Spectral Cues Research Articles

The role of spectral cues in vertical plane elevation perception

The role of spectral cues in vertical plane elevation perception

Modeling perceived externalization of a static, lateral sound image

Perceived externalization is a relevant feature to create an immersive acoustic environment with headphone reproduction. In the present study, listener-specific acoustic transfer characteristics for an azimuth angle of 90° were modified to investigate the role of monaural spectral cues, interaural level differences (ILDs), and temporal fluctuations of ILDs on perceived externalization in anechoic and reverberant environments. Listeners’ ratings suggested that each acoustic cue was important for perceived externalization. If only one correct acoustic cue remained in the ear signals, the sound image could not be perceived as fully externalized. Reverberation did reduce but not eliminate the influences of monaural spectral and ILD cues on perceived externalization. Additionally, the spectral details of the ipsilateral ear signal were more important for perceived externalization than those in the contralateral ear signal. A computational model was proposed to quantify those relationships and predict externalization ratings by comparing the acoustic cues extracted from the target (modified) and template (non-processed) binaural signals after several auditory processing steps. The accuracy of predicted externalization ratings was higher than 90% under all experimental conditions.

Assessment of fighting ability in the vocal cichlid Metriaclima zebra in face of incongruent audiovisual information.

ABSTRACTInformation transfer between individuals typically depends on multiple sensory channels. Yet, how multi-sensory inputs shape adaptive behavioural decisions remains largely unexplored. We tested the relative importance of audio and visual sensory modalities in opponent size assessment in the vocal cichlid fish, Metriaclima zebra, by playing back mismatched agonistic sounds mimicking larger or smaller opponents during fights of size-matched males. Trials consisted in three 5-min periods: PRE (visual), PBK (acoustic+visual) and POST (visual). During PBK agonistic sounds of smaller (high frequency or low amplitude) or larger (low frequency or high amplitude) males were played back interactively. As a control, we used white noise and silence. We show that sound frequency but not amplitude affects aggression, indicating that spectral cues reliably signal fighting ability. In addition, males reacted to the contrasting audio-visual information by giving prevalence to the sensory channel signalling a larger opponent. Our results suggest that fish can compare the relevance of information provided by different sensory inputs to make behavioural decisions during fights, which ultimately contributes to their individual fitness. These findings have implications for our understanding of the role of multi-sensory inputs in shaping behavioural output during conflicts in vertebrates.

The effects of musicality and language background on cue integration in pitch perception.

Pitch perception involves the processing of multidimensional acoustic cues, and listeners can exhibit different cue integration strategies in interpreting pitch. This study aims to examine whether musicality and language experience have effects on listeners' pitch perception strategies. Both Mandarin and English listeners were recruited to participate in two experiments: (1) a pitch classification experiment that tested their relative reliance on f0 and spectral cues, and (2) the Montreal Battery of Evaluation of Musical Abilities that objectively quantified their musical aptitude as continuous musicality scores. Overall, the results show a strong musicality effect: Listeners with higher musicality scores relied more on f0 in pitch perception, while listeners with lower musicality scores were more likely to attend to spectral cues. However, there were no effects of language experience on musicality scores or cue integration strategies in pitch perception. These results suggest that less musical or even amusic subjects may not suffer impairment in linguistic pitch processing due to the multidimensional nature of pitch cues.

Suprathreshold Processing and Cocktail Party Listening in Younger and Older Adults with Normal Hearing

Present study aimed to investigate the effect of age and suprathreshold processing on cocktail party listening in individuals with normal hearing sensitivity. A total of 92 participants with normal hearing sensitivity were included in the study. They were divided into two groups based on their age. Fifty two young normal hearing adults in the age range of 20–40 years and 40 older normal hearing adults in the age range of 60-80 years. Tests administered included speech perception in noise test, spatial selective attention, gap detection thresholds, temporal modulation transfer function, inter-aural time difference, differential limen of frequency and ripple noise discrimination. Results showed that older adults performed poorer than younger adults in all the tests. Also, temporal cues showed a better relation with speech perception in noise compared to the spectral cues. This can be attributed to the disrupted neural synchrony which is due to poor frequency selectivity as observed through ripple noise discrimination. Individuals rely more on temporal cues due to poorer frequency resolution and phase locking mechanism and also on top down processes such as selective attention too. A degraded speech input would lead them to rely more on their higher cognition.

