Synthetic Stimuli Research Articles

Rapid Synaptic Depression Explains Nonlinear Modulation of Spectro-Temporal Tuning in Primary Auditory Cortex by Natural Stimuli

In this study, we explored ways to account more accurately for responses of neurons in primary auditory cortex (A1) to natural sounds. The auditory cortex has evolved to extract behaviorally relevant information from complex natural sounds, but most of our understanding of its function is derived from experiments using simple synthetic stimuli. Previous neurophysiological studies have found that existing models, such as the linear spectro-temporal receptive field (STRF), fail to capture the entire functional relationship between natural stimuli and neural responses. To study this problem, we compared STRFs for A1 neurons estimated using a natural stimulus, continuous speech, with STRFs estimated using synthetic ripple noise. For about one-third of the neurons, we found significant differences between STRFs, usually in the temporal dynamics of inhibition and/or overall gain. This shift in tuning resulted primarily from differences in the coarse temporal structure of the speech and noise stimuli. Using simulations, we found that the stimulus dependence of spectro-temporal tuning can be explained by a model in which synaptic inputs to A1 neurons are susceptible to rapid nonlinear depression. This dynamic reshaping of spectro-temporal tuning suggests that synaptic depression may enable efficient encoding of natural auditory stimuli.

Duration Affects Vowel Perception in Estonian and Finnish

Identification of vowels in quantity languages is usually considered to be independent of vowel duration since duration is used to realise the quantity oppositions and thus supposed to not be available as a cue for other features. To test the role of microdurational variations in vowel category perception in Estonian and Finnish listening experiments with synthetic stimuli were carried out, involving five vowel pairs along the close-open axis. The results show that in the case of high-mid vowel pairs vowel openness correlates positively with stimulus duration; in mid-low vowel pairs such correlation was only found for some of the Finnish subjects. We explain the observed difference between high-mid and mid-low pairs with the hypothesis that in case of shorter perceptual distances in vowel quality (high-mid area of vowel space) intrinsic duration plays the role of a secondary feature to enhance perceptual contrast between vowels, whereas in case of mid-low oppositions the perceptual distance is large enough to guarantee the necessary perceptual contrast by spectral features alone and vowel intrinsic duration as an additional cue is not needed.

English /r/-/l/ category assimilation by Japanese adults: Individual differences and the link to identification accuracy

Native speakers of Japanese often have difficulty identifying English /r/ and /l/, and it has been thought that second-language (L2) learning difficulties like this are caused by how L2 phonemes are assimilated into ones native phonological system. This study took an individual difference approach to examining this relationship by testing the category assimilation of Japanese speakers with a wide range of English /r/-/l/ identification abilities. All Japanese subjects were assessed in terms of (1) their accuracy in identifying English /r/ and /l/, (2) their assimilation of /r/ and /l/ into their Japanese flap category, (3) their production of /r/ and /l/, and (4) their best-exemplar locations for /r/, /l/, and Japanese flap in a five-dimensional set of synthetic stimuli (F1, F2, F3, closure duration, and transition duration). The results demonstrated that Japanese speakers assimilate /l/ into their flap category more strongly than they assimilate /r/. However, there was little evidence that category assimilation was predictive of English /r/-/l/ perception and production. Japanese speakers had three distinct best exemplars for /r/, /l/, and flap, and only their representation of F3 in /r/ and /l/ was predictive of identification ability.

Off on the Wrong Foot: Local Features in Biological Motion

Biological-motion perception consists of a number of different phenomena. They include global mechanisms that support the retrieval of the coherent shape of a walker, but also mechanisms which derive information from the local motion of its parts about facing direction and animacy, independent of the particular shape of the display. A large body of the literature on biological-motion perception is based on a synthetic stimulus generated by an algorithm published by James Cutting in 1978 (Perception 7 393-405). Here we show that this particular stimulus lacks a visual invariant inherent to the local motion of the feet of a natural walker, which in more realistic motion patterns indicates the facing direction of a walker independent of its shape. Comparing Cutting's walker to a walker derived from motion-captured data of real human walkers, we find no difference between the two displays in a detection task designed such that observers had to rely on global shape. In a direction discrimination task, however, in which only local motion was accessible to the observer, performance on Cutting's walker was at chance, while direction could still be retrieved from the stimuli derived from the real walker.

