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Abstract The Effective Perceived Noise Level (EPNL) is the primary metric used for assessing subjective response to aircraft noise. The EPNL comprises calculation of the Perceived Noise Level (in PNdB), and takes into account flyover duration and the presence of pure tones to arrive at an adjusted EPNL value. With the presence of a single significant tone, EPNL has been found to be reasonably effective for the assessment of aircraft noise annoyance. Several authors have, however, suggested that EPNL is not capable of quantifying the subjective response to aircraft noise that contains multiple complex tones. The noise source referred to as "Buzz-saw" noise is a typical example of complex tonal content in aircraft noise with an important effect on both cabin and community noise impact. This paper presents the results of a series of listening tests where a number of participants were exposed to samples of aircraft noise with six variants of aircraft engines, assumed representative of the contemporary twin engine aircraft fleet. On the basis of the findings of these listening tests, the Aures tonality method significantly outperforms the EPNL tone correction method when assessing the subjective response to aircraft noise during take-off with the presence of multiple complex tones. The participants reported 'high pitch' as one of the least preferable aircraft noise characteristics, and consequently, the psychoacoustics metric Sharpness was found to be another important contributor to subjective response to the noise of two specific aircraft engine groups (out of the six considered). The limitations of Aures tonality are discussed, in particular for aircraft noise with both a series of complex tones spaced evenly across the frequency spectrum with relatively even sound levels and less subjectively dominant single frequency tones (compared to broadband noise). In line with these limitations, further work is proposed for more effective assessment of subjective response to aircraft noise containing significant tonal content in the form of numerous closely spaced or other complex tones. [ABSTRACT FROM AUTHOR]

When a wideband harmonic tone complex (wHTC) is passed through a noise vocoder, the resulting sounds can have spectra with large peak-to-valley ratios, but little or no periodicity strength in the autocorrelation functions. We measured judgments of pitch strength for normal-hearing listeners for noise-vocoded wideband harmonic tone complexes (NV-wHTCs) relative to standard and anchor stimuli. The standard was a 1-channel NV-wHTC and the anchor was either the unprocessed wHTC or an infinitely-iterated rippled noise (IIRN). Although there is variability among individuals, the magnitude judgment functions obtained with the IIRN anchor suggest different listening strategies among individuals. In order to gain some insight into possible listening strategies, test stimuli were analyzed at the output of an auditory filterbank model based on gammatone filters. The weak periodicity strengths of NV-wHTCs observed in the stimulus autocorrelation functions are augmented at the output of the gammatone filterbank model. Six analytical models of pitch strength were evaluated based on summary correlograms obtained from the gammatone tone filterbank. The results of the filterbank analysis suggest that, contrary to the weak or absent periodicity strengths in the stimulus domain, temporal cues contribute to pitch strength perception of noise-vocoded harmonic stimuli such that listeners' judgments of pitch strength reflect a nonlinear, weighted average of the temporal information between the fine structure and the envelope. [ABSTRACT FROM AUTHOR]

Objectives: To examine behavioural and neural processing of pitch cues in adults with normal hearing (NH) and adults with sensorineural hearing loss (SNHL). Methods: All participants completed a test of behavioural sensitivity to pitch cues using the TFS1 test (Moore and Sek, 2009a). Cortical potentials (N1, P2 and acoustic change complex) were recorded in response to frequency shifted (deltaF) tone complexes in an 'ABA' pattern. Results: The SNHL group performed more poorly than the NH group for the TFS1 test. P2 was more reflective of pitch differences between the complexes than N1. The presence of acoustic change complex in response to the TFS transitions in the ABA stimulus varied with deltaF. Acoustic change complex amplitudes were reduced for the group with SNHL compared to controls. Conclusion: Behavioural performance and cortical responses reflect pitch processing depending on the salience of pitch cues. [ABSTRACT FROM AUTHOR]

