schedulers for Multipath Communication

Multipath communication is a well-developed technology that enhances communication effectiveness and resilience. Moreover, it can flexibly utilize network resources through load balancing among available paths. However, traditionally, deploying such load balancing functions on network devices is costly due to the required configuration changes and complicated signaling mechanisms on the devices’ control planes. Programming Protocol-independent Packet Processors (P4) has recently emerged as a programming language that enables programmability on the data plane, with the potential to relieve such issues in multipath communication. This work introduces and implements three P4-based multipath schedulers that can split traffic over several paths in wireless networks. The first is P4-based Random Splitting, which distributes traffic randomly. The second is P4-based Weighted Round Robin, with path scheduling based on weights in accordance with path capability. The last is P4-based Dynamic Weighted Round Robin (DWRR), which can improve bandwidth utilization by shifting the weights following dynamic changes in the available bandwidth (i.e., when congestion occurs). We have extensively evaluated the implementation of these three P4-based schedulers in a Mininet-WiFi/P4 environment with User Datagram Protocol (UDP) traffic. The results show that these schedulers can achieve multipath communication with the designed scheduling mechanisms.

Luminescence of Ti-Sapphire coatings prepared by plasma electrolytic oxidation and their application in temperature sensing

15 µm thick Ti-Sapphire coatings were synthesised at room temperature by the plasma electrolytic oxidation (PEO) method for 20 min from the pure aluminium substrate and with the addition of the TiO2 particles in various concentrations in the supporting electrolyte. The coatings are featured by microscopic pores typical for PEO surfaces. The dominant is the alpha phase of alumina with the small presence of the gamma phase. The estimated average crystalline size is 41 nm. Ti is uniformly distributed in these polycrystalline ceramic coatings and does not affect morphology or phase content. Photoluminescence of PEO-created coatings shows typical absorption, excitation, and emission features of Ti-Sapphire with two broad-overlapping excitation bands in the green and blue spectral region due to the Jahn-Teller splitting of the 2Eg level and the Stokes shifted emission centred at 720 nm. 2Eg energy state splitting is equal to 2195 cm−1 and 10 Dq ≈ 19,300 cm−1. The highest emission intensity was observed in the coating prepared with the 0.1 g/L TiO2 powder concentration, i.e. 0.32 at% of incorporated Ti3+. Emission spectra recorded at temperatures ranging from 100 K to 300 K revealed the Mott-Seitz temperature dependence of emission intensity with the 1180 cm−1 activation energy. The fit to the McCumber-Sturge relation gave, for the first time, the value of Debye temperature of 594 K of Al2O3:Ti. Non-contact, luminescence temperature sensing from the temperature-induced changes in the emission bandwidth gave a high sensitivity of 3.2 cm−1 K−1 and 0.19 K temperature resolution. The PEO created Ti-sapphire coatings are a promising multifunctional barrier level – optical temperature sensor material for applications in harsh environments or on large aluminium surfaces. It shows potential to be used as a planar waveguide Ti-Sapphire laser active medium.

Bandwidth adaptive behavioral model with dynamic structures for radio frequency power amplifiers

To cope with the degradation of digital predistortion when bandwidth changes, a bandwidth adaptive behavioral model with dynamic structures for radio frequency (RF) power amplifiers (PAs) is proposed in this article. By applying the nonlinear post-compensation technology, PA's nonlinearity is decomposed and analyzed. Short-time Fourier transform and transfer functions are adopted to study the influence of bandwidth variation on the linear memory effect. Based on PA's memory effect analysis, a bandwidth adaptive model with dynamic structures and a coefficient update scheme with low complexity are proposed. Experiments carried on PAs show that the proposed model achieves similar linearization performance as other conventional models. Simultaneously, the proposed model has fewer coefficients and a reduction in the coefficient update of at least 50%.