Probing the early visual system with naturalistic, synthetic images

Event Abstract Back to Event Probing the early visual system with naturalistic, synthetic images The physiology of early visual cortex has traditionally been studied with simple stimuli such as bars and gratings. While this approach has revealed much of what we know, it is also likely to have provided an incomplete view of early visual processing in natural vision. There has thus been a growing interest in using natural images, namely photographic depictions of natural environments, to study cortical processing. A frequent criticism of this approach, however, is that natural images are so complex that it is difficult to understand precisely which of their features drive the observed physiological effects. Our aim is to develop a new class of stimuli that captures much of the statistical richness of natural images while still allowing full parametric manipulation. We have combined the development of this method with its application to neurophysiological experiments in primary visual cortex and with computational modeling of the experimental data. Our approach is based on characterizing the statistics of natural scenes in the context of an algorithm that generates synthetic images [1]. The algorithm is based on a steerable pyramid of oriented filters, which has a clear biological correlate in the receptive field properties of neurons in primary visual cortex (V1). The resulting parameter space is quite high dimensional. Here we focused on the joint statistics of the magnitude of filter activations, and defined two perceptually relevant parameters: H, the entropy of filter activity across orientations, which measures how well defined the average orientation of the image is; and L, the spatial extent of correlation among parallel filters, capturing the extent of edges and lines in the image. We analyzed an ensemble of natural scenes to find the parameter ranges typically encountered in such scenes and then generated artificial images by choosing values from each of the distributions. Interestingly, we found that natural images tend to cluster in a corner of the space defined by our parameters, that has little overlap with sinusoidal gratings. We synthesized images, varying H and L independently to obtain a parametric set of synthetic, naturalistic images. To test the applicability of our approach, we recorded the responses of single units in V1 of anesthetized macaque monkeys to synthetic stimuli presented either to the classical receptive field or extending into the non-classical receptive field (nCRF). The nCRF experiments showed a rich variety of nonlinear effects, including: a) clear dependency of nCRF surround suppression on the parameter H, and, to a less extent, on L ; and b) reduced suppression, and in some cases facilitation, when the center and the surround of the cells’ receptive field were stimulated with different statistics. Gain control models of cortical processing have been effective in explaining some V1 nonlinearities in response to grating stimuli; we are testing the ability of Gaussian Scale Mixtures, a class of generative model of natural image statistics related to divisive gain control, to account for our data.

Effects of Dynamic Attributes of Smiles in Human and Synthetic Faces: A Simulated Job Interview Setting

We examined the effects of the temporal quality of smile displays on impressions and decisions made in a simulated job interview. We also investigated whether similar judgments were made in response to synthetic (Study 1) and human facial stimuli (Study 2). Participants viewed short video excerpts of female interviewees exhibiting dynamic authentic smiles, dynamic fake smiles, or neutral expressions, and rated them with respect to a number of attributes. In both studies, perceivers’ judgments and employment decisions were significantly shaped by the temporal quality of smiles, with dynamic authentic smiles generally leading to more favorable job, person, and expression ratings than dynamic fake smiles or neutral expressions. Furthermore, authentically smiling interviewees were judged to be more suitable and were more likely to be short-listed and selected for the job. The findings show a high degree of correspondence in the effects created by synthetic and human facial stimuli, suggesting that temporal features of smiles similarly influence perceivers’ judgments and decisions across the two types of stimulus.

The Effect of Temporal Gap Identification on Speech Perception by Users of Cochlear Implants

This study examined the ability of listeners using cochlear implants (CIs) and listeners with normal hearing (NH) to identify silent gaps of different duration and the relation of this ability to speech understanding in CI users. Sixteen NH adults and 11 postlingually deafened adults with CIs identified synthetic vowel-like stimuli that were either continuous or contained an intervening silent gap ranging from 15 ms to 90 ms. Cumulative d', an index of discriminability, was calculated for each participant. Consonant and consonant-nucleus-consonant (CNC) word identification tasks were administered to the CI group. Overall, the ability to identify stimuli with gaps of different duration was better for the NH group than for the CI group. Seven CI users had cumulative d' scores that were no higher than those of any NH listener, and their CNC word scores ranged from 0% to 30%. The other 4 CI users had cumulative d' scores within the range of the NH group, and their CNC word scores ranged from 46% to 68%. For the CI group, cumulative d' scores were significantly correlated with their speech testing scores. The ability to identify silent gap duration may help explain individual differences in speech perception by CI users.

