Biomedical subjects

M Florentine

Publications and source records attributed to M Florentine.

At least 37 records · Page 2Linked to original sources

PubMed1989

Comodulation masking release for three types of modulator as a function of modulation rate.

To investigate the dependence of 'Comodulation Masking Release' (CMR) on the type and frequency of modulator, thresholds were measured for a 4-kHz tone masked by modulated and unmodulated noises. The maskers were a 400-Hz wide band of noise centered on 4 kHz (NOCUE), the same noise with a 2700-Hz lowpass noise added (LPCUE), and a wideband noise with a passband between 3 and 6 kHz (WBCUE). In each condition three types of modulator were used: a square wave, a sinewave, and a lowpass noise. Several frequencies of each type of modulator were used, allowing measurement of the interaction between envelope frequency (fe) and modulator type. Thresholds were lower in the presence than in the absence of modulation for all modulator types, except when fe was high (e.g. 100 Hz). The 'Modulated-Unmodulated Difference' (MUD) decreased monotonically with increasing fe in all conditions. For any given fe, MUDs generally were greater for square-wave and lowpass-noise modulation than for sinusoidal modulation. As significant MUDs were sometimes obtained even in the NOCUE condition, the MUD was not an accurate measure of CMR. Therefore, CMR was defined as the difference between the MUD obtained in the NOCUE condition and that obtained in each cue condition, for each combination of fe and modulator type. Measured this way, the CMR for our 4-kHz signals did not vary systemically with fc over the range studied. When a CMR was obtained it was smaller for sinusoidal modulation than for either square-wave or lowpass-noise modulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1988

Temporal integration in normal hearing, cochlear impairment, and impairment simulated by masking.

To assess temporal integration in normal hearing, cochlear impairment, and impairment simulated by masking, absolute thresholds for tones were measured as a function of duration. Durations ranged from 500 ms down to 15 ms at 0.25 kHz, 8 ms at 1 kHz, and 2 ms at 4 and 14 kHz. An adaptive 2I, 2AFC procedure with feedback was used. On each trial, two 500-ms observation intervals, marked by lights, were presented with an interstimulus interval of 250 ms. The monaural signal was presented in the temporal center of one observation interval. The results for five normal and six impaired listeners show: (1) normal listeners' thresholds decrease by about 8 to 10 dB per decade of duration, as expected; (2) listeners with cochlear impairments generally show less temporal integration than normal listeners; and (3) listeners with impairments simulated using masking noise generally show the same amount of temporal integration as normal listeners tested in the quiet. The difference between real and simulated impairments indicates that the reduced temporal integration observed in impaired listeners probably is not due to splatter of energy to frequency regions where thresholds are low, but reflects reduced temporal integration per se.

Acoustic Stimulation↗

PubMed1987

Measurement of right ventricular volume using cine computed tomography.

Volume measurements of the right ventricle are clinically important, particularly in the assessment of congenital heart disease. The complex configuration of the right ventricular cavity, however, makes assessment of its volume difficult. Cine computed tomography (CT) permits depiction of cardiac anatomy in parallel, sequential, high-resolution tomographic images. To test whether cine CT would allow accurate, reproducible determination of right ventricular volumes, 11 excised, fixed canine hearts were scanned ex vivo. The endocardial contours of the right ventricular cavity were traced by two independent observers. The right ventricular cavity areas were measured in each image and right ventricular volume calculated by a Simpson's rule approximation. Actual right ventricular volume (range 24-86.5 mL) was measured by cavity fluid capacity. Right ventricular volumes derived from cine CT data correlated closely with actual volumes (R = .96, cine CT volume = 0.99 X [actual volume] + 0.2 mL). Interobserver correlation was excellent (R = .99). It is concluded that cine CT scanning permits accurate, reproducible determination of right ventricular volume ex vivo. This technique should be immediately applicable to the noninvasive evaluation of right ventricular function in children and adults.

Animals↗

PubMed1987

Level discrimination as a function of level for tones from 0.25 to 16 kHz.

