Types Of Background Noise Research Articles

Computational auditory models in predicting noise reduction performance for wideband telephony applications

The performance of several noise reduction algorithms intended for wideband telephony was evaluated both subjectively and objectively. The chosen algorithms were based on statistical modeling, spectral subtraction, Wiener filtering, or subspace modelling principles. A customized wideband noise reduction database containing speech samples corrupted by three types of background noises at three SNR levels, along with their enhanced versions was created. The overall quality of the speech samples in the database was subsequently rated by a group of listeners with normal hearing capabilities. Comprehensive statistical analyses were performed to assess the reliability of the subjective data, and to assess the performance of noise reduction algorithms across varied noisy conditions. The subjective quality ratings were then used to investigate the performance of several auditory model-based objective quality metrics. Key results from these investigations include: (a) there was a high degree of inter- and intra-subject reliability in the subjective ratings, (b) noise reduction algorithms enhance speech quality for only a subset of the noise conditions, and (c) auditory model-based metrics perform similarly in predicting speech quality ratings, when speech quality scores pertaining to a particular noise condition were averaged.

Auditory filter tuning inferred with short sinusoidal and notched-noise maskers.

The physiology of the medial olivocochlear reflex suggests that a sufficiently long stimulus (>100 ms) may reduce cochlear gain and result in broadened frequency selectivity. The current study attempted to avoid gain reduction by using short maskers (20 ms) to measure psychophysical tuning curves (PTCs) and notched-noise tuning characteristics, with a 4-kHz signal. The influence of off-frequency listening on PTCs was evaluated using two types of background noise. Iso-level curves were derived using an estimate of the cochlear input/output (I/O) function, which was obtained using an off-frequency masker as a linear reference. The influence of masker duration on PTCs was assessed using a model that assumed long maskers (>20 ms) evoked gain reduction. The results suggested that the off-frequency masker was a valid linear reference when deriving I/O functions and that off-frequency listening may have occurred in auditory filters apical to the signal place. The iso-level curves from this growth-of-masking study were consistent with those from a temporal-masking-curve study by Eustaquio-Martin and Lopez-Poveda [J. Assoc. Res. Otolaryngol. 12, 281-299. (2011)], suggesting that either approach may be used to derive iso-level curves. Finally, model simulations suggested that masker duration may not influence estimates of frequency selectivity.

Influence of background noise on the performance in the odor sensitivity task: effects of noise type and extraversion

Recent research demonstrated that background noise relative to silence impaired subjects' performance in a cognitively driven odor discrimination test. The current study aimed to investigate whether the background noise can also modulate performance in an odor sensitivity task that is less cognitively loaded. Previous studies have shown that the effect of background noise on task performance can be different in relation to degree of extraversion and/or type of noise. Accordingly, we wanted to examine whether the influence of background noise on the odor sensitivity task can be altered as a function of the type of background noise (i.e., nonverbal vs. verbal noise) and the degree of extraversion (i.e., introvert vs. extrovert group). Subjects were asked to conduct an odor sensitivity task in the presence of either nonverbal noise (e.g., party sound) or verbal noise (e.g., audio book), or silence. Overall, the subjects' mean performance in the odor sensitivity task was not significantly different across three auditory conditions. However, with regard to the odor sensitivity task, a significant interaction emerged between the type of background noise and the degree of extraversion. Specifically, verbal noise relative to silence significantly impaired or improved the performance of the odor sensitivity task in the introvert or extrovert group, respectively; the differential effect of introversion/extraversion was not observed in the nonverbal noise-induced task performance. In conclusion, our findings provide new empirical evidence that type of background noise and degree of extraversion play an important role in modulating the effect of background noise on subjects' performance in an odor sensitivity task.

Characteristics of noise-canceling headphones to reduce the hearing hazard for MP3 users

Three pairs of headphones [standard iPod ear buds and two noise-canceling headphones (NCHs)] were chosen to investigate frequency characteristics of noise reduction, together with their attenuation effects on preferred listening levels (PLLs) in the presence of various types of background noise. Twenty-six subjects with normal hearing chose their PLLs in quiet, street noise, and subway noise using the three headphones and with the noise-canceling system on/off. Both sets of NCHs reduced noise levels at mid- and high-frequencies. Further noise reductions occurred in low frequencies with the noise canceling system switched on. In street noise, both NCHs had similar noise reduction effects. In subway noise, better noise reduction effects were found in the expensive NCH and with noise-canceling on. A two way repeated measures analysis of variance showed that both listening conditions and headphone styles were significant influencing factors on the PLLs. Subjects tended to increase their PLLs as the background noise level increased. Compared with ear buds, PLLs obtained from NCHs-on in the presence of background noise were reduced up to 4 dB. Therefore, proper selection and use of NCHs appears beneficial in reducing the risk of hearing damage caused by high music listening levels in the presence of background noise.