Categorical perception of a natural, multivariate signal: Mating call recognition in túngara frogs

Categorical perception is common in humans, but it is not known whether animals perceive continuous variation in their own multidimensional social signals categorically. There are two components to categorical perception: labeling and discrimination. In the first, continuously variable stimuli on each side of a category boundary are labeled. In the second, there is strong discrimination between stimuli from opposite sides of the boundary, whereas stimuli on the same side of the boundary are not discriminated. Here, we show that female túngara frogs respond categorically to complex mating calls that vary simultaneously along multiple dimensions and are within the natural range of signal variation. In response to a transect of synthetic stimuli that varied continuously and systematically in seven dimensions, female túngara frogs label mating calls as either conspecific or not conspecific. For pairs of stimuli that differed by the same magnitude, females discriminate those in different categories but not those in the same category. In addition, latency to respond was significantly shorter when stimuli were in the same versus different categories. Because responses to mating calls are critical in generating species recognition and sexual selection, this finding has implications for both animal perception and the influences of mate choice on the tempo and mode of evolution.

Bias dependent response reversal in chemically sensitive metal oxide semiconductor capacitors

Conditions for reversal of the voltage shift in chemically sensitive metal oxide semiconductor capacitors are surveyed with the pulsed illumination technique in Si∕SiO2∕Me0 capacitors, with annular Pd and Au gates under controlled H2 in N2 and NO2 in synthetic air stimuli, respectively. The polarity of the response is bias dependent. Above the threshold voltage, negative voltage shifts ensue from positive charges accumulated on the gate-dielectric interface for donor stimuli such as H2, whereas positive shifts indicate negative charge accumulation for acceptors such as NO2. Below the threshold voltage, the necessary charge compensation can be satisfied by proportional changes in the semiconductor-gate interface state population, which induce chemical shifts of opposite polarity.

Objective phonological and subjective perceptual characteristics of syllables modulate spatiotemporal patterns of superior temporal gyrus activity

Natural consonant–vowel syllables are reliably classified by most listeners as voiced or voiceless. However, our previous research [Liederman, J., Frye, R., Fisher, J.M., Greenwood, K., Alexander, R., 2005. A temporally dynamic context effect that disrupts voice onset time discrimination of rapidly successive stimuli. Psychon Bull Rev. 12, 380–386] suggests that among synthetic stimuli varying systematically in voice onset time (VOT), syllables that are classified reliably as voiceless are nonetheless perceived differently within and between listeners. This perceptual ambiguity was measured by variation in the accuracy of matching two identical stimuli presented in rapid succession. In the current experiment, we used magnetoencephalography (MEG) to examine the differential contribution of objective (i.e., VOT) and subjective (i.e., perceptual ambiguity) acoustic features on speech processing. Distributed source models estimated cortical activation within two regions of interest in the superior temporal gyrus (STG) and one in the inferior frontal gyrus. These regions were differentially modulated by VOT and perceptual ambiguity. Ambiguity strongly influenced lateralization of activation; however, the influence on lateralization was different in the anterior and middle/posterior portions of the STG. The influence of ambiguity on the relative amplitude of activity in the right and left anterior STG activity depended on VOT, whereas that of middle/posterior portions of the STG did not. These data support the idea that early cortical responses are bilaterally distributed whereas late processes are lateralized to the dominant hemisphere and support a “how/what” dual-stream auditory model. This study helps to clarify the role of the anterior STG, especially in the right hemisphere, in syllable perception. Moreover, our results demonstrate that both objective phonological and subjective perceptual characteristics of syllables independently modulate spatiotemporal patterns of cortical activation.

Chromatic discrimination of natural objects

Studies of chromatic discrimination are typically based on homogeneously colored patches. Surfaces of natural objects, however, cannot be characterized by a single color. Instead, they have a chromatic texture, that is, a distribution of different chromaticities. Here we study chromatic discrimination for natural images and synthetic stimuli with a distribution of different chromaticities under various states of adaptation. Discrimination was measured at the adaptation point, where the mean chromaticity of the test stimuli was the same as the chromaticity of the adapting background, and away from the adaptation point. At the adaptation point, discrimination for natural objects resulted in threshold contours that were selectively elongated in a direction of color space matching the chromatic variation of the colors within the natural object. Similar effects occurred for synthetic stimuli. Away from the adaptation point, discrimination thresholds increased and threshold ellipses were elongated along the contrast axis connecting adapting color and test color. Away from the adaptation point, no significant differences between the different stimulus classes were found. The effect of the chromatic texture on discrimination seemed to be masked by the overall increase in discrimination thresholds. Our results show that discrimination of chromatic textures, either synthetic or natural, differs from that of simple uniform patches when the chromatic variation is centered at the adaptation point.

