Pitch identification of simultaneous diotic and dichotic two-tone complexes

This study examines subjects' ability to recognize the pitches of two missing fundamentals in two simultaneous two-tone complexes whose partials are distributed in various ways between subjects' ears. The data show that identification performance is affected on different levels. Limited frequency resolution in the peripheral auditory system can degrade performance, but only if none of the four stimulus partials is aurally resolved. Identification performance is only weakly dependent on the manner of distributing partials between the ears. In some cases it was found that, probably at a very central level (e.g., attention), the identification processes of both simultaneous pitches interfere with one another. Some subjects are more likely to identify the pitch of one two-tone complex when the harmonic order of the other complex is higher than when this harmonic order is lower. Finally, some subjects tend to hear the complex tones analytically, i.e., perceive pitches of single partials instead of the missing fundamentals for some distribution of partials between the ears.     

Effects of masker waveform and signal-to-masker phase relation on diotic and dichotic masking by reproducible noise

The proportions of hits and false alarms were estimated for the detection of a 500-Hz sinusoidal signal in each of 25, reproducible samples of wideband, white, Gaussian noise. The effects of signal phase were investigated under diotic (MoSo) and dichotic (MoS pi) conditions and compared to the predictions of two major models of binaural hearing. Averaging the data over samples obscured important across-sample and across-subject differences in performance. The proportions of hits and false alarms for individual noise samples presented under the MoSo condition were highly correlated with those for the same noise samples under the dichotic MoS pi condition, suggesting that the cues determining performance under these conditions are related. Signal-to-masker phase had a large effect on the proportion of hits under the MoSo condition, but only a small effect under the MoS pi condition. The Vector model predicts a large effect of signal phase under the MoS pi condition, and is, therefore, imcompatible with this aspect of the data. The expected value of the decision variable of the EC model is independent of signal phase. However, when the variance of the decision variable is also considered, the EC model does predict changes in the proportion of hits with the phase of the signal, comparable to those observed here. Further, it was shown that, if minor changes in the form of the EC model's decision variable or in the distribution of the internal noise parameters are assumed, the expected value of the decision variable also changes with the phase of the signal.     

Spectral integration of broadband signals in diotic and dichotic masking experiments.

The method of G?ssler [Acustica 4, 408-414 (1954)] was used to measure the audibility of multicomponent signals as a function of their bandwidth against a broadband, white-noise masker. Test signals were composed of 1 to 41 sinusoids with a spectral spacing of 10 Hz and were always spectrally centered around 400 Hz. Masker duration was 400 ms and the 300-ms signals were centered within the noise intervals. A three-interval forced-choice procedure with adaptive level adjustment was applied. NoSo, NoSm, NoS pi, and N pi So masked thresholds were obtained for four subjects. A comparison of the diotic and the three dichotic conditions yields no significant difference in the bandwidth dependence and suggests equal integration bandwidths for all conditions. However, the original results of G?ssler could not be replicated: Neither were the overall levels of signals with a bandwidth below the critical bandwidth constant nor were the results for broadband signals in accordance with a single-band model of detection. The narrow-band data are much better described by calculating the overall signal level at the output of a rounded exponential filter [Patterson et al., J. Acoust. Soc. Am. 72, 1788-1803 (1982)] with an equivalent rectangular bandwidth of 65 Hz. For broader signal bandwidths, the signal level at threshold increases as predicted by a multiband model.     

