Narrowband Signals In Noise Research Articles

Using computer techniques for vibration damage estimation under stochastic loading using the Monte Carlo Method for aerospace applications

The main focus of this article is a review of legacy methods for vibration damage estimation under stochastic loading and extending research made by Dirlik and Bendat using two combined methods: FEM and Monte Carlo simulation, for which we used Python programming for aerospace applications. For some aircraft, regulated by the RTCA international aviation standard DO-160G (Environmental Conditions and Test Procedures for Airborne Equipment), stochastic loading is defined as one of the requirements. This article will focus on the stochastic loading impact on the fatigue life assessment made on a dummy sample, and frequency and time domain damage estimation shall be considered in parallel to compare both results. Additionally, dummy PSD responses shall be defined in the frequency domain for signal statistical parameters research. The article introduces Rainflow Cycle Counting methods in the frequency domain for procedures used commercially in aerospace applications. The first method introduced and developed further is the Dirlik method of Rainflow Cycle Counting in the frequency domain, which is the most popular method in commercial use. The second technique introduced and developed further was established by Bendat — the Narrow Band Method. The new empirical equation presented in this paper is the modification of the Narrow Band Method fitted for general use (narrow band, wide band, and white noise signals). A new approach for the integration of spectral moments is introduced in this paper, allowing for an accurate evaluation of the signal statistic parameters in the frequency domain for use in the modified Dirlik and Narrow Band methods. Research results also revealed new phenomena not researched by Dirlik, such as high vibration damage variation from stochastic loading, which depends on the frequency resolution (the block size used in Inverse Fourier Transformation). This discovery will be the subject of further study. Research results presented in this paper will also be utilised to combine stochastic and deterministic loading scenarios for military helicopters, as well as fighter aircraft, and will be the subject of further research.

Improved Aures tonality metric for complex sounds

This paper proposes improvements to the Aures’ tonality metric, which can be used for estimating the frequency masking of complex sounds. The perception of tonality has been extensively studied in simple sounds, such as pure tones and narrowband noise signals, but there are no solid conclusions in the case of complex sounds. Previously, Aures’ method has been mostly used in the psychoacoustic analysis of noise signals. The modifications presented here are a better spectral resolution, a lowered tonal threshold, and a different exponent in one of their weighting functions. These may appear to be minor changes from the original Aures (OA) method, but they have proven to be significant for perception. The improved Aures (IA) method has been validated by a subjective test using three different multitone signals in the presence of a narrowband noise, whose result is the subjectively perceived masking thresholds. Results show that the IA method presents an average error of 0.8 dB when predicting the subjective masking thresholds provided by the test, while the average errors of the OA and a baseline spectral flatness method exceed 5 dB. In addition, a second subjective test has been carried out to assess the perceptual equalization of a music signal using the proposed IA and spectral flatness methods. The second test confirms that the IA method is preferred. Therefore, the improved Aures method is proposed as a reliable tonality metric for complex sounds, such as multi-tone signals and music.

A Computational Model for Evaluating Transient Auditory Storage of Acoustic Features in Normal Listeners.

Humans are able to detect an instantaneous change in correlation, demonstrating an ability to temporally process extremely rapid changes in interaural configurations. This temporal dynamic is correlated with human listeners’ ability to store acoustic features in a transient auditory manner. The present study investigated whether the ability of transient auditory storage of acoustic features was affected by the interaural delay, which was assessed by measuring the sensitivity for detecting the instantaneous change in correlation for both wideband and narrowband correlated noise with various interaural delays. Furthermore, whether an instantaneous change in correlation between correlated interaural narrowband or wideband noise was detectable when introducing the longest interaural delay was investigated. Then, an auditory computational description model was applied to explore the relationship between wideband and narrowband simulation noise with various center frequencies in the auditory processes of lower-level transient memory of acoustic features. The computing results indicate that low-frequency information dominated perception and was more distinguishable in length than the high-frequency components, and the longest interaural delay for narrowband noise signals was highly correlated with that for wideband noise signals in the dynamic process of auditory perception.

Results of the hidden correlation study narrowband noise signals for information and measurement systems and diagnostic tools for medical purposes

Results of the hidden correlation study narrowband noise signals for information and measurement systems and diagnostic tools for medical purposes

Stapedius reflex evoked in free sound field in cochlear implant users compared to normal-hearing listeners

Objective To determine the relation between stapedius reflex thresholds in cochlear implant users evoked once through direct electric stimulation on single channels (ESRT) and once through acoustic stimulation in free sound field. For comparison, stapedius reflex thresholds were obtained in free sound field in a normal-hearing control group. Design For each participant a new ESRT-based fitting was created. Stapedius reflex thresholds were obtained for this new fitting in free sound field for different loudness adjustments. Acoustic stimuli for eliciting the stapedius reflex were narrow band noise signals covering the audiometric frequency range. Study sample N = 29 experienced CI users (34 ears) and N = 10 normal hearing listeners. Results ESRT-based fitting resulted in different stapedius reflex behaviour compared to normal-hearing listeners. A frequency dependence was observed. Stapedius reflex thresholds decreased with increasing centre frequencies of acoustic narrow band noise stimuli. A linear relation between upper stimulation levels on the implant channels and corresponding stapedius reflex thresholds evoked in free sound field was found. Conclusion The found correlation may be a guideline for adjusting the electrical dynamic range during cochlear implant fitting. This allows the implant system to mimic the natural reflex behaviour in the best possible way and potentially avoid overstimulation.