Spectral and Temporal Envelope Cues for Human and Automatic Speech Recognition in Noise.

Acoustic features of speech include various spectral and temporal cues. It is known that temporal envelope plays a critical role for speech recognition by human listeners, while automated speech recognition (ASR) heavily relies on spectral analysis. This study compared sentence-recognition scores of humans and an ASR software, Dragon, when spectral and temporal-envelope cues were manipulated in background noise. Temporal fine structure of meaningful sentences was reduced by noise or tone vocoders. Three types of background noise were introduced: a white noise, a time-reversed multi-talker noise, and a fake-formant noise. Spectral information was manipulated by changing the number of frequency channels. With a 20-dB signal-to-noise ratio (SNR) and four vocoding channels, white noise had a stronger disruptive effect than the fake-formant noise. The same observation with 22 channels was made when SNR was lowered to 0 dB. In contrast, ASR was unable to function with four vocoding channels even with a 20-dB SNR. Its performance was least affected by white noise and most affected by the fake-formant noise. Increasing the number of channels, which improved the spectral resolution, generated non-monotonic behaviors for the ASR with white noise but not with colored noise. The ASR also showed highly improved performance with tone vocoders. It is possible that fake-formant noise affected the software's performance by disrupting spectral cues, whereas white noise affected performance by compromising speech segmentation. Overall, these results suggest that human listeners and ASR utilize different listening strategies in noise.

Lexical bias in word recognition by cochlear implant listeners.

When hearing an ambiguous speech sound, listeners show a tendency to perceive it as a phoneme that would complete a real word, rather than completing a nonsense/fake word. For example, a sound that could be heard as either /b/ or /ɡ/ is perceived as /b/ when followed by _ack but perceived as /ɡ/ when followed by "_ap." Because the target sound is acoustically identical across both environments, this effect demonstrates the influence of top-down lexical processing in speech perception. Degradations in the auditory signal were hypothesized to render speech stimuli more ambiguous, and therefore promote increased lexical bias. Stimuli included three speech continua that varied by spectral cues of varying speeds, including stop formant transitions (fast), fricative spectra (medium), and vowel formants (slow). Stimuli were presented to listeners with cochlear implants (CIs), and also to listeners with normal hearing with clear spectral quality, or with varying amounts of spectral degradation using a noise vocoder. Results indicated an increased lexical bias effect with degraded speech and for CI listeners, for whom the effect size was related to segment duration. This method can probe an individual's reliance on top-down processing even at the level of simple lexical/phonetic perception.

The Effects of Duration and Level on Spectral Modulation Perception.

Purpose Spectral modulation detection is an increasingly common assay of suprathreshold auditory perception and has been correlated with speech perception performance. Here, the potential effects of stimulus duration and stimulus presentation level on spectral modulation detection were investigated. Method Spectral modulation detection thresholds were measured as a function of modulation frequency in young, normal-hearing listeners. The standard stimulus was a bandpass noise, and signal stimuli were created by superimposing sinusoidal spectral modulation on the bandpass noise carrier. The modulation was sinusoidal on a log2 frequency axis and a log10 (dB) amplitude scale with a random starting phase (0-2π radians). In 1 experiment, stimulus durations were 50, 100, 200, or 400 ms (at fixed level 81 dB SPL). In a 2nd experiment, stimuli were presented at sensation levels of 10, 20, 30, 40, and 60 dB SL (fixed at a duration of 400 ms). Results Spectral modulation detection thresholds were similarly low for the 400- and 200-ms durations, increased slightly for the 100-ms duration, and increased markedly for the 50-ms duration. Thresholds were lowest for 40 dB SL; increased slightly for 20, 30, and 60 dB SL; and markedly higher for the 10-dB SL condition. Conclusions The increase in thresholds for the shortest durations and lowest sensational levels is consistent with previous investigations of auditory spectral profile analysis. The effects of presentation level and stimulus duration are important considerations in the context of understanding potential relationships between the perception of spectral cues and speech perception, when designing investigations and interpreting data related to spectral envelope perception, and in the context of models of auditory perception. As examples, 2 simple models based on auditory nerve output that have been used to explain spectrotemporal modulation in previous investigations produced an output inconsistent with the present results. Plain language summary Intensity variations across audio frequency lead to spectral shapes that are essential and sometimes signature features of various sounds in the environment, including speech. Here, we show how laboratory measures of spectral shape perception depend on presentation level and stimulus duration.