Speech Intelligibility and Passive, Level-Dependent Earplugs

Noise-induced hearing loss is one of the most common occupational diseases. Military personnel are at especially high risk due to the broad range of military noise hazards and the frequency of exposure. Hearing protectors are vital for this particular workforce, yet they can impede the ability to understand necessary communication in the field. Level-dependent hearing protectors are designed to protect the auditory system from the hazards of impulse noise, while preserving the ability to hear speech and other important auditory signals. The aim of this study was to evaluate the effect of two different passive, level-dependent earplugs (Combat Arms Earplugs; Sonic II Ear valves) on speech understanding of normal-hearing listeners in the presence of low-level background noise. The Combat Arms Earplug, developed specifically for use by military personnel, represented devices that attenuate impulse noise using small orifices and the Sonic II ear valve represented devices using an internal diaphragm. This study used a repeated-measures experimental design. Four scrambled lists of each of the four Northwestern University No. 6 50-word lists were presented in random order at 65 dB SPL in the presence of quiet and two different types of background noise: multitalker and military vehicle noise; using three ear conditions: NP (open ear), CA (Combat Arms Earplugs), and SO (Sonic II earplugs); and three signal-to-noise ratios (SNRs): -10, 0, and +10 dB. Word recognition scores (WRSs) of 18 native English-speaking adults with normal hearing sensitivity were measured in all test conditions. The percentage of words correctly repeated was used to determine differences between the two different level-dependent devices, types of background noise, and SNRs. Results showed a statistically significant increase in WRS as SNR increased from -10 to +10 dB. A repeated-measures analysis of variance for ear condition × noise × SNR indicated a significant main effect for SNR but not for type of noise or ear condition. A slight but significant interaction was found for SNR and ear condition. SNR had great impact on the ability of listeners to understand speech in the presence of background noise; however, the type of noise and the type of level-dependent device used did not. The results of the study support the notion that individuals potentially subjected to high-level impulse noise should be able to use level-dependent earplugs in low-level continuous noise without compromising speech understanding. More specifically, the passive, level-dependent earplugs currently used by military personnel do not appear to be detrimental to speech communication for listeners with normal hearing when the speech is at an average conversational level and the listener is actively attending to the signal.

Clinical Evaluation of Signal-to-Noise Ratio–Based Noise Reduction in Nucleus® Cochlear Implant Recipients

The aim of this study was to investigate whether a real-time noise reduction algorithm provided speech perception benefit for Cochlear™ Nucleus® cochlear implant recipients in the laboratory. The noise reduction algorithm attenuated masker-dominated channels. It estimated the signal-to-noise ratio of each channel on a short-term basis from a single microphone input, using a recursive minimum statistics method. In this clinical evaluation, the algorithm was implemented in two programs (noise reduction programs 1 [NR1] and 2 [NR2]), which differed in their level of noise reduction. These programs used advanced combination encoder (ACE™) channel selection and were compared with ACE without noise reduction in 13 experienced cochlear implant subjects. An adaptive speech reception threshold (SRT) test provided the signal-to-noise ratio for 50% sentence intelligibility in three different types of noises: speech-weighted, cocktail party, and street-side city noise. In all three noise types, mean SRTs for both NR programs were significantly better than those for ACE. The greatest improvement occurred for speech-weighted noise; the SRT benefit over ACE was 1.77 dB for NR1 and 2.14 dB for NR2. There were no significant differences in speech perception scores between the two NR programs. Subjects reported no degradation in sound quality with the experimental programs. The noise reduction algorithm was successful in improving sentence perception in speech-weighted noise, as well as in more dynamic types of background noise. The algorithm is currently being trialed in a behind-the-ear processor for take-home use.

Event-related potentials and perception of signals in several types of background noise.