Spectral structure across the syllable specifies final-stop voicing for adults and children alike

Traditional accounts of speech perception generally hold that listeners use isolable acoustic "cues" to label phonemes. For syllable-final stops, duration of the preceding vocalic portion and formant transitions at syllable's end have been considered the primary cues to voicing decisions. The current experiment tried to extend traditional accounts by asking two questions concerning voicing decisions by adults and children: (1) What weight is given to vocalic duration versus spectral structure, both at syllable's end and across the syllable? (2) Does the naturalness of stimuli affect labeling? Adults and children (4, 6, and 8 years old) labeled synthetic stimuli that varied in vocalic duration and spectral structure, either at syllable's end or earlier in the syllable. Results showed that all listeners weighted dynamic spectral structure, both at syllable's end and earlier in the syllable, more than vocalic duration, and listeners performed with these synthetic stimuli as listeners had performed previously with natural stimuli. The conclusion for accounts of human speech perception is that rather than simply gathering acoustic cues and summing them to derive strings of phonemic segments, listeners are able to attend to global spectral structure, and use it to help recover explicitly phonetic structure.

An event-related fMRI investigation of voice-onset time discrimination

The discrimination of voice-onset time, an acoustic–phonetic cue to voicing in stop consonants, was investigated to explore the neural systems underlying the perception of a rapid temporal speech parameter. Pairs of synthetic stimuli taken from a [da] to [ta] continuum varying in voice-onset time (VOT) were presented for discrimination judgments. Participants exhibited categorical perception, discriminating 15-ms and 30-ms between-category comparisons and failing to discriminate 15-ms within-category comparisons. Contrastive analysis with a tone discrimination task demonstrated left superior temporal gyrus activation in all three VOT conditions with recruitment of additional regions, particularly the right inferior frontal gyrus and middle frontal gyrus for the 15-ms between-category stimuli. Hemispheric differences using anatomically defined regions of interest showed two distinct patterns with anterior regions showing more activation in the right hemisphere relative to the left hemisphere and temporal regions demonstrating greater activation in the left hemisphere relative to the right hemisphere. Activation in the temporal regions appears to reflect initial acoustic–perceptual analysis of VOT. Greater activation in the right hemisphere anterior regions may reflect increased processing demands, suggesting involvement of the right hemisphere when the acoustic distance between the stimuli are reduced and when the discrimination judgment becomes more difficult.

Experience-dependence of neural responses to social versus isolate conspecific songs in the forebrain of female Zebra Finches

Early exposure to conspecific song influences the ontogeny of behavioural discrimination between social and isolate songs of males in non-singing female Zebra Finches (Taeniopygia guttata). We explored the potential neural basis of this behavioural plasticity in song preference of female Zebra Finches, reared by both parents in a conspecific colony (controls) or by mothers only in sound-attenuation chambers (father-absent treatment). Comparing extracellular recordings of auditory neurons in the primary auditory forebrain area Field L showed that single units consistently responded with greater response strengths to male songs, over the synthetic stimuli of both frequency-matched pure tone assemblages and reversed conspecific songs, irrespective of females’ ontogenetic treatment. Contrary to expectations, consistent response selectivity for social versus isolate Zebra Finch songs was detected from neurons only in father-absent females and not in control subjects. These results based on statistical analyses of data from single neurons were confirmed by a contingency analysis that used female subjects as independent datapoints. Our findings suggest that differences in the early social and/or auditory experience affect the neurophysiological responses to specific classes of male songs in auditory forebrain neurons of female Zebra Finches. Contrary to expectations, patterns of neuronal discrimination in the Field L complex do not parallel patterns of experience-dependent behavioural discrimination between social and isolate conspecific songs.

