A note on pure-tone masking by broadband noise under free-field and insert-phone conditions (L)

2005 ◽  
Vol 117 (2) ◽  
pp. 490-491 ◽  
Author(s):  
Adrianus J. M. Houtsma
Keyword(s):  
Pure Tone ◽  
Free Field ◽  
Broadband Noise

scholarly journals Equal-loudness levels measured with the method of constant stimuli Equal-loudness level contours for pure tone under free-field listening conditions (II).

1997 ◽  
Vol 18 (6) ◽  
pp. 337-340 ◽  
Author(s):  
Hisashi Takeshima ◽  
Yôiti Suzuki ◽  
Masazumi Kumagai ◽  
Toshio Sone ◽  
Takeshi Fujimori ◽  
...  
Keyword(s):  
Pure Tone ◽  
Free Field ◽  
Loudness Level ◽  
Method Of Constant Stimuli

scholarly journals Turbomachinery Noise Predictions: Present and Future

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 92-116 ◽  
Author(s):  
Stéphane Moreau
Keyword(s):  
Hybrid Methods ◽  
Free Field ◽  
Broadband Noise ◽  
Large Eddy Simulations ◽  
Analytical Models ◽  
Flat Plates ◽  
Tonal Noise ◽  
Noise Sources ◽  
Large Eddy ◽  
Rans Simulations

In future Ultra-High By-Pass Ratio turboengines, the turbomachinery noise (fan and turbine stages mainly) is expected to increase significantly. A review of analytical models and numerical methods to yield both tonal and broadband contributions of such noise sources is presented. The former rely on hybrid methods coupling gust response over very thin flat plates of finite chord length, either isolated or in cascade, and acoustic analogies in free-field and in a duct. The latter yields tonal noise with unsteady Reynolds-Averaged Navier–Stokes (u-RANS) simulations, and broadband noise with Large Eddy Simulations (LES). The analytical models are shown to provide good and fast first sound estimates at pre-design stages, and to easily separate the different noise sources. The u-RANS simulations are now able to give accurate estimates of tonal noise of the most complex asymmetric, heterogeneous fan-Outlet Guiding Vane (OGV) configurations. Wall-modeled LES on rescaled stage configurations have now been achieved on all components: a low-pressure compressor stage, a transonic high-pressure turbine stage and a fan-OGV configuration with good overall sound power level predictions for the latter. In this case, hybrid Lattice–Boltzmann/very large-eddy simulations also appear to be an excellent alternative to yield both contributions accurately at once.

Acoustic Reflex Testing in Neonatal Hearing Screening and Subsequent Audiological Evaluation

2018 ◽  
Vol 61 (7) ◽  
pp. 1784-1793
Author(s):  
Lilian Cássia Bórnia Jacob-Corteletti ◽  
Eliene Silva Araújo ◽  
Josilene Luciene Duarte ◽  
Fernanda Zucki ◽  
Kátia de Freitas Alvarenga
Keyword(s):  
Risk Factors ◽  
Birth Weight ◽  
Gestational Age ◽  
Pure Tone ◽  
Broadband Noise ◽  
Acoustic Reflex ◽  
Group I ◽  
Group Ii ◽  
Gestational Age At Birth ◽  
Age At Birth

