Susceptibility of Rice to Oebalus pugnax (F.) (Hemiptera: Pentatomidae) Feeding at Different Levels of Grain Maturity and Impacts on Insecticide Termination.

The stages of rice, Oryza sativa L. (Poales: Poaceae), grain maturity that are most susceptible to rice stink bug, Oebalus pugnax (F.), damage have been identified; however, the stage at which they are no longer capable of causing appreciable damage during grain maturity is unclear. The objective of this study was to determine the susceptibility of rice to rice stink bug feeding at different levels of grain maturity and determine an insecticide termination timing. Rice stink bug damage was examined using five levels of grain maturity described as percent of kernels reaching mature straw coloration referred to as hard dough (20, 40, 60, 80, and 100%) across a range of infestation levels using single panicle sleeve cages and large cages. Hybrid and conventional cultivar rice panicles at 20, 40, and 60% hard dough were found to be susceptible to indirect yield loss, as two rice stink bugs per panicle resulted in over 7% peck. In large cage trials, 25 rice stink bugs caused 0.7-1% peck to hybrid and conventional rice plots at 20% hard dough. Much less damage was observed once rice reached 60% hard dough, where peck averages only reached 0.4%. Decreased damage at 60% hard dough was validated using uncaged trials where 0.4% additional peck was observed in unsprayed plots. These data indicate that rice in the early stages of hard dough is susceptible to large levels of indirect yield loss, but unless significant densities of rice stink bug are present at 60% hard dough, no more sampling or applications are necessary.

Comparison of direct and indirect sampling methods for tarnished plant bug (Hemiptera: Miridae) in flowering cotton.

A complex of hemipterans, especially the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become a major target of insecticides in flowering cotton, Gossypium hirsutum L., in the mid-southern United States. Sampling protocols for this complex during this period of cotton development are poorly established, resulting in uncertainty about when infestations warrant treatment. Nine direct and indirect sampling methods were evaluated for bias, precision, and efficiency in cotton throughout the Mid-South during 2005 and 2006. The tarnished plant bug represented 94% of the bug complex in both years. Sweep-net and black drop-cloth methods were more efficient than other direct sampling methods, but they were biased toward adults and nymphs, respectively. Sampling dirty blooms was the most efficient indirect sampling method. The sweep-net, whole-plant, and dirty-bloom methods were more accurate than the other sampling methods evaluated based on correlations with other sampling methods. Variability attributed to the person collecting the sample was significant for all sampling methods, but least significant for the dirty-square method. Further research is needed to establish thresholds based on sweep-net, drop-cloth, dirty-square, and dirty-bloom sampling methods as these methods provide the best combinations of accuracy and efficiency for sampling tarnished plant bugs in cotton.

Spectrum shaping with a hardware digital filter.

Digital filters have certain characteristics which make possible some things that are either difficult or essentially impossible using analog equipment. Among the most useful characteristics are steep transition band slopes and the capability to shape the passband transfer function in great detail. Unlike most digital filters implemented in software, hardware digital filters can be used to filter signals in real-time. Also, they can be designed to provide a linear phase response. They have some disadvantages as well, however, including moderately high cost, the need for supporting equipment, and at the present time, the need for a moderate degree of computer programming and interfacing skill. We have used hardware digital filters in a number of applications. These applications and the relevant filter performance characteristics are described.

The effect of equating loudness on audibility-based hearing aid selection procedures.

Recently the articulation index (AI) has received a great deal of attention as a means to select hearing aid characteristics and to evaluate the merits of different hearing aid selection methods. These evaluations were based on the seldom modified assumption that the listening condition producing the largest AI is the best condition. The negative consequences of the differences in hearing aid conditions were seldom considered. In this paper it is shown that higher AIs are often achieved at the cost of substantially greater loudness. When gain adjustments are made to equate loudness across conditions, very different conclusions are reached about the relative merits of selection methods and the value of certain frequency-gain response modifications.

Evaluating relative speech recognition performance using the proficiency factor and rationalized arcsine differences.

This study evaluated two measures that have been used to compare the performance of particular subjects to outcomes predicted by the articulation index (Al). One measure was the proficiency factor, that is, the ratio between the Al derived from a test score and the Al derived from objective measurements of speech and noise spectra. The other measure was the difference between rationalized arcsine transforms of the observed score and the score predicted from the Al. The results indicated that rationalized arcsine differences are statistically superior to proficiency factors for comparing two sets of scores. Proficiency factors are best used to correct the Al, and thus an expected score, for the effects of subject variables that might bias the comparison. An assessment procedure that combines the strengths of both measures is described.

Prediction and statistical evaluation of speech recognition test scores.

A speech test evaluation and presentation system is described. The test presentation subsystem has the flexibility and speed of live-voice testing while using recorded test materials. The speech test evaluation subsystem compares an individual subject's test performance on a monosyllabic word test with that of an average person with the same hearing loss. The elements needed to make such evaluations are discussed. Also, a trial of the procedure is described. The primary purpose of the trial was to obtain data that would provide a basis for statistical probability statements about individual monosyllabic word test results obtained in clinical settings. Data were collected from three audiology clinics in three different types of settings. Except for a few cases with highly asymmetric speech scores, all nonconductive hearing losses were included. Subject ages ranged from 8 to 92 years. Importance-weighted average pure-tone hearing losses ranged from 0.4 to 97.6 dB HL. Fifty-word recognition scores and audiograms for 2609 ears were included in the main analysis. Twenty-five-word recognition scores and audiograms for another 932 ears from one clinic were used in a subsidiary analysis. Results indicated that distributions of absolute speech recognition scores in hearing-impaired samples are highly skewed. However, after transformation of the scores into rationalized arcsine units (rau), the differences between individual subject scores and scores predicted from the audiogram were reasonably well described by the normal distribution. The standard deviation of this distribution of differences, for the data combined across the three audiology clinics, was approximately 13