Method for Estimating the Latent Correlation of Narrowband Noise Signals

The concept of hidden correlation of noise signals is introduced. Theoretically, the existence of a hidden correlation between narrow-band noise signals extracted simultaneously from a broadband band-limited noise is proved. A method for estimating the latent correlation of narrow-band noise signals has been developed and experimentally investigated. An experiment was conducted where a temporal fragment of band-limited noise was used as the signal under investigation, the basis of which is shot noise. It was found that when applying the Pearson criterion between the signal at the center frequency and the sum of the signals at the mirror frequencies, virtually no correlation is found, and when using the proposed method for analyzing the same signals, a strong hidden correlation is found. The proposed method is useful for specialists involved in digital signal processing, as well as developers of measuring tools using a new technology for extracting a useful signal from noise – the method of mirror noise images.

Method of estimation of hidden correlation of narrowband noise signals

The concept of hidden correlation of noise signals is introduced. The existence of a hidden correlation between narrowband noise signals isolated simultaneously from broadband band-limited noise is theoretically proved. A method for estimating the latent correlation of narrowband noise signals has been developed and experimentally investigated. As a result of the experiment, where a time frag ent of band-limited noise, the basis of which is shot noise, is used as the studied signal, it is established: when applying the Pearson criterion, there is practically no correlation between the signal at the Central frequency and the sum of signals at mirror frequencies; when applying the proposed method for the analysis of the same signals, a strong hidden correlation is found. The proposed method is useful for researchers, engineers and metrologists engaged in digital signal processing, as well as developers of measuring instruments using a new technology for isolating a useful signal from noise – the method of mirror noise images.

A two adaptive filters-based method for reducing effects of acoustic feedback in single-channel feedforward ANC systems

In most of the existing approaches for neutralizing the effects of acoustic feedback in feed-forward active noise control (FF-ANC) systems, three adaptive filters have been employed. Besides the noise control and feedback neutralization filters (FBNF), a third disturbance removal filter has been exploited to obtain suitable signals for (apposite) adaptation of the other two (adaptive filters). In this paper, we develop an effective acoustic feedback neutralization method which does not require any supplementary third adaptive filter. The proposed method incorporates a probe signal with a time-varying gain and a novel variable step-size strategy for adaptation of the FBNF. During the transient state, the FBNF is excited by a large variance probe signal and a large valued step-size. This enhances the convergence rate of the FBNF. As the FF-ANC system converges, the level of probe noise is decreased to achieve good residual error attenuation performance (at steady-state). Furthermore, the step-size is also reduced to a small value to improve the steady-state performance of the acoustic FBNF. Simulations results show that the proposed two adaptive filters-based method outperforms the existing methods for broad-band reference noise sources and yields better steady-state residual error attenuation performance for narrow-band noise signals.

Effect of a Low-Frequency Noise Signal on the Supply Circuit of the Millimeter-Band Generator of Single-Frequency and Chaotic Oscillations Designed on an Avalanche Transit-Time Diode

The effect of a low-frequency noise signal on the supply circuit of a millimeter-band generator of single-frequency and chaotic oscillations designed on an avalanche transit-time diode has been experimentally investigated. Generation of noise oscillations under the action of a low-frequency narrowband (~3 MHz) noise signal on the supply circuit of an avalanche transit-time diode in a single-frequency self-oscillator based on a 7-millimeter-wave avalanche transit-time diode has been obtained for the first time and the possibility of control of the spectral characteristic of a 8-millimeter-band noise generator on an avalanche transit-time diode zusing such an impact has been demonstrated.

Horizontal Localization in Simulated Unilateral Hearing Loss.

