Simultaneous relative cue reliance in speech-on-speech masking.

Modern hearing research has identified the ability of listeners to segregate simultaneous speech streams with a reliance on three major voice cues, fundamental frequency, level, and location. Few of these studies evaluated reliance for these cues presented simultaneously as occurs in nature, and fewer still considered the listeners' relative reliance on these cues owing to the cues' different units of measure. In the present study trial-by-trial analyses were used to isolate the listener's simultaneous reliance on the three voice cues, with the behavior of an ideal observer [Green and Swets (1966). (Wiley, New York), pp.151-178] serving as a comparison standard for evaluating relative reliance. Listeners heard on each trial a pair of randomly selected, simultaneous recordings of naturally spoken sentences. One of the recordings was always from the same talker, a distracter, and the other, with equal probability, was from one of two target talkers differing in the three voice cues. The listener's task was to identify the target talker. Among 33 clinically normal-hearing adults only one relied predominantly on voice level, the remaining were split between voice fundamental frequency and/or location. The results are discussed regarding their implications for the common practice in studies of using target-distracter level as a dependent measure of speech-on-speech masking.

Límites de referencia de las concentraciones de lípidos en embarazos no complicados / Reference limits for lipids during pregnancy without complications

Resumen OBJETIVO: Definir los límites de referencia de las concentraciones de lípidos en gestaciones no complicadas. MATERIALES Y MÉTODOS: Estudio observacional, retrospectivo y analítico efectuado en pacientes embarazadas sanas atendidas en el servicio de Obstetricia del Hospital Churruca-Visca de Buenos Aires, Argentina. Criterios de inclusión: pacientes embarazadas con edad entre 14 y 43 años. Criterios de exclusión: pacientes en tratamiento farmacológico que pudiera afectar el metabolismo lipídico o tener complicaciones obstétricas o neonatales. RESULTADOS: Se estudiaron 163 embarazadas con edad promedio de 27.2 ± 6.5 años, que se categorizaron en cuatro grupos. En el primer trimestre el colesterol no HDL fue significativamente diferente entre las cuatro categorías de IMC (p < 0.05). En el segundo trimestre se encontraron iguales resultados para colesterol no HDL y LDL (p < 0.05) mientras que las concentraciones de triglicéridos fueron significativamente diferentes de acuerdo con las cinco categorías de edad (p < 0.05). En el tercer trimestre no se encontraron diferencias en las concentraciones de lípidos por edad ni por IMC. Tampoco se obtuvieron diferencias por ganancia de peso (menos o más de 10 kg). CONCLUSIONES: Las concentraciones de lípidos y lipoproteínas se incrementaron a lo largo del embarazo. No hubo diferencia significativa entre mujeres con bajo y peso normal versus sobrepeso-obesidad. Es necesario reunir más información de valores de referencia de lípidos y lipoproteínas para poder definir el estado de dislipidemia en las embarazadas.

Abstract OBJECTIVE: To define the reference limits of lipid concentrations in uncomplicated gestations. MATERIALS AND METHODS: Observational, retrospective and analytical study carried out in healthy pregnant patients treated in the obstetrics service of the Churruca-Visca Hospital. Inclusion criteria: being pregnant and between 14 and 43 years of age. Exclusion criteria: being in pharmacological treatment that could affect lipid metabolism or have obstetric or neonatal complications. RESULTS: 163 pregnant women were studied with an average age of 27.2 ± 6.5 years, which was categorized into four groups. In the first trimester non-HDL cholesterol was significantly different among the four categories of BMI (p <0.05). In the second quarter, the same results were found for non-HDL and LDL cholesterol (p <0.05), while triglyceride concentrations were significantly different according to the five age categories (p <0.05). In the third quarter there were no differences in lipid concentrations by age or BMI. Nor were differences obtained by weight gain (less or more than 10 kg). CONCLUSIONS: Lipid and lipoprotein concentrations increased during pregnancy. There was no significant difference between women with low and normal weight versus overweight-obesity. It is necessary to gather more information on reference values of lipids and lipoproteins in order to define the state of dyslipidemia in pregnant women.

Practice Variation in the Immediate Postoperative Care of Pediatric Kidney Transplantation: A National Survey.

