A simple formula for the fundamental optical absorption of alkali halide melts

Significant similarities — with respect to absorption of ultraviolet — between the crystalline and liquid phases of the alkali halides are considered. It is shown that a simple formula which emerged from an earlier application of local electron transfer concepts to the fundamental absorption of the alkali halide crystals appears to apply equally well (i.e. within experimental error) to their melts. This formula fits the observations relating to the fundamental absorption of five molten alkali halides and yields predictions for all the others — which will, it is hoped, stimulate experimental activity.     

Encoding voice fundamental frequency into vibrotactile frequency.

Measured in this study was the ability of eight hearing and five deaf subjects to identify the stress pattern in a short sentence from the variation in voice fundamental frequency (F0), when presented aurally (for hearing subjects) and when transformed into vibrotactile pulse frequency. Various transformations from F0 to pulse frequency were tested in an attempt to determine an optimum transformation, the amount of F0 information that could be transmitted, and what the limitations in the tactile channel might be. The results indicated that a one- or two-octave reduction of F0 vibrotactile frequency (transmitting every second or third glottal pulse) might result in a significant ability to discriminate the intonation patterns associated with moderate-to-strong patterns of sentence stress in English. However, accurate reception of the details of the intonation pattern may require a slower than normal pronounciation because of an apparent temporal indeterminacy of about 200 ms in the perception of variations in vibrotactile frequency. A performance deficit noted for the two prelingually, profoundly deaf subjects with marginally discriminable encodings offers some support for our previous hypothesis that there is a natural association between auditory pitch and perceived vibrotactile frequency.     

A simple frequency formula for clamped rectangular plates

A simple formula is proposed to predict the vibration frequencies of completely clamped rectangular plates, of arbitrary aspect ratio, vibrating in any mode. The development is based on experimental evidence obtained using the technique of holographic interferometry. Comparisons are made with both published results from the literature and experimental values obtained by the authors, and show excellent agreement in all cases.     

Layerwise optimization for the maximum fundamental frequency of laminated composite plates

A new concept of a layerwise optimization approach (LOA) is proposed to optimize vibration behavior for the maximum natural frequency of laminated composite plates. Design variables are taken to be the fiber orientation angles in all N layers. This usually causes a rapid increase in computation time due to the search for optimum solutions in the N-dimensional space. The LOA makes possible this multi-dimensional optimization into only N times repetition in a one-dimensional search. The idea is based on the physical consideration that the outer layer has more stiffening effect than the inner layer in the bending of plates and is more influential in determining the natural frequency. In numerical examples, a Ritz method is employed to calculate the natural frequencies of laminated rectangular plates under any combination of the three classical edge conditions. Results are corroborated by comparing with other optimum solutions available in the literature.     

The perception of fundamental frequency declination

A series of experiments was carried out to investigate how fundamental frequency declination is perceived by speakers of English. Using linear predictor coded speech, nonsense sentences were constructed in which fundamental frequency on the last stressed syllable had been systematically varied. Listeners were asked to judge which stressed syllable was higher in pitch. Their judgments were found to reflect normalization for expected declination; in general, when two stressed syllables sounded equal in pitch, the second was actually lower. The pattern of normalization reflected certain major features of production patterns: A greater correction for declination was made for wide pitch range stimuli than for narrow pitch range stimuli. The slope of expected declination was less for longer stimuli than for shorter ones. Lastly, amplitude was found to have a significant effect on judgments, suggesting that the amplitude downdrift which normally accompanies fundamental frequency declination may have an important role in the perception of phrasing.     

Nonconscious control of fundamental voice frequency

The aim of this paper is to answer the question whether "perception-action" dissociation, which is well documented in vision, may also be found in auditory information processing. Trained singers were asked to produce vowel sounds into a microphone. The sound that each singer produced was fed back to their ears via headphones. Two seconds after the sound production had begun, the auditory feedback was shifted in pitch by a certain degree (9, 19, 50, or 99 cents in either direction). In every set of sounds, instances without any pitch shifts also appeared. After each trial, participants reported whether they were aware of a pitch change or not. It was found that even though the participants were unaware of subtle pitch changes, the fundamental frequency of their vowel production was found to shift slightly in the opposite direction to the pitch shift. These results show that auditory information is processed by two separate systems: one for perception and one for action. They also show that the function of the auditory control system differs from the visual control system. The latter is used to control bodily movements while the function of the former is a nonconscious, instant control of vocalization.     

