The spike train statistics for consonant and dissonant musical accords

The simple system composed of three neural-like noisy elements is considered. Two of them (sensory neurons or sensors) are stimulated by noise and periodic signals with different ratio of frequencies, and the third one (interneuron) receives the output of these two sensors and noise. We propose the analytical approach to analysis of Interspike Intervals (ISI) statistics of the spike train generated by the interneuron. The ISI distributions of the sensory neurons are considered to be known. The frequencies of the input sinusoidal signals are in ratios, which are usual for music. We show that in the case of small integer ratios (musical consonance) the input pair of sinusoids results in the ISI distribution appropriate for more regular output spike train than in a case of large integer ratios (musical dissonance) of input frequencies. These effects are explained from the viewpoint of the proposed theory.Comment: 22 pages, 6 figure

Consonance perception beyond the traditional existence region of pitch

Some theories posit that the perception of consonance is based on neural periodicity detection, which is dependent on accurate phase locking of auditory nerve fibers to features of the stimulus waveform. In the current study, 15 listeners were asked to rate the pleasantness of complex tone dyads (2 note chords) forming various harmonic intervals and bandpass filtered in a high-frequency region (all components >5.8 kHz), where phase locking to the rapid stimulus fine structure is thought to be severely degraded or absent. The two notes were presented to opposite ears. Consonant intervals (minor third and perfect fifth) received higher ratings than dissonant intervals (minor second and tritone). The results could not be explained in terms of phase locking to the slower waveform envelope because the preference for consonant intervals was higher when the stimuli were harmonic, compared to a condition in which they were made inharmonic by shifting their component frequencies by a constant offset, so as to preserve their envelope periodicity. Overall the results indicate that, if phase locking is indeed absent at frequencies greater than ∼5 kHz, neural periodicity detection is not necessary for the perception of consonance

An activity-centric conceptual framework for assessing and creating positive urban soundscapes

The Positive Soundscapes Project is an interdisciplinary investigation of soundscape perception [1]. The project seeks to develop a rounded view of human perception of soundscapes by drawing together methods from the disciplines of engineering sound quality [2], acoustics, psychoacoustics, physiology [3], as well as sound art, acoustic ecology and social science [4]. In the acoustics community, sound in the environment, especially that made by other people has overwhelmingly been considered in negative terms as both intrusive and undesirable. The strong focus of traditional engineering acoustics on reducing noise levels ignores the many possibilities for characterizing positive aspects of the soundscape, whereas art and social science disciplines interpret soundscape perception as a multimodal and multi-dimensional concept. The project team come from a wide range of disciplines and are applying their experiences to investigate soundscapes from different aspects to produce a more nuanced and complete picture of listener response than has so far been achieved. In order for the team behind the project to achieve this, an underpinning framework is required, by which to approach and move the project forward, while aligning thinking from the different disciplines. This paper describes a high-level first iteration of the conceptual framework, which is structured in three parts. The use and potential application of the framework within the Positive Soundscapes Project is then discussed

An overview of the major phenomena of the localization of sound sources by normal-hearing, hearing-impaired, and aided listeners

Localizing a sound source requires the auditory system to determine its direction and its distance. In general, hearing-impaired listeners do less well in experiments measuring localization performance than normal-hearing listeners, and hearing aids often exacerbate matters. This article summarizes the major experimental effects in direction (and its underlying cues of interaural time differences and interaural level differences) and distance for normal-hearing, hearing-impaired, and aided listeners. Front/back errors and the importance of self-motion are noted. The influence of vision on the localization of real-world sounds is emphasized, such as through the ventriloquist effect or the intriguing link between spatial hearing and visual attention

Teologija na tržištu

One task intended to measure sensitivity to temporal fine structure (TFS) involves the discrimination of a harmonic complex tone from a tone in which all harmonics are shifted upwards by the same amount in hertz. Both tones are passed through a fixed bandpass filter centered on the high harmonics to reduce the availability of excitation-pattern cues and a background noise is used to mask combination tones. The role of frequency selectivity in this "TFS1" task was investigated by varying level. Experiment 1 showed that listeners performed more poorly at a high level than at a low level. Experiment 2 included intermediate levels and showed that performance deteriorated for levels above about 57 dB sound pressure level. Experiment 3 estimated the magnitude of excitation-pattern cues from the variation in forward masking of a pure tone as a function of frequency shift in the complex tones. There was negligible variation, except for the lowest level used. The results indicate that the changes in excitation level at threshold for the TFS1 task would be too small to be usable. The results are consistent with the TFS1 task being performed using TFS cues, and with frequency selectivity having an indirect effect on performance via its influence on TFS cues. (C) 2015 Acoustical Society of America

Perception of noise from large wind turbines(EFP-06 Project)