INTRODUCTION: Advances in organ allocation, surgical technique, immunosuppression, and long-term follow-up have led to a significant improvement in kidney transplant outcomes. Although there are clear recommendations for several aspects of kidney transplant management, there are no pediatric-specific guidelines for immediate postoperative care. The aim of this survey is to examine practice variations in the immediate postoperative care of pediatric kidney transplant patients. METHODS: We surveyed medical directors of Pediatric Acute Lung Injury and Sepsis Investigators (PALISI)-affiliated pediatric intensive care units regarding center-specific immediate postoperative management of pediatric kidney transplantation. RESULTS: The majority of PALISI centers admit patients to the pediatric intensive care unit postoperatively, and 97% of the centers involve a pediatric nephrologist in immediate postoperative care. Most patients undergo invasive hemodynamic monitoring; 97% of centers monitor invasive arterial blood pressure and 88% monitor central venous pressure. Most centers monitor serum electrolytes every 4 to 6 hours. Wide variation exists regarding blood pressure goal, fluid replacement type, frequency of obtaining kidney ultrasound, and use of prophylactic anticoagulation. CONCLUSION: There is consistent practice across PALISI centers in regards to many aspects of immediate postoperative management of pediatric kidney transplantation. However, variation still exists in some management aspects that warrant further discussions to reach a national consensus.

Relación entre circunferencia de cintura y factores de riesgo metabólicos en mujeres argentinas / Relationship Between Waist Circumference and Metabolic Risk Factors in Argentine Women

Introducción: El síndrome metabólico (SM) agrupa factores de riesgo para enfermedad cardiovascular. Dentro de estos factores se encuentra la obesidad central, evaluada generalmente a través de la circunferencia de la cintura (CC) Objetivo: Analizar el comportamiento de las distintas variables que agrupan el SM (definición ATP III) en relación a los cambios en la CC. Sujetos: Se incluyeron 253 mujeres que concurrieron al Servicio de Endocrinología. Se evaluaron medidas antropométricas y presión arterial, así como glucemia en ayunas y lipidograma. Las pacientes fueron agrupadas por quintilos por CC: Q1 (56-80 cm), Q2 (80.1-89 cm), Q3 (89.1-96 cm), Q4 (96.1-103 cm) y Q5 (103.1-150 cm. Resultados: Existe una correlación positiva entre la CC y el IMC (p < 0,0001, r: 0,87).Asimismo, se observa una correlación positiva entre la CC y los valores de triglicéridos (p <0,0001, r: 0,28), glucemia (p = 0,0001, r: 0,24), presión arterial (PA) sistólica (p < 0,0001, r: 0,27) y diastólica (p < 0,0007, r: 0,21) y una correlación negativa entre la CC y los niveles de HDL (p < 0,0001, r: -0,25). Conclusiones: A medida que aumenta la CC, aumentan los factores de riesgo cardiovasculares (presión arterial diastólica, glucemia, triglicéridos, descenso del HDL).

Introduction: Metabolic syndrome (MS) is a group of risk factors for cardiovascular disease. These factors include central obesity, usually assessed through waist circumference (WC). Objective: To analyze the behavior of the different MS variables (ATP III definition) in relation to changes in WC. Subjects: We included 253 women who attended the Service of Endocrinology. We performed anthropometric, blood pressure, fasting glucose and lipid profile measurements. Patients were grouped into quintiles by WC: Q1 (56-80 cm), Q2 (80.1-89 cm), Q3 (89.1-96 cm), Q4 (96.1-103 cm) and Q5 (103.1-150 cm. Results: There is a positive correlation between WC and BMI (p < 0.0001, r = 0.87). In addition, there is a positive correlation between WC and triglyceride levels (p < 0.0001, r: 0.28), glucose (p = 0.0001, r = 0.24), systolic blood pressure (BP) (p < 0.0001, r = 0.27) and diastolic BP (p <0.0007, r: 0.21) and a negative correlation between WC and HDL levels (p < 0.0001, r = -0.25). Conclusions: As WC increases, cardiovascular risk factors (diastolic blood pressure, blood glucose, triglycerides, decreased HDL) increase.