Output Pulse Characteristics of a Mamyshev Fiber Oscillator

The dependence of the output pulse characteristics of a Mamyshev fiber oscillator on cavity parameters is investigated in detail. We analyze the change in pulse spectrum bandwidth, pulse duration, dechirped pulse duration and chirp with the change in fiber group velocity dispersion, fiber nonlinearity, gain, and filters by putting forward a numerical model. In particular, as one of the most important components, the effect of filters bandwidth and the central wavelength interval between them is discussed. The passive fibers are classified into two kinds according to their locations in the cavity, which are the one before the gain fiber and the one after the gain fiber. Numerical simulation results show that a wide spectrum can be obtained by increasing the nonlinearity of the second passive fiber, while the change in nonlinearity of the first passive fiber has a weak effect on spectrum broadening. A wide spectrum could also be obtained by increasing the nonlinearity or the small-signal gain coefficient of the gain fiber. A Yb-doped Mamyshev fiber oscillator is demonstrated. The results show the increase in pump power, which agrees reasonably well with the numerical simulation results.

КОДИРОВАНИЕ ИЗОБРАЖЕНИЙ СПЕКТРОГРАММ ДЛЯ ОБЕСПЕЧЕНИЯ ПЕРЕМЕННОЙ СКОРОСТИ ПЕРЕДАЧИ АУДИОДАННЫХ С СОХРАНЕНИЕМ КАЧЕСТВА ИХ ЗВУЧАНИЯ

In the applications of audio control and fixation in the conditions of information-technical counteraction, noise clearing, formation of digital watermarks, audio fingerprinting, protective text audio markers, etc., a compact representation of speech signals for subsequent transmission-storage is required while maximal preserving the similarity of the sound quality of restored speech with the original, elimination of accompanying interferences. Theproposed audio codec is based on the narrow-band sine Gaussian model of speech analysis/synthesis, where its representation as a superposition of harmonic components weighted by a Gaussian window applies to all types of speech frames, as well as on universal and special methods of construction and image processing of narrow-band dynamic spectrograms, in particular, by the application of compression-recovery algorithms to them, which will allow to regulate the speech stream speed within a wide range of 1.2–16Kbit/s with adaptation to changes of the audio data transmission-storage channel bandwidth, caused, in particular, by both objective factors and the actions of an intruder. This work aims to select the best parameters on the spectrogram images that reduce the overall bitrate, remove the influence of noise and interference and allow using of spectral inversion methods and algorithms to recover the speech signal with the same or better quality. The parameters are extracted from the spectrogram images obtained using of the short-time Fourier transform, using methods to extract the amplitudes, frequencies, phases and development tracks of selected local or global maxima (peaks) of the speech signal on the spectral slices. The communication channel can transmit either the parameters themselves, or the results of compression-encoding of the image to restore the image of the original spectrogram with the selection of peak parameters already on it with the subsequent synthesis of speech or for direct spectral inversion of the image into speech. It is possible to correct the reconstructed spectrogram by using a priori information about the speaker's speech from his pre-generated voice database.

A temperature-insensitive FBG acceleration sensor with sinusoid-shaped curved beams

PurposeThis study aims to solve the problem of temperature cross sensitivity of fiber Bragg grating in structural health monitoring, proposing a novel acceleration sensor based on strain chirp effect which is insensitive to temperature.Design/methodology/approachA kind of M-shaped double cantilever beam structure is developed. The fiber grating is pasted in the gradient strain region of the beam, and the chirp effect is produced under the action of non-uniform stress, and then the change of acceleration is converted into the change of reflection bandwidth to demodulate and eliminate the temperature interference. Through theoretical analysis, simulation and experimental verification with rectangular beam sensor.FindingsThe results show that the sinusoidal curvature beam sensor is insensitive to the change of temperature and is more likely to produce chirp effect. The sensitivity is about 317 pm/g, and the natural frequency is 56 Hz.Originality/valueThis paper fulfils an insensitive to temperature changes sensor which has effectively solved the temperature cross-sensitivity problem in building structure health monitoring.

