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At least 37 records · Page 2Linked to original sources
PubMed2000

Comparison of linear gain and wide dynamic range compression hearing aid circuits II: aided loudness measures.

OBJECTIVES: The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growth. DESIGN: Ten adolescents and young adults with moderate to severe sensorineural hearing loss were fitted monaurally with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Threshold, upper limit of comfort and loudness growth were measured in the unaided, linear gain and WDRC conditions for warble tones, environmental sounds and speech. Twelve adult listeners with normal hearing also were tested monaurally in the unaided condition to provide normative data for comparison purposes. RESULTS: The WDRC hearing aid provided a greater input dynamic range than the linear circuit for all stimuli. The dynamic range was normalized for more subjects with the WDRC than the linear hearing aid. In addition, exponential loudness growth functions fitted to the loudness growth data showed that, on average, loudness growth was more normalized with the WDRC hearing aid fitted to DSL[i/o] targets than the linear hearing aid fitted to DSL[i/o] targets. CONCLUSIONS: WDRC processing, fitted using the DSL[i/o] method, has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides an audible, comfortable and tolerable amplified signal across a wider range of inputs than linear gain processing, without the need for volume control adjustments.

Adolescent↗
PubMedDate not supplied

Dynamic range and language abilities in deaf adolescents.

The relationship between language abilities and dynamic range was studied in two groups of significantly deaf adolescents. One group (N = 21) attended a school for the deaf, and the other (N = 23) consisted of either students in regular schools or those attending units for the deaf within regular schools. Two measures of dynamic range were obtained, and language ability was defined by performance on a syntactic abilities test. Acoustic reflexes were also obtained and the relationship to language abilities was determined. Dynamic range was observed to be a highly significant predictor of language score within the deaf school group, but did not relate to language score within the regular school group. Presence or absence of the acoustic reflex bore no apparent relationship to language ability.

Adolescent↗
PubMed1998

Anatomic region-based dynamic range compression for chest radiographs using warping transformation of correlated distribution.

The purpose of this paper is to investigate the effectiveness of our novel dynamic range compression (DRC) for chest radiographs. The purpose of DRC is to compress the gray scale range of the image when using narrow dynamic range viewing systems such as monitors. First, an automated segmentation method was used to detect the lung region. The combined region of mediastinum, heart, and subdiaphragm was defined based on the lung region. The correlated distributions, between a pixel value and its neighboring averaged pixel value, for the lung region and the combined region were calculated. According to the appearance of overlapping of two distributions, the warping function was decided. After pixel values were warped, the pixel value range of the lung region was compressed while preserving the detail information, because the warping function compressed the range of the averaged pixel values while preserving the pixel value range for the pixels which had had the same averaged pixel value. The performance was evaluated with our criterion function which was the contrast divided by the moment, where the contrast and the moment represent the sum of the differences between the pixel values and the averaged values of eight pixels surrounding that pixel, and the sum of the differences between the pixel values and the averaged value of all pixels in the region-of-interest, respectively. For 71 screening chest images from Johns Hopkins University Hospital (Baltimore, MD), this method improved our criterion function at 11.7% on average. The warping transformation algorithm based on the correlated distribution was effective in compressing the dynamic range while simultaneously preserving the detail information.

Humans↗
PubMed1984

Dynamic range and asymmetry of the auditory filter.

This experiment was designed to measure the shape and asymmetry of the auditory filter over a wider dynamic range than has been measured previously. Thresholds were measured for 2-kHz sinusoidal signals in the presence of two 800-Hz-wide noise bands, one above and one below the signal frequency. The spectrum level of the noise was 45 dB (re: 20 muPa), and the noise bands were placed both symmetrically and asymmetrically about the signal frequency. The deviation of the signal frequency from the nearer edge of each noise band varied from 0 to 0.8 times the signal frequency. Each ear of six subjects was tested, and the subjects' ages ranged from 22 to 74 years. The auditory filters derived from the data were somewhat asymmetric, with steeper slopes on the high-frequency side; the degree of asymmetry varied across subjects. The asymmetry could be characterized as a uniform stretching of the (linear) frequency scale on one side of the filter. The dynamic range of the auditory filter exceeded 60 dB in the younger listeners, but the dynamic range and sharpness of the filter tended to decrease with increasing age.