Relación entre circunferencia de cintura y factores de riesgo metabólicos en mujeres argentinas / Relationship Between Waist Circumference and Metabolic Risk Factors in Argentine Women

Introducción: El síndrome metabólico (SM) agrupa factores de riesgo para enfermedad cardiovascular. Dentro de estos factores se encuentra la obesidad central, evaluada generalmente a través de la circunferencia de la cintura (CC) Objetivo: Analizar el comportamiento de las distintas variables que agrupan el SM (definición ATP III) en relación a los cambios en la CC. Sujetos: Se incluyeron 253 mujeres que concurrieron al Servicio de Endocrinología. Se evaluaron medidas antropométricas y presión arterial, así como glucemia en ayunas y lipidograma. Las pacientes fueron agrupadas por quintilos por CC: Q1 (56-80 cm), Q2 (80.1-89 cm), Q3 (89.1-96 cm), Q4 (96.1-103 cm) y Q5 (103.1-150 cm. Resultados: Existe una correlación positiva entre la CC y el IMC (p < 0,0001, r: 0,87).Asimismo, se observa una correlación positiva entre la CC y los valores de triglicéridos (p <0,0001, r: 0,28), glucemia (p = 0,0001, r: 0,24), presión arterial (PA) sistólica (p < 0,0001, r: 0,27) y diastólica (p < 0,0007, r: 0,21) y una correlación negativa entre la CC y los niveles de HDL (p < 0,0001, r: -0,25). Conclusiones: A medida que aumenta la CC, aumentan los factores de riesgo cardiovasculares (presión arterial diastólica, glucemia, triglicéridos, descenso del HDL).(AU)

Introduction: Metabolic syndrome (MS) is a group of risk factors for cardiovascular disease. These factors include central obesity, usually assessed through waist circumference (WC). Objective: To analyze the behavior of the different MS variables (ATP III definition) in relation to changes in WC. Subjects: We included 253 women who attended the Service of Endocrinology. We performed anthropometric, blood pressure, fasting glucose and lipid profile measurements. Patients were grouped into quintiles by WC: Q1 (56-80 cm), Q2 (80.1-89 cm), Q3 (89.1-96 cm), Q4 (96.1-103 cm) and Q5 (103.1-150 cm. Results: There is a positive correlation between WC and BMI (p < 0.0001, r = 0.87). In addition, there is a positive correlation between WC and triglyceride levels (p < 0.0001, r: 0.28), glucose (p = 0.0001, r = 0.24), systolic blood pressure (BP) (p < 0.0001, r = 0.27) and diastolic BP (p <0.0007, r: 0.21) and a negative correlation between WC and HDL levels (p < 0.0001, r = -0.25). Conclusions: As WC increases, cardiovascular risk factors (diastolic blood pressure, blood glucose, triglycerides, decreased HDL) increase.(AU)

Dendritic cell-derived tumor necrosis factor α modifies airway epithelial cell responses.

Mucosal dendritic cells (DC) are intimately associated with the airway epithelium and thus are ideally situated to be first responders to pathogens. We hypothesize that DC drive innate immune responses through early release of tumor necrosis factor (TNF) α, which drives airway epithelial cell responses. In a mouse model, TNFα release was significantly increased following a single exposure to German cockroach (GC) frass, an event independent of neutrophil recruitment into the airways. While lung epithelial cells and alveolar macrophages failed to release TNFα following GC frass exposure, bone marrow-derived DC (BMDC) produced substantial amounts of TNFα suggesting their importance as early responding cells. This was confirmed by flow cytometry of pulmonary myeloid DC. Addition of GC frass-pulsed BMDC or conditioned media from GC frass-pulsed BMDC to primary mouse tracheal epithelial cells (MTEC) or MLE-15 cells induced chemokine (C-C) motif ligand (CCL) 20 and granulocyte macrophage (GM) colony-stimulating factor (CSF), both of which are important for DC recruitment, survival and differentiation. Importantly, DC do not produce CCL20 or GM-CSF following allergen exposure. Blocking TNFα receptor 1 (TNFR1) completely abolished chemokine production, suggesting that BMDC-derived TNFα induced airway epithelial cell activation and enhancement of the innate immune response. Lastly, blocking TNFR1 in vivo resulted in significantly decreased CCL20 and GM-CSF production in the lungs of mice. Together, our data strongly suggest that DC-derived TNFα plays a crucial role in the initiation of innate immune responses through the modification of airway epithelial cell responses.