Effect of small cation occupancy and anomalous Griffiths phase disorder in nonstoichiometric magnetic perovskites

The structural, magnetic, magnetocaloric and Griffiths phase (GP) disorder of non-stoichiometric perovskite manganites La0.8−xSr0.2−yMn1+x+yO3 are reported here. Determination of valence states and structural phases evidenced that the smaller cations Mn2+ and Mn3+ will not occupy the A-site of a perovskite under atmospheric synthesis conditions. The same analysis also supports that the vacancy in the A-site of a perovskite induces a similar vacancy in the B-site. The La3+ and Sr2+ cation substitutions in the A-site with vacancy influences the magnetic phase transition temperature (TC) inversely, which is explained in terms of the electronic bandwidth change. An anomalous non-linear change of the GP has been observed in the Sr-substituted compounds. The agglomeration of Mn3+-Mn4+ pairs (denoted as dimerons), into small ferromagnetic clusters, has been identified as the reason for the occurrence of the GP. A threshold limit of the dimeron formation explains the observed non-linear behaviour of the GP formation. The Sr-substituted compounds show a relatively large value of isothermal entropy change (maximum 3.27 J/kgK at μ0H=2T) owing to its sharp magnetic transition, while the broad change of magnetization in the La-substituted compound enhances the relative cooling power (maximum 98 J/kg at μ0H=2T).

Effects of Gamma and Electron Beam Irradiation on FBG and DFB-FL

This paper reports the comparative experimental study concerning the irradiation effects of gamma-ray and electron beam on fiber Bragg grating (FBG) and distributed feedback fiber laser (DFB-FL). The obvious reflection wavelength shifts are observed for FBGs and DFB-FLs without evident changes in reflectivity and bandwidth under the current experimental irradiation condition, up to 60 kGy gamma radiation and 100 kGy electron beam radiation, respectively. Especially for DFB-FLs, evident attenuation in output power is observed and the rising tendency of the attenuation under increasing irradiation dose is demonstrated as well. Thus, the DFB-FLs are more suitable for radiation detection as compared to passive FBGs.

A reconfigurable band-stop filter using piezoelectric-piezomagnetic superlattices with an external DC electric field

A novel reconfigurable band-stop filter using piezomagnetic-piezoelectric superlattices with the external direct-current (DC) electric field (PPSED) is presented. The center frequency of the forbidden band is reduced from to Hz in the band-stop filter as the thickness ratio of the piezoelectric domain to the piezomagnetic domain increases from to 9. The change of the forbidden bandwidth and the center frequency shows that the band-stop filter constructed by the PPSED is reconfigurable. The coupled polaritonic band structure is asymmetric with respect to the forward and backward directions and the forbidden bandwidth can be tuned by the DC electric field via the electro-optic effect. Unlike pure piezoelectric superlattices with the DC electric field, the forbidden bandwidth decreases with the increase of the electric field in the PPSED. The bandwidth tunability by the DC electric field can provide a guidance for the reconfigurable band-stop filter design to work in broadband frequencies.

Dynamic Bandwidth Allocation for Internet of Things System Using Elastic Wireless Local Area Network

Rapid technological development, triggering various applications development that are increasingly innovative. One of them is the Internet of Things (IoT) system that makes human works easier and more effective. Along with sensor technology development in monitoring and controlling through IoT systems, a mechanism is needed to manage bandwidth so that IoT system can function optimally, especially in buildings designated as public areas. Smart building supported by various integrated sensors to maintain safety and comfort in the area. This study proposes the application of Elastic WLAN as a model for dynamic bandwidth management in IoT systems. In this model, IoT bandwidth changes automatically according to the number of traffic measurements for each IoT connected to the network As an effort to determine the performance of the elastic WLAN mechanism, this study succeeded in developing a prototype IoT device that implements Elastic WLAN on an Access-Point Raspberry Pi by using two temperature sensors placed in separate locations. The system successfully allocates bandwidth to each IoT according to the amount of data input from each temperature sensor installed. The higher the amount of data captured by the sensor, the system will automatically allocate the higher bandwidth to the sensor system, and vice versa.

Analyzing the vocal tract characteristics for out-of-breath speech.

In this work, vocal tract characteristic changes under the out-of-breath condition are explored. Speaking under the influence of physical exercise is called out-of-breath speech. The change in breathing pattern results in perceptual changes in the produced sound. For vocal tract, the first four formants show a lowering in their average frequency. The bandwidths BF1 and BF2 widen, whereas the other two get narrowed. The change in bandwidth is small for the last three. For a speaker, the change in frequency and bandwidth may not be uniform across formants. Subband analysis is carried out around formants for comparing the variation of the vocal tract with the source. A vocal tract adaptive empirical wavelet transform is used for extracting formant specific subbands from speech and source. The support vector machine performs the subband-based binary classification between the normal and out-of-breath speech. For all speakers, it shows an F1-score improvement of 4% over speech subbands. Similarly, a performance improvement of 5% can be seen for both male and female speakers. Furthermore, the misclassification amount is less for source compared to speech. These results suggest that physical exercise influences the source more than the vocal tract.

