Frequency Modulation Detection Research Articles

Structural rotor rub-impact diagnosis under intricate noise interferences based on targeted component extraction and stochastic resonance enhancement

Rub-impact is a common nonlinear fault of the rotor system, occurring in rotating machines with radial clearance between the rotor and the stator, which may lead to serious consequences. Since the vibration response of rotor rub-impact is shown as multicomponent with time-varying characteristics of undulatory instantaneous frequency, it is desired to exploit advanced signal processing methods for rub-related feature excavation and failure diagnosis under complex noise interferences, which is of crucial significance to ensure the stable and efficient operation of the whole unit. This paper concerns the processing of acceleration signals and proposes a novel intrawave frequency modulation detection approach for structural rotor rubbing diagnosis based upon targeted component extraction and stochastic resonance enhancement. First, the acquired vibratory acceleration signal is converted into displacement signal via a two-stage integration strategy. Next, to extract the rotating frequency component of high information clarity for further time–frequency analysis from the multicomponent signal, an especially designed improved variational mode decomposition method based on the modified target frequency index is put forward, and the instantaneous frequency of the objective component is estimated. Then, the optimum stochastic resonance is leveraged for intrawave frequency modulation enhancement. Finally, the rotor rub-related symptom can be distinctly revealed and the diagnostic procedure can be performed. The effectiveness and superiority of the proposed rotor rub-impact diagnosis approach are demonstrated through both simulations and experiments, indicating that it is suitable to be implemented in practical applications, with high noise-resistance ability, and can efficiently extract the potential characteristics of rotor rub-impact malfunction from multicomponent signals.

Benefits of Harmonicity for Hearing in Noise Are Limited to Detection and Pitch-Related Discrimination Tasks.

Harmonic complex tones are easier to detect in noise than inharmonic complex tones, providing a potential perceptual advantage in complex auditory environments. Here, we explored whether the harmonic advantage extends to other auditory tasks that are important for navigating a noisy auditory environment, such as amplitude- and frequency-modulation detection. Sixty young normal-hearing listeners were tested, divided into two equal groups with and without musical training. Consistent with earlier studies, harmonic tones were easier to detect in noise than inharmonic tones, with a signal-to-noise ratio (SNR) advantage of about 2.5 dB, and the pitch discrimination of the harmonic tones was more accurate than that of inharmonic tones, even after differences in audibility were accounted for. In contrast, neither amplitude- nor frequency-modulation detection was superior with harmonic tones once differences in audibility were accounted for. Musical training was associated with better performance only in pitch-discrimination and frequency-modulation-detection tasks. The results confirm a detection and pitch-perception advantage for harmonic tones but reveal that the harmonic benefits do not extend to suprathreshold tasks that do not rely on extracting the fundamental frequency. A general theory is proposed that may account for the effects of both noise and memory on pitch-discrimination differences between harmonic and inharmonic tones.

A Phase-Sensitive Optical Time Domain Reflectometry with Non-Uniform Frequency Multiplexed NLFM Pulse.

In the domain of optical fiber distributed acoustic sensing, the persistent challenge of extending sensing distances while concurrently improving spatial resolution and frequency response range has been a complex endeavor. The amalgamation of pulse compression and frequency division multiplexing methodologies has provided certain advantages. Nevertheless, this approach is accompanied by the drawback of significant bandwidth utilization and amplified hardware investments. This study introduces an innovative distributed optical fiber acoustic sensing system aimed at optimizing the efficient utilization of spectral resources by combining compressed pulses and frequency division multiplexing. The system continuously injects non-linear frequency modulation detection pulses spanning various frequency ranges. The incorporation of non-uniform frequency division multiplexing augments the vibration frequency response spectrum. Additionally, nonlinear frequency modulation adeptly reduces crosstalk and enhances sidelobe suppression, all while maintaining a favorable signal-to-noise ratio. Consequently, this methodology substantially advances the spatial resolution of the sensing system. Experimental validation encompassed the multiplexing of eight frequencies within a 120 MHz bandwidth. The results illustrate a spatial resolution of approximately 5 m and an expanded frequency response range extending from 1 to 20 kHz across a 16.3 km optical fiber. This achievement not only enhances spectral resource utilization but also reduces hardware costs, making the system even more suitable for practical engineering applications.