El litio y su influencia en la función tiroidea / Lithium and the influence in thyroid function

El Litio, utilizado como tratamiento de primera línea en la enfermedad maníaco depresiva, genera cambios en la fisiología tiroidea. En los últimos trabajos entre los años 1999 y 2007, se ha encontrado una alta prevalencia de hipofunción tiroidea en pacientes bipolares principalmente en el sexo femenino y a mayor edad. Aparentemente su aparición no se correlaciona con la duración del tratamiento ni con la Litemia. Dada la escasa literatura existente acerca de este tema, el objetivo de esta revisión es actualizar los datos últimamente publicados.

Lithium, used as a first line treatment in maniac depression disease, affects the thyroid gland function. In the last papers published between 1999 and 2007, it has been found a high prevalence of hypothyroidism in bipolar patients, especially in females and when starting lithium at a later age. The duration of treatment and Lithemia seams to have no correlation with the begining of hypothyroidism. Because of the poor literature written about this issue, the aim of this review is to update the last papers published.

Long-term evaluation of patient satisfaction and reflux symptoms after laparoscopic fundoplication with Collis gastroplasty.

BACKGROUND: Esophageal shortening is a complication of advanced gastroesophageal reflux disease (GERD). For patients with short esophagus, Collis gastroplasty combined with fundoplication provides excellent symptomatic relief from GERD disease. The literature lacks studies comparing satisfaction and reflux symptoms between patients who underwent Nissen fundoplication with Collis gastroplasty and those who had primary fundoplication alone. This study aimed to assess long-term satisfaction and GERD-related quality of life after laparoscopic Collis-Nissen fundoplication, and to compare them with those for Nissen fundoplication alone. METHODS: A nested case-control study was conducted. In this study, 14 cases of laparoscopic Collis-Nissen fundoplications were matched for age, gender, and length of the follow-up period to a cohort of 120 control subjects who underwent laparoscopic Nissen fundoplication. All the patients were mailed a follow-up survey which included a Short Form-12 (SF-12) health status (quality-of-life) questionnaire (a validated quality-of-life instrument), a Quality of Life in Reflux and Dyspepsia (QOLRAD) questionnaire (a GERD-specific quality-of-life instrument), and queries regarding long-term satisfaction and medication use. RESULTS: Both groups showed a significant postoperative increase in QOLRAD mean scores (p = 0.01). However, the difference in the delta (postoperative-preoperative) score between the two groups was not significant (Fig. 1). There were no differences in mental (MCS) or physical (PCS) SF-12 scores between the two groups. The rate of satisfaction with the surgery was similar in the Nissen-Collis fundoplication (87.5%) and Nissen fundoplication (87%) groups. CONCLUSIONS: Collis gastroplasty combined with Nissen fundoplication is an effective procedure for patients with a shortened esophagus diagnosed intraoperatively during antireflux surgery. Patient satisfaction, postoperative quality of life, and QOLRAD score improvement after this procedure are comparable with those observed in patients treated with Nissen fundoplication alone.

Predictors of success after laparoscopic gastric bypass: a multivariate analysis of socioeconomic factors.

BACKGROUND: Laparoscopic gastric bypass (LGB) has proven efficacy in causing significant and durable weight loss. However, the degree of postoperative weight loss and metabolic improvement varies greatly among individuals. Our study is aimed to identify independent predictors of successful weight loss after LGB. METHODS: Socioeconomic demographics were prospectively collected on patients undergoing LGB. Primary endpoint was percent of excess weight loss (EWL) at 1-year follow-up. Insufficient weight loss was defined as EWL or=52.8%. According to this definition, 147 patients (81.7%) achieved successful weight loss 1 year after LGB. On univariate analysis, preoperative BMI had a significant effect on EWL, with patients with BMI <50 achieving a higher percentage of EWL (91.7% vs 61.6%; p = 0.001). Marriage status was also a significant predictor of successful outcome, with single patients achieving a higher percentage of EWL than married patients (89.8% vs 77.7%; p = 0.04). Race had a noticeable but not statistically significant effect, with Caucasian patients achieving a higher percentage of EWL than African Americans (82.9% vs 60%; p = 0.06). Marital status remained an independent predictor of success in the multivariate logistic regression model after adjusting for covariates. Married patients were at more than two times the risk of failure compared to those who were unmarried (OR 2.6; 95% CI: 1.1-6.5, p = 0.04). CONCLUSIONS: Weight loss achieved at 1 year after LGB is suboptimal in superobese patients. Single patients with BMI < 50 had the best chance of achieving greater weight loss.

Heller myotomy vs Heller myotomy plus Dor fundoplication: cost-utility analysis of a randomized trial.