Difference limens for level (delta L in dB = 20 log [(p + delta p)/p], where p is pressure) were measured as a function of level for tones at 0.25, 0.5, 1, 2, 4, 8, 10, 12, 14, and 16 kHz. At each frequency, test levels encompassed the range from near threshold to 95 dB SPL in steps of 10 dB or smaller. The stimulus duration was 500 ms and the interstimulus interval was 250 ms. An adaptive two-alternative forced-choice procedure with feedback was used. Results for six normal listeners show individual differences among listeners, but the general trends seen in the average data clearly are present in the individual data and show the following. First, the delta Ls at all but the highest frequencies are generally smaller at high levels than at low levels. Second, the delta Ls at equal SPLs are largely independent of frequency up to about 4 kHz, but increase with frequency above 4 kHz. Third, at 8 and 10 kHz, the delta Ls are clearly nonmonotonic functions of level, showing consistent deterioration in the mid-level delta Ls relative to the low- and high-level delta Ls. The present data are discussed qualitatively in terms of current models of level discrimination.

Acoustic Stimulation↗

PubMed1986

Level discrimination of tones as a function of duration.

Difference limens for level [delta Ls (dB) = 20 log[p + delta p)/p), where p is the pressure] were measured as a function of duration for tones at 250, 500, and 8000 Hz. Stimulus durations ranged from 2 ms to 2 s, and the stimulus power was held constant. Rise and fall times were 1 ms. The interstimulus interval was 250 ms. At each frequency, three levels were tested: 85, 65, and approximately 40 dB SPL. An adaptive two-alternative forced-choice procedure with feedback was used. For three normal listeners, delta Ls decreased as duration increased, up to at least 2 s, except at 250 Hz. At 250 Hz, delta L stopped decreasing at durations between 0.5 and 1 s. In a double logarithmic plot of delta L versus duration, the rate of decrease is generally well fitted by a sloping line. The average slope is -0.28; it is steeper at high levels than at low levels. Because the average slope is shallower than the -0.5 slope predicted for an optimum detector, it may be that fast adaptation of auditory-nerve activity and/or memory effects interfere with level discrimination of long-duration tones. Finally, the delta Ls at 8 kHz decreased nonmonotonically with increasing level.

Adult↗

PubMed1986

Decision rules in detection of simple and complex tones.

Detection of simple and complex tones in the presence of a 64-dB SPL uniformly masking noise was examined in two experiments. In both experiments, the signals were either pure tones (220, 1100, or 3850 Hz) or an 18-tone complex consisting of equally intense components between 110 and 7260 Hz. In experiment 1, psychometric functions were obtained for detection in a 2I, 2AFC task. Results for eight normal listeners show that the psychometric functions are parallel for simple and complex tones. As expected, the masked thresholds for the pure tones are 43-44 dB SPL independent of frequency; the masked threshold for the complex tone is about 37 dB SPL per tone. These results indicate that the simultaneous presence of signal energy in many auditory channels aids detection. In experiment 2, psychometric functions were obtained with all four signals presented in random order within a block of trials. Results for four normal listeners show that the psychometric functions are parallel to one another and to those obtained in experiment 1. The thresholds are elevated to about 46 dB for the pure tones and to 40.5 dB for the complex tone. These results are nearly, but not quite, consistent with a multiband energy-detector model using an optimum decision rule; it appears that listeners may only make an unweighted sum of decision variables across an optimum selection of channels.

Acoustic Stimulation↗

PubMed1984

Balloon embolization to occlude a Blalock-Taussig shunt.

Balloon embolization was used to successfully occlude a large residual Blalock-Taussig shunt. The use of an "upstream" nondetachable balloon catheter to reduce flow and turbulence during final positioning of the detachable balloon may have made the technique safer and more precise.

Cardiac Catheterization↗

PubMed1984

Temporal gap detection in sensorineural and simulated hearing impairments.

The objectives of this study were to assess the effect of the configuration of a hearing loss on gap detection and to determine if hearing impairment affects temporal resolution, per se. The minimum detectable gap duration, MDG, in a low-pass (cut-off at 7 kHz) noise was measured monaurally as a function of sound pressure level in six listeners with normal hearing, seven with hearing impairments of primarily cochlear origin, and eight with impairments simulated by masking. The impaired listeners' MDGs at 80 and 90 dB vary from about 3.5 ms (equal to the normal MDG) to about 8 ms and show little correlation with their average HL. At lower levels, the MDG is enlarged for all impaired listeners owing to the decreased SL of the noise. Most of the enlargement of the MDG could be reproduced by presenting a normal listener with a masking noise spectrally shaped to simulate the impaired listener's audiogram. However, at high levels, some impaired listeners performed worse than their simulated-loss counterparts, indicating that temporal resolution per se may be reduced in some, but not all, impaired listeners.

Adult↗

PubMed1984

Lateralization and frequency selectivity in normal and impaired hearing.