Electrophysiological and behavioral assessment of binaural processing: Effects of age

Spatial hearing deteriorates with age, but the basis(es) of this age-dependency is not clear and could reflect both bottom-up and top-down factors. Since binaural processing depends in part on interaural time difference cues, this study assessed binaural temporal acuity using both objective and behavioral measures. Three tasks incorporating interaural time/phase differences were tested: (1) in-phase and out-of-phase frequency modulation (FM) detection as a function of FM rate; (2) upper frequency limit of in-phase versus out-of-phase tone discrimination; and (3) minimum audible angle for low frequency tones. Each task incorporated parallel behavioral and electrophysiological measures: For behavior, forced-choice adaptive methods were employed; for electrophysiology, the acoustic change complex (ACC) was recorded. Additional measures of peripheral auditory function, as well as cognitive status, were also collected. Young and middle-aged adults (n = 20 per age group) with normal audiometric hearing were tested. Differences in behavioral measures of binaural performance were noted between the two age groups and these were reflected to some extent in the ACC results. However, group differences were also noted in terms of cochlear function and in terms of cognitive abilities. This pattern of results suggests that age-related deterioration in spatial perception is likely to be multi-faceted.

Assessing mechanisms of frequency discrimination by comparison of different measures over a wide frequency range

It has been hypothesized that auditory detection of frequency modulation (FM) for low FM rates depends on the use of both temporal (phase locking) and place cues, depending on the carrier frequency, while detection of FM at high rates depends primarily on the use of place cues. To test this, FM detection for 2 and 20 Hz rates was measured over a wide frequency range, 1–10 kHz, including high frequencies for which temporal cues are assumed to be very weak. Performance was measured over the same frequency range for a task involving detection of changes in the temporal fine structure (TFS) of bandpass filtered complex tones, for which performance is assumed to depend primarily on the use of temporal cues. FM thresholds were better for the 2- than for the 20-Hz rate for center frequencies up to 4 kHz, while the reverse was true for higher center frequencies. For both FM rates, the thresholds, expressed as a proportion of the center frequency, were roughly constant for center frequencies from 6 to 10 Hz, consistent with the use of place cues. For the TFS task, thresholds worsened progressively with increasing frequency above 4 kHz, consistent with the weakening of temporal cues.

Sensitivity to Frequency Modulation is Limited Centrally.

Modulations in both amplitude and frequency are prevalent in natural sounds and are critical in defining their properties. Humans are exquisitely sensitive to frequency modulation (FM) at the slow modulation rates and low carrier frequencies that are common in speech and music. This enhanced sensitivity to slow-rate and low-frequency FM has been widely believed to reflect precise, stimulus-driven phase locking to temporal fine structure in the auditory nerve. At faster modulation rates and/or higher carrier frequencies, FM is instead thought to be coded by coarser frequency-to-place mapping, where FM is converted to amplitude modulation (AM) via cochlear filtering. Here, we show that patterns of human FM perception that have classically been explained by limits in peripheral temporal coding are instead better accounted for by constraints in the central processing of fundamental frequency (F0) or pitch. We measured FM detection in male and female humans using harmonic complex tones with an F0 within the range of musical pitch but with resolved harmonic components that were all above the putative limits of temporal phase locking (>8 kHz). Listeners were more sensitive to slow than fast FM rates, even though all components were beyond the limits of phase locking. In contrast, AM sensitivity remained better at faster than slower rates, regardless of carrier frequency. These findings demonstrate that classic trends in human FM sensitivity, previously attributed to auditory nerve phase locking, may instead reflect the constraints of a unitary code that operates at a more central level of processing.SIGNIFICANCE STATEMENT Natural sounds involve dynamic frequency and amplitude fluctuations. Humans are particularly sensitive to frequency modulation (FM) at slow rates and low carrier frequencies, which are prevalent in speech and music. This sensitivity has been ascribed to encoding of stimulus temporal fine structure (TFS) via phase-locked auditory nerve activity. To test this long-standing theory, we measured FM sensitivity using complex tones with a low F0 but only high-frequency harmonics beyond the limits of phase locking. Dissociating the F0 from TFS showed that FM sensitivity is limited not by peripheral encoding of TFS but rather by central processing of F0, or pitch. The results suggest a unitary code for FM detection limited by more central constraints.