BACKGROUND: The addition of a Dor antireflux procedure reduces the risk of pathologic gastroesophageal reflux (GER) by ninefold following laparoscopic Heller myotomy for achalasia. It is not clear, however, how these benefits compare with the increased cost of the fundoplication. The objective of this study was to estimate the cost-effectiveness of Heller myotomy plus Dor fundoplication compared with Heller alone in patients with achalasia. METHODS: We conducted a cost-utility analysis using the Markov simulation model to examine the two treatment alternatives. The model estimated the total expected costs of each strategy over a 10-year time horizon. Data for the model were derived from our randomized clinical trial. The strategies were compared using the method of incremental cost-effectiveness analysis. RESULTS: The incidence of pathologic GER was 47.6% (10 of 21 patients) in the Heller group and 9.1% (2 of 22 patients) in the Heller plus Dor group using an intention-to-treat analysis (p = 0.005). Heller plus Dor was associated with a significant reduction in the risk of GERD (relative risk 0.11; 95% confidence interval 0.02-0.59; p = 0.01). The cost of surgery was significantly higher for Heller plus Dor than for Heller alone (mean difference $942; p = 0.04), secondary to a longer operating room time (mean difference 40 min; p = 0.01). At a time horizon of 10 years, when proton pump inhibitor (PPI) therapy costs are considered, the cost-utility analysis demonstrates that Heller plus Dor surgery is associated with a total cost of $6,861 per patient and a quality-adjusted life expectancy of 9.9 years, whereas Heller-alone surgery is associated with a cost of $9,541 per patient and a quality-adjusted life expectancy of 9.5 years. CONCLUSIONS: In achalasia patients, Heller myotomy plus Dor fundoplication is preferred to Heller alone because it is both more effective in preventing postoperative GERD and more cost-effective at a time horizon of 10 years.

Endoscopic evaluation of the gastrojejunostomy in laparoscopic gastric bypass. A series of 340 patients without postoperative leak.

BACKGROUND: A significant and potentially deadly complication of the Roux-en-Y gastric bypass is leakage from the gastrojejunostomy (GJ). The aim of our study was to evaluate the efficacy of intraoperative endoscopy in preventing postoperative anastomotic leakage. METHODS: The study enrolled 340 consecutive patients undergoing laparoscopic gastric bypass procedures performed from January 2001 to July 2004. In all cases, an endoscopist performed video gastroscopy to evaluate the integrity of the GJ using air insufflation of the pouch after distal clamping of the Roux limb. Intraoperative leaks were repaired and the anastomosis was retested. Demographic, operative, and endoscopic data were collected and analyzed. Logistic regression was used in both univariate and multivariate modeling to identify independent preoperative variables associated with the presence of intraoperative leak. Model parameters were estimated by the maximum likelihood method. From these estimates, odds ratios (ORs) with 95% confidence intervals (CIs) were computed. RESULTS: There were no postoperative anastomotic leaks or mortalities in our series. Overall, endoscopic evaluation of the GJ resulted in the detection of 56 intraoperative leaks (16.4%). There was a significant difference in the incidence of intraoperative leakage for patients older than 40 years (21%) vs those younger than 40 years (10.5%; p = 0.01). In the initial 91 cases, the GJ was performed by the end-to-end anastomosis (EEA) technique; the subsequent 249 were performed with a combination of linear stapling and handsewn technique. There was a trend toward more leakage in the GIA group (18%) versus EEA (12%); however, the difference was not significant (p = 0.188). Age remained an independent risk factor for leak detected intraoperatively in the multivariate logistic regression model after adjusting for covariates. Age >40 years increased the risk of intraoperative leakage by 2.3 times (OR, 2.3; 95% CI, 1.2-4.6; p = 0.01). The rate of postoperative anastomotic stricture was the same among patients detected with an intraoperative leak (5.4%) and those without (5.6%; p = 0.934). CONCLUSIONS: Endoscopic evaluation of the GJ is a sensitive and reliable technique for demonstrating anastomotic integrity and preventing postoperative morbidity after gastric bypass. Age >40 years was identified as an independent risk factor for intraoperative leak in this series.

Three year's experience with the Stretta procedure: did it really make a difference?