Approximate expressions for the fundamental frequency of vibration of several dynamic systems

An approximate formula for the frequency of vibration of several dynamic systems is presented. This approximation is an extension of the existing approximate formulae for vibrating plates. The formula is applied to the problem of a vibrating membrane, and the free vibration of a shallow lake.     

Upper and lower bounds for fundamental natural frequency of beams

A better upper bound than the Rayleigh quotient is the Timoshenko quotient, the evaluation of which depends on a pair of compatible admissible moment and displacement functions. Based on both Rayleigh and Timoshenko quotients, a lower bound is readily computed. By means of an iteration procedure, both the upper and lower bound converge to the fundamental natural frequency.     

YIN,a fundamental frequency estimator for speech and music

An algorithm is presented for the estimation of the fundamental frequency (F0) of speech or musical sounds. It is based on the well-known autocorrelation method with a number of modifications that combine to prevent errors. The algorithm has several desirable features. Error rates are about three times lower than the best competing methods, as evaluated over a database of speech recorded together with a laryngograph signal. There is no upper limit on the frequency search range, so the algorithm is suited for high-pitched voices and music. The algorithm is relatively simple and may be implemented efficiently and with low latency, and it involves few parameters that must be tuned. It is based on a signal model (periodic signal) that may be extended in several ways to handle various forms of aperiodicity that occur in particular applications. Finally, interesting parallels may be drawn with models of auditory processing.     

A spectral/temporal method for robust fundamental frequency tracking

In this paper, a fundamental frequency (F(0)) tracking algorithm is presented that is extremely robust for both high quality and telephone speech, at signal to noise ratios ranging from clean speech to very noisy speech. The algorithm is named "YAAPT," for "yet another algorithm for pitch tracking." The algorithm is based on a combination of time domain processing, using the normalized cross correlation, and frequency domain processing. Major steps include processing of the original acoustic signal and a nonlinearly processed version of the signal, the use of a new method for computing a modified autocorrelation function that incorporates information from multiple spectral harmonic peaks, peak picking to select multiple F(0) candidates and associated figures of merit, and extensive use of dynamic programming to find the "best" track among the multiple F(0) candidates. The algorithm was evaluated by using three databases and compared to three other published F(0) tracking algorithms by using both high quality and telephone speech for various noise conditions. For clean speech, the error rates obtained are comparable to those obtained with the best results reported for any other algorithm; for noisy telephone speech, the error rates obtained are lower than those obtained with other methods.     

Comparison of various automatic means for measuring mean fundamental frequency

The purpose of this paper was to evaluate the reliability of, and agreement among, six speech analysis systems in the determination of fundamental frequency. Five male and five female speakers provided oral reading and sustained vowel samples for analysis. Each sample was analyzed five times by each system. The results indicated high reliability for all of the systems for both sexes and both utterance types. Agreement among the systems was high for the male sustained vowels and the female oral reading samples. In contrast, poor agreement occurred among the systems for the male oral reading samples and the female sustained vowels. The findings indicate that the output of these automatic methods tends to be consistent over repeated trials within the systems in their extraction of fundamental frequency; however, agreement among these systems varies.     

Heterodyne frequency measurements on the nitric oxide fundamental band

Heterodyne frequency measurements have been made on the fundamental band of nitric oxide from 1750 to 1931 cm⁻¹. Based on the analysis of these new measurements, minor changes are made in the band constants and an improved list of calculated energy levels for the v = 0 and v = 1 states is given.     