The effect of diotic and dichotic level-randomization on the binaural masking-level difference

Detection thresholds for tones in narrow-band noise were measured for two binaural configurations: N(o)S(o) and N(o)S(pi). The 30-Hz noise band had a mean overall level of 65 dB SPL and was centered on 250, 500, or 5000 Hz. Signals and noise were simultaneously gated for 500, 110, or 20 ms. Three conditions of level randomization were tested: (1) no randomization; (2) diotic randomization--the stimulus level (common to both ears) was randomly chosen from an uniformly distributed 40-dB range every presentation interval; and (3) dichotic randomization--the stimulus levels for each ear were each independently and randomly chosen from the 40-dB range. Regardless of binaural configuration, level randomization had small effects on thresholds at 500 and 110 ms, implying that binaural masking-level differences (BMLDs) do not depend on interaural level differences for individual stimuli. For 20-ms stimuli, both diotic and dichotic randomization led to markedly poorer performance than at 500- and 110-ms durations; BMLDs diminished with no randomization and dichotic randomization but not with diotic randomization. The loss of BMLDs at 20 ms, with degrees-of-freedom (2WT) approximately 1, implies that changes in intracranial parameters occurring during the course of the observation interval are necessary for BMLDs when mean-level and mean-intracranial-position cues have been made unhelpful.     

啁啾光脉冲的振幅调制和相位扰动对压缩光脉冲的影响

 通过采用分步傅里叶变换法求解非线性薛定谔方程,模拟了啁啾光脉冲有振幅调制和相位扰动下的自相位调制（SPM）对压缩光脉冲对比度和预脉冲宽度的影响。结果表明：啁啾光脉冲的振幅调制深度和相位扰动深度越大,则压缩后的光脉冲对比度越小;啁啾光脉冲的振幅调制周期和相位扰动周期越小,则压缩光脉冲的预脉冲宽度越大。     

Beam quality of truncated laser beams with amplitude modulations and phase fluctuations in turbulence

The closed-form expressions for the Rayleigh range z_R and the M²-factor of truncated laser beams with amplitude modulations (AMs) and phase fluctuations (PFs) in turbulence are derived, and the beam quality is studied by taking the z_R and the M²-factor as the characteristic parameters of beam quality. The M²-factor of truncated laser beams with AMs and PFs is always larger than that of truncated Gaussian beams both in free space and in turbulence. However, in turbulence the beam quality of truncated laser beams with AMs and PFs may be better than that of truncated Gaussian beams if the z_R is taken as the characteristic parameter of beam quality. For laser beams with AMs and PFs in turbulence, the beam quality expressed in terms of z_R is consistent with that in terms of the M²-factor versus the phase fluctuation parameter α, but not versus the intensity modulation parameter σ_A. The beam quality of truncated laser beams with AMs and PFs is less sensitive to turbulence than that of truncated Gaussian beams. The beam quality of laser beams with smaller α and larger σ_A is less affected by turbulence than those with larger α and smaller σ_A.     

Propagation properties of apertured laser beams with amplitude modulations and phase fluctuations through atmospheric turbulence

The propagation properties of apertured laser beams with amplitude modulations (AMs) and phase fluctuations (PFs) through atmospheric turbulence are studied in detail both analytically and numerically. The analytical expressions for the average intensity, power in the bucket (PIB) and Strehl ratio (S _R ) of apertured laser beams with AMs and PFs propagating through atmospheric turbulence are derived. It is found that the worse the phase fluctuation and the higher the amplitude modulation are, the less laser beams are affected by turbulence. Furthermore, apertured Gaussian beams are more sensitive to turbulence than apertured laser beams with AMs and PFs. The average intensity of apertured laser beams with AMs and PFs may be even larger than that of apertured Gaussian beams due to turbulence. In particular, the influence of turbulence on the average maximum intensity of apertured laser beams with PFs and AMs may become serious if an unsuitable truncated parameter is chosen, which should be avoided in practice.     