The onset-time difference delta T required to lateralize a 30-ms bifrequency tone burst toward the leading ear was measured as a function of the frequency difference delta F between the tone in the left ear and the tone in the right ear. At center frequencies of 0.5 and 4 kHz, four normal listeners tested at 80 and 100 dB SPL had delta Ts that were relatively constant at subcritical delta Fs, but increased at delta Fs wider than a critical band. At 1 kHz, delta T increased with delta F even at subcritical delta Fs. Ten listeners with cochlear impairments were tested at 100 dB SPL. Seven had normal delta Ts at 4 kHz, despite hearing losses between 50 and 70 dB. At 0.5 and 1 kHz, mildly impaired listeners had nearly normal lateralization functions, whereas more severely imparied listeners had very large delta Ts and no frequency selectivity. These and other findings indicate that listeners even with moderate to severe hearing losses can lateralize normally on the basis of interaural differences in onset envelope, but not on the basis of temporal differences in the fine structure.

Adolescent↗

PubMed1983

Tuning curves and pitch matches in a listener with a unilateral, low-frequency hearing loss.

Psychoacoustical tuning curves and interaural pitch matches were measured in a listener with a unilateral, moderately severe hearing loss of primarily cochlear origin below 2 kHz. The psychoacoustical tuning curves, measured in a simultaneous-masking paradigm, were obtained at 1 kHz for probe levels of 4.5-, 7-, and 13-dB SL in the impaired ear, and 7-dB SL in the impaired ear, and 7-dB SL in the normal ear. Results show that as the level of the probe increased from 4.5- to 13-dB SL in the impaired ear, (1) the frequency location of the tip of the tuning curve decreased from approximately 2.85 to 2.20 kHz and (2) the lowest level of the masker required to just mask the probe increased from 49- to 83-dB SPL. The tuning curve in the normal ear was comparable to data from other normal listeners. The interaural pitch matches were measured from 0.5 to 6 kHz at 10-dB SL in the impaired ear and approximately 15- to 20-dB SL in the normal ear. Results show reasonable identity matches (e.g., a 500-Hz tone in the impaired ear was matched close to a 500-Hz tone in the normal ear), although variability was significantly greater for pitch matches below 2 kHz. The results are discussed in terms of their implications for models of pitch perception.

Adult↗

PubMed1983

Intensity discrimination as a function of level and frequency and its relation to high-frequency hearing.

This paper examines how intensity discrimination depends on the test frequency, the level, and the subjects's high-frequency hearing. Three experiments were performed. In the first experiment, intensity discrimination of pulsed tones was measured as a function of level at 1 and 14 kHz in five listeners. Results show less deviation from Weber's law at 14 kHz than at 1 kHz. In the second experiment, intensity discrimination was measured for a 1-kHz tone at 90-dB SPL as a function of the cutoff frequency of a high-pass masking noise in two listeners. Results show that the audibility of very high frequencies is important for frequency discrimination at 1 kHz. The DL increased by a factor between 1.5 and 2.0 as the cutoff frequency of the noise was lowered from 19 to 6 kHz. In the third experiment, thresholds from 6 to 20 kHz and intensity discrimination for a 1-kHz tone was measured in 12 listeners. Results show that the DLs at 80-dB SPL are correlated with the ability to hear very high frequencies. Results of all three experiments are consistent with the multiband version of the excitation-pattern model for intensity discrimination [Florentine and Buus, J. Acoust. Soc. Am. 70, 1646-1654 (1981)].

Adult↗

PubMed1982

The SISI test: a review. Part I.

This is the first of two papers reviewing the SISI test. Following a discussion of the history of clinical intensity discrimination tests, a large body of data on the SISI test is reviewed with special attention to its procedure, as well as its validity and reliability. The following conclusions are drawn: (1) Sufficient practice should be given prior to the onset of data collection. (2) The number of presentations can safely be reduced to 10 if the patient either responds consistently or does not respond at all. (3) SISI possesses good validity and reliability. Used in conjunction with other tests, it gives valuable diagnostic information.

Hearing Disorders↗

PubMed1982

The SISI test: a review. Part II.