Suppression of Nonlinear Optical Effects in DWDM-PON by Frequency Modulation Non-Coherent Detection

We propose a simple and cost-effective method, using a direct frequency modulation (FM) and noncoherent detection (NCD) scheme, to suppress the nonlinear optical effects in dense wavelength division multiplexed (DWDM) optical communication. The FM transmitter comprises a directly modulated distributed feedback laser and a saturable semiconductor optical amplifier. In the NCD receiver, an optical slope filter as the FM to intensity modulation (IM) signal convertor is placed before a conventional photodetector. Because the FM signal has more evenly distributed optical power, bit-pattern-dependent nonlinear effects are consequently suppressed. After analyzing the nonlinear effects in the FM-NCD system and traditional IM direct detection (IM-DD) system, we found that the minimum achievable BER of the proposed FM-NCD scheme is 40 dB smaller. Moreover, a 2 Tbps (10 Gb/s × 200 channels) capacity was achieved by the FM-NCD system in 100 km DWDM passive optical networks (PONs), which is twice the capacity of the IM-DD system (10 Gb/s × 100 channels) under the same condition. These results indicate that WDM-PONs with the cost-effective FM-NCD scheme are strong candidates for future broad access networks and show great potential for the combination of optical access and metro networks for future generations of PONs.

Psychophysical performance differences associated with auditory spatial attention in older listeners with and without hearing loss

In a busy listening environment with multiple speakers, even normal-hearing listeners may face difficulties in understanding speech (i.e., “the cocktail party problem”). Individual factors related to bottom-up and/or top-down processing difficulties may be associated with the listener’s ability to attend to speech, a key component in navigating complex acoustic environments. The present study tested listeners on a battery of psychophysical measures and compared listener performance to cortical measures (EEG) of spatial-change tuning and auditory spatial attention. The behavioral tests measured both perceptual and cognitive performance and included: frequency modulation detection, spectro-temporal modulation sensitivity, spatial release from masking, temporal gap detection, auditory and non-auditorysustained attention, and visuo-spatial problem solving. The EEG paradigm tested the listener’s ability to attend to moving speech in quiet or background babble in the free field. Older listeners with and without hearing loss (n = 20 per group) demonstrated wide individual performance for some measures and significant correlations between behavioral thresholds and cortical responses, consistent with a more refined view of age-related hearing loss and a need for a more holistic approach in diagnoses for individuals beyond standard clinical tests. [Work supported by NIH R21DC017832.]

Masking effects of amplitude modulation on frequency-modulated tones

Human sensitivity to frequency modulation (FM) is best for low carrier frequencies (<∼4–5 kHz) and slow modulation rates (<5–10 Hz). This high sensitivity is thought to be afforded by neural phase locking to temporal fine structure (TFS). At faster rates and higher carriers, TFS cues may no longer be available, with sensitivity to FM relying instead on conversion to amplitude modulation (AM) via cochlear filtering. One way to test this hypothesis is to measure the masking produced by additional AM, with the prediction that AM masking will be more pronounced when FM is encoded via AM than via TFS cues. This study tested AM masking of FM and of “simulated FM,” which involves out-of-phase AM dyads. FM detection was measured for carrier frequencies of 1 and 6 kHz and modulation rates of 2 and 20 Hz with and without AM masking. Preliminary results suggest that FM and simulated FM sensitivity is more affected by AM at fast than slow rates at both low and high carrier frequencies. Overall, the results do not provide support for the idea that AM interference can be used to distinguish between TFS- and envelope-based codes for FM. [Work supported by NIH grant R21 DC019409.]

The Relative Contribution of Cochlear Synaptopathy and Reduced Inhibition to Age-Related Hearing Impairment for People With Normal Audiograms.