Differential Adaptation in Azimuth and Elevation to Acute Monaural Spatial Hearing after Training with Visual Feedback.

Sound localization in the horizontal plane (azimuth) relies mainly on binaural difference cues in sound level and arrival time. Blocking one ear will perturb these cues, and may strongly affect azimuth performance of the listener. However, single-sided deaf listeners, as well as acutely single-sided plugged normal-hearing subjects, often use a combination of (ambiguous) monaural head-shadow cues, impoverished binaural level-difference cues, and (veridical, but limited) pinna- and head-related spectral cues to estimate source azimuth. To what extent listeners can adjust the relative contributions of these different cues is unknown, as the mechanisms underlying adaptive processes to acute monauralization are still unclear. By providing visual feedback during a brief training session with a high-pass (HP) filtered sound at a fixed sound level, we investigated the ability of listeners to adapt to their erroneous sound-localization percepts. We show that acutely plugged listeners rapidly adjusted the relative contributions of perceived sound level, and the spectral and distorted binaural cues, to improve their localization performance in azimuth also for different sound levels and locations than those experienced during training. Interestingly, our results also show that this acute cue-reweighting led to poorer localization performance in elevation, which was in line with the acoustic–spatial information provided during training. We conclude that the human auditory system rapidly readjusts the weighting of all relevant localization cues, to adequately respond to the demands of the current acoustic environment, even if the adjustments may hamper veridical localization performance in the real world.

Long-term evaluation of sound localisation in single-sided deaf adults fitted with a BAHA device.

To perform a long-term evaluation of the localisation capabilities in the horizontal plane of single-sided deaf patients fitted with a BAHA device. Single-centre retrospective study. Twenty-one adults with single-sided deafness (SSD) with normal hearing in the contralateral ear (pure tone average <20dB, SDS>90%) rehabilitated with a Cochlear BAHA device from 2003 to 2012 on the deaf side over a median follow-up of 8years. The task used in this paper is a sound localisation identification task with a set-up of seven loudspeakers on a semi-circular array at 30-degree intervals performed at three periods: before BAHA, initially and at last follow-up. Our main criterion of judgement was the root-mean-square (RMS) localisation error. In addition, the Bern Benefit in Single-Sided Deafness Questionnaire (BBSS) was administered. The mean RMS localisation error was initially estimated at 64° without any rehabilitation (for a chance level RMS estimated at 81°). Initially, with the BAHA device, the RMS localisation error dropped to 51°. At the last follow-up evaluation, a significant decrease at 23° was noted. Concerning the Bern Questionnaire, 19% of the patients (n=4) did not report any change (score of 0), 33% (n=7) are satisfied (score of +1 or +2) and 48% (n=10) are very satisfied with the BAHA device (score better than +3). Improvement of sound localisation in the horizontal plane for some SSD patients is likely related to altered processing of monaural spectral cues. The time needed to learn to use the azimuth-dependent spectral cues takes time. Long-term follow-up should be considered for studies investigating sound localisation performance.

Spectrum as a perceptual cue to vowel length in Czech, a quantity language.

Vowel length contrasts in quantity languages are typically realized primarily through duration. This study tested whether spectral cues contribute to the perceptual identification of the short-long monophthongal contrasts in two varieties of Czech. Results showed that listeners attend to spectrum as well as to duration, both for the high vowel-length pairs, which display consistent spectral differentiation in production, and for the remaining contrasts, whose spectral differences are subtle. Reliance on spectrum was generally higher for Bohemian than Moravian listeners. The findings reveal the utilization of spectrum for vowel length perception in Czech, which is described as a "true" quantity language.