Purpose The aims of the study were to examine the acoustic reflex screening and threshold in healthy neonates and those at risk of hearing loss and to determine the effect of birth weight and gestational age on acoustic stapedial reflex (ASR). Method We assessed 18 healthy neonates (Group I) and 16 with at least 1 risk factor for hearing loss (Group II); all of them passed the transient evoked otoacoustic emission test that assessed neonatal hearing. The test battery included an acoustic reflex screening with activators of 0.5, 1, 2, and 4 kHz and broadband noise and an acoustic reflex threshold test with all of them, except for the broadband noise activator. Results In the evaluated neonates, the main risk factors were the gestational age at birth and a low birth weight; hence, these were further analyzed. The lower the gestational age at birth and birth weight, the less likely that an acoustic reflex would be elicited by pure-tone activators. This effect was significant at the frequencies of 0.5, 1, and 2 kHz for gestational age at birth and at the frequencies of 1 and 2 kHz for birth weight. When the broadband noise stimulus was used, a response was elicited in all neonates in both groups. When the pure-tone stimulus was used, the Group II showed the highest acoustic reflex thresholds and the highest percentage of cases with an absent ASR. The ASR threshold varied from 50 to 100 dB HL in both groups. Group II presented higher mean ASR thresholds than Group I, this difference being significant at frequencies of 1, 2, and 4 kHz. Conclusions Birth weight and gestational age at birth were related to the elicitation of the acoustic reflex. Neonates with these risk factors for hearing impairment were less likely to exhibit the acoustic reflex and had higher thresholds.

scholarly journals Noise Elimination of a Multi-tone Broadband Noise with Hybrid Helmholtz Mufflers Using a Simulated Annealing Method

2012 ◽  
Vol 37 (4) ◽  
pp. 489-498 ◽  
Author(s):  
Min-Chie Chiu
Keyword(s):  
Simulated Annealing ◽  
Shape Optimization ◽  
Noise Reduction ◽  
Noise Level ◽  
Pure Tone ◽  
Helmholtz Resonator ◽  
Broadband Noise ◽  
Simulated Annealing Method ◽  
Machine Room ◽  
Annealing Method

Abstract Noise control is essential in an enclosed machine room where the noise level has to comply with the occupational safety and health act. In order to overcome a pure tone noise with a high peak value that is harmful to human hearing, a traditional reactive muffler has been used. However, the traditional method for designing a reactive muffler has proven to be time-consuming and insufficient. In order to efficiently reduce the peak noise level, interest in shape optimization of a Helmholtz muffler is coming to the forefront. Helmholtz mufflers that deal with a pure tone have been adequately researched. However, the shape optimization of multi-chamber Helmholtz mufflers that deal with a broadband noise hybridized with multiple tones within a constrained space has been mostly ignored. Therefore, this study analyzes the sound transmission loss (STL) and the best optimized design for a hybrid Helmholtz muffler under a space- constrained situation. On the basis of the plane wave theory, the four-pole system matrix used to evaluate the acoustic performance of a multi-tone hybrid Helmholtz muffler is presented. Two numerical cases for eliminating one/two tone noises emitted from a machine room using six kinds of mufflers (muffler A~F) is also introduced. To find the best acoustical performance of a space-constrained muffler, a numerical assessment using a simulated annealing (SA) method is adopted. Before the SA operation can be carried out, the accuracy of the mathematical model has been checked using the experimental data. Eliminating a broadband noise hybridized with a pure tone (130 Hz) in Case I reveals that muffler C composed of a one- chamber Helmholtz Resonator and a one-chamber dissipative element has a noise reduction of 54.9 (dB). Moreover, as indicated in Case II, muffler F, a two-chamber Helmholtz Resonator and a one-chamber dissipative element, has a noise reduction of 69.7 (dB). Obviously, the peak values of the pure tones in Case I and Case II are efficiently reduced after the muffler is added. Consequently, a successful approach in eliminating a broadband noise hybridized with multiple tones using optimally shaped hybrid Helmholtz mufflers and a simulated annealing method within a constrained space is demonstrated.

Active Noise Control Using Multi-Layered Perceptron Neural Networks

1997 ◽  
Vol 16 (2) ◽  
pp. 109-144 ◽  
Author(s):  
M.O. Tokhi ◽  
R. Wood
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Network Architecture ◽  
Noise Control ◽  
Learning Algorithm ◽  
Free Field ◽  
Active Noise Control ◽  
Three Dimensional ◽  
Broadband Noise ◽  
Active Noise

This paper presents the development of a neuro-adaptive active noise control (ANC) system. Multi-layered perceptron neural networks with a backpropagation learning algorithm are considered in both the modelling and control contexts. The capabilities of the neural network in modelling dynamical systems are investigated. A feedforward ANC structure is considered for optimum cancellation of broadband noise in a three-dimensional propagation medium. An on-line adaptation and training mechanism allowing a neural network architecture to characterise the optimal controller within the ANC system is developed. The neuro-adaptive ANC algorithm thus developed is implemented within a free-field environment and simulation results verifying its performance are presented and discussed.

scholarly journals Equal-loudness level contours for pure tone under free field listening conditions. (I). Some data and considerations on experimental conditions.