The frequency following response (FFR), a scalp-recorded measure of phase-locked brainstem activity, is often assumed to reflect the pitch of sounds as perceived by humans. In two experiments, we investigated the characteristics of the FFR evoked by complex tones. FFR waveforms to alternating-polarity stimuli were averaged for each polarity and added, to enhance envelope, or subtracted, to enhance temporal fine structure information. In experiment 1, frequency-shifted complex tones, with all harmonics shifted by the same amount in Hertz, were presented diotically. Only the autocorrelation functions (ACFs) of the subtraction-FFR waveforms showed a peak at a delay shifted in the direction of the expected pitch shifts. This expected pitch shift was also present in the ACFs of the output of an auditory nerve model. In experiment 2, the components of a harmonic complex with harmonic numbers 2, 3, and 4 were presented either to the same ear ("mono") or the third harmonic was presented contralaterally to the ear receiving the even harmonics ("dichotic"). In the latter case, a pitch corresponding to the missing fundamental was still perceived. Monaural control conditions presenting only the even harmonics ("2 + 4") or only the third harmonic ("3") were also tested. Both the subtraction and the addition waveforms showed that (1) the FFR magnitude spectra for "dichotic" were similar to the sum of the spectra for the two monaural control conditions and lacked peaks at the fundamental frequency and other distortion products visible for "mono" and (2) ACFs for "dichotic" were similar to those for "2 + 4" and dissimilar to those for "mono." The results indicate that the neural responses reflected in the FFR preserve monaural temporal information that may be important for pitch, but provide no evidence for any additional processing over and above that already present in the auditory periphery, and do not directly represent the pitch of dichotic stimuli. [ABSTRACT FROM AUTHOR]

AN ALGORITHM IS GIVEN WITH THE PURPOSE OF BUILDING complex tones for which waveform circularity is shown and for which pitch circularity may be heard. The tones consist of sawtooth and square acoustical waves. It is proposed that a perceptual illusion, analogous to those described by Shepard (1964), can be then created. The signal may comprise an infinite number of harmonics, as in the case of natural sounds. Using the equitempered scale, an appropriate mathematical formula is given. [ABSTRACT FROM AUTHOR]

Abstract: Harmonic complex tones are a particularly important class of sounds found in both speech and music. Although these sounds contain multiple frequency components, they are usually perceived as a coherent whole, with a pitch corresponding to the fundamental frequency (F0). However, when two or more harmonic sounds occur concurrently, e.g., at a cocktail party or in a symphony, the auditory system must separate harmonics and assign them to their respective F0s so that a coherent and veridical representation of the different sounds sources is formed. Here we review both psychophysical and neurophysiological (single-unit and evoked-potential) findings, which provide some insight into how, and how well, the auditory system accomplishes this task. A survey of computational models designed to estimate multiple F0s and segregate concurrent sources is followed by a review of the empirical literature on the perception and neural coding of concurrent harmonic sounds, including vowels, as well as findings obtained using single complex tones with mistuned harmonics. [Copyright &y& Elsevier]

Abstract: Hemispheric asymmetries for processing duration of non-verbal and verbal sounds were investigated in 60 right-handed subjects. Two dichotic tests with attention directed to one ear were used, one with complex tones and one with consonant–vowel syllables. Stimuli had three possible durations: 350, 500, and 650ms. Subjects judged whether the duration of a probe was same or different compared to the duration of the target presented before it. Target and probe were part of two dichotic pairs presented with 1s interstimulus interval and occurred on the same side. Dependent variables were reaction time and accuracy. Results showed a significant right ear advantage for both dependent variables with both complex tones and consonant–vowel syllables. This study provides behavioural evidence of a left hemisphere specialization for duration perception of both musical and speech sounds in line with the current view based on a parameter – rather than domain-specific structuring of hemispheric perceptual asymmetries. [Copyright &y& Elsevier]

Abstract: The present study focused on functional coupling between human bilateral auditory cortices and on possible influence of right over left auditory cortex during dichotic listening of complex non-verbal tones having near (competing) compared with distant non-competing fundamental frequencies. It was hypothesized that dichotic stimulation with competing tones would induce a decline of functional coupling between the two auditory cortices, as revealed by a decrease of electroencephalography coherence and an increase of directed transfer function from right (specialized for the present stimulus material) to left auditory cortex. Electroencephalograph was recorded from T3 and T4 scalp sites, overlying respectively left and right auditory cortices, and from Cz scalp site (vertex) for control purposes. Event-related coherence between T3 and T4 scalp sites was significantly lower for all electroencephalography bands of interest during dichotic listening of competing than non-competing tone pairs. This was a specific effect, since event-related coherence did not differ in a monotic control condition. Furthermore, event-related coherence between T3 and Cz and between T4 and Cz scalp sites showed no significant effects. Conversely, the directed transfer function results showed negligible influence at group level of right over left auditory cortex during dichotic listening. These results suggest a decrease of functional coupling between bilateral auditory cortices during competing dichotic stimuli as a possible neural substrate for the lateralization of auditory stimuli during dichotic listening. [Copyright &y& Elsevier]