Background and ObjectivesThe ability to localize a sound source is one of the binaural hearing benefits in a horizontal plane based on interaural time difference and interaural intensity difference. Unilateral or bilateral asymmetric hearing loss will affect binaural hearing and lead to sound locating errors. In this cross sectional analytical descriptive study, the localization error was investigated when participants turned their heads to the sound source with closed eyes and after simulating unilateral hearing loss by placing earplugs inside the right ear canal. Subjects and MethodsThis cross sectional analytical descriptive study was carried out on 30 right-handed adults, 22 female and 8 male (average: 25 years, standard deviation: 3.16). They were selected with the available random access method. Horizontal localization was evaluated with five speakers located at 0, ±30, and ±60 degree azimuths at a 1-meter distance from the examinee. Narrow-band noise signals were delivered at 35 dB SL in two “without earplug” and “with earplug” situations and the results were compared. The study was performed between September and December 2016 in Tehran, Iran. ResultsSignificant differences were observed in localization errors between the “with earplug” and “without earplug” situations. The localization differences were greater for left-side speakers (-30 and -60 degrees) compared with right-side speakers (+30 and +60 degrees). The differences were more apparent at 4,000 and 6,000 Hz, which confirmed the effect of unilateral simulated hearing loss on interaural latency differences. ConclusionsSimulating hearing loss by using an earplug in one ear (right) increased localization errors at all frequencies. The errors increased at higher frequencies.

The effect of a low-frequency noise signal on a single-frequency millimeter-band oscillator based on an avalanche-transit diode

Noise-wave generation in a single-frequency oscillator based on a 7-mm-band avalanche-transit diode has been implemented for the first time under the action of a low-frequency narrow-band (~3 MHz) noise signal on an avalanche-transit-diode feed circuit.

Development of two-input adaptive noise canceller for wideband and narrowband noise signals

In this paper, the development of the single-stage two-input adaptive noise canceller that proposed by Widrow et al. is investigated. It is shown that the use of multi-stage cancellers instead of a single stage improves the performance of the conventional two-input adaptive noise canceller in a real life high-noise environment. In such environment, the background noise may contain both the wideband and narrowband (sinusoidal) noise components. In this contribution, the wideband noise and sinusoidal noise signals can be significantly suppressed using a new multi-stage adaptive noise cancellation scheme based on adaptive line enhancer (ALE) and Least Mean Square (LMS) filter. The proposed scheme is comprised of two stages. The first stage uses ALE filters, which are used to cancel the sinusoidal noise from the primary and reference input signals, whereas the wideband noise is cancelled using LMS adaptive filter in the second stage. The good performance of the proposed scheme has been verified via real-time implementation on the Texas Instruments TMS320C6713DSK.

A new adaptive strategy to improve online secondary path modeling in active noise control systems using fractional signal processing approach

In this paper, a new adaptive strategy based on fractional signal processing is proposed using multi-directional step size fractional least mean square algorithm for online secondary path modeling, which is a fundamental problem in practical active noise control systems, as opposed to the generally-employed increasing step size strategy that compromises model accuracy for faster convergence. The design approach presents step size strategy in relation with disturbance signal in the desired response of modeling filter which is not available directly so an indirect approach is used to track its variations. Comparative results for narrowband and broadband noise signals show that the proposed technique outperforms other state-of-the-art methods in terms of model accuracy and convergence rate.

Temporary threshold shift after impulse-noise during video game play: Laboratory data

Objective: Prevention of temporary threshold shift (TTS) after laboratory-based exposure to pure-tones, broadband noise, and narrowband noise signals has been achieved, but prevention of TTS under these experimental conditions may not accurately reflect protection against hearing loss following impulse noise. This study used a controlled laboratory-based TTS paradigm that incorporated impulsive stimuli into the exposure protocol; development of this model could provide a novel platform for assessing proposed therapeutics. Design: Participants played a video game that delivered gunfire-like sound through headphones as part of a target practice game. Effects were measured using audiometric threshold evaluations and distortion product otoacoustic emissions (DPOAEs). The sound level and number of impulses presented were sequentially increased throughout the study. Study sample: Participants were normal-hearing students at the University of Florida who provided written informed consent prior to participation. Results: TTS was not reliably induced by any of the exposure conditions assessed here. However, there was significant individual variability, and a subset of subjects showed TTS under some exposure conditions. Conclusions: A subset of participants demonstrated reliable threshold shifts under some conditions. Additional experiments are needed to better understand and optimize stimulus parameters that influence TTS after simulated impulse noise.

Dependency of tonality perception on frequency, bandwidth, and duration

Psychoacoustic studies show that a narrowband noise masker exhibits a stronger simultaneous masking effect than a tonal masker with the same signal power placed at the noise center frequency. Consequently, perceptual audio codecs commonly incorporate some sort of tonality estimation as part of their perceptual model. However, common tonality estimation techniques do not necessarily reflect the perception of tonality by human listeners. As long as the tone and narrowband noise signals are long enough, they are easily distinguishable for normal hearing listeners. However, if the stimulus duration decreases, both signal types approach the shape of impulses, and therefore, at some point become audibly identical. Consequently, at a given frequency and noise bandwidth, there is a duration threshold below which the signals cannot be distinguished. A series of so-called “2-AFC 3-step up-down” psychoacoustic tests are designed and carried out to investigate the frequency and bandwidth dependency of these duration thresholds. The test results, collected from 32 listeners, are statistically evaluated and confirm a decreasing threshold for increasing center frequency and bandwidth. These results can be used to improve psychoacoustic models for audio codecs by using tonality estimators with frequency and bandwidth adapted temporal resolution.

