MODELLING OF THE NOISE SPECTRA OF AXIAL FLOW FANS IN A FREE FIELD

1997 ◽  
Vol 200 (4) ◽  
pp. 379-399 ◽  
Author(s):  
S.F. Wu ◽  
S.G. Su ◽  
H.S. Shah
Keyword(s):  
Free Field ◽  
Axial Flow ◽  
Noise Spectra

Modeling of noise spectra of axial flow fans in free field.

1996 ◽  
Vol 99 (4) ◽  
pp. 2509-2529
Author(s):  
Shigong Su ◽  
Sean F. Wu ◽  
Hemant S. Shah
Keyword(s):  
Free Field ◽  
Axial Flow ◽  
Noise Spectra

Investigation of Centrifugal Blower Noise

1999 ◽  
Author(s):  
Christopher L. Banks ◽  
Sean F. Wu
Keyword(s):  
Radiation Pattern ◽  
Free Field ◽  
Sound Radiation ◽  
Noise Generation ◽  
Centrifugal Blower ◽  
Noise Radiation ◽  
Passenger Vehicles ◽  
Generation Mechanisms ◽  
Semi Empirical ◽  
Noise Spectra

Abstract This paper presents the results of an ongoing investigation of noise radiation from centrifugal blowers used in passenger vehicles. The semi-empirical formulation previously derived by the authors (1998) for predicting noise spectra of centrifugal blowers running in a free field is extended to centrifugal blowers installed in a HVAC scroll housing. Because of the presence of the scroll and cutoff, the flow fields are different from those in a free field. Accordingly, the noise generation mechanisms become much more difficult to analyze and model. The previous model assumed a monopole type sound radiation pattern, and predicted the broadband component of the noise spectra well. This model is extended to include the contributions of both monopole and directional dipole sound radiation. It is this complex radiation that is characteristic of a centrifugal blower situated inside a scroll housing with a cutoff. Comparisons of the calculated and measured noise spectra were demonstrated, and good agreements were obtained in all cases.

The Effect of Nonlinear Amplitude Growth on the Speech Perception Benefits Provided by a Single-Sided Vocoder

2019 ◽  
Vol 62 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Jessica M. Wess ◽  
Joshua G. W. Bernstein
Keyword(s):  
Transfer Functions ◽  
Spatial Configuration ◽  
Free Field ◽  
Spatial Separation ◽  
Compression And Expansion ◽  
Interaural Difference ◽  
Interaural Differences ◽  
Single Sided Deafness ◽  
Perceptual Separation ◽  
Loudness Growth

PurposeFor listeners with single-sided deafness, a cochlear implant (CI) can improve speech understanding by giving the listener access to the ear with the better target-to-masker ratio (TMR; head shadow) or by providing interaural difference cues to facilitate the perceptual separation of concurrent talkers (squelch). CI simulations presented to listeners with normal hearing examined how these benefits could be affected by interaural differences in loudness growth in a speech-on-speech masking task.MethodExperiment 1 examined a target–masker spatial configuration where the vocoded ear had a poorer TMR than the nonvocoded ear. Experiment 2 examined the reverse configuration. Generic head-related transfer functions simulated free-field listening. Compression or expansion was applied independently to each vocoder channel (power-law exponents: 0.25, 0.5, 1, 1.5, or 2).ResultsCompression reduced the benefit provided by the vocoder ear in both experiments. There was some evidence that expansion increased squelch in Experiment 1 but reduced the benefit in Experiment 2 where the vocoder ear provided a combination of head-shadow and squelch benefits.ConclusionsThe effects of compression and expansion are interpreted in terms of envelope distortion and changes in the vocoded-ear TMR (for head shadow) or changes in perceived target–masker spatial separation (for squelch). The compression parameter is a candidate for clinical optimization to improve single-sided deafness CI outcomes.

Underlying Structure of Auditory-Visual Consonant Perception by Hearing-Impaired Children and the Influences of Syllabic Compression

1988 ◽  
Vol 31 (2) ◽  
pp. 156-165 ◽  
Author(s):  
P. A. Busby ◽  
Y. C. Tong ◽  
G. M. Clark
Keyword(s):  
Hearing Aids ◽  
Free Field ◽  
Acoustic Parameter ◽  
Hearing Impaired ◽  
Visual Signal ◽  
Underlying Structure ◽  
Choice Procedure ◽  
Release Times ◽  
Impaired Children ◽  
Hearing Impaired Children

The identification of consonants in a/-C-/a/nonsense syllables, using a fourteen-alternative forced-choice procedure, was examined in 4 profoundly hearing-impaired children under five conditions: audition alone using hearing aids in free-field (A),vision alone (V), auditory-visual using hearing aids in free-field (AV1), auditory-visual with linear amplification (AV2), and auditory-visual with syllabic compression (AV3). In the AV2 and AV3 conditions, acoustic signals were binaurally presented by magnetic or acoustic coupling to the subjects' hearing aids. The syllabic compressor had a compression ratio of 10:1, and attack and release times were 1.2 ms and 60 ms. The confusion matrices were subjected to two analysis methods: hierarchical clustering and information transmission analysis using articulatory features. The same general conclusions were drawn on the basis of results obtained from either analysis method. The results indicated better performance in the V condition than in the A condition. In the three AV conditions, the subjects predominately combined the acoustic parameter of voicing with the visual signal. No consistent differences were recorded across the three AV conditions. Syllabic compression did not, therefore, appear to have a significant influence on AV perception for these children. A high degree of subject variability was recorded for the A and three AV conditions, but not for the V condition.

Human Event-Related Potentials to Higher-Order Acoustic Spatial Changes

2002 ◽  
Vol 16 (2) ◽  
pp. 114-118 ◽  
Author(s):  
Timo Ruusuvirta ◽  
Heikki Hämäläinen
Keyword(s):  
Working Memory ◽  
Mismatch Negativity ◽  
Spatial Information ◽  
Free Field ◽  
Event Related Potentials ◽  
Negative Polarity ◽  
Positive Polarity ◽  
Spatial Changes ◽  
Related Potentials ◽  
Human Event

Abstract Human event-related potentials (ERPs) to a tone continuously alternating between its two spatial loci of origin (middle-standards, left-standards), to repetitions of left-standards (oddball-deviants), and to the tones originally representing these repetitions presented alone (alone-deviants) were recorded in free-field conditions. During the recordings (Fz, Cz, Pz, M1, and M2 referenced to nose), the subjects watched a silent movie. Oddball-deviants elicited a spatially diffuse two-peaked deflection of positive polarity. It differed from a deflection elicited by left-standards and commenced earlier than a prominent deflection of negative polarity (N1) elicited by alone-deviants. The results are discussed in the context of the mismatch negativity (MMN) and previous findings of dissociation between spatial and non-spatial information in auditory working memory.

Spatial audio displays for speech communications: A comparison of free field and virtual acoustic environments

1999 ◽  
Author(s):  
W. Todd Nelson ◽  
Robert S. Bolia ◽  
Mark A. Ericson ◽  
Richard L. McKinley
Keyword(s):  
Free Field ◽  
Spatial Audio ◽  
Acoustic Environments

Hemodynamic effects of pump flow reduction in patients with axial flow pumps during exercise training

2012 ◽  
Vol 60 (S 01) ◽  
Author(s):  
P Ganslmeier ◽  
HJ Schneider ◽  
A Keyser ◽  
M Michl ◽  
M Foltan ◽  
...  
Keyword(s):  
Exercise Training ◽  
Axial Flow ◽  
Hemodynamic Effects ◽  
Flow Reduction ◽  
Pump Flow
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