Adult↗
PubMed1992

Evaluation of a dual-channel full dynamic range compression system for people with sensorineural hearing loss.

This article describes an evaluation of an in the ear hearing aid, which applies fast-acting full dynamic range compression independently in two frequency bands. This can compensate for the loudness recruitment typically associated with sensorineural hearing loss. The crossover frequency between the two bands and the gain and compression ratio in each band are programmable to suit the individual patient. Twenty subjects with moderate sensorineural hearing loss were tested in a counterbalanced order using the aid programmed as a linear amplifier (condition L) and as a two-band compressor (condition C). All subjects were fitted binaurally. Subjects were also tested without hearing aids (condition U) and using the hearing aids that they normally wore (condition Own). Speech intelligibility was measured in quiet at three sound levels (50, 65, and 80 dB SPL), and speech reception thresholds (SRTs) in 12-talker babble were measured under monaurally and binaurally aided conditions, with the speech and babble both coincident and spatially separated. In condition C, speech intelligibility in quiet was high at all sound levels. Speech intelligibility at the two lower levels decreased in condition L, and decreased still further in conditions Own and U. Condition C gave, on average, better speech intelligibility in babble (lower SRTs) than conditions L, Own, or U. The advantage of condition C over condition L varied across subjects and was correlated with the dynamic range for tones at high frequencies; small dynamic ranges were associated with greater benefit from compression. A significant advantage for binaural aiding was found both when the speech and noise were spatially separated and when they were coincident. The binaural advantage was similar for the C and L conditions, indicating that the independent compression at the two ears did not adversely affect the use of binaural cues. Questionnaires on the subjects' experiences with the aids in everyday life indicated that they generally preferred condition C over condition L.

Adult↗
PubMed1993

Maximizing the dynamic range of the humphrey field analyzer for blue-on-yellow perimetry.

The conditions employed for blue-on-yellow perimetry (i.e. a blue stimulus filter and a high luminance yellow background) are in conflict with those that allow a maximum dynamic range. A modification is described for increasing the dynamic range of the Humphrey Field Analyzer (HFA) for blue-on-yellow perimetry. The position of the HFA stimulus bulb was lowered by reducing the length of both terminals. A concave mirror with a 28 mm radius of curvature was positioned behind the lowered stimulus bulb to give a filament image partly above and partly overlapping the original filament profile within the confines of the size V stimulus patch diameter. The modification achieved a 60% increase in the light output on the default 0 dB value of 10,000 apostilbs and, therefore, a useable dynamic range for blue-on-yellow perimetry of 2.94 log units. The effective increase in voltage supply to the stimulus bulb permitted a filament life of 260 operating hours. Furthermore, the modification ensured the correct calibration of the instrument.

Color↗
PubMed1998

Increasing age reduces expression of long-term depression and dynamic range of transmission plasticity in CA1 field of the rat hippocampus.

Long-term depression, depotentiation and long-term potentiation of field excitatory postsynaptic potentials in the CA1 field of the hippocampus were studied in slices from two-, 12-, 24- and 36-week-old rats. Long-term potentiation was induced by stimulating afferent fibres for 1 s at 100 Hz. Long-term depression was induced either by stimulating the afferent pathways twice for 15 min at 1 Hz (protocol 1), giving in total 1800 pulses, or by stimulating the fibres at 5 min intervals twice at 1 Hz for 5 min followed by 5 min stimulation at 5 Hz (protocol 2), giving in total 2100 pulses. We found significant long-term depression in slices of all groups stimulated with protocol 1; however, the magnitude of long-term depression in slices from 24- and 36-week-old rats was significantly lower than that in slices from two- and 12-week old rats, although there was no such difference in the magnitude of long-term potentiation between slices. Stimulation protocol 2 induced long-term depression only in slices from two- and 12-week-old rats. Comparison of the dynamic range of transmission plasticity in slices from two- and 36-week-old rats, calculated as the difference between the nearly saturated long-term potentiation and nearly saturated depotentiation, revealed a significantly smaller dynamic range in slices from 36-week-old rats in comparison with slices from two-week-old animals. The decrease in the dynamic range in slices from 36-week-old rats was due to a diminished capacity to depotentiate the nearly saturated long-term potentiation and not due to a decreased long-term potentiation expression in these slices. In contrast to long-term depression, in which the slope of the field excitatory postsynaptic potentials consistently and significantly decreased below the baseline level, the nearly saturated depotentiation did not decrease below the original, pre-long potentiation baseline level. The results demonstrate that increasing age reduces expression of long-term depression and the dynamic range of transmission plasticity.