1989 ◽  
Vol 10 (6) ◽  
pp. 329-338 ◽  
Author(s):  
Seiki Suzuki ◽  
Yoiti Suzuki ◽  
Shunichi Kono ◽  
Toshio Sone ◽  
Masazumi Kumagai ◽  
...  
Keyword(s):  
Pure Tone ◽  
Free Field ◽  
Experimental Conditions ◽  
Loudness Level

Complex and Pure-Tone Signals in the Evaluation of Hearing-Aid Characteristics

1990 ◽  
Vol 33 (2) ◽  
pp. 380-385 ◽  
Author(s):  
Patricia G. Stelmachowicz ◽  
Dawna E. Lewis ◽  
Richard C. Seewald ◽  
David B. Hawkins
Keyword(s):  
Hearing Aids ◽  
Pure Tone ◽  
Hearing Aid ◽  
Broadband Noise ◽  
Clinical Implications ◽  
Maximum Output ◽  
Complex Signals ◽  
Theoretical Issues

In recent years, a number of commercially available systems have been developed to analyze the electroacoustic characteristics of hearing aids. In addition to pure-tone signals, these systems often use a wide variety of complex signals such as broadband noise, clicks, and multitonal complexes. In this paper, a number of practical and theoretical issues concerning the use of pure-tone and complex signals in the evaluation of hearing-aid characteristics are described. The circumstances under which discrepancies in estimated gain and maximum output might occur using these two types of signals are described and the clinical implications of these differences are discussed.

Masking in Three-Dimensional Auditory Displays

1992 ◽  
Vol 34 (3) ◽  
pp. 255-265 ◽  
Author(s):  
Theodore J. Doll ◽  
Thomas E. Hanna ◽  
Joseph S. Russotti
Keyword(s):  
Head Movement ◽  
Signal To Noise Ratio ◽  
Free Field ◽  
Three Dimensional ◽  
Angular Separation ◽  
Broadband Noise ◽  
Auditory Display ◽  
Signal To Noise ◽  
Correlated Sources ◽  
Auditory Displays

The extent to which simultaneous inputs in a three-dimensional (3D) auditory display mask one another was studied in a simulated sonar task. The minimum signal-to-noise ratio (SNR) required to detect an amplitude-modulated SOO-Hz tone in a background of broadband noise was measured using a loudspeaker array in a free field. Three aspects of the 3D array were varied: angular separation of the sources, degree of correlation of the background noises, and listener head movement. Masking was substantially reduced when the sources were uncorrelated. The SNR needed for detection decreased with source separation, and the rate of decrease was significantly greater with uncorrelated sources than with partially or fully correlated sources. Head movement had no effect on the SNR required for detection. Implications for the design and application of 3D auditory displays are discussed.

Spontaneous and sound-evoked discharge characteristics of complex-spiking neurons in the dorsal cochlear nucleus of the unanesthetized decerebrate cat

1995 ◽  
Vol 73 (2) ◽  
pp. 550-561 ◽  
Author(s):  
K. Parham ◽  
D. O. Kim
Keyword(s):  
Cochlear Nucleus ◽  
Pure Tone ◽  
Broadband Noise ◽  
Dorsal Cochlear Nucleus ◽  
Projection Neurons ◽  
Response Latencies ◽  
Discharge Characteristics ◽  
Decerebrate Cat ◽  
Complex Spikes ◽  
Cartwheel Cells

