Search results for "Acoustics"
showing 10 items of 984 documents
Binaural release from masking in forward-masked intensity discrimination: Evidence for effects of selective attention
2012
In a forward-masked intensity discrimination task, we manipulated the perceived lateralization of the masker via variation of the interaural time difference (ITD). The maskers and targets were 500 Hz pure tones with a duration of 30 ms. Standards of 30 and 60 dB SPL were combined with 60 or 90 dB SPL maskers. As expected, the presentation of a forward masker perceived as lateralized to the other side of the head as the target resulted in a significantly smaller elevation of the intensity difference limen than a masker lateralized ipsilaterally. This binaural release from masking in forward-masked intensity discrimination cannot be explained by peripheral mechanisms because varying the ITD l…
Sequential grouping modulates the effect of non-simultaneous masking on auditory intensity resolution.
2012
The presence of non-simultaneous maskers can result in strong impairment in auditory intensity resolution relative to a condition without maskers, and causes a complex pattern of effects that is difficult to explain on the basis of peripheral processing. We suggest that the failure of selective attention to the target tones is a useful framework for understanding these effects. Two experiments tested the hypothesis that the sequential grouping of the targets and the maskers into separate auditory objects facilitates selective attention and therefore reduces the masker-induced impairment in intensity resolution. In Experiment 1, a condition favoring the processing of the maskers and the targ…
Effects of whole-body vertical shock-type vibration on human ability for fine manual control
1991
The effects of vertical (z-axis) whole-body shock-type vibration on the ability for fine manual control were examined. The amplitudes and frequency of the shocks was varied, but a constant frequency-weighted acceleration of 1.25 m/s2 r.m.s. was maintained. The examination of the shock's effects was carried out using an experimental system that simulated the actual workplace of earth-moving machinery. Control was measured using a first-order pursuit tracking-test, in which a seated subject was asked to use both hands to direct a cursor on a monitor using a steering wheel. Although the magnitude of shocks (peak amplitude of 6-10 m/s2) and the number of shocks per unit time (shock cycle of 10-…
Transmission of Vertical Whole Body Vibration to the Human Body
2008
According to experimental studies, low-amplitude high-frequency vibration is anabolic to bone tissue, whereas in clinical trials, the bone effects have varied. Given the potential of whole body vibration in bone training, this study aimed at exploring the transmission of vertical sinusoidal vibration to the human body over a wide range of applicable amplitudes (from 0.05 to 3 mm) and frequencies (from 10 to 90 Hz). Vibration-induced accelerations were assessed with skin-mounted triaxial accelerometers at the ankle, knee, hip, and lumbar spine in four males standing on a high-performance vibration platform. Peak vertical accelerations of the platform covered a range from 0.04 to 19 in units …
Factors limiting performance in a multitone intensity-discrimination task: disentangling non-optimal decision weights and increased internal noise.
2013
To identify factors limiting performance in multitone intensity discrimination, we presented sequences of five pure tones alternating in level between loud (85 dB SPL) and soft (30, 55, or 80 dB SPL). In the "overall-intensity task", listeners detected a level increment on all of the five tones. In the "masking task", the level increment was imposed only on the soft tones, rendering the soft tones targets and loud tones task-irrelevant maskers. Decision weights quantifying the importance of the five tone levels for the decision were estimated using methods of molecular psychophysics. Compatible with previous studies, listeners placed higher weights on the loud tones than on the soft tones i…
Temporal expectation and spectral expectation operate in distinct fashion on neuronal populations
2013
The formation of temporal expectation (i.e., the prediction of ‘when’) is of prime importance to sensory processing. It can modulate sensory processing at early processing stages probably via the entrainment of low-frequency neuronal oscillations in the brain. However, sensory predictions involve not only temporal expectation but also spectral expectation (i.e., the prediction of ‘what’). Here we investigated how temporal expectation may interrelate with spectral expectation by explicitly setting up temporal expectation and spectral expectation in a target detection task. We found that temporal expectation and spectral expectation interacted on reaction time (RT). RT was shorter when target…
The effect of MPEG audio compression on multidimensional set of voice parameters
2002
The MPEG-1 Layer 3 compression schema of audio signal, or commonly known as mp3, has caused a great impact in recent years as it has reached high compression rates while also conserving a high sound quality. Previous listening tests have shown that music and speech samples compressed at high bitrates are virtually indistinguishable from the original samples, but very little is known about how compression acoustically affects the voice signal. In Experiment 1 the spectral composition of original and compressed speech signals were analyzed by means of the Long-Term Average Spectrum using the Computerized Speech Laboratory (Kay Elemetrics Corp. (Pine Brook, NJ, USA)). In Experiment 2 a set of …
Modeling the impact of soft tissue on axial transmission measurements of ultrasonic guided waves in human radius
2008
Recent in vitro and simulation studies have shown that guided waves measured at low ultrasound frequencies (f=200 kHz) can characterize both material properties and geometry of the cortical bone wall. In particular, a method for an accurate cortical thickness estimation from ultrasound velocity data has been presented. The clinical application remains, however, a challenge as the impact of a layer of soft tissue on top of the bone is not yet well established, and this layer is expected to affect the dispersion and relative intensities of guided modes. The present study is focused on the theoretical modeling of the impact of an overlying soft tissue. A semianalytical method and finite-differ…
Perihepatic lymph nodes and antiviral response in chronic HCV-associated hepatitis.
2003
To identify predictive factors of response to interferon alpha (IFN-alpha) plus ribavirin therapy in patients with chronic hepatitis C (CHC), the presence of lymphadenopathy (LyA) of the hepatoduodenal ligament and other variables were investigated. A total of 110 patients with histologically proven CHC were enrolled in this study. Ultrasound (US) was performed at the start and end of therapy and 6 months after stopping therapy. At baseline, LyA was present in 35 (43.7%) of 80 patients with alanine aminotransferase (ALT) values and grading was significantly higher than in the LyA-negative group. LyA was more frequent in nonresponders (nonR) than in relapsers (relR) or sustained responders (…
Analysis of Internal Jugular Vein Insufficiency—A Comparison of Two Ultrasound Methods
2006
Abstract Jugular venous valve insufficiency is a contributing factor to different pathologic conditions. For assessment of insufficiency, two ultrasound techniques have been developed, that are based on very different methodology (direct Doppler assessment versus air contrast ultrasound venography [ACUV]). This study was conducted to compare these two methods to improve comparability of existing studies and diagnostic accuracy in future studies. The function of 40 valves was determined in 20 individuals during a Valsalva maneuver. For direct Doppler assessment, valvular competence was assessed on basis of Doppler recordings, following recently established criteria. Valvular insufficiency in…