BACKGROUND: Endoscopic treatment is merging as a new option for GERD treatment. Many modalities have been used with modest short-term success, but no long-term follow-ups have been published. We present our 3-yr experience at Vanderbilt University using endoscopic radiofrequency energy (Stretta procedure) for GERD treatment. METHODS: Patients with follow-up >6 months were prospectively studied under IRB protocol. All were mailed SF-12 health status questionnaire and GERD specific quality-of-life (QOLRAD) questionnaires, queries about satisfaction with Stretta, and medication use. All were invited for 24-hour pH study. RESULTS: Eighty-six Stretta procedures were performed between 8/2000 and 7/2003 on 85 patients; all were outpatients, 89% under conscious sedation. Seventy-seven patients qualified for the study; 61 completed the survey, 24 returned for pH study. Follow-up was 26.2 +/- 7.5 months (6-36). All were on daily PPIs, with proven GERD by pH study or endoscopy. Mean preoperative acid exposure time was 7.8+/-2.6%, mean DeMeester score was 40.2+/-17.6. Postoperative mean acid exposure time was 5.1+/-3.3 (p=0.001), DeMeester score was 29.5+/-20.5 (p=0.041). Normal postoperative acid exposure time (pH<4 in <4.2%) was achieved in 42% of patients tested. Patients were then divided according to medication use at the end of f/u in 2 groups: Responders (off or >50% decrease in PPI dose), and nonresponders (on >50% of original PPI dose, or had fundoplication). Response rate was 60% (39 patients), 8 nonresponders underwent fundoplication (12%). Satisfaction rate was 73%. Statistically significant difference was found between the 2 groups in all measurements; SF-12 physical and mental score for responders were 45.5+/-10.2, and 52.6+/-7.8; and for nonresponders were 37.8+/-11.2 and 40.9+/-11.3 (p=0.012, p=0.0001), respectively. Statistically significant difference was also found between responders and nonresponders in postoperative acid exposure (4.5+/-3.34 vs 7.2+/-2.3, p=0.034), and DeMeester score (26.3+/-20.4 vs 39.7+/-20.2, p=0.05). Paired T test was used to compare pre- and postoperative acid exposure in each group; statistically significant difference was found only among responders: total reflux time was 7.50+/-2.3 preop and 4.5+/-3.34 postop (p=0.0001), whereas for nonresponders it was 8.6+/-3.7 and 7.2+/-2.3 (p=0.8), DeMeester scores pre- and postop among responders were 40.0+/-19.7 and 26.3+/-20.4, respectively (p=0.016), whereas for nonresponders it was 40.5+/-14.3 and 39.7+/-20.2 (p=0.79). CONCLUSIONS: Stretta is a safe modestly effective, totally endoscopic treatment for GERD. Symptomatic improvement when achieved is often associated with correlating improvement in distal acid exposure. This exposure normalizes in nearly half the treated patients.

Endoscopic treatment modalities for gastroesophageal reflux disease.

A debate has been going for decades between surgeons and gastroenterologists about the treatment of choice for gastroesophageal reflux disease (GERD). The lower esophageal sphincter (LES) has been historically far from the reach of gastroenterologists, who adopted the symptomatic treatment as their approach to reflux disease through reduction of gastric acid. As for surgeons, reaching the LES was only possible by invading the thoracic or abdominal cavity. Although their approach was later refined to become "minimally" invasive, it was still deemed too invasive by others to allow it to be the "gold standard." Simple logic should lead one to think about the "natural route" as the easiest way to reach the LES. This concept has opened the door for the new era of GERD treatment through "endoscopic modality." Seven different techniques are currently being used to treat patients with GERD. We review the mechanism of action, potential side effects, efficacy, durability, and results from the most recent or largest experience of each. This review shows that endoscopic treatment has definitely earned its place as a viable option for GERD treatment in selected patients. With the available data from clinical trials, it is not possible to determine the best modality available, and the endoscopic treatment of choice is to be determined with further studies.

Auditory detection of hollowness.