Many factors contribute to successful perception of auditory stimuli in noise, including neural encoding in the central auditory system. Physiological measures such as event-related potentials (ERPs) can provide a view of neural encoding that may inform our understanding of listeners’ abilities to perceive signals in the presence of background noise. We set out to determine the effect of stimulus type on neural encoding and perception of signals in noise. Nine young, normal-hearing adults participated. ERPs were recorded (the N1-P2 and P3), and a sentence-in-noise identification task was completed in quiet and in three noise conditions: (1) steady-state speech spectrum noise, (2) interrupted noise, and (3) four-talker babble. Stimuli were presented at a signal-to-noise ratio of −3 dB. Results demonstrated significant effects of noise type on both physiological and behavioral measures with the four-talker babble condition showing the largest decrements in ERP and behavioral measures relative to testing in quiet. In addition, significant correlations were found between ERPs and sentence-in-noise measures. Differential effects of noise type on N1 and P3 ERPs will be discussed and compared with behavioral results. Results suggest that ERPs may be a useful tool for measuring neurophysiological correlates of energetic and informational masking.

Cortical Encoding of Signals in Noise: Effects of Stimulus Type and Recording Paradigm

Perception-in-noise deficits have been demonstrated across many populations and listening conditions. Many factors contribute to successful perception of auditory stimuli in noise, including neural encoding in the central auditory system. Physiological measures such as cortical auditory-evoked potentials (CAEPs) can provide a view of neural encoding at the level of the cortex that may inform our understanding of listeners' abilities to perceive signals in the presence of background noise. To understand signal-in-noise neural encoding better, we set out to determine the effect of signal type, noise type, and evoking paradigm on the P1-N1-P2 complex. Tones and speech stimuli were presented to nine individuals in quiet and in three background noise types: continuous speech spectrum noise, interrupted speech spectrum noise, and four-talker babble at a signal-to-noise ratio of -3 dB. In separate sessions, CAEPs were evoked by a passive homogenous paradigm (single repeating stimulus) and an active oddball paradigm. The results for the N1 component indicated significant effects of signal type, noise type, and evoking paradigm. Although components P1 and P2 also had significant main effects of these variables, only P2 demonstrated significant interactions among these variables. Signal type, noise type, and evoking paradigm all must be carefully considered when interpreting signal-in-noise evoked potentials. Furthermore, these data confirm the possible usefulness of CAEPs as an aid to understand perception-in-noise deficits.

Seismic sensor array for monitoring an avalanche start zone: design, deployment and preliminary results

AbstractIn snow, acoustic emissions originate from the breaking of bonds between snow crystals and the formation of cracks. Previous research has shown that acoustic signals emanate from a natural snowpack. The relation between these signals and the stability of the snowpack has thus far remained elusive. Studies on other hazardous gravitational processes suggest that damage accumulation precedes major failure. If increased cracking activity could be detected in snow this might be used for avalanche prediction. We report on the development of a seismic sensor array to continuously monitor acoustic emissions in an avalanche start zone. During three winters, over 1400 sensor days of continuous acoustic data were collected. With the aid of automatic cameras and a microphone the main types of background noise were identified. Seismic signals generated by avalanches were also identified. Spectrograms from seismic signals generated by avalanches exhibit a unique triangular shape unlike any source of background noise, suggesting that automatic detection and classification of events is possible. Furthermore, discriminating between loose-snow and snow-slab avalanches is possible. Thus far we have not identified precursor events for natural dry-snow slab avalanche release. Detailed investigation of one dry-snow slab avalanche showed that signals observed prior to the release originated from background noise or small loose-snow avalanches.

Ct3d: tracking microglia motility in 3D using a novel cosegmentation approach

Motivation: Cell tracking is an important method to quantitatively analyze time-lapse microscopy data. While numerous methods and tools exist for tracking cells in 2D time-lapse images, only few and very application-specific tracking tools are available for 3D time-lapse images, which is of high relevance in immunoimaging, in particular for studying the motility of microglia in vivo.Results: We introduce a novel algorithm for tracking cells in 3D time-lapse microscopy data, based on computing cosegmentations between component trees representing individual time frames using the so-called tree-assignments. For the first time, our method allows to track microglia in three dimensional confocal time-lapse microscopy images. We also evaluate our method on synthetically generated data, demonstrating that our algorithm is robust even in the presence of different types of inhomogeneous background noise.Availability: Our algorithm is implemented in the ct3d package, which is available under http://www.picb.ac.cn/patterns/Software/ct3d; supplementary videos are available from http://www.picb.ac.cn/patterns/Supplements/ct3d.Contact: axel@picb.ac.cn; forestdu@ion.ac.cnSupplementary information: Supplementary data are available at Bioinformatics online.