Older people often show auditory temporal processing deficits and speech-in-noise intelligibility difficulties even when their audiogram is clinically normal. The causes of such problems remain unclear. Some studies have suggested that for people with normal audiograms, age-related hearing impairments may be due to a cognitive decline, while others have suggested that they may be caused by cochlear synaptopathy. Here, we explore an alternative hypothesis, namely that age-related hearing deficits are associated with decreased inhibition. For human adults (N = 30) selected to cover a reasonably wide age range (25-59 years), with normal audiograms and normal cognitive function, we measured speech reception thresholds in noise (SRTNs) for disyllabic words, gap detection thresholds (GDTs), and frequency modulation detection thresholds (FMDTs). We also measured the rate of growth (slope) of auditory brainstem response wave-I amplitude with increasing level as an indirect indicator of cochlear synaptopathy, and the interference inhibition score in the Stroop color and word test (SCWT) as a proxy for inhibition. As expected, performance in the auditory tasks worsened (SRTNs, GDTs, and FMDTs increased), and wave-I slope and SCWT inhibition scores decreased with ageing. Importantly, SRTNs, GDTs, and FMDTs were not related to wave-I slope but worsened with decreasing SCWT inhibition. Furthermore, after partialling out the effect of SCWT inhibition, age was no longer related to SRTNs or GDTs and became less strongly related to FMDTs. Altogether, results suggest that for people with normal audiograms, age-related deficits in auditory temporal processing and speech-in-noise intelligibility are mediated by decreased inhibition rather than cochlear synaptopathy.

Mid-infrared Frequency Modulation Detection of HCN and Its Reaction with O Atoms behind Shock Waves.

Hydrogen cyanide (HCN) is the primary cyanide species in combustion processes and plays a key role in the formation of NOx in the combustion of fossil fuels, nitrogen-containing biofuels, and blended hydrocarbon-ammonia mixtures. Robust, sensitive, and time-resolved in situ laser diagnostic methods are needed to gain insight into the combustion chemistry of HCN. Mid-infrared frequency modulation spectroscopy (MIR-FMS) has recently been established as such a quantitative technique for HCN detection behind shock waves. With a minimum detectable fractional absorption of 2 × 10-4 at a time resolution of 5 μs, an improved spectrometer design enabled the detection of HCN behind shock waves down to the ppm mole fraction level. An Allan noise analysis revealed that a further improvement toward shot-noise limited detection should be possible when fast mid-infrared photodetectors with a higher saturation limit will become available. HCN kinetic profiles in the presence of O(3P) atoms from thermal N2O decomposition have been measured in the temperature range 1448 K < T < 1954 K. The determined total rate constants for the key HCN oxidation reaction HCN + O, k/(cm3 mol-1 s-1) = 1.88 × 1014 exp(-64.5 kJ mol-1/RT)(+28%, -37%), turn out to be largely consistent with previous measurements. These data complete the set of available rate constant studies, by now covering the temperature range 450 K < T < 2500 K and relying on the detection of almost all feasible reactant and product species.

Relation between temporal fine structure processing and global processing speed

Strelcyk et al. (2019) recently found that interaural phase discrimination in older hearing-impaired listeners was correlated with both visuospatial processing speed and interaural level discrimination. This suggests that temporal fine structure (TFS) processing relies on global processing speed and/or spatial cognition, though it is possible that, generally, complex auditory discrimination engages multiple cognitive domains. Here, 50 Veterans (mean age = 48.1, range = 30–60) with normal or near-normal hearing completed batteries of temporal processing and cognitive tests. Composite cognitive test scores reflecting processing speed/executive function (PS-EX) and working memory (WM) were obtained. Temporal processing tasks included measures of envelope (ENV; gap duration discrimination, forward masking) and TFS (frequency modulation detection, interaural phase modulation detection) processing. Bayesian hierarchical regression was used to fit psychometric functions simultaneously to all ENV and TFS tasks in all subjects. Fixed effects of PS-EX and WM on thresholds and slopes were estimated for the psychometric functions in each temporal task. In general, (i) PS-EX and WM influenced both TFS and ENV thresholds, but not slopes; and (ii) TFS thresholds were best explained by PS-EX scores while ENV thresholds were best explained by WM scores. These findings suggest a specific relation between global processing speed and TFS.

