Browsing by Subject "noise"

Now showing 1 - 5 of 5

An Audible Demonstration Of The Speed Of Sound In Bubbly Liquids
(2008-10) Wilson, Preston S.; Roy, Ronald A.; Wilson, Preston S.
The speed of sound in a bubbly liquid is strongly dependent upon the volume fraction of the gas phase, the bubble size distribution, and the frequency of the acoustic excitation. At sufficiently low frequencies, the speed of sound depends primarily on the gas volume fraction. This effect can be audibly demonstrated using a one-dimensional acoustic waveguide, in which the flow rate of air bubbles injected into a water-filled tube is varied by the user. The normal modes of the waveguide are excited by the sound of the bubbles being injected into the tube. As the flow rate is varied, the speed of sound varies as well, and hence, the resonance frequencies shift. This can be clearly heard through the use of an amplified hydrophone and the user can create aesthetically pleasing and even musical sounds. In addition, the apparatus can be used to verify a simple mathematical model known as Wood's equation that relates the speed of sound of a bubbly liquid to its void fraction. (c) 2008 American Association of Physics Teachers.
Ground Noise Survey at a Proposed Submarine Test Facility on Lake Travis
(Institute for Geophysics, 1987-12-18) Nakamura, Yosio; Sawyer, Dale S.; Roper, Phillip H.
Masking Release And Modulation Interference In Cochlear Implant And Simulation Listeners
(2013-06) Jin, Su-Hyun; Nie, Yingjiu; Nelson, Peggy; Jin, Su-Hyun
Purpose: To examine the effects of temporal and spectral interference of masking noise on sentence recognition for listeners with cochlear implants (CI) and normal-hearing persons listening to vocoded signals that simulate signals processed through a CI (NH-Sim). Method: NH-Sim and CI listeners participated in the experiments using speech and noise that were processed by bandpass filters. Depending on the experimental condition, the spectra of the maskers relative to that of speech were set to be completely embedded with, partially overlapping, or completely separate from, the speech. The maskers were either steady or amplitude modulated and were presented at +10 dB signal-to-noise ratio. Results: NH-Sim listeners experienced progressively more masking as the masker became more spectrally overlapping with speech, whereas CI listeners experienced masking even when the masker was spectrally remote from the speech signal. Both the NH-Sim and CI listeners experienced significant modulation interference when noise was modulated at a syllabic rate (4 Hz), suggesting that listeners may experience both modulation interference and masking release. Thus, modulated noise has mixed and counteracting effects on speech perception. Conclusion: When the NH-Sim and CI listeners with poor spectral resolution were tested using syllabic-like rates of modulated noise, they tended to integrate or confuse the noise with the speech, causing an increase in speech errors. Optional training programs might be useful for CI listeners who show more difficulty understanding speech in noise.
Speaking style adaptations across the lifespan
(2014-04) Ferracane, Elisa; Gilbert, Rachael; Smiljanic, Rajka; Johnson, Karen; Trimble-Quiz, Cristabella; Smiljanic, Rajka
In everyday life, speech communication occurs in suboptimal or adverse conditions (e.g., talking to a listener who is hard of hearing; presence of noise in the environment). This study examines how talkers change the way they speak in response to challenging communicative situations. We investigate what consequences such changes have on intelligibility and whether speaking style adaptations vary with the talker's age.
Warning Signal Brightness Variation: Sexual Selection May Work Under The Radar Of Natural Selection In Populations Of A Polytypic Poison Frog
(2013-05) Crothers, Laura R.; Cummings, Molly E.; Crothers, Laura R.; Cummings, Molly E.
Though theory predicts consistency of warning signals in aposematic species to facilitate predator learning, variation in these signals often occurs in nature. The strawberry poison frog Dendrobates pumilio is an exceptionally polytypic (populations are phenotypically distinct) aposematic frog exhibiting variation in warning color and brightness. In the Solarte population, males and females both respond differentially to male brightness variation. Here, we demonstrate through spectrophotometry and visual modeling that aposematic brightness variation within this population is likely visible to two putative predators (crabs, snakes) and conspecifics but not to the presumed major predator (birds). This study thus suggests that signal brightness within D. pumilio populations can be shaped by sexual selection, with limited opportunity for natural selection to influence this trait due to predator sensory constraints. Because signal brightness changes can ultimately lead to changes in hue, our findings at the within-population level can provide insights into understanding this polytypism at across-population scales.