Sensorimotor adaptation to feedback perturbations of vowel acoustics and its relation to perception

The role of auditory feedback in speech motor control was explored in three related experiments. Experiment 1 investigated auditory sensorimotor adaptation: the process by which speakers alter their speech production to compensate for perturbations of auditory feedback. When the first formant frequency (F1) was shifted in the feedback heard by subjects as they produced vowels in consonant-vowel-consonant (CVC) words, the subjects' vowels demonstrated compensatory formant shifts that were maintained when auditory feedback was subsequently masked by noise-evidence of adaptation. Experiment 2 investigated auditory discrimination of synthetic vowel stimuli differing in F1 frequency, using the same subjects. Those with more acute F1 discrimination had compensated more to F1 perturbation. Experiment 3 consisted of simulations with the directions into velocities of articulators model of speech motor planning, which showed that the model can account for key aspects of compensation. In the model, movement goals for vowels are regions in auditory space; perturbation of auditory feedback invokes auditory feedback control mechanisms that correct for the perturbation, which in turn causes updating of feedforward commands to incorporate these corrections. The relation between speaker acuity and amount of compensation to auditory perturbation is mediated by the size of speakers' auditory goal regions, with more acute speakers having smaller goal regions.

Functional Connectivity Between Auditory Areas Field L and CLM and Song System Nucleus HVC in Anesthetized Zebra Finches

A key discovery that has emerged from studies of the vocal system in songbirds is that neurons in these regions respond preferentially to playback of the bird's own song (BOS). This BOS selectivity is not a general property of neurons in primary and secondary auditory forebrain regions, field L and caudolateral mesopallium (CLM). Moreover, anatomical studies have been unable to conclusively define a direct projection from field L and/or CLM to HVC, a central structure for integrating sensory and motor information in the vocal system. To examine the communication between these regions, we used simultaneous dual-electrode recording in anesthetized male zebra finches and cross-correlation analysis to estimate the functional connectivity between auditory areas, field L and CLM, and HVC. We found that >or=18% of neurons in field L and 33% of neurons in CLM are functionally connected to HVC, most with auditory forebrain leading-HVC latencies ranging from 0.5 to 15 ms. These results indicate that field L and CLM communicate extensively with HVC through both direct and indirect anatomical connections. To further explore the role of the auditory forebrain cells that are functionally connected with HVC, we assessed their responsiveness and selectivity for a variety of natural and synthetic auditory stimuli. We found that field L and CLM neurons that are functionally connected to HVC exhibit generic auditory forebrain properties including the lack of BOS selectivity. This finding puts further constraints on the neural architecture and the nature of the nonlinearity that leads to BOS-selective auditory responses in the vocal control nuclei.

Voice Register in Khmu’: Experiments in Production and Perception

Some Khmu’ dialects have phonologically distinctive voice registers.Auditory observations have claimed a stable distinction between clear voice andhigh pitch for Register 1 and breathy voice and low pitch for Register 2 in theKhmu’ Rawk dialect of northern Thailand. Word pairs distinguished only by registerwere recorded by 25 native speakers. Acoustic analysis yielded F0 and overallamplitude contours, frequencies of F1 and F2 in quasi-steady states of the vowels,relative intensities of higher harmonics to that of the first harmonic, and voweldurations. When circumstances caused early attention to perception testing, thewords of only 8 speakers had been analyzed for properties other than amplitudeand F0. Since the only significant factor that had emerged by then was F0 contour,the synthetic stimuli were made with just a series of seven contours. The labelingby 32 native speakers yielded two categories, demonstrating the sufficiency of F0as an acoustic cue. The completed acoustic analysis showed a significant effect ofone of the harmonic ratios for the women only, suggesting a conservative bias.The language has been shifting toward tonality and may have reached it.

Perceptual Weighting of Stop Consonant Cues by Normal and Impaired Listeners in Reverberation Versus Noise

To determine if listeners with normal hearing and listeners with sensorineural hearing loss give different perceptual weightings to cues for stop consonant place of articulation in noise versus reverberation listening conditions. Nine listeners with normal hearing (23-28 years of age) and 10 listeners with sensorineural hearing loss (31-79 years of age, median 66 years) participated. The listeners were asked to label the consonantal portion of synthetic CV stimuli as either /p/ or /t/. Two cues were varied: (a) the amplitude of the spectral peak in the F4/F5 frequency region of the burst was varied across a 30-dB range relative to the adjacent vowel peak amplitude in the same frequency region, (b) F2/F3 formant transition onset frequencies were either appropriate for /p/, /t/ or neutral for the labial/alveolar contrast. Weightings of relative amplitude and transition cues for voiceless stop consonants depended on the listening condition (quiet, noise, or reverberation), hearing loss, and age of listener. The effects of age with hearing loss reduced the perceptual integration of cues, particularly in reverberation. The effects of hearing loss reduced the effectiveness of both cues, notably relative amplitude in reverberation. Reverberation and noise conditions have different perceptual effects. Hearing loss and age may have different, separable effects.

