Tone Pulses Research Articles

Modeling human auditory evoked brainstem responses to speech syllables

Auditory evoked brainstem responses (ABR) are routinely used to assess the neural encoding of sound. Various types of stimuli have been historically considered, and there is a current increasing trend towards the use of syllables, speech and complex (non-speech) sounds. Despite the peripheral origin of ABRs, the nonlinear processing within the cochlea and brainstem makes interpreting responses to these new stimuli a challenge. A recent model was developed [Ro/nne et al. (2012)] to simulate ABRs to transient sounds such as tone pulses, clicks and rising chirps as a function of stimulus level. The present study extends this model to simulate synthetic /ba/, /da/ and /ga/ syllable-evoked ABRs, where the stimuli only differ in their spectral energy of the second formant, f2, within their first 60 ms. The model takes the convolution of the instantaneous discharge rates using a “humanized” nonlinear auditory-nerve model of Zilany et al. (2009) and an empirically derived unitary response function, assumed to reflect contributions from different cell populations within the auditory brainstem. The ABR model was used to explore the physiological basis and spectro-temporal characteristics of key features observed in syllable-evoked ABRs in the literature [Skoe et al. (2011), Hornickel et al. (2009)].

Temporal integration near threshold fine structure–The role of cochlear processing

The hearing thresholds of normal hearing listeners often show quasi-periodic variations when measured with a high frequency resolution. This hearing threshold fine structure is related to other frequency specific variations in the perception of sound such as loudness and amplitude modulated tones at low intensities. The detection threshold of a pulsed tone also depends not only on the pulse duration, but also on the position of its frequency within threshold fine structure. The present study investigates if psychoacoustical data on detection of a pulsed tone can be explained with a nonlinear and active transmission line cochlea model. The model was successfully applied to other psychoacoustical data at low intensities, various types of otoacoustic emissions and physiological data. The simulations show differences in detection thresholds for tones placed in a minimum or a maximum of the fine structure, but lack a decrease of thresholds with increased pulse duration. The model was extended by including a temporal integrator which introduces a low-pass behavior of the data with different slopes of the predicted threshold curves, producing good agreement with the data. On the basis of the model simulations, it will be discussed to which extent temporal and spectral aspects contribute to the data.

Weighting of spatial and spectro-temporal cues for auditory scene analysis by human listeners.

The auditory system creates a neuronal representation of the acoustic world based on spectral and temporal cues present at the listener's ears, including cues that potentially signal the locations of sounds. Discrimination of concurrent sounds from multiple sources is especially challenging. The current study is part of an effort to better understand the neuronal mechanisms governing this process, which has been termed “auditory scene analysis”. In particular, we are interested in spatial release from masking by which spatial cues can segregate signals from other competing sounds, thereby overcoming the tendency of overlapping spectra and/or common temporal envelopes to fuse signals with maskers. We studied detection of pulsed tones in free-field conditions in the presence of concurrent multi-tone non-speech maskers. In “energetic” masking conditions, in which the frequencies of maskers fell within the ±1/3-octave band containing the signal, spatial release from masking at low frequencies (∼600 Hz) was found to be about 10 dB. In contrast, negligible spatial release from energetic masking was seen at high frequencies (∼4000 Hz). We observed robust spatial release from masking in broadband “informational” masking conditions, in which listeners could confuse signal with masker even though there was no spectral overlap. Substantial spatial release was observed in conditions in which the onsets of the signal and all masker components were synchronized, and spatial release was even greater under asynchronous conditions. Spatial cues limited to high frequencies (>1500 Hz), which could have included interaural level differences and the better-ear effect, produced only limited improvement in signal detection. Substantially greater improvement was seen for low-frequency sounds, for which interaural time differences are the dominant spatial cue.

Effects of perinatal oxycodone exposure on the cardiovascular response to acute stress in male rats at weaning and in young adulthood