Relation between loudness in categorical units and loudness in phons and sones

Data are presented on the relation between loudness measured in categorical units (CUs) using a standardized loudness scaling method (ISO 16832, 2006) and loudness expressed as the classical standardized measures phon and sone. Based on loudness scaling of narrowband noise signals by 31 normal-hearing subjects, sound pressure levels eliciting the same categorical loudness were derived for various center frequencies. The results were comparable to the standardized equal-loudness level contours. A comparison between the loudness function in CUs at 1000 Hz and the standardized loudness function in sones indicates a cubic relation between the two loudness measures.

Loudness of sounds with a subcritical bandwidth

The predicted loudness for narrowband signals with bandwidths smaller than the bandwidth of the auditory filter, i.e., with a subcritical bandwidth, depends on the type of loudness model. While models analyzing the long-term spectrum (stationary loudness models) predict loudnesses for these subcritical signals which are independent of the bandwidth of the sound, models sensitive to the temporal structure of the signal (dynamic loudness models) predict higher loudnesses for narrowband noise signals than for tones due to the inherent level fluctuations of the noise. The present study measures the loudness of subcritical sounds for center frequencies of 750, 1500, and 3000 Hz. For all three center frequencies, the level of the narrowband noise had to be up to 5 dB higher than the level of the equally-loud tone at the center frequency. This experimental finding is at odds with both predictions, i.e., the loudness is neither the same for all signals nor is the level of the narrowband noise smaller than that of...

Spectral profile cues in comodulation masking release

Previous work on spectral shape discrimination has shown that detection of a level increment in one tone of a tonal complex is dependent on spectral position, with thresholds forming a "bowl" pattern for components spanning 200 to 5000 Hz [Green, D. M., (1988). Profile Analysis: Auditory Intensity Discrimination (Oxford University Press, New York)]. The current study examined whether a similar bowl occurs for comodulation masking release, a paradigm in which dynamic spectral cues could be used to detect an added signal. Maskers were logarithmically spaced 15-Hz-wide bands of noise. The signal was a tone or a copy of the on-signal masker band. When the masker was composed of one or more random bands, thresholds were relatively consistent across frequency. When the masker was a set of comodulated bands, thresholds for both signal types formed a bowl, but the minimum threshold occurred at a higher signal frequency for the tonal than for the narrowband noise signal. Results for additional conditions indicate that spectral effects depend on both absolute frequency and relative frequency of the signal within the masker. Data collected with flanking maskers presented contralateral to the signal and on-signal masker indicate that peripheral effects may play a role in threshold elevation at high signal frequencies with narrowband noise signals.

Broadband Microwave Correlator of Noise Signals

Broadband Microwave Correlator of Noise SignalsA real narrowband noise signal representation in the form of an analytical signal in the Hilbert space is presented in the paper. This analytical signal is illustrated in a variable complex plane as a mark with defined amplitude, phase, pulsation and instantaneous frequency. A block diagram of a broadband product detector in a quadrature system is presented. Measurement results of an autocorrelation function of a noise signal are shown and the application of such solution in a noise radar for precise determination of distance changes as well as velocities of these changes are also presented. Conclusions and future plans for applications of the presented detection technique in broadband noise radars bring the paper to an end.

Underwater hearing sensitivity of harbor seals (Phoca vitulina) for narrow noise bands between 0.2 and 80 kHz

The underwater hearing sensitivities of two 1.5-year-old female harbor seals were quantified in a quiet pool built specifically for acoustic research, by using a behavioral psychoacoustic technique. The animals were trained to respond when they detected an acoustic signal and not to respond when they did not ("go/no-go" response). Fourteen narrowband noise signals (1/3-octave bands but with some energy in adjacent bands), at 1/3-octave center frequencies of 0.2-80 kHz, and of 900 ms duration, were tested. Thresholds at each frequency were measured using the up-down staircase method and defined as the stimulus level resulting in a 50% detection rate. Between 0.5 and 40 kHz, the thresholds corresponded to a 1/3-octave band noise level of approximately 60 dB re 1 microPa (SD+/-3.0 dB). At lower frequencies, the thresholds increased to 66 dB re 1 microPa and at 80 kHz the thresholds rose to 114 dB re 1 microPa. The 1/3-octave noise band thresholds of the two seals did not differ from each other, or from the narrowband frequency-modulated tone thresholds at the same frequencies obtained a few months before for the same animals. These hearing threshold values can be used to calculate detection ranges of underwater calls and anthropogenic noises by harbor seals.