This is the second of two papers reviewing the SISI test. In this paper we discuss modifications of SISI, and the effects of contralateral masking and tone decay. We also compare SISI to other psychoacoustic site of lesion tests and discuss the implications of the results obtained in SISI. The following conclusions are drawn: (1) SISI performed at high levels appears powerful in detecting retrocochlear impairments. (2) Contralateral masking is advisable when cross-hearing cues are present. The masking level should be minimized and a noise level 10 dB below the level of the contralaterilized tone provides sufficient masking. (3) SISI remains valid despite the presence of tone decay. (4) High SISI scores in cochlearly impaired listeners do not indicate improved auditory acuity.

Audiometry, Pure-Tone↗

PubMed1980

Frequency selectivity in normally-hearing and hearing-impaired observers.

This study compares frequency selectivity--as measured by four different methods--in observers with normal hearing and in observers with conductive (nonotosclerotic), otosclerotic, noise-induced, or degenerative hearing losses. Each category of loss was represented by a group of 7 to 10 observers, who were tested at center frequencies of 500 Hz and 4000 Hz. For each group, the following four measurements were made: psychoacoustical tuning curves, narrow-band masking, two-tone masking, and loudness summation. Results showed that (a) frequency selectivity was reduced at frequencies where a cochlear hearing loss was present, (b) frequency selectivity was reduced regardless of the test level at which normally-hearing observers and observers with cochlear impairment were compared, (c) all four measures of frequency selectivity were significantly correlated and (d) reduced frequency selectivity was positively correlated with the amount of cochlear hearing loss.

Hearing Loss↗

PubMed1979

A model of loudness summation applied to noise-induced hearing loss.

The main contention of this paper is that Zwicker's model of loudness summation is applicable to observers with noise-induced hearing loss when certain parameters of the model are modified. Two types of measurement were obtained in observers with normal hearing and noise-induced hearing loss: loudness summation as a function of level and narrow-band masking. These measurements provided a basis for modifying the parameters of the model. Results suggest that the model of loudness summation is applicable to observers with noise-induced hearing loss when the presence of recruitment and reduced frequency selectivity is taken into account.

Hearing Loss, Noise-Induced↗

PubMed1978

Loudness of complex sounds as a function of the standard stimulus and the number of components.

The purpose of this study was twofold: to determine if the measured loudness level of a signal depends on the standard stimulus used and to measure loudness as a function of the number of components in a wide-band signal. The stimuli were a pure tone, tone complexes with frequency separations of 231 and 1592 Hz, and noise bands with widths of 220 and 1592 Hz. The center frequency was 1 kHz and the loudness level was approximately 65 phons. Loudness matches between all combinations of stimuli showed that the measured loudness of the sounds did not depend on the standard stimulus used and the measured loudness level of a wide-band sound increased as a function of the number of components. Individual observers were consistent in their loudness estimations; the greatest source of variability was among subjects. Additional measurements indicated that the rate at which loudness increased beyond the critical band appeared to be greater for noise bands that for two-tone complexes.

Acoustic Stimulation↗

PubMed1978

Estimation of the critical bandwidth from loudness summation data.

An automatic method for critical band estimation from loudness summation data is presented. A mathematical model, based on a power function, is fitted to the data and the critical bandwidth is defined at the intersection of the asymptotes. The model is designed for clinical use, involving the treatment of the data from single test persons; it represents an operational solution to a difficult task. The model is able to describe data from normals and patients with a sensorineural hearing loss. Variability of the critical band estimates, intrasubject as well as intersubject, is larger than for visually obtained estimates. However, visual estimation is difficult, subjective, and probably heavily biased. The model produces estimates which in logarithmic form have a Normal distribution at medium loudness level, while visual estimation gives rise to irregular distributions at all levels. A normal range for model estimates from sets of data obtained at medium loudness level is defined by mean and standard deviation.

Auditory Perception↗

PubMed1976

Critical band in auditory lateralization.

A new and powerful procedure for determining frequency analysis in the auditory system, as evidence by the critical band, is described. The onset time difference, delta T, needed to lateralize 30-msec tone bursts toward the leading ear was measured as a function of the frequency difference, delta F, between the brust in one ear and the burst in the other ear. When delta F was less than the critical band, threshold delta T was constant at 100 mu sec or less, depending on center frequency; beyond the critical band, delta T increased with delta F. These dichotically measured critical bandwidths increased from 110 Hz at a center frequency of 500 Hz to 1100 Hz at a center frequency of 6000 Hz. They were unaffected by varying signal level from 25 to 80 dB or signal duration from 10 to 300 msec. The sam e critical-band values have been measured with monaural stimuli in loudness summation, maskin, detection, phase perception, consonance, and so forth.

Acoustic Stimulation↗