Frequency Effects in Cross-linguistic Stop Place Perception: A Case of /t/-/k/ in Japanese and English

UC Berkeley Phonology Lab Annual Report (2007) Frequency Effects in Cross-Linguistic Stop Place Perception: A Case of /t/ - /k/ in Japanese and English Reiko Kataoka and Keith Johnson 1. Introduction The study described in this paper is an attempt to answer the question ‘Which aspect of speech perception is altered by linguistic experience and how this alteration is done?’ As Strange and Jenkins stated, “[t]he knowledge of a language possessed by a normal adult is a product of many years of exposure to a specific language environment” (1978: 125). Therefore, if linguistic knowledge influences speech perception, then adult listeners would perceive speech sounds in language-specific ways. Evidence of experience-based speech perception has been accumulated from both cross-linguistic and within language studies. One source of evidence is the phenomena called categorical perception (Liberman, et al. 1957, 1961a, 1961b), which is characterized by difficulty in discriminating acoustically similar patterns in the single phonemic category and near perfect discrimination for acoustic patterns that straddle different categories. Categorical perception has been replicated with listeners of various language groups, and it seems to be an undeniable fact that linguistic experience influences listeners’ ability to discriminate speech stimuli. However, exactly which aspect of linguistic experience is responsible for language-specific speech perception is not well understood. This is the primary question addressed in this paper. Also, it is often reported that listeners react to speech sounds differently depending on whether they use a continuous mode or a categorical mode of memory (see, for example, Pisoni 1973). Thus, it is of interest to test whether experience-based perception is elicited when the listening task calls for auditory acoustic perception. The goal of this study is to obtain answers of these two questions. The first question was treated by testing whether a particular aspect of linguistic structure—phoneme frequency— influences speech perception; and the second question was treated by testing whether the linguistic knowledge has any effect in an auditory acoustic perception task. The rest of the paper is organized as follows. Section 2 provides reviews of previous studies on the experience-based auditory perception, and gives rationales for the particular ways current experiment is designed. Section 3 describes the experimental study, provides the results, and discusses the results. Finally, Section 4 discusses the implications of some of the findings from current study for theories of speech perception. 2. Background 2.1. Experience-based speech perception One of the prime examples of experience-based speech perception is categorical perception, a phenomena originally defined by Liberman, Harris, Hoffman, and Griffith (1957). Categorical perception can be demonstrated in an experiment that uses a series of synthetic consonant-vowel stimuli, ranging across two or more initial consonant categories (e.g. ten-equal- step /da/-/ga/ continuum), and involves identification and discrimination tasks. One of the defining characteristics of categorical perception is predictability of discrimination accuracy from the identification result. In its strongest form, categorical perception predicts that listeners

The effect of fundamental frequency on the brightness dimension of timbre

The dependency of the brightness dimension of timbre on fundamental frequency (FO) was examined experimentally. Subjects compared the timbres of 24 synthetic stimuli, produced by the combination of six values of spectral centroid to obtain different values of expected brightness, and four FO's, ranging over 18 semitones. Subjects were instructed to ignore pitch differences. Dissimilarity scores were analyzed by both ANOVA and multidimensional scaling (MDS). Results show that timbres can be compared between stimuli with different FO's over the range tested, and that differences in FO affect timbre dissimilarity in two ways. First, dissimilarity scores reveal a term proportional to FO difference that shows up in the MDS solution as a dimension correlated with FO and orthogonal to other timbre dimensions. Second, FO affects systematically the timbre dimension (brightness) correlated with spectral centroid. Interestingly, both terms covaried with differences in FO rather than chroma or consonance. The first term probably corresponds to pitch. The second can be eliminated if the formula for spectral centroid is modified by introducing a corrective factor dependent on FO.