有振幅调制和相位畸变光束的远场光谱移动与光谱开关

基于瑞利衍射公式,研究了被光阑衍射的具有振幅调制和相位畸变光束的远场光谱变化规律。结果表明,有振幅调制和相位畸变光束在远场也会出现光谱异变现象和光谱开关效应,光阑截断参数、光束的相位畸变参数、振幅调制参数、光强调制参数对远场光谱的跃迁量和光谱开关产生影响。通过数值计算结果分析讨论了光阑截断参数及光束各参数影响远场光谱的规律。     

Propagation characteristics of laser beams with amplitude modulations and phase fluctuations in apertured fractional Fourier transforming system

The apertured fractional Fourier transforming system is introduced and applied to treat the propagation of Gaussian beams with amplitude modulations and phase fluctuations. Based on the treatment that a rectangular function can be expanded into an approximate sum of complex Gaussian functions with finite numbers, the analytical expressions for the mutual intensity distribution of laser beams with amplitude modulations and phase fluctuations passing through the apertured fractional Fourier transforming system are obtained. Some numerical simulations are illustrated for their propagation properties.     

Binaural processing of noisy stimuli: internal/external noise ratios for diotic and dichotic stimuli

A set of ten digitized statistically similar Gaussian maskers was used in one-internal tone-in-noise detection experiments under diotic (NoSo) and dichotic (NoS pi) interaural conditions. Stimulus/response matrices were generated for each masker in the presence or absence of a target 500-Hz tone. For both NoSo and NoS pi, nonparametric analyses show that response probabilities and sensitivities vary significantly across noise waveforms, indicating a considerable external noise component in subject response variability. A parametric model is developed that maps individual stimulus waveforms onto a decision axis, facilitating evaluation of internal/external noise variance ratios. For both NoSo and NoS pi, internal and external noise variance are of similar magnitude.     

Correction of strong phase and amplitude modulations by two deformable mirrors in a multistaged Ti:sapphire laser

We describe a novel scheme consisting of two deformable bimorph mirrors that can free ultrashort laser pulses from simultaneously present strong wave-front distortions and intensity-profile modulations. This scheme is applied to the Max-Planck-Institut für Quantenoptik 10-TW Advanced Titanium-Sapphire Laser (ATLAS) facility. We demonstrate that with this scheme the focusability of the ATLAS pulses can be improved from 10(18) to 2x10(19) W/cm(2) without any penalty in recompression fidelity.     

Frequency resolution for diotic and dichotic listening conditions compared using the bandlimiting measure and a modified bandlimiting measure

Two experiments were performed that examined the relation between frequency selectivity for diotic and dichotic stimuli. Subjects were eight normal-hearing listeners. In each experiment, a 500-Hz pure tone of 400-ms duration was presented in continuous noise. In the diotic listening conditions, a signal and noise were presented binaurally with no interaural differences (So and No, respectively). In the dichotic listening conditions, the signal or noise at one ear was 180 degrees out-of-phase relative to the respective stimulus at the other ear (S pi and N pi, respectively). The first experiment examined frequency selectivity using the bandlimiting measure. Here, signal thresholds were determined as a function of masker bandwidth (50, 100, 250, 500, and 1000 Hz) for SoNo, S pi No, and SoN pi listening conditions. The second experiment used a modified bandlimiting measure. Here, signal thresholds (So and S pi) were determined with a relatively narrow No band of masker energy (50 Hz wide) centered about the signal. Then, a second No narrow-band masker (30 Hz wide) was added at another frequency region, and signal thresholds were reestablished. The results of the two experiments indicated that listeners process a wider band of frequencies when resolving dichotic stimuli than when resolving diotic or monotic stimuli. The results also indicated that the bandlimiting measure may underestimate the spectral band processed upon dichotic stimulation. Results are interpreted in terms of an across-ear and across-frequency processing of waveform amplitude envelope.     