The airborne sounds produced by freely vibrating hollow and solid bars were synthesized according to the equations of bar motion from theoretical acoustics, and were presented to listeners over headphones. In a two-interval, forced-choice task, listeners were asked to distinguish between the hollow and solid bar sounds as bar length was varied at random from one presentation to the next. All other physical properties of the bar were held constant across trials. Listener decision strategies for detecting hollowness in iron, aluminum, and wood bars were determined from regression weights describing the relation between the listener's response and the frequency, intensity, and decay modulus of the individual partials comprising these sounds. The obtained weights were compared to those of a hypothetical listener that bases judgments on the acoustic relations intrinsic to hollowness, as determined from the equations for motion. Results indicate that listeners adopt roughly one of two decision strategies, either basing judgments on the appropriate acoustic relations, or basing judgments predominantly on frequency alone. The decision strategy of some listeners also changed from one type to the other with a change in bar material or upon replication of the same condition. The results are interpreted in terms of the vulnerability of the intrinsic acoustic relations to small perturbations in acoustic parameters, as would be associated with listener internal noise. They demonstrate that basic limits of human sensitivity can have a profound effect on the identification of rudimentary source attributes from sound, even in conditions where acoustic variation is largely dictated by physical variation in the source.

Children's detection of pure-tone signals with random multitone maskers.

Preschoolers and adults were asked to detect a 1000-Hz signal, which was masked by a multitone complex. The frequencies and amplitudes of the components in the complex varied randomly and independently on each presentation. A staircase, cued two-interval, forced-choice procedure disguised as a "listening game" was used to obtain signal thresholds in quiet and in the presence of the multitone maskers. The number of components in the masker was fixed within an experimental condition and varied from 2 to 906 across experimental conditions. Thresholds were also measured with a broadband noise masker. Eight preschool children and eight adults were tested. Although individual differences were large, among both adults and children, there was little difference between the groups in the mean amount of masking produced by the maskers with large numbers of components (400 and 906). There was also a small but significant difference between adults and children in the mean amount of masking produced by the broadband noise. The difference between the groups was much larger with smaller numbers of components. Data obtained from the adults were basically similar to that previously reported [cf. Neff and Green, Percept. Psychophys. 41, 409-415 (1987); Oh and Lutfi, J. Acoust. Soc. Am. 104, 3489-3499 (1998)]: maskers comprised of 10-40 components produced as much as 30 to 60 dB of masking in some, but not all listeners. Those same maskers produced larger amounts of masking (70-83 dB) in many of the preschool children, although, as in the adult group, individual differences were large. The component-relative-entropy (CoRE) model [Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)] was used to describe the differences in performance between the children and adults. According to this model the average child appears to integrate information over a larger number of auditory filters than the average adult.

Effect of masker harmonicity on informational masking.

Detection thresholds for a tone in an unfamiliar tonal pattern can be greatly elevated under conditions of masker uncertainty [Neff and Green, Percept. Psychophys. 41, 409-415 (1987); Oh and Lutfi, J. Acoust. Soc. Am. 101, 3148 (1997)]. The present experiment was undertaken to determine whether harmonicity of masker tones can reduce the detrimental effect of masker uncertainty. Inharmonic maskers were comprised of m=2-49 frequency components selected at random on each presentation within 100-10000 Hz, excluding frequencies between 920-1080. Harmonic maskers were comprised of frequency components selected at random within this same range, but constrained to have a fundamental frequency of 200 Hz. For inharmonic maskers the signal was a 1000-Hz tone. For harmonic-maskers the signal was a tone whose frequency was either harmonically (1000 Hz) or inharmonically (1047 Hz) related to the masker. In all conditions the amount of masking was greatest for m = 20-40 components. At this point, harmonic maskers with harmonic signal produced an average of 9-12 dB less masking than inharmonic maskers. Harmonic maskers with inharmonic signal produced an average of 16-20 dB less masking.

Correlational analysis of acoustic cues for the discrimination of auditory motion.

The sound of a source moving in a straight path and passing directly in front of the listener on the azimuthal plane was synthesized over headphones to include three dynamic cues for motion: Doppler effect, overall intensity, and interaural time difference. Discriminability of a change in displacement, velocity, and acceleration of this source was measured using a standard two-interval, forced-choice procedure. In each case, the relative reliance or weight given to the three acoustic cues was estimated from correlations of the listener's response with small independent pertubations imposed on cues from trial to trial. Group estimates of threshold agreed well with results from past studies, while the obtained pattern of weights depended on the individual, starting velocity, and discrimination task. For the discrimination of displacement at moderate velocity (10 m/s), responses were most highly correlated with intensity or interaural time difference. For the discrimination of velocity and, to a lesser extent, acceleration, responses were most highly correlated with Doppler effect. At higher velocity (50 m/s) responses in all discrimination tasks were most strongly correlated with Doppler effect with few exceptions. Randomizing source spectrum or roving distance of the source from trial to trial did not significantly affect the pattern of results. The results suggest that motion perception is mutable, and not in all cases based on a single invariant acoustic cue.