Aging↗
PubMed1990

The effect of automatic gain control in hearing-impaired listeners with different dynamic ranges.

The purpose of this study was to evaluate the effect of Automatic Gain Control (AGC) on the speech perception of hearing-impaired listeners with varying degrees of reduced dynamic range. Linearly amplified and AGC recordings of the CUNY-Nonsense Syllable Test (CUNY-NST) were constructed in quiet and in noise. They were presented to 30 subjects with flat to gradually sloping sensorineural hearing loss separated into three groups of ten by mean width of dynamic range for puretones. Analysis of the CUNY-NST scores revealed that: (1) AGC significantly improved speech perception in quiet for the subjects with narrower dynamic ranges; (2) the improvement in speech perception with AGC in quiet was dependent upon the manner of articulation of the stimulus; (3) consonant confusions in quiet for AGC were more often due to place errors compared to the linear condition which may be a reflection of a reduction in distinctive feature errors; and (4) linear amplification resulted in higher CUNY-NST scores than did AGC in the presence of back-ground noise.

Aged↗
PubMed1996

"Colored" noise waveforms and quadrupole excitation for the dynamic range expansion of Fourier transform ion cyclotron resonance mass spectrometry.

Fourier transform ion cyclotron resonance (FTICR) mass spectrometry offers unparalleled analytical performance in most regards but has a dynamic range of typically no better than 10(2)-10(3). This limitation reportedly arises from two opposing constraints, involving the maximum number of ions that can be effectively trapped (10(6)-10(7)) and the minimum number of ions required to produce a detectable signal (10(2)-10(3)). A potential solution to this dynamic range limitation is presented, based on the application of selected-ion accumulation using quadrupole excitation. We show that lower concentration species can be effectively accumulated in the FTICR trapped ion cell, while the more abundant species are continually removed by the application of quadrupolar excitation in the form of band-limited or "colored" noise waveforms. The result is that "room" is made in the cell for lower abundance species, even during extended accumulation periods. This approach was demonstrated with mixtures of the bovine proteins, insulin, ubiquitin, and cytochrome c. For normal accumulation, the dynamic range was approximately 100. The application of selected-ion accumulation in the form of colored noise allowed the extension by 2 orders of magnitude and the detection of species of 1 x 10(-8) M concentration from a solution also containing another component at 9 x 10(-5) M. With this method, a putative new low abundance variant of bovine insulin was observed, and selected-ion accumulation and subsequent collisionally activated dissociation were used for its identification. Dipolar magnetron excitation was also explored to enhance selected-ion accumulation and was found to reduce the amount of buffer gas required for complete removal of the undesired species by a factor of 5. Further possible improvements are discussed, as are the complications due to the required balance between magnetron and cyclotron damping rates.

Amino Acid Sequence↗
PubMed1993

Suppression and the dynamic range of hearing.