Do listeners rely on dynamic spectral properties in the recognition of high-pitched vowels?

Previous research has demonstrated that intrinsic spectral changes play a significant role in vowel perception. It is possible that dynamic properties are of particular importance at high fundamental frequencies (f o) where the transfer function of the vocal tract is severely undersampled. The purpose of the present work was to determine whether the phonological function of vowels with very high f os can be preserved if listeners' identification is based exclusively on static spectral cues. Harmonic additive synthesis was used to generate 324 steady-state versions of the vowels /i y e o ɛ a o u/ with nine different f os between 220 and 880 Hz (all 250 ms). The gross spectral shape of each synthesized sound corresponded to a smoothed spectrum derived from a respective template vowel that was naturally produced in isolation by a female native German talker. Native German listeners either identified the spoken or re-synthesized isolated vowels in a two-alternative choice task. Preliminary data showed that listeners' sensitivity (A′) was above chance level in both conditions at all f os, but significantly higher in the spoken vowel condition. This supports the prediction that dynamic properties enhance listeners' identification at very high f os, but also indicates that phonological distinctiveness is to some degree preserved at high f os even when no dynamic spectral information is present. [Work supported by the Swiss National Science Foundation (SNSF) grants P2ZHP1_168375168375 and P400PG_180693180693.]Previous research has demonstrated that intrinsic spectral changes play a significant role in vowel perception. It is possible that dynamic properties are of particular importance at high fundamental frequencies (f o) where the transfer function of the vocal tract is severely undersampled. The purpose of the present work was to determine whether the phonological function of vowels with very high f os can be preserved if listeners' identification is based exclusively on static spectral cues. Harmonic additive synthesis was used to generate 324 steady-state versions of the vowels /i y e o ɛ a o u/ with nine different f os between 220 and 880 Hz (all 250 ms). The gross spectral shape of each synthesized sound corresponded to a smoothed spectrum derived from a respective template vowel that was naturally produced in isolation by a female native German talker. Native German listeners either identified the spoken or re-synthesized isolated vowels in a two-alternative choice task. Preliminary data showed that li...

Transmission of ultraviolet, visible and near-infrared solar radiation to plants within a seasonal snow pack

Sunlight is strongly attenuated by the snowpack, causing irradiance to decrease exponentially with depth. The strength of attenuation is wavelength dependent across the spectrum. Changes in received irradiance and its spectral composition are used by plants as cues for the timing of phenology, and it is known that at shallow depths in the snowpack there is sufficient light for plants to photosynthesize if conditions are otherwise favourable. The spectral composition of solar radiation under snow in the visible region was already determined in the 1970s using scanning spectroradiometers, but spectral attenuation within the ultraviolet region (UV-B 280–315 nm, UV-A 315–400 nm) has not been well characterised because it is difficult to measure. We measured vertical transects of spectral irradiance (290–900 nm) transmitted through a settled seasonal snowpack. The peak transmission of radiation was in the UV-A region in the upper centimetres of the snowpack and transmittance generally declined at longer wavelengths. Given the known action spectra of plant photoreceptors, these results illustrate the possibility that changing UV-A : visible and red : far-red radiation ratios under the snowpack may serve as spectral cues for plants; potentially priming plants for the less stable environment they experience following snowmelt. Array spectrometers open opportunities for rapid and continuous measurement of irradiance in challenging environments, e.g. beneath the snowpack, and capturing changing light conditions for plants. Future research is needed to couple the spectral transmittance of snowpacks differing in their longevity and crystal structure with measurements of the perception and response to radiation by plants under snow.

The monaural spectral cues identified by a reverse correlation analysis of free-field auditory localization data.