Abstract: Sound intensity is the primary and most elementary feature of auditory signals. Its discrimination plays a fundamental role in different behaviours related to auditory perception such as sound source localization, motion detection, and recognition of speech sounds. This study was aimed at investigating hemispheric asymmetries for processing intensity of complex tones and consonant-vowel syllables. Forty-four right-handed non-musicians were presented with two dichotic matching-to-sample tests with focused attention: one with complex tones of different intensities (musical test) and the other with consonant-vowel syllables of different intensities (speech test). Intensity differences (60, 70, and 80dBA) were obtained by altering the gain of a synthesized harmonic tone (260Hz fundamental frequency) and of a consonant-vowel syllable (/ba/) recorded from a natural voice. Dependent variables were accuracy and reaction time. Results showed a significant clear-cut left ear advantage in both tests for both dependent variables. A monaural control experiment ruled out possible attentional biases. This study provides behavioural evidence of a right hemisphere specialization for the perception of the intensity of musical and speech sounds in healthy subjects. [Copyright &y& Elsevier]

The influence of temporal cues on sequential stream segregation was investigated using five elderly hearing-impaired listeners. In experiment 1, an alternating pattern of A and B tones was used. Each tone was a harmonic complex with a 100-Hz fundamental, with one of three passbands (1250–2500, 1768–3636, or 2500–5000 Hz) and one of three component-phase relationships (cosine, alternating, or random). The complexes had an overall level of 96 dB SPL. The detection of a change in relative timing of the A and B tones was measured in a two-interval-forced-choice paradigm. The sequence in one interval remained isochronous while the sequence in the other started isochronously but became increasingly irregular with the addition of a cumulative delay between the A and B tones. Component phase relationship and passband difference both had significant effects on the minimum detectable delay, indicating that temporal structure produced obligatory stream segregation. In experiment 2, subjects continuously reported whether tones presented in a 30-s ABA–ABA– sequence were perceived as segregated or integrated. Differences in component phase between A and B significantly increased perceived segregation, but passband did not. In conclusion, stream segregation due to differences in temporal structure is robust in elderly subjects with cochlear hearing loss and comparable to that found previously in young normally hearing subjects. [Copyright &y& Elsevier]

The present magnetoencephalography (MEG) study on auditory evoked magnetic fields (AEFs) was aimed at verifying whether during dichotic listening the contralateral auditory pathway inhibits the ipsilateral one, as suggested by behavioural and patient studies. Ten healthy subjects were given a randomized series of three complex tones (261,293 and 391 Hz, 500 ms duration), which were delivered monotically and dichotically with different intensities [60, 70 or 80 dBA (audio decibels)]. MEG data were recorded from the right auditory cortex. Results showed that the M100 amplitude over the right auditory cortex increased progressively when tones of increasing intensity were provided at the ipsilateral (right) ear. This effect on M100 was abolished when a concurrent tone of constant intensity was delivered dichotically at the contralateral (left) ear, suggesting that the contralateral pathway inhibited the ipsilateral one. The ipsilateral inhibition was present only when the contralateral tone fundamental frequency was similar to the ipsilateral tone. It was proposed that the occlusion mechanism would be exerted in cortical auditory areas as the dichotic effects were observed at M100 but not M50 component. This is the first evidence showing a neurophysiological inhibition driven by the contralateral auditory pathway over the ipsilateral one during dichotic listening. [ABSTRACT FROM AUTHOR]

Objectives: To determine whether the process responsible for the mismatch negativity (MMN) might be involved in the analysis of temporal sound patterns for information.Methods: Synthesized musical instrument tones of ‘clarinet’ timbre were delivered in a continuous sequence at 16 tones/s, such that there was virtually no N1 potential to each individual tone. The standard sequence comprised 4 or 5 adjacent notes of the diatonic scale, presented either as a regularly repeated, rising pattern or pseudo-randomly. The deviant stimuli were 1–5 consecutive tones of higher pitch than the standards.Results: A MMN was evoked by a single deviant tone, 1 or 5 semitones above the pitch range of the standards. The response to the 5-semitone deviant was significantly larger (mean of 7.3 μV) when the standard pattern was regular as compared with pseudo-random. The MMN latency, on the other hand, was only influenced by the magnitude of pitch deviation. A second MMN was evoked by a second deviant tone, immediately (SOA 62.5 ms) following the first. Further consecutive MMNs were not consistently evoked.Conclusions: The large amplitude of these MMNs can be attributed to the use of complex tones, continuous presentation and a rapid rate of pitch changes, such that no waveform subtraction was required. Over and above the probability with which each individual tone occurs in the standard sequence, the mismatch process is influenced by its temporal structure, i.e. can be regarded as a temporal pattern analyzer. Contrary to the findings of some other groups, we found that two consecutive deviants can evoke an MMN, even at high rates of presentation such that both occur within the postulated ‘temporal window of integration’ of ca. 170 ms. These findings suggest that the mismatch process might be involved in the extraction of sequential information from repetitive and non-repetitive sound patterns. [Copyright &y& Elsevier]