Oxycodone (OXY) is one of the most commonly abused opiates during pregnancy. Perinatal opiate exposure (POE) is associated with neurobehavioral and hormone changes. Little is known about the effects of perinatal OXY on the cardiovascular (CV) responses to stress.Objectives: to determine the effects of POE on: (1) CV responses to acute stress and ability to discriminate using a classical conditioning paradigm; (2) changes in CV response to the paradigm and retention of the ability to discriminate from postnatal day (PD) 40 to young adulthood.Methods: Pregnant rats were given i.v. OXY or vehicle (CON) daily. OXY and CON males were fitted with BP telemetry units. Offspring were classically conditioned by following a pulsed tone (CS+) with tail shock. A steady tone (CS−) was not followed by shock. BP and HR were recorded during resting periods and conditioning. Changes in BP, HR from composite analysis were compared. The paradigm was repeated on PD 75.Results: At PD 40, OXY rats had a lower baseline mean BP (OXY: 114.8 ± 1.0 vs. CON: 118.3 ± 1.0 mm Hg; mean ± SEM) but larger amplitude of the conditional BP increase during the stress response (OXY: +3.9 ± 0.4 vs. CON: +1.7 ± 0.4 mm Hg). Both OXY and CON rats were able to discriminate between CS+ and CS−. At PD 75, the effects of OXY on the increased amplitude of the conditional BP had dissipated (CON: +3.4 ± 2.3 vs. OXY: +4.5 ± 1.4 mm Hg). BP responses to the stress and non-stress stimuli did not differ in the OXY group, suggesting that OXY may have decreased the ability of the offspring to discriminate (OXY: CS+: 147.1 ± 1.6, CS−: 145.9 ± 1.6 mm Hg vs. CON: CS+: 155.4 ± 2.7, CS−: 147.8 ± 2.7 mm Hg).Conclusion: POE is associated with subtle alterations in stress CV responses in weanling rats which dissipate when the conditioning is repeated at an early adult age. Although POE effect on the ability to discriminate at weanling age could not be detected, POE may impair retention of this ability in adulthood.

Repeated exposure to a tone transiently alters spectral tuning bandwidth of neurons in the central nucleus of inferior colliculus in juvenile rats

Early acoustic experience changes tonal frequency tuning in the inferior colliculus (IC) and the primary auditory cortex. The contributions of IC plasticity to cortical frequency map reorganization are not entirely clear. While most cortical plasticity studies exposed animals to pulsed tones, studies of IC plasticity used either noise or a continuous tone. Here we compared the effects of repeated exposure to single-frequency tone pips on cortical and IC frequency representations in juvenile rats. We found that while tone exposure caused a long-lasting increase in cortical representations of the exposure frequency, changes to IC neurons were limited to a transient narrowing of tuning bandwidth. These results suggest that previously documented cortical frequency map reorganization does not depend on similar changes in the subcortical auditory nuclei.

Modeling auditory evoked brainstem responses to transient stimuli

A quantitative model is presented that describes the formation of auditory brainstem responses (ABRs) to tone pulses, clicks, and rising chirps as a function of stimulation level. The model computes the convolution of the instantaneous discharge rates using the "humanized" nonlinear auditory-nerve model of Zilany and Bruce [J. Acoust. Soc. Am. 122, 402-417 (2007)] and an empirically derived unitary response function which is assumed to reflect contributions from different cell populations within the auditory brainstem, recorded at a given pair of electrodes on the scalp. It is shown that the model accounts for the decrease of tone-pulse evoked wave-V latency with frequency but underestimates the level dependency of the tone-pulse as well as click-evoked latency values. Furthermore, the model correctly predicts the nonlinear wave-V amplitude behavior in response to the chirp stimulation both as a function of chirp sweeping rate and level. Overall, the results support the hypothesis that the pattern of ABR generation is strongly affected by the nonlinear and dispersive processes in the cochlea.

Calculation of the reverberation spectrum for Doppler-based sonar

For monostatic sonar using long pulsed tone signals, the problem of evaluating the spectrum of reverberation due to sound wave scattering by a rough sea surface is solved. Relatively simple computational schemes are proposed, which make it possible (i) to transform the three-dimensional spectra of surface waves to the frequency-angular characteristics of reverberation and (ii) to choose the optimal operating frequency band for a Doppler sonar from the point of view of reverberation. For typical wind wave characteristics measured in shallow water areas, the spectral levels of reverberation are estimated in the frequency band of acoustic signals within 0.4–2 kHz.

The relationship between the behavioral activity and the underwater vocalization of the beluga whale (Delphinapterus leucas)

The underwater vocalizations of the beluga whale summering in Onega Bay (64°24′N, 35°49′E) were recorded in June–July of 2008. The vocalizations were classified into five major whistle types, four types of pulsed tones, click series, and noise vocalizations. To determine the relationship between the behavioral activity and the underwater vocalizations, a total of fifty-one 2 minute-long samples of the audio records were analyzed in the next six behavioral contexts: directional movements, quiet swimming, resting, social interactions, individual hunting behavior, and the exploration of hydrophones by beluga whales. The overall vocalization rate and the percentage of the main types of signals depend on the behavior of the belugas. We suggest that one of the whistle types (the “stereotype whistle”) is used by belugas for long-distance communications, while other whistle types (with the exception of “squeaks”) and three types of pulsed tones (with the exception of “vowels”) are used for short distance communication. The percentage of “squeaks” and “vowels” was equally high in all the behavioral situations. Thus, we assume that “squeaks” are contact signals. “Vowels” have a specific physical structure and probably play a role in identification signals. A high rate of the click series was observed in the process of social interactions.