The results from experiments that have examined intensity discrimination in the presence of notched noise indicate that spread of excitation is not necessary for the auditory system to maintain a large dynamic range. In those experiments the notched noise and the pedestal were simultaneously present. It is possible, therefore, that the notched noise suppressed the pedestal, and increased the dynamic range by reducing the excitation level [A. R. Palmer and E. F. Evans, Hear. Res. 7, 305-323 (1982)]. In the experiment described here, spread of excitation was masked nonsimultaneously in order to avoid suppressive effects. The brief sinusoidal pedestal was presented in a 13-ms gap between two bursts of a masking complex. The masking complex consisted of two sinusoids at frequencies of 0.8fc and 1.2fc (where fc was the pedestal frequency), each having a level either the same as, or 10 dB below the pedestal level, and a notched noise with a spectrum level 40 dB below the level of the sinusoids. Detection thresholds were measured to ensure that the complex was effective in masking spread of excitation. Weber fractions were measured at two pedestal frequencies, 1 and 4 kHz, and at eight pedestal levels at each frequency, covering a range of 70 dB. The results indicate that, although the masking complex raised the Weber fraction by up to 10 dB in some conditions, performance was no worse at high levels than at medium or low levels. This suggests that the auditory system can maintain a large dynamic range in the absence of suppression and spread of excitation.

Acoustic Stimulation↗
PubMed1978

Speech recognition with dynamic range reduction: (1) deaf and normal subjects in laboratory conditions.

Processing to reduce the dynamic range of speech should increase intelligibility and protect the impaired ear from overloading. There are theoretical and practical objections to using AGC devices to reduce dynamic range. These are overcome by using recently available signal processing employing high frequency carrier clipping. An increase in intelligibility of speech with this HFCC has been demonstrated, for normal subjects with simulated deafness, and for most partially hearing patients. Intelligibility is not improved for some patients; possibly due to their having learned to extract features which are lost. These patients may also benefit after training.

Acoustics↗
PubMed2000

Effects of galanin on wide-dynamic range neuron activity in the spinal dorsal horn of rats with sciatic nerve ligation.

Galanin is a 29-amino acid peptide with a suggested role in nociception. The effect of galanin on wide-dynamic range neuron discharge frequency in rats with nerve ligation, used as a model of neurogenic pain, was investigated by extracellular recording methods. Seven to 14 days after sciatic nerve ligation, 0.1, 0.5 or 1 nmol of galanin was administered directly on the dorsal surface of the L3-L5 spinal cord of rats with sciatic nerve ligation. It was found that galanin inhibited the activity of wide-dynamic range neurons dose-dependently, an effect was more pronounced in sciatic nerve ligated rats than intact rats. Furthermore, when 1 nmol of galantide, the galanin antagonist, was administered on the dorsal surface of the L3-L5 spinal cord, the wide-dynamic range neuron discharge frequency increased significantly. The results suggest that galanin plays an important role in the modulation of presumed nociception in mononeuropathy.

Animals↗
PubMed1992

Patient experiences with multiband full dynamic range compression.

This investigation compared performance for 18 experienced hearing aid patients with a multiband full dynamic range compression hearing device and their previously worn linear or automatic gain control hearing aids. Performance was evaluated using a variety of clinical tests. These included functional gain and dynamic range measurements, speech recognition, and real ear measurements. Patients rated their performance with the multiband compression device and their previously worn aids on a rating scale pertaining to a variety of real life listening situations. Statistical analysis of data derived from test results shows significantly improved performance on all measures using the multiband compression aid over their conventional aids. Patients rated their performance higher with the compression instrument than with the conventional aids. Differences in performance on clinical tests and subjective patient responses appear to be related to the different signal processing schemes used in the two groups of devices.

Adolescent↗
PubMedDate not supplied

Evaluation of inherent gray-level dynamic range in a digital image using the runs test and join-count statistics.

The dynamic range of the gray level of a digital image is limited by the noise it contains. Two statistical methods called "runs test" and "join-count statistic" are used to measure the noise level in a digital image. A residual image is formed by subtracting an original image from its smoothed version. Theoretically, the noise level in the residual image should be identical to that in the original image. The noise level is determined by examining each bit plane of the residual image individually starting from the least significant bit up to the bit plane whose statistic does not show a random pattern. Images from three digital modalities: computerized tomography, magnetic resonance, and computed radiography are used to evaluate the gray-level dynamic range. Both methods are easy to implement and fast to perform.