1. We examined the spontaneous and sound-evoked discharge characteristics of 20 complex-spiking units recorded in the dorsal cochlear nucleus (DCN) of 15 unanesthetized, decerebrate cats. 2. The extracellularly recorded complex spikes consisted of bursts of two to five action potentials whose size gradually decreased during the burst. Complex spikes were observed both in the spontaneous and sound-evoked activity of the units in our sample. 3. The spontaneous rates (SRs) of DCN complex-spiking units ranged from 0 to 30 spikes/s. Spontaneous activity consisted of complex and simple (i.e., the common single neuronal action potential) spikes. Comparison of the SR distributions of the DCN complex-spiking units with that of a total sample of 194 DCN units (from 9 cats) suggests that the complex-spiking units tended to be in the lower half of the DCN SR distribution. 4. Sound-evoked discharges could consist of both complex and simple spikes. On the basis of their sound-driven responses, we divided the DCN complex-spiking units into two groups. The majority (15 of 20, 75%) were weakly driven by pure tones and inhibited by broadband noise. They tended to have broad response areas. Their response latencies to pure tone and noise stimuli were relatively long (10-20 ms). The recording depths of these units tended to be superficial (i.e., 10 of 15 units were located within 400 microns of the dorsal surface of the DCN). A minority (5 of 20, 25%) of the complex-spiking units were strongly driven by pure tone and broadband noise stimuli. These units had more clearly defined excitatory regions of response areas than the weakly driven units. Their response latencies to pure tone and noise stimuli were short (< 10 ms). The recording depths of these units tended to be deeper (i.e., 4 of 5 units were located at 400-700 microns) than those of the weakly driven units. 5. Intracellular recording and labeling studies of in vitro DCN slice preparations have correlated complex spikes with the superficially located cartwheel cells. Given the complex spikes of the units, many of which were located superficially, we suggest that our sample, particularly the weakly driven group of neurons, corresponds to the cartwheel cells. 6. Cartwheel cells are putative inhibitory interneurons whose axons primarily contact on the main projection neurons of DCN, the fusiform cells. The present finding of sound-evoked discharges by the superficially located complex-spiking units suggests that cartwheel cells should play a role in modifying the sound-evoked responses of the fusiform cells.

Shape Optimization of Mufflers Composed of Multiple Rectangular Fin-Shaped Chambers Using Differential Evolution Method

2015 ◽  
Vol 40 (3) ◽  
pp. 311-319 ◽  
Author(s):  
Min-Chie Chiu ◽  
Ying-Chun Chang ◽  
Ho-Chih Cheng ◽  
Wei-Ting Tai
Keyword(s):  
Differential Evolution ◽  
Pure Tone ◽  
Wave Theory ◽  
Broadband Noise ◽  
Acoustic Performance ◽  
Constrained Problem ◽  
Numerical Assessment ◽  
Successful Approach ◽  
Pure Tones ◽  
The Mathematical Model

Abstract There has been considerable research done on multi-chamber mufflers used in the elimination of industrial venting noise. However, most research has been restricted to lower frequencies using the plane wave theory. This has led to underestimating acoustical performances at higher frequencies. Additionally, because of the space-constrained problem in most plants, the need for optimization of a compact muffler seems obvious. Therefore, a muffler composed of multiple rectangular fin-shaped chambers is proposed. Based on the eigenfunction theory, a four-pole matrix used to evaluate the acoustic performance of mufflers will be deduced. A numerical case for eliminating pure tones using a three-fin-chamber muffler will also be examined. To delineate the best acoustical performance of a space-constrained muffler, a numerical assessment using the Differential Evolution (DE) method is adopted. Before the DE operation for pure tone elimination can be carried out, the accuracy of the mathematical model must be checked using experimental data. The results reveal that the broadband noise has been efficiently reduced using the three-fin-chamber muffler. Consequently, a successful approach in eliminating a pure tone using optimally shaped three-fin-chamber mufflers and a differential evolution method within a constrained space has been demonstrated.

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