Spectral loudness summation of nonsimultaneous tone pulses

The level of broadband signals is usually lower than that of equally loud narrow-band signals. This effect, referred to as spectral loudness summation, is commonly measured for broadband signals where all frequency components are presented simultaneously. The present study investigated to what extent spectral loudness summation also occurs for nonsimultaneously presented frequency components. Spectral loudness summation was measured in normal-hearing listeners with an adaptive forced-choice procedure for sequences of short tone pulses with varying frequencies, randomly chosen from a set of five frequencies. In addition, spectral loudness summation was measured for the simultaneous presentation of all five frequencies. The comparison stimulus consisted of tone pulses with the same frequency for all tone pulses of the sequence and the same repetition rate and overall duration as the test signal. The pulse duration was 10, 20, 50, or 100 ms and the inter-pulse interval ranged from 0 to 390 ms. In general, a considerable nonsimultaneous spectral loudness summation was found for short pulse durations and inter-pulse intervals, but a residual effect was also observed for the largest inter-pulse interval. The data are discussed in the light of repetition-rate dependent spectral loudness summation and effects of persistence of specific loudness after tone-pulse offset.

Measuring and modeling the bubble population produced by an underwater explosion

Underwater explosions have been studied intensively in the United States since 1941 [e.g., R. H. Cole, Underwater Explosions (Princeton University Press, Princeton, NJ, 1945), pp. 3-13]. Research to date has primarily focused on the initial shock and subsequent pressure waves caused by the oscillations of the "gas-globe" resulting from charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, after the gas-globe rises through the water column and breaks the surface, there remains behind a cloud of bubbles and perhaps debris from the explosion container which has been markedly less studied. A recent experiment measured the spatial and temporal acoustic response of the bubble cloud resulting from a 13.6 kg PBXN-111 charge detonated at 15.2 m (50 ft) depth. A directional projector was used to propagate linear frequency-modulated (5-65 kHz) and 40 kHz tonal pulses through the bubble cloud. Two hydrophone arrays were positioned so as to measure the energy lost in propagating through the bubble cloud. Three methods have been utilized to invert measurements and estimate the bubble population. The bubble population estimates have been used to develop a model for the bubble population resulting from an underwater explosion.

Tympanal mechanics and neural responses in the ears of a noctuid moth

Ears evolved in many groups of moths to detect the echolocation calls of predatory bats. Although the neurophysiology of bat detection has been intensively studied in moths for decades, the relationship between sound-induced movement of the noctuid tympanic membrane and action potentials in the auditory sensory cells (A1 and A2) has received little attention. Using laser Doppler vibrometry, we measured the velocity and displacement of the tympanum in response to pure tone pulses for moths that were intact or prepared for neural recording. When recording from the auditory nerve, the displacement of the tympanum at the neural threshold remained constant across frequencies, whereas velocity varied with frequency. This suggests that the key biophysical parameter for triggering action potentials in the sensory cells of noctuid moths is tympanum displacement, not velocity. The validity of studies on the neurophysiology of moth hearing rests on the assumption that the dissection and recording procedures do not affect the biomechanics of the ear. There were no consistent differences in tympanal velocity or displacement when moths were intact or prepared for neural recordings for sound levels close to neural threshold, indicating that this and other neurophysiological studies provide good estimates of what intact moths hear at threshold.