Estimating the contribution of central noise from composite performance across multiple tasks

According to signal detection theory, the ability to detect a signal is limited only by internal noise, which comprises peripheral and central sources. Here, we develop a statistical approach to parse central from peripheral noise. Fifty-two Veterans (mean age = 47.8, range = 30–60) with normal or near-normal hearing performed AXB discrimination for several temporal processing tasks: gap duration discrimination, forward masking, frequency modulation detection, and interaural phase modulation detection. After training, a single adaptive run (40 reversals) was completed for each task. Subjects also completed speech-in-noise testing (“Theo-Victor-Michael") with four masker types (48 trials ea.): speech-shaped noise, speech-envelope modulated noise, one and two competing talkers. Composite speech performance was estimated using principal component analysis. Bayesian hierarchical regression was used to estimate two-parameter psychometric functions (threshold, slope) simultaneously for all temporal tasks and subjects. Crucially, fixed (group-level) thresholds were estimated per task but only a single random (subject-level) intercept was estimated (mean across-task deviation from the group thresholds). We assume central noise is the primary factor limiting across-task performance. The principal speech scores were entered as regressors on this “central threshold.” Indeed, central threshold was correlated with the principal speech scores, suggesting that central noise limits temporal processing and speech-in-noise.

Research on linear frequency modulation detection technology based on fractional fourier transform

Research on linear frequency modulation detection technology based on fractional fourier transform

Relating Suprathreshold Auditory Processing Abilities to Speech Understanding in Competition.

(1) Background: Difficulty hearing in noise is exacerbated in older adults. Older adults are more likely to have audiometric hearing loss, although some individuals with normal pure-tone audiograms also have difficulty perceiving speech in noise. Additional variables also likely account for speech understanding in noise. It has been suggested that one important class of variables is the ability to process auditory information once it has been detected. Here, we tested a set of these “suprathreshold” auditory processing abilities and related them to performance on a two-part test of speech understanding in competition with and without spatial separation of the target and masking speech. Testing was administered in the Portable Automated Rapid Testing (PART) application developed by our team; PART facilitates psychoacoustic assessments of auditory processing. (2) Methods: Forty-one individuals (average age 51 years), completed assessments of sensitivity to temporal fine structure (TFS) and spectrotemporal modulation (STM) detection via an iPad running the PART application. Statistical models were used to evaluate the strength of associations between performance on the auditory processing tasks and speech understanding in competition. Age and pure-tone-average (PTA) were also included as potential predictors. (3) Results: The model providing the best fit also included age and a measure of diotic frequency modulation (FM) detection but none of the other potential predictors. However, even the best fitting models accounted for 31% or less of the variance, supporting work suggesting that other variables (e.g., cognitive processing abilities) also contribute significantly to speech understanding in noise. (4) Conclusions: The results of the current study do not provide strong support for previous suggestions that suprathreshold processing abilities alone can be used to explain difficulties in speech understanding in competition among older adults. This discrepancy could be due to the speech tests used, the listeners tested, or the suprathreshold tests chosen. Future work with larger numbers of participants is warranted, including a range of cognitive tests and additional assessments of suprathreshold auditory processing abilities.

Psychoacoustic thresholds measured using the Portable Automated Rapid Testing (PART) iPad application in a large cohort of older listeners

Traditional methods used to assess the auditory processing capabilities of individuals have limited clinical applications as they are time consuming and require specialized hardware. Portable Automated Rapid Testing (PART) is a free application that allows various clinical assessments to be conducted in an automated and rapid fashion using commercially available consumer headphones. Use of this platform in an uncontrolled listening environment has been validated in young listeners with normal hearing, yielding thresholds similar to those reported in laboratory studies. Here, we report auditory processing capabilities measured using PART in a large cohort of older listeners with varying hearing capabilities. Psychoacoustic thresholds for gap detection, spectrotemporal modulation detection, dichotic and diotic frequency modulation detection, and spatial release from masking were obtained from 70 older listeners (age range: 40—75 years; 3-frequency PTA: 8.33—48.33 dB HL). Initial analyses revealed that the thresholds obtained using PART were similar to thresholds obtained in a laboratory environment. Results demonstrate that PART can be used with older listeners with minimal instruction and validate the use of a consumer platform and rapid techniques for the assessment of auditory processing capabilities in older adults with a range of hearing ability.