Multivariable State-Feedback Controller Design for PV Inverter Connected to a Weak Grid

This paper presents a robust multi-input multi-output (MIMO) state-feedback control scheme for a photovoltaic (PV) inverter connected to a weak grid. For a weak grid, the point of common coupling (PCC) voltage is very sensitive to the power disturbances and it is dynamically coupled to the PLL dynamics. So far, most of the control methods do not take into accounts these couplings. Therefore, in this paper, the MIMO controller was designed taking into account the dynamics of the phase-locked loop (PLL) and coupling effects between PCC voltage and the active power to enhance the system’s robustness. As result, the robust performance of the PV inverter interfaced to a weak grid was yielded. In addition, the sensitivity of the system to PLL was eliminated, allowing the use of larger PLL bandwidth even in a very weak grid. Based on the eigenvalues analysis method, a comparative study between the proposed control method and the conventional vector control method was performed. The proposed method is verified with simulations in PLECS and real-time simulations in the RT Box. The results show that the proposed MIMO control method preserves the system stability robustness against any change of grid strength, generated power and PLL bandwidth.

Study on changes of voice characteristics after adenotonsillectomy or adenoidectomy in children

Objective: To study voice changes in children after adenotonsillectomy or adenoidectomy and the relationship with the vocal tract structure. Methods: Fifty patients were recruited in this study prospectively, aged from 4 to 12 years old with the median age of 6. They were underwent adenotonsillectomy or adenoidectomy in Beijing Tongren Hospital, Capital Medical University from July 2019 to August 2020. In the cases, there are 31 males and 19 females. Thirty-six patients underwent adenotonsillectomy and 14 patients underwent adenoidectomy alone. Twenty-two children (13 males, 9 females) with Ⅰ degree of bilateral tonsils without adenoid hypertrophy and no snoring were selected as normal controls. Adenoid and tonsil sizes were evaluated. Subjective changes of voice were recorded after surgery. Moreover, voice data including fundamental frequency(F0), jitter, shimmer, noise to harmonic ratio(NHR), maximum phonation time(MPT), formant frequencies(F1-F5) and bandwidths(B1-B5) of vowel/a/and/i/were analyzed before, 3 days and 1 month after surgery respectively.SPSS 23.0 was used for statistical analysis. Results: Thirty-six patients(72.0%,36/50) complained of postoperative voice changes. The incidence was inversely correlated with age. In children aged 4-6, 7-9, and 10-12, the incidence was 83.3%(25/30), 63.6%(7/11) and 44.4%(4/9) respectively. Voice changes appeared more common in children underwent adenotonsillectomy(77.8%,28/36) than in those underwent adenoidectomy alone(57.1%,8/14), but there was no statistical difference. After operation, for vowel/a/, MPT(Z=2.18,P=0.041) and F2(t=2.13,P=0.040) increased, B2(Z=2.04,P=0.041) and B4(Z=2.00,P=0.046) decreased. For vowel/i/, F2(t=2.035,P=0.050) and F4(t=4.44,P=0.0001) increased, B2(Z=2.36,P=0.019) decreased. Other acoustic parameters were not significantly different from those before surgery. The F2(r=-0.392, P =0.032) of vowel/a/and F2(r=-0.279, P=0.048) and F4 (r=-0.401, P =0.028) of vowel/i/after adenotonsillectomy were significantly higher than those of adenoidectomy alone. Half of patients with postopertive voice changes can recover spontaneously 1 month after surgery. Conclusions: Voice changes in children underwent adenotonsillectomy or adenoidectomy might be related to their changes in formants and bandwidths. The effect of adenotonsillectomy on voice was more significant compared with that of adenoidectomy alone. The acoustic parameters did not change significantly after surgery except MPT.