순음청력검사기를 위한 리눅스 기반 실시간 스펙트럼 분석기 개발

순음청력검사기는 청력의 손실 여부를 측정하기 위해 사용되는 중요한 의료기기이기 때문에 IEC와 ANSI에서는 순음청력검사기와 관련된 표준을 제시하고 있다. 본 논문은 순음청력검사기가 표준을 준수하는지 검사하기 위해 개발한 리눅스 기반 실시간 스펙트럼 분석기에 대해 기술한다. 본 논문의 실시간 스펙트럼 분석기는 청력 레벨 측정뿐 아니라 IEC에서 규정하고 있는 주파수 정확도, 청력 레벨 선형성, 고조파 왜곡, 단속음, 협대역 잡음에 대한 규정 준수 여부를 판단할 수 있는 기능을 제공한다. 개발한 실시간 스펙트럼 분석기를 상용 보정 시스템과 비교하여 검증한다. Because the puretone audiometer is an important medical instrument used to diagnose hearing loss, the IEC and ANSI has been published a specification with which audiometer should comply. This paper describes development of Linux based real-time spectrum analyzer which is dedicated to puretone audiometer. It can measure not only hearing level but also compliance of IEC standard for puretone audiometer such as frequency accuracy, harmonic distortion, pulsed tone, narrow band noise and linearity. We have verified our real-time spectrum analyzer through comparing to commercial product.

Comparing Pure-, Pulsed, and Warbled Tone Thresholds in Adults at 3000 and 6000 Hz

Pulsed and warbled tones are suitable substitutions for pure tones in hearing threshold measurement according to the 2005 American Speech-Language-Hearing Association guidelines. These guidelines also recommend measuring thresholds at 3000 and 6000 Hz. To date, there is no research directly supporting substitution of pulsed or warbled tones for pure tones at 3000 and 6000 Hz for listeners with normal hearing or with hearing loss. This study compared pure-, pulsed, and warbled tone thresholds at 3000 and 6000 Hz. Forty-seven adults with normal hearing and 16 adults with sensorineural hearing loss participated in this study. Air-conduction thresholds were elicited with pure tones at octave intervals from 250 to 8000 Hz and with pure-, pulsed, and warbled tone stimuli at 3000 and 6000 Hz. Small mean differences in thresholds were obtained using each of the 3 stimulus types for both listeners with normal hearing and hearing loss. Some of the mean differences tested were found to be statistically significant. The differences were nevertheless small and in all cases within the clinically accepted 5-dB step size. Although substitutions did not violate the 5-dB step size, the slope of a listener's hearing loss may be a factor in the inaccuracy of measurement during the substitution of warbled tones for pure tones.

Discrimination of stimulus variance.

In real-world settings, auditory signals such as speech are highly variable and differ across occurrences and sources. The question addressed is our sensitivity to such differences in global stimulus variability. In a variance discrimination task, the stimuli were sequences of five 100-ms tone pulses separated by 30 ms. The frequency of each tone was sampled independently from a probability distribution that was Gaussian on logarithmic frequency. In the non-signal interval of the 2IFC task, the sampled distribution had a mean frequency Mf and variance Vf. In the signal interval, the variance of the sequence was Vf + ΔVf. The task was to choose the interval with the larger variance; feedback was provided. To restrict the use of decision strategies, Mf was randomly chosen for each presentation(M̄ f=2 kHz). Psychometric functions |P(C) vs ΔVf| were obtained for various values of Vf , and overall performance was poorer than that of an ideal observer. However, like the ideal, Weber’s law behavior was observed: Constant ΔVf / Vf yielded the same performance. Degrading the Ideal with a fixed frequency resolution noise and a multiplicative computational noise provides an excellent account of the real data. [Work supported by NIDCD DC00683.]

Quality calls: phylogeny and biogeography of a new genus of neotropical katydid (Orthoptera: Tettigoniidae) with ultra pure-tone ultrasonics

This paper describes Artiotonus, a new genus of tropical katydid from Colombia and Ecuador. These acoustic ensiferans are represented by three species with a geographic distribution generally restricted to the rainforest of the Bolivar geosyncline of northwestern South America (Pacific). A phylogenetic analysis based on 28 morphological and six behavioural characters produced a tree (A. artius, (A. tinae, A. captivus)) with a consistency index of 0.9. All species are defined by a few autapomorphic changes. The most reliable character for identification is the temporal pattern of the calling song, suggesting a recent genetic divergence. Biogeographic analysis indicates that such genetic divergence began with geographic isolation produced before the Holocene transgression. Species of this genus are remarkable in that the calling song of males exhibits a narrow spectrum with a high quality factor (37–42), unusual values for such ultrasonic signals. A broad discussion on the evolution of tonal calls and pulse trains is offered.