Erratum: “Speech reception by listeners with real and simulated hearing impairment: Effects of continuous and interrupted noise” [J. Acoust. Soc. Am. 128, 342–359 (2010)

Figures ​Figures55​566​677 of the original version of this paper erroneously omitted some of the descriptive material that assists in understanding the data presented. These amended figure captions provide clarification of these figures. Figure 5 Measurements of masked speech-reception thresholds (dB SPL) in 30 dB SPL continuous background noise types for Unaided (top panel) and NAL-RP aided (bottom panel) listening conditions. In each panel, the dB SPL threshold is plotted for the 10 HI listeners ... Figure 6 Measurements of masked speech-reception thresholds (S∕N) in four different background noise types for Unaided and NAL-RP aided listening conditions. In each panel, S∕N is plotted for a given HI listener (light gray) and for the corresponding ... Figure 7 Masking release (MR) as a function of noise level in Unaided and in NAL-RP aided listening conditions. In each panel, MR is plotted for a given HI listener (light gray) and for the corresponding AM-SIM (medium gray) and NAM-SIM (dark gray) groups. The ...

Robust Detection of Underwater Transient Signals Using EVRC Noise Suppression Module

Detection of transient signals is generally done by examining power and spectral variation of the received signal, but it becomes a difficult task when the background noise gets large. In this paper, we propose a robust transient detection algorithm using the EVRC noise suppression module. We define new parameters from the outputs of the EVRC noise suppression module for transient detection. Experimental results with various types of underwater transients have shown that the proposed method outperforms the conventional energy-based method and achieved performance improvement of detection rate by 7% to 15% for various types of background noise.

Diversity Coherent and Incoherent Receivers for Free-Space Optical Communication in the Presence and Absence of Interference

When communicating optically through the clear atmospheric channel, not only is there atmospheric turbulence and background noise, but there may also be interference from other sources such as other users in a multiple access system. Even if the interference is off axis, its signal can couple into the receiver through scattering. We would like our communication system to perform well in the presence of interference, background noise, and fading. This paper investigates the performance of diversity coherent and incoherent receivers in the presence of fading, background noise, and various interference types. We find that diversity coherent detection provides significant power gain over diversity direct detection and that most of the benefit of diversity coherent detection can be achieved with a small amount of diversity. Moreover, we find that diversity always improves the performance of coherent detection, whereas in the presence of worst-case interference, diversity degrades the performance of direct detection. This paper also describes a sensible way to select the amount of diversity and power margin to deal with atmospheric turbulence and interference and quantifies the amount of interference that the system can handle while still achieving a given outage probability.

Effects of Various Background Noises on Speech Intelligibility of Normal Hearing Subjects

Background and Objectives：In auditory tests, several kinds of background noises have been used；multitalker babble noise, speech noise and white noise, etc. The aim of the present study was to evaluate the effects of different types of background noises on speech intelligibility. Subjects and Method：Sixty volunteers having pure-tone thresholds less than 25 dB HL participated in this study. Their ages ranged from teens to sixties with ten subjects in each age group (mean age=40±15.4 years, m=25, f= 35) We used three types of background noises used in this study；multitalker babble noise using the voices of Korean speakers, speech noise using English sentences and white noise. Fifty percent recognition of signal to noise ratios (SNRs) and word recognition scores (WRSs) at -10, -5, 0 dB SNR conditions were measured at 70 dB HL of noise intensity. Results：Fifty percent recognition of SNRs on multitalker babble, speech and white noise were -12.4±1.4 dB, -13.7±1.0 dB and -15.8 ±1.0 dB, respectively and they were significantly different each other (p<0.05). Multitalker babble noise generated the lowest WRSs followed by speech noise and then white noise (p<0.05). Conclusion：These results support that multitalker babble noise using the voices of Korean speakers influence on normal listener’s speech intelligibility more than speech noise from English sentences or white noise. (Korean J Otorhinolaryngol-Head Neck Surg 2009;52:307-11)

Human Tracking System Integrating Sound and Face Localization Using an Expectation-Maximization Algorithm in Real Environments

We have developed a human tracking system for use by robots that integrate sound and face localization. Conventional systems usually require many microphones and/or prior information to localize several sound sources. Moreover, they are incapable of coping with various types of background noise. Our system, the cross-power spectrum phase analysis of sound signals obtained with only two microphones, is used to localize the sound source without having to use prior information such as impulse response data. An expectation-maximization (EM) algorithm is used to help the system cope with several moving sound sources. The problem of distinguishing whether sounds are coming from the front or back is also solved with only two microphones by rotating the robot's head. A developed method that uses facial skin colors classified by another EM algorithm enables the system to detect faces in various poses. It can compensate for the error in the sound localization for a speaker and also identify noise signals entering from undesired directions by detecting a human face. A developed probability-based method is used to integrate the auditory and visual information in order to produce a reliable tracking path in real-time. Experiments using a robot showed that our system can localize two sounds at the same time and track a communication partner while dealing with various types of background noise.