The outer-ear's location-dependent pattern of spectral filtering generates cues used to determine a sound source's elevation as well as front-back location. The authors aim to identify these features using a reverse correlation analysis (RCA), combining free-field localization behaviour with the associated head-related transfer functions' (HRTFs) magnitude spectrum from a sample of 73 participants. Localization responses were collected before and immediately after introducing a pair of outer-ear inserts which modified the listener's HRTFs to varying extent. The RCA identified several different features responsible for eliciting localization responses. The efficacy of these was examined using two models of monaural localization. In general, the predicted performance was closely aligned with the free-field localization error for the bare-ear condition; however, both models tended to grossly over-estimate the localization error based on HRTFs modified by the outer-ear inserts. The RCA's feature selection notably had the effect of better aligning the predicted performance of both models to the actual localization performance. This suggests that the RCA revealed sufficient detail for both models to correctly predict localization performance and also limited the influence of filtered-out elements in the distorted HRTFs that contributed to the degraded accuracy of both models.

Underwater sound localization abilities of harbor seals (Phoca vitulina) for high-frequency noise band stimuli in the median plane.

Pinnipeds use a variety of acoustic information underwater for social interactions, hunting, and predator avoidance. Thus, the ability to accurately localize a sound source in the environment can have a clear survival value. Nonetheless, the sound localization mechanisms for seals underwater still have to be clarified, especially for sounds received in the median plane. In this study, the sound localization abilities of five harbor seals for high-frequency noise band stimuli were measured underwater in the median plane. The seals' minimum audible angles (MAAs) were determined for two different high-frequency noise band stimuli using a two-alternative forced-choice procedure. Noise 1 had a frequency range between 8 and 16 kHz. Noise 2 contained frequencies between 14 and 16 kHz. Psychoacoustic results for the tested harbor seals show that the seals were able to localize these stimuli in the median plane underwater with MAAs between 5.1° and 17.5°. The results suggest that spectral cues improve the seals' ability to localize high-frequency sound signals in the median plane.

Perception of Tamil Mono-Syllabic and Bi-Syllabic Words in Multi-Talker Speech Babble by Young Adults with Normal Hearing.

Background and ObjectivesThis study compared the perception of mono-syllabic and bisyllabic words in Tamil by young normal hearing adults in the presence of multi-talker speech babble at two signal-to-noise ratios (SNRs). Further for this comparison, a speech perception in noise test was constructed using existing mono-syllabic and bi-syllabic word lists in Tamil.Subjects and MethodsA total of 30 participants with normal hearing in the age range of 18 to 25 years participated in the study. Speech-in-noise test in Tamil (SPIN-T) constructed using mono-syllabic and bi-syllabic words in Tamil was used as stimuli. The stimuli were presented in the background of multi-talker speech babble at two SNRs (0 dB and +10 dB SNR). ResultsThe effect of noise on SPIN-T varied with SNR. All the participants performed better at +10 dB SNR, the higher of the two SNRs considered. Additionally, at +10 dB SNR performance did not vary significantly for neither mono-syllabic or bi-syllabic words. However, a significant difference existed at 0 dB SNR.ConclusionsThe current study indicated that higher SNR leads to better performance. In addition, bi-syllabic words were identified with minimal errors compared to mono-syllabic words. Spectral cues were the most affected in the presence of noise leading to more of place of articulation errors for both mono-syllabic and bi-syllabic words.

The Role of Temporal Acoustic Exaggeration in High Variability Phonetic Training: A Behavioral and ERP Study.

High variability phonetic training (HVPT) has been found to be effective in helping adult learners acquire non-native phonetic contrasts. The present study investigated the role of temporal acoustic exaggeration by comparing the canonical HVPT paradigm without involving acoustic exaggeration with a modified adaptive HVPT paradigm that integrated key temporal exaggerations in infant-directed speech (IDS). Sixty native Chinese adults participated in the training of the English /i/ and /i/ vowel contrast and were randomly assigned to three subject groups. Twenty were trained with the typical HVPT paradigm (the HVPT group), twenty were trained under the modified adaptive approach with acoustic exaggeration (the HVPT-E group), and twenty were in the control group. Behavioral tasks for the pre- and post- tests used natural word identification, synthetic stimuli identification, and synthetic stimuli discrimination. Mismatch negativity (MMN) responses from the HVPT-E group were also obtained to assess the training effects in within- and across- category discrimination without requiring focused attention. Like previous studies, significant generalization effects to new talkers were found in both the HVPT group and the HVPT-E group. The HVPT-E group, by contrast, showed greater improvement as reflected in larger progress in natural word identification performance. Furthermore, the HVPT-E group exhibited more native-like categorical perception based on spectral cues after training, together with corresponding training-induced changes in the MMN responses to within- and across- category differences. These data provide the initial evidence supporting the important role of temporal acoustic exaggeration with adaptive training in facilitating phonetic learning and promoting brain plasticity at the perceptual and pre-attentive neural levels.