Additivity of nonsimultaneous masking for short Gaussian-shaped sinusoids

The additivity of nonsimultaneous masking was studied using Gaussian-shaped tone pulses (referred to as Gaussians) as masker and target stimuli. Combinations of up to four temporally separated Gaussian maskers with an equivalent rectangular bandwidth of 600 Hz and an equivalent rectangular duration of 1.7 ms were tested. Each masker was level-adjusted to produce approximately 8 dB of masking. Excess masking (exceeding linear additivity) was generally stronger than reported in the literature for longer maskers and comparable target levels. A model incorporating a compressive input/output function, followed by a linear summation stage, underestimated excess masking when using an input/output function derived from literature data for longer maskers and comparable target levels. The data could be predicted with a more compressive input/output function. Stronger compression may be explained by assuming that the Gaussian stimuli were too short to evoke the medial olivocochlear reflex (MOCR), whereas for longer maskers tested previously the MOCR caused reduced compression. Overall, the interpretation of the data suggests strong basilar membrane compression for very short stimuli.

Adaptive Computation for Sensing Acoustical Environmental Change in the Auditory Cortex

Mismatch Negativity (MMN) is an evoked potential in response to an acoustical environmental change. Hypothesizing that, for animals to survive, MMN plays important roles in sensing environmental atmosphere, we investigated MMN in the auditory cortex of anesthetized rats in response to changes of frequency and harmony of test tone pulses. We first confirmed in behavioral experiments that rats could categorize consonant and dissonant chords, and thus distinguish this kind of sound feature quality, or ‘qualia.’ In physiological experiments, a surface microelectrode array mapped auditory evoked middle-latency response (P1) and MMN. We found that MMN could be elicited from the difference of qualia between consonant and dissonant chords and that the distributions of chord-elicited MMN were different from those of tone-elicited MMN. In response to pure tones, while middle-latency response (P1) was focally evoked from primary and anterior auditory cortex (A1, AAF), MMN spread toward ventral auditory cortex (VAF) in addition to A1 and AAF. In response to chords, MMN also widely spread over the auditory cortex, yet the largest activation spot was obtained in AAF. We also found an asymmetric property of MMN: Changes from low- to high-frequency tones and from dissonant to consonant chords produced larger MMN. Taken together, MMN in the auditory cortex can be elicited by changes of distinguishable qualia in an asymmetric form, suggesting that MMN reflects a detection of change of particular environmental atmosphere of sounds, which are potentially important for a survival.

Audiovisual stimulation with synchronized pulsed tones and flickering lights set at a delta frequency can induce a sedative effect

The perioperative period is a source of significant fear and anxiety for patients. Therefore, anxiolytic and sedative drugs are administered routinely, before and during surgery [1]. However, a larger dose of sedatives can delay the recovery in the ambulatory setting and be associated with an increased risk for complications.

Longitudinal Analysis of Arterial Blood Pressure and Heart Rate Response to Acute Behavioral Stress in Rats with Type 1 Diabetes Mellitus and in Age-Matched Controls

We recorded via telemetry the arterial blood pressure (BP) and heart rate (HR) response to classical conditioning following the spontaneous onset of autoimmune diabetes in BBDP/Wor rats vs. age-matched, diabetes-resistant control (BBDR/Wor) rats. Our purpose was to evaluate the autonomic regulatory responses to an acute stress in a diabetic state of up to 12 months duration. The stress was a 15-s pulsed tone (CS+) followed by a 0.5-s tail shock. The initial, transient increase in BP (i.e., the “first component,” or C1), known to be derived from an orienting response and produced by a sympathetic increase in peripheral resistance, was similar in diabetic and control rats through ∼9 months of diabetes; it was smaller in diabetic rats 10 months after diabetes onset. Weakening of the C1 BP increase in rats that were diabetic for >10 months is consistent with the effects of sympathetic neuropathy. A longer-latency, smaller, but sustained “second component” (C2) conditional increase in BP, that is acquired as a rat learns the association between CS+ and the shock, and which results from an increase in cardiac output, was smaller in the diabetic vs. control rats starting from the first month of diabetes. A concomitant HR slowing was also smaller in diabetic rats. The difference in the C2 BP increase, as observed already during the first month of diabetes, is probably secondary to the effects of hyperglycemia upon myocardial metabolism and contractile function, but it may also result from effects on cognition. The small HR slowing concomitant with the C2 pressor event is probably secondary to differences in baroreflex activation or function, though parasympathetic dysfunction may contribute later in the duration of diabetes. The nearly immediate deficit after disease onset in the C2 response indicates that diabetes alters BP and HR responses to external challenges prior to the development of structural changes in the vasculature or autonomic nerves.

Audiovisual stimulation with synchronized pulsed tones and flickering lights set at a delta frequency can induce a sedative effect

Audiovisual stimulation with synchronized pulsed tones and flickering lights set at a delta frequency can induce a sedative effect