The effect of extending high-frequency bandwidth on the Acceptable Noise Level (ANL) of hearing-impaired listeners

This study examined the effects of extending high-frequency bandwidth, for both a speech signal and a background noise, on the acceptable signal-to-noise ratio (SNR) of listeners with mild sensorineural hearing loss through utilization of the Acceptable Noise Level (ANL) procedure. In addition to extending high-frequency bandwidth, the effects of reverberation time and background noise type and shape were also examined. The study results showed a significant increase in the mean ANL (i.e. participants requested a better SNR for an acceptable listening situation) when high-frequency bandwidth was extended from 3 to 9 kHz and from 6 to 9 kHz. No change in the ANL of study participants was observed as a result of isolated modification to reverberation time or background noise stimulus. An interaction effect, however, of reverberation time and background noise stimulus was demonstrated. These findings may have implications for future design of hearing aid memory programs for listening to speech in the presence of broadband background noise.

Performance Study of Objective Speech Quality Measurement for Modern Wireless-VoIP Communications

Wireless-VoIP communications introduce perceptual degradations that are not present with traditional VoIP communications. This paper investigates the effects of such degradations on the performance of three state-of-the-art standard objective quality measurement algorithms--PESQ, P.563, and an extended E-model. The comparative study suggests that measurement performance is significantly affected by acoustic background noise type and level as well as speech codec and packet loss concealment strategy. On our data, PESQ attains superior overall performance and P.563 and E-model attain comparable performance figures.

Objective Quality Evaluation Method for Noise-Reduced Speech

We present a method for the objective quality evaluation of noise-reduced speech in wideband speech communication services, which utilize speech with a wider bandwidth (e. g., 7kHz) than the usual telephone bandwidth. Experiments indicate that the amount of residual noise and the distortion of speech and noise, which are quality factors, influence the perceived quality degradation of noise-reduced speech. From the results, we observe the principal relationships between these quality factors and perceived speech quality. On the basis of these relationships, we propose a method that quantifies each quality factor in noise-reduced speech by analyzing signals that can be measured and assesses the over-all perceived quality of noise-reduced speech using values of these quality factors. To verify the validity of the method, we perform a subjective listening test and compare subjective quality of noise-reduced speech with its estimation. In the test, we use various types of background noise and noise-reduction algorithms. The verification results indicate that the correlation between subjective quality and its objective estimation is sufficiently high regardless of the type of background noise and noise-reduction algorithm.

A comparison between two methods for speech transmission quality assessment with noise simulation at receiver's side

Two auditory experiments are presented that were designed in order to compare two different methods for the assessment of speech quality when noise at listener's side is present: (1) Headphone presentation with samples pre‐recorded over a head and torso simulator, and (2) test participants located in a noisy environment, rendered by a 4.1 loudspeaker system. Real‐world types of background noise were employed as well as a variety of user terminals. The correlation between corresponding overall quality scores amounts to r = 0.9. Hence, a headphone presentation can replace a loudspeaker noise simulation in principle, leading to the consequence that a simpler experimental set‐up is sufficient for assessing the speech quality when noise is present at the receiver's side. However, there exist certain differences between both quality scores. For example, in most cases clean wideband (50‐7000 Hz) and standard narrow‐band (300‐3400 Hz) speech are rated slightly lower if the samples are presented over a headphone a...

Noise annoyance indicators for various industrial noise sources: Results and comparisons

Characterizing the environmental impact of an industrial plant goes through a better understanding of the noise annoyance caused by industrial noise sources, which are numerous and various. A first step was to construct a perceptive typology of various industrial noise sources from a categorization test and based on perceived similarities. Now, laboratory tests are carried out, for each perceptive category separately, through the same experimental procedure, by testing the influence of the sound pressure level and of the noise spectral characteristics (low frequency noise, tonal noiseœ) on noise annoyance. The effect of spectral modifications due to the noise propagation on noise annoyance is also assessed. Subjects have also to judge the annoyance induced by an ambient noise exposure, built with a background noise and an industrial noise for which the emergence level is controlled. Different types of background noises are studied. Through a statistical analysis, indicators are developed for each percepti...