Is noise from large wind turbines more annoying than noise from small wind turbines? This is a question that is discussed widely in the context of a new generation of large wind turbines replacing the traditional smaller ones. To date legislation takes noise levels and the tonality of noise sources into account. However, many more influencing factors are known from the psychoacoustic literature. Examples are the nature of the listening environment, spectral and temporal characteristics of the sound, and the influence of masking noise. An earlier part of the EFP-06 project established the measurable differences between large and small wind turbines. It concluded that spectral characteristics are generally very similar apart from a slight increase in the low frequency content of large turbines. In this study on the perception of wind turbine noise, audibility thresholds and equal annoyance contours have been established for idealised wind turbine sounds containing low frequency tones. The listening test simulated an indoor scenario and an outdoor scenario with and without masking garden noise. The focus has been on the question whether annoyance changes with the frequency of a tone. The test sounds consisted of a broadband spectrum with a specific tone at one of the frequencies 32, 44, 72, 115, 180 and 400 Hz. Idealised sounds with features broadly representative of wind turbine sounds were used. The participant were asked to imagine being in different scenarios. The outdoor scenario presented sounds broadly representative of a wind turbine at three A-weighted sound pressure levels, each with and without garden noise, whereas the indoor scenario omitted the garden noise since the facade attenuation rendered it inaudible. A comparative adaptive method was used to establish relative equal annoyance levels in the form of equal annoyance contours. The results enable comparisons between different scenarios, broadband levels, tone frequencies, masked and unmasked ‘wind turbine’ sound, and two different prominence levels for the reference tone. Temporal variation like “swishing” was avoided to keep the research questions well focused. In a second part of the study wind turbine recordings from a large and a small wind turbine were compared in annoyance with steady traffic noise. The recordings were manipulated to include the effect of sound propagation and façade attenuation. They were also normalised to equal A-weighted levels.The study concludes:Tones in quiet were heard at levels that agree well with hearing thresholds published elsewhere. As the broadband noise level increases the tones were heard at levels that were determined by the masking level. Masking thresholds predicted by the ISO 1996-2 standard have been shown to agree well with the measured tonal audibility thresholds as long as the masking noise clearly exceeds the hearing threshold of the tones. As low levels can frequently occur indoors in the neighbourhood of wind turbines when the Danish noise regulations are observed it would be useful to extend the standard to include a method to evaluate the hearing threshold. One possible method published by Pedersen (2008) to establish the audibility of broadband spectra has been successfully tested for two examples: a broadband spectrum of room background noise and the broadband spectra of wind turbine noise at levels close to the hearing threshold. The calculated critical band levels agree to within 2 dB with perceived audibility. Theoretical considerations support the conclusion that the method should be adequate for use in standard applications. Low frequency tones had to be adjusted to higher tone levels above the masking threshold to be equally annoying as higher frequency tones. Garden noise was not shown to reduce annoyance because different scenarios could not be compared easily. It was shown that increasing the tone level by 5 dB increases the equal annoyance level by a smaller value both for tone frequencies lower than 180 Hz and at 400 Hz. This casts doubt on the appropriateness of the adjustment used in the ISO 1996-2 standard which adds penalty adjustments which are increasing linearly with sound pressure level above masking. Relative sensation levels were calculated from equal annoyance contours to determine whether low frequency tones are relatively more annoying than high frequency tones. The frequency dependence was not shown to be significant. The main influence on these levels is the tone level above masking level: Tones at higher levels are more annoying than tones at lower levels above masking. Both findings are common for the indoor and outdoor scenarios. To compare real recordings of a large and a small wind turbine a test protocol was developed. This method was successfully trialled. The comparison between normalised recordings showed the spectral characteristics of the small turbine to be more annoying outdoors than those of the large turbine recording. This has been attributed to the different spectral characteristics of the two turbines. These differences are effectively masked by garden noise and the equal annoyance ratings change accordingly. The indoor scenario does also not find the turbines to be differently annoying. If these results can be reproduced in other listening experiments then it follows that the specific differences in spectral content will determine the annoyance levels from a wind turbine more than whether it is a small or a large turbine. It would also mean that the differences in annoyance between wind turbines get smaller when sufficient masking noise is present. Presently, the finding that the small turbine is more annoying cannot be generalised to large and small wind turbines or to a wider range of wind and terrain conditions than were used in the test. The listener responses were however consistent and therefore demonstrate the potential of the comparison method. Another significant achievement of this project was of technical nature: It was the design of an immersive sound reproduction system that is calibrated to high precision over the largest part of the audible frequency range including low frequencies down to 30 Hz. It has been shown that this design is possible and that the stimuli sound realistic. Future listening test with similar requirements will therefore be easy to design and fast to perform.In answer to the initial question whether large turbines are more annoying than small wind turbines, the results of this study find no evidence for a significant difference in annoyance between small and large wind turbines as long as total noise levels and tonal characteristics are taken into account in the assessment. Temporal variations of wind turbine noise such as the level of swishing might also have to be evaluated in the future

Tuning of Human Modulation Filters Is Carrier-Frequency Dependent

Licensed under the Creative Commons Attribution License

The upper frequency limit for the use of phase locking to code temporal fine structure in humans:A compilation of viewpoints

The relative importance of neural temporal and place coding in auditory perception is still a matter of much debate. The current article is a compilation of viewpoints from leading auditory psychophysicists and physiologists regarding the upper frequency limit for the use of neural phase locking to code temporal fine structure in humans. While phase locking is used for binaural processing up to about 1500 Hz, there is disagreement regarding the use of monaural phase-locking information at higher frequencies. Estimates of the general upper limit proposed by the contributors range from 1500 to 10000 Hz. The arguments depend on whether or not phase locking is needed to explain psychophysical discrimination performance at frequencies above 1500 Hz, and whether or not the phase-locked neural representation is sufficiently robust at these frequencies to provide useable information. The contributors suggest key experiments that may help to resolve this issue, and experimental findings that may cause them to change their minds. This issue is of crucial importance to our understanding of the neural basis of auditory perception in general, and of pitch perception in particular