Biometry↗
PubMed1997

Quality control of CGH: impact of metaphase chromosomes and the dynamic range of hybridization.

With the recent rapid expansion in the use of the comparative genomic hybridization (CGH) technique, increased attention to quality control is essential. In the present study, we show that despite optimization and standardization of metaphase preparation techniques and the commercial availability of metaphase spreads, batch-to-batch variability of the preparations remains a significant problem. To facilitate reliable CGH analysis despite this variability, we have developed a rapid denaturation test to assess the quality of the preparations without hybridization and quantitative image analysis criteria for assuring the day-to-day quality of CGH experiments, including sensitivity, specificity, and dynamic range. Monitoring the dynamic range of the hybridizations was found to be particularly critical for achieving sensitive and reliable CGH results. This reliability can be achieved, for example, by hybridization of a green-labeled normal male DNA against red-labeled female DNA and monitoring of the green:red ratio of the X chromosome in relation to that of the autosomes.

Chromosome Banding↗
PubMed1998

Cochlear mechanisms of frequency and intensity coding. II. Dynamic range and the code for loudness.

Our preceding paper described SPL-dependent changes in the shape of transfer functions recorded from inner and outer hair cells as well as supporting cells, in the 500-2500 Hz regions of the Mongolian gerbil cochlea. As SPL was increased, large shifts were observed in the peak of the transfer function. A strongly compressive nonlinearity was also observed at CF. This paper examines the data from the perspective of intensity coding in the auditory periphery. Based on the data, we offer a new explanation for the mechanisms underlying the different dynamic ranges of low and high threshold auditory neurons. We also find that, for pure tone stimuli, the growth of excitation at the characteristic place saturates rapidly, and cannot encode the wide dynamic range of loudness. The data are analyzed to explore other excitation pattern candidates for loudness coding. The growth of the peak of the IHC transfer function, as well as the growth of the response area, have been found to be linearly related to loudness growth over most of its dynamic range. Implications of the data for auditory intensity coding are discussed.

Animals↗
PubMed1998

Analog filtering of large solvent signals for improved dynamic range in high-resolution NMR.

The large solvent signal from samples in H2O solvent still challenges the dynamic range capability of any spectrometer. The solvent signal can be largely removed with a pair of simple resistor-capacitor (RC) high-pass filters when the solvent frequency is set at center band (zero frequency) using quadrature detection, with RC approximately 0.5 ms. However, an approximately 0.5-ms transient remains at initial time, which we reduce fourfold for a short time only, just before the A/D converter, by means of a variable-gain amplifier, and later restore with software. This modification can result in a nearly fourfold increase in dynamic range. When we converted to a frequency-shifted mode (A. G. Redfield and S. D. Kunz, 1994, J. Magn. Reson. A 108, 234-237) we replaced the RC high-pass filter with a quadrature feedback notch filter tuned to the solvent frequency (5.06 kHz). This filter is an example of a class of two-input/two-output filters which maintain the spectral integrity (image-free character) of quadrature signals. Digital filters of the same type are also considered briefly. We discuss the implications of these ideas for spectrometer input design, including schemes for elimination of radiation damping, and effects of probe bandwidth on extreme oversampling.

Filtration↗
PubMed1997

Desensitization of the GABAA receptor shifts the dynamic range of retinal horizontal cells due to light and dark adaptation.

The effects of the GABAergic pathway on the dynamic range of the light response of cone-driven horizontal cells (HCs) in the carp retina were investigated using conventional intracellular recordings and computer simulations. The amplitude of the HC responses to repetitive test flashes was altered by background illumination in control Ringer's solution, but was not changed following the application of picrotoxin or bicuculline, which suggests that GABAA receptors mediate the subsequent change in light response. This phenomenon was simulated by introducing the desensitization mechanism of the GABAA receptor into a cone-HC network model. These results suggest that desensitization of the GABAA receptor shifts the dynamic range of the HCs due to light and dark adaptation.

Adaptation, Ocular↗