The influence of spectral composition on spring and autumn phenology in trees.

Several recent reviews highlight the molecular mechanisms that underpin phenological responses to temperature and photoperiod; however, these have mostly overlooked the influence of solar radiation and its spectral composition on these processes. For instance, solar radiation in the blue and ultraviolet (UV) regions of the spectrum, as well as the red/far-red (R:FR) ratio, can influence spring and autumn phenology. Solar radiation reaching the Earth changes diurnally and seasonally; however, rising global temperatures, latitudinal range shifts and light pollution are likely to produce novel combinations of phenological cues for tree species. Here, we review the literature on phenological responses to spectral composition. Our objective was to explore the natural variation in spectral composition using radiative transfer models and to reveal any species-specific or ecotype-specific responses relating to latitudinal origin. These responses are likely to be most pronounced at high latitudes where spectral composition varies most throughout the year. For instance, trees from high latitudes tend to be more sensitive to changes in R:FR than those from low latitudes. The effects of blue light and UV radiation on phenology have not been studied as much as those of R:FR, but the limited results available suggest both could be candidate cues affecting autumn leaf colouration and senescence. Failure of more-southern species and ecotypes to adapt and use spectral cues during northwards range shifts could result in mistimed phenology, potentially resulting in frost damage, reduced fitness and limited range expansion. Future areas for research should look to establish how consistently different functional types of tree respond to spectral cues and identify photoreceptor-mediated mechanisms that allow plants to combine information from multiple light cues to coordinate the timing of phenological events. It should then be feasible to consider the synchronous or sequential action of light cues within a hierarchy of environmental factors regulating phenology.

Language-dependent cue weighting: An investigation of perception modes in L2 learning

This study examines relative weighting of two acoustic cues, vowel duration and spectra, in the perception of high front vowels by Japanese learners of English. Studies found that Japanese speakers rely heavily on duration to distinguish /iː/ and /ɪ/ in American English (AmE) as influenced by phonemic length in Japanese /ii/ and /i/, while spectral cues are more important for native AmE speakers. However, little is known as to whether and how this non-native perceptual weighting can change as a result of L2 learning. By employing computational and experimental methods, the present study shows that Japanese learners of English exhibit different cue weighting depending on which language they think they hear. The experiment shows that listeners use more spectral cues and less durational cues when they think they are listening to ‘English’ stimuli as opposed to ‘Japanese’ stimuli, despite the stimuli being identical. This result is generally in line with our computer simulation, which predicts distinct developmental paths in first language (L1) and second language (L2) perception. The Second Language Linguistic Perception (L2LP) model, which incorporates the language mode hypothesis, provides a comprehensive explanation for the current findings.

3D printed pinna embedded in circumaural hearing devices for spectral cue preservation

Innovations in additive manufacturing [three-dimensional (3D) printing] have allowed for the fabrication of objects as complex as the human ear. The visible part of the human outer ear (pinna) serves as a funnel and a natural filter for incoming sound. Spectral cues generated by the pinna help with auditory localization and externalization. In an attempt to preserve spectral cues when using circumaural hearing devices, the present work explored the use of 3D printing to fabricate individualized pinna within custom-designed and fabricated hearing devices. Through 3D scanning, a computer aided design (CAD) model of a pinna from an anthropometric mannequin was generated to replicate human pinnae. Multiple 3D printing technologies were used to fabricate the CAD model, investigating different material options, dimensional accuracies, and overall printing costs. The fabricated pinnae were subjected to acoustic testing to assess spectral cue preservation by comparing mannequin head-related transfer functions obt...