Better place-coding of the fundamental frequency in cochlear implants

In current cochlear implant systems, the fundamental frequency F0 of a complex sound is encoded by temporal fluctuations in the envelope of the electrical signals presented on the electrodes. In normal hearing, the lower harmonics of a complex sound are resolved, in contrast with a cochlear implant system. In the present study, it is investigated whether "place-coding" of the first harmonic improves the ability of an implantee to discriminate complex sounds with different fundamental frequencies. Therefore, a new filter bank was constructed, for which the first harmonic is always resolved in two adjacent filters, and the balance between both filter outputs is directly related to the frequency of the first harmonic. The new filter bank was compared with a filter bank that is typically used in clinical processors, both with and without the presence of temporal cues in the stimuli. Four users of the LAURA cochlear implant participated in a pitch discrimination task to determine detection thresholds for F0 differences. The results show that these thresholds decrease noticeably for the new filter bank, if no temporal cues are present in the stimuli. If temporal cues are included, the differences between the results for both filter banks become smaller, but a clear advantage is still observed for the new filter bank. This demonstrates the feasibility of using place-coding for the fundamental frequency.     

Perceptual learning of fundamental frequency discrimination: effects of fundamental frequency, harmonic number, and component phase

Thresholds (F0DLs) were measured for discrimination of the fundamental frequency (F0) of a group of harmonics (group B) embedded in harmonics with a fixed F0. Miyazono and Moore [(2009). Acoust. Sci. & Tech. 30, 383386] found a large training effect for tones with high harmonics in group B, when the harmonics were added in cosine phase. It is shown here that this effect was due to use of a cue related to pitch pulse asynchrony (PPA). When PPA cues were disrupted by introducing a temporal offset between the envelope peaks of the harmonics in group B and the remaining harmonics, F0DLs increased markedly. Perceptual learning was examined using a training stimulus with cosine-phase harmonics, F0 = 50 Hz, and high harmonics in group B, under conditions where PPA was not useful. Learning occurred, and it transferred to other cosine-phase tones, but not to random-phase tones. A similar experiment with F0 = 100 Hz showed a learning effect which transferred to a cosine-phase tone with mainly high unresolved harmonics, but not to cosine-phase tones with low harmonics, and not to random-phase tones. The learning found here appears to be specific to tones for which F0 discrimination is based on distinct peaks in the temporal envelope.     

The dependency of timbre on fundamental frequency

The dependency of the timbre of musical sounds on their fundamental frequency (F0) was examined in three experiments. In experiment I subjects compared the timbres of stimuli produced by a set of 12 musical instruments with equal F0, duration, and loudness. There were three sessions, each at a different F0. In experiment II the same stimuli were rearranged in pairs, each with the same difference in F0, and subjects had to ignore the constant difference in pitch. In experiment III, instruments were paired both with and without an F0 difference within the same session, and subjects had to ignore the variable differences in pitch. Experiment I yielded dissimilarity matrices that were similar at different F0's, suggesting that instruments kept their relative positions within timbre space. Experiment II found that subjects were able to ignore the salient pitch difference while rating timbre dissimilarity. Dissimilarity matrices were symmetrical, suggesting further that the absolute displacement of the set of instruments within timbre space was small. Experiment III extended this result to the case where the pitch difference varied from trial to trial. Multidimensional scaling (MDS) of dissimilarity scores produced solutions (timbre spaces) that varied little across conditions and experiments. MDS solutions were used to test the validity of signal-based predictors of timbre, and in particular their stability as a function of F0. Taken together, the results suggest that timbre differences are perceived independently from differences of pitch, at least for F0 differences smaller than an octave. Timbre differences can be measured between stimuli with different F0's.     

Extended frequency range measurements for determining the Kneser-type acoustic relaxation time

In the present paper, the authors discuss studies carried out for many years dealing particularly with two compounds: benzene and carbon disulphide and compare them with the results obtained by numerous acoustics researchers. These compounds are typical liquids in which acoustic Kneser-type relaxation occurs, caused by an irreversible vibrational and translational (VT) transition. Since magnitudes describing the relaxation process were diverse in many papers, we have undertaken an attempt to clarify these differences and to indicate how to avoid errors resulting from instrumental imperfections and the disregard of the considerable measurement errors when investigating velocity dispersion in the hypersonic (GHz) range. The results of these researches changed the interpretation of previous papers.