Pitch discrimination interference: the role of pitch pulse asynchrony

Gockel, Carlyon, and Plack [J. Acoust. Soc. Am. 116, 1092-1104 (2004)] showed that discrimination of the fundamental frequency (F0) of a target tone containing only unresolved harmonics was impaired when an interfering complex tone with fixed F0 was added to the target, but filtered into a lower frequency region. This pitch discrimination interference (PDI) was greater when the interferer contained resolved harmonics than when it contained only unresolved harmonics. Here, it is examined whether this occurred because, when the interferer contained unresolved harmonics, "pitch pulse asynchrony (PPA)" between the target and interferer provided a cue that enhanced performance; this was possible in the earlier experiment because both target and interferer had components added in sine phase. In experiment 1, it was shown that subjects were moderately sensitive to the direction of PPA across frequency regions. In experiments 2 and 3, PPA cues were eliminated by adding the components of the target only, or of both target and interferer, in random phase. For both experiments, an interferer containing resolved harmonics produced more PDI than an interferer containing unresolved harmonics. These results show that PDI is smaller for an interferer with unresolved harmonics even when cues related to PPA are eliminated.     

Passive mode locking in the blue spectral region

The spectral range for passive mode-locking of flashlamp pumped dye lasers has been extended towards the blue (452– 515 nm) by employing the saturable absorber 2-(p-dimethylaminostyryl)-pyridylmethyl iodide (DASPI). Fully modulated trains of picosecond pulses with megawatt peak powers have been obtained.     

A parametric model of the spectral periodicity of stimulus frequency otoacoustic emissions

A model for estimating the spectral period of stimulus frequency otoacoustic emissions (SFOAEs) is presented. The model characterizes the frequency spectrum of an SFOAE in terms of four parameters which can be directly related to cochlear mechanical quantities featuring in the theory of SFOAE generation proposed by Zweig and Shera [J. Acoust. Soc. Am. 98, 2018-2047 (1995)]. The results of applying the parametric model to SFOAEs generated by cochlear models suggest that it gives a sensitive measure of spectral period. It is concluded that the parametric model may be a useful tool for detecting small changes in cochlear function using SFOAE measurements.     

Optical properties of chalcogenide glasses in the terahertz spectral region

Optical properties of chalcogenide glasses of three different compositions (As₂S₃, As₂S₃ × As₂Se₃, and As₂Se₃) are studied via terahertz pulsed spectroscopy. Absorption coefficients and refractive indices are measured in a frequency range of 0.2–1.6 THz. The results show that the phonon modes of the studied materials vary with the composition of the glasses.     

Luminescence of human blood serum in the longwave spectral region

An investigation is made of the absorption, fluorescence, and fluorescence excitation spectra of human blood serum whole and diluted with a sodium-phosphate buffer solution. Time characteristics of the longwave serum luminescence are obtained. The quantum yield of background fluorescence upon excitation by radiation with λexc=500 is found to be 0.5%. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 433–436, May–June, 1999.     

On the role of spectral diffusion in single-molecule spectroscopy

This paper reports on measurements of fluorescence excitation spectra of single impurity molecules of terrylene in n-decane at T=1.7 K. Spectra measured within the same spectral interval but at consecutive instants of time exhibit zero-phonon (ZP) lines of single impurity molecules of several species, differing in the behavior of the line shape and frequency in time. On the one hand, one observes stable ZP lines, well approximated with a Lorentzian. On the other, one sees spectral features with a profile varying from one spectrum to another, with only individual fragments of such a profile allowing the Lorentzian approximation; such features are interpreted assuming the presence of unstable impurity molecules, the ZP lines of which display small (a few tens of MHz) spectral jumps with a time interval of about 10 s. Such molecules exhibit a substantial decrease in the spectral jump frequency within a measurement period of the order of 5000 s, which is attributed to a decrease in the contribution due to spectral diffusion resulting from sample structure relaxation.     

Crystalline Pr:SrAl12O19 waveguide laser in the visible spectral region

We fabricated waveguides in Pr:SrAl(12)O(19) crystals by direct femtosecond laser writing. The propagation losses were calculated to be as low as 0.16 dB/cm at a wavelength of 633 nm. Laser oscillation in a diode-pumped waveguide at a wavelength of 643.5 nm was realized. The output power of the waveguide laser was 28.1 mW at a slope efficiency of 8%.     

The Role of Pitch Memory in Pitch Discrimination and Pitch Matching

Accurate control of vocal pitch (fundamental frequency) requires coordination of sensory and motor systems. Previous research has supported the relationship between perceptual accuracy and vocal pitch matching accuracy. The purpose of this study was to investigate the role of memory for pitch in pitch matching and pitch discrimination ability. Three experimental tasks were used. First, a pitch matching task was completed, in which the participants listened to target tones and vocally matched the pitch of the tones. The second task was a pitch discrimination task that required the participants to judge the pitch (same or different) of complex tone pairs. The third task was pitch discrimination with memory interference task that was similar to the pitch discrimination task except interference tones were added. Results of the pitch matching and pitch discrimination tasks yielded a significant correlation between these values. When there was memory interference, pitch discrimination ability was poorer, and there was no significant correlation between pitch discrimination and pitch matching. These results support earlier findings of a relationship between pitch discrimination and pitch matching abilities. The results also suggest a possible role of pitch memory in both tasks. These findings may have implications for abilities related to accurate pitch control.     

Optical activity of CdS crystals in exciton spectral region

Natural optical activity of wurtzite CdS crystals has been studied for the first time both theoretically and experimentally in the spectral region of the B_n=1 exciton resonance. It has been shown that the observed optical activity is due to mixing the longitudinal Γ_5L exciton state with the transverse Γ₁ state by the energy terms linear in wave vector.     

Temperature dependence of the optical spectral weight in the cuprates: role of electron correlations

We compare calculations based on the dynamical mean-field theory of the Hubbard model with the infrared spectral weight W(Omega,T) of La(2-x)SrxCuO4 and other cuprates. Without using fitting parameters we show that most of the anomalies found in W(Omega,T) with respect to normal metals, including the existence of two different energy scales for the doping and the T dependence of W(Omega,T), can be ascribed to strong correlation effects.     

On the role of envelope fluctuation processing in spectral masking

This study examines the role of temporal cues in spectral masking, such as beats and intrinsic envelope fluctuations. Predictions from the modulation-filterbank model developed by Dau et al. [J. Acoust. Soc. Am. 102, 2906-2919 (1997)] are compared to average masking patterns from Moore et al. [J. Acoust. Soc. Am. 104, 1023-1038 (1998)]. In these experiments, tones and narrow-band noises have been used as the signal and the masker, so that all four signal-masker combinations are considered. In addition, model predictions are compared with new experimental data in conditions of notched-noise masking, where the masker consisted of two narrow-band noises whose bandwidth and frequency separation were varied systematically. The model uses a peripheral filtering stage with linear and symmetric Gammatone filters, an adaptation stage that includes a static compressive nonlinearity for stationary input stumuli and a higher sensitivity for envelope fluctuation, and a modulation filterbank that analyzes the output for each peripheral channel. For low and medium masker levels, the model accounts very well for the masking patterns in all signal-masker conditions, as well as for the notched-noise conditions. In contrast, predictions from a version of the model that acts like an energy detector account for only some of the notched-noise data, and generally do not account for the shape of the masking patterns. For a high masker level, the simulations suggest the use of asymmetric filters, with a steeper high-frequency slope than is used in the linear model, consistent with results from previous studies. In addition, several nonlinear effects become apparent at this masker level, which cannot be accounted for by the current model.