Level discrimination of single tones in a multitone complex by normal-hearing and hearing-impaired listeners.

A conditional-on-a-single-stimulus (COSS) analysis procedure [B. G. Berg, J. Acoust. Soc. Am. 86, 1743-1746 (1989)] was used to estimate how well normal-hearing and hearing-impaired listeners selectively attend to individual spectral components of a broadband signal in a level discrimination task. On each trial, two multitone complexes consisting of six octave frequencies from 250 to 8000 Hz were presented to listeners. The levels of the individual tones were chosen independently and at random on each presentation. The target tone was selected, within a block of trials, as the 250-, 1000-, or 4000-Hz component. On each trial, listeners were asked to indicate which of the two complex sounds contained the higher level target. As a group, normal-hearing listeners exhibited greater selectivity than hearing-impaired listeners to the 250-Hz target, while hearing-impaired listeners showed greater selectivity than normal-hearing listeners to the 4000-Hz target, which is in the region of their hearing loss. Both groups of listeners displayed large variability in their ability to selectively weight the 1000-Hz target. Trial-by-trial analysis showed a decrease in weighting efficiency with increasing frequency for normal-hearing listeners, but a relatively constant weighting efficiency across frequency for hearing-impaired listeners. Interestingly, hearing-impaired listeners selectively weighted the 4000-Hz target, which was in the region of their hearing loss, more efficiently than did the normal-hearing listeners.

Informational masking by everyday sounds.

Tone-in-noise detection is severely degraded when only a few spectral components of the noise are presented at random on each trial [Neff and Green, Percept. Psychophys. 41, 409-415 (1987)]. The elevations in threshold are attributed to uncertainty regarding the noise caused by sparse sampling of noise components-informational masking is the term used to describe the result. The present experiment was undertaken to determine how informational masking is affected when sparse sampling is from a set of common everyday sounds instead of noise. On each presentation a different masker waveform of constant total power was synthesized from the magnitude and phase of a fixed number, m, of spectral components (m = 2-921 across blocks of trials). The components were selected at random from 1 of 50 common environmental sounds (e.g., baby crying, door slamming, phone ringing), or 1 of 50 samples of Gaussian noise. Masked thresholds for a 1.0-kHz signal in the presence of both types of maskers were obtained using an adaptive, two-interval, forced-choice procedure. Results with noise replicated earlier, results showing largest elevations in threshold for 10-20 sampled components. Results with everyday sounds showed a similar pattern with thresholds elevated above those for noise by as much as 10 dB at the larger values of m. The differences in masked thresholds were systematically related to differences in the ensemble variance of masker spectra, as predicted by a model previously applied to noise [Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)]. Not predicted was the result of a subsequent trial-by-trial analysis in which 9-11 dB less masking was observed for samples from everyday sounds rated as easily recognized by listeners. The results suggest that listeners fail to exploit lawful dependencies among spectral components of everyday sounds to aid detection, unless enough information is available for the sound to be easily recognized.

Nonmonotonicity of informational masking.

Neff and Green [Percept. Psychophys. 41, 409-415 (1987)] report that the masking of single tones by random-frequency multitone maskers varies nonmonotonically with number of masker components (peaking at 10-50 components). In this paper it is shown that such results are well predicted by a model (the component-relative-entropy model, CoRE) wherein thresholds increase linearly with the ensemble variance of masker spectra smoothed by peripheral auditory filters [R. A. Lutfi, J. Acoust. Soc. Am. 94, 748-758 (1993)]. Three experiments were conducted. In the first, the nonmonotonic relation was replicated for 9 of 11 listeners in conditions similar to those of Neff and Green. In the second, the frequencies of masker components were fixed and the levels of components were varied randomly across presentations to simulate Gaussian noise. In this case, the nonmonotonicity and the total amount of masking for these listeners were shown to be significantly reduced. In the third experiment, masked thresholds for the signal were found to vary monotonically with the frequency spacing of masker components for a fixed number of masker components. Large individual differences among listeners were obtained in some experimental conditions. Individual as well as mean thresholds were well predicted by the CoRE model with an appropriate selection of the values of the two free parameters of the model for each listener.