Erratum: Double-pass consistency for amplitude- and frequency-modulation detection in normal-hearing listeners [J. Acoust. Soc. Am. 150, 3631-3647 (2021)

Erratum: Double-pass consistency for amplitude- and frequency-modulation detection in normal-hearing listeners [J. Acoust. Soc. Am. 150, 3631-3647 (2021)

Ion-specific nanoscale compaction of cysteine-modified poly(acrylic acid) brushes revealed by 3D scanning force microscopy with frequency modulation detection.

Stimuli-responsive polyelectrolyte brushes adapt their physico-chemical properties according to pH and ion concentrations of the solution in contact. We synthesized a poly(acrylic acid) bearing cysteine residues at side chains and a lipid head group at the terminal, and incorporated them into a phospholipid monolayer deposited on a hydrophobic silane monolayer. The ion-specific, nanoscale response of polyelectrolyte brushes was detected by using three-dimensional scanning force microscopy (3D-SFM) combined with frequency modulation detection. The obtained topographic and mechanical landscapes indicated that the brushes were uniformly stretched, undergoing a gradual transition from the brush to the bulk electrolyte in the absence of divalent cations. When 1 mM calcium ions were added, the brushes were uniformly compacted, exhibiting a sharper brush-to-bulk transition. Remarkably, the addition of 1 mM cadmium ions made the brush surface significantly rough and the mechanical landscape highly heterogeneous. Currently, cadmium-specific nanoscale compaction of the brushes is attributed to the coordination of thiol and carboxyl side chains with cadmium ions, as suggested for naturally occurring, heavy metal binding proteins.

Double-pass consistency for amplitude- and frequency-modulation detection in normal-hearing listeners.

Amplitude modulation (AM) and frequency modulation (FM) provide crucial auditory information. If FM is encoded as AM, it should be possible to give a unified account of AM and FM perception both in terms of response consistency and performance. These two aspects of behavior were estimated for normal-hearing participants using a constant-stimuli, forced-choice detection task repeated twice with the same stimuli (double pass). Sinusoidal AM or FM with rates of 2 or 20 Hz were applied to a 500-Hz pure-tone carrier and presented at detection threshold. All stimuli were masked by a modulation noise. Percent agreement of responses across passes and percent-correct detection for the two passes were used to estimate consistency and performance, respectively. These data were simulated using a model implementing peripheral processes, a central modulation filterbank, an additive internal noise, and a template-matching device. Different levels of internal noise were required to reproduce AM and FM data, but a single level could account for the 2- and 20-Hz AM data. As for FM, two levels of internal noise were needed to account for detection at slow and fast rates. Finally, the level of internal noise yielding best predictions increased with the level of the modulation-noise masker. Overall, these results suggest that different sources of internal variability are involved for AM and FM detection at low audio frequencies.

Quantitative and Sensitive Mid-Infrared Frequency Modulation Detection of HCN behind Shock Waves

Despite its key role for the study and modeling of nitrogen chemistry and NOx formation in combustion processes, HCN has only rarely been detected under high-temperature conditions. Here, we demonstrate quantitative detection of HCN behind incident and reflected shock waves using a novel sensitive single-tone mid-infrared frequency modulation (mid-IR-FM) detection scheme. The temperature-dependent pressure broadening of the P(26) line in the fundamental CH stretch vibration band was investigated in the temperature range 670K≤T≤1460K, yielding a pressure broadening coefficient for argon of 2γAr296K=(0.093±0.007)cm−1atm−1 and a temperature exponent of nAr=0.67±0.07. The sensitivity of the detection scheme was characterized by means of an Allan analysis, showing that HCN detection on the ppm mixing ratio level is possible at typical shock wave conditions. In order to demonstrate the capability of mid-IR-FM spectroscopy for future high-temperature reaction kinetic studies, we also report the first successful measurement of a reactive HCN decay profile induced by its reaction with oxygen atoms.