剪切波对时间反转调相的经颅聚焦超声的影响*

为研究颅骨中的剪切波对经颅聚焦超声的影响,该文利用Kelvin-Voigt固体声波方程并结合时间反转法,分别模拟了考虑剪切波和不考虑剪切波时,256-单元平面相控阵为实现超声经颅聚焦所需的相位调控,并将这两种相位调控都分别作用于考虑剪切波和不考虑剪切波时的聚焦情形。对这两种相位调控以及基于它们的经颅聚焦超声场的对比分析结果表明:聚焦深度较大时,剪切波对基于时间反转进行的相位调控影响较小;不过,剪切波对经颅聚焦超声场的强度分布影响较大,忽略剪切波会导致对焦域处声场聚焦强度的高估以及对颅骨附近声能量沉积的低估。     

The pulse-train auditory aftereffect and the perception of rapid amplitude modulations

Prolonged listening to a pulse train with repetition rates around 100 Hz induces a striking aftereffect, whereby subsequently presented sounds are heard with an unusually "metallic" timbre [Rosenblith et al., Science 106, 333-335 (1947)]. The mechanisms responsible for this auditory aftereffect are currently unknown. Whether the aftereffect is related to an alteration of the perception of temporal envelope fluctuations was evaluated. Detection thresholds for sinusoidal amplitude modulation (AM) imposed onto noise-burst carriers were measured for different AM frequencies (50-500 Hz), following the continuous presentation of a periodic pulse train, a temporally jittered pulse train, or an unmodulated noise. AM detection thresholds for AM frequencies of 100 Hz and above were significantly elevated compared to thresholds in quiet, following the presentation of the pulse-train inducers, and both induced a subjective auditory aftereffect. Unmodulated noise, which produced no audible aftereffect, left AM detection thresholds unchanged. Additional experiments revealed that, like the Rosenblith et al. aftereffect, the effect on AM thresholds does not transfer across ears, is not eliminated by protracted training, and can last several tens of seconds. The results suggest that the Rosenblith et al. aftereffect is related to a temporary alteration in the perception of fast temporal envelope fluctuations in sounds.     

Stability of surface-helical waves with low amplitude relative to the modulations

The condition for the stability of helical waves in semiconductor rods and plates relative to modulations is derived. The necessary numerical calculations were performed for the semiconductors Ge, Si, and InSb. The conditions under which selfmodulation of the helical waves can be observed are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 92–97, October, 1987.     

Dynamics of frequency and amplitude modulations in vocalizations produced by eastern towhees, Pipilo erythrophthalmus

Eastern towhees, Pipilo erythrophthalmus (Emberizidae, Passeriformes), appear to estimate source-SPL using spectral or temporal variables. Nevertheless, vocalizations are dynamic by nature and it remains unclear whether subjects pay attention to correlations between discrete variables or pay attention to the dynamics that these variables summarize. Sine functions are used to describe coarse (slow, < 10 Hz) frequency and amplitude modulations in towhee calls and correlations between variables are identified. Towhee calls are also finely (rapidly, > 400 Hz) modulated in both amplitude and frequency. Fine amplitude and frequency modulations correlate well (occur in phase) over relatively low fundamental frequencies (< approximately 3.5 kHz) and tend to have greater amplitudes and frequencies over these same frequencies. Modulations and correlations between modulations might exist due to stable dynamic interactions that occur within and between the physical forces that function to produce modulations in vocalizations. Results support the hypothesis that towhees communicate within separate sound frequency channels defined to each side of approximately 3.5 kHz.     

FPGA-based amplitude and phase detection in DLLRF

The new generation particle accelerator requires a highly stable radio frequency (RF) system. The stability of the RF system is realized by the Low Level RF (LLRF) subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal's amplitude and phase is fundamental to LLRF controls. High-speed ADC (Analog to Digital Converter), DAC (Digital to Analog Converter) and FPGA (Field Programmable Gate Array) play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter, algorithm's defects and non-linearity of devices, which is helpful for future work on high precision detection and control.     

FPGA-based amplitude and phase detection in DLLRF

The new generation particle accelerator requires a highly stable radio frequency（RF） system. The stability of the RF system is realized by the Low Level RF（LLRF） subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal＇s amplitude and phase is fundamental to LLRF controls. High-speed ADC（Analog to Digital Converter） ,DAC（Digital to Analog Converter） and FPGA（Field Programmable Gate Array） play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter,algorithm＇s defects and non-linearity of devices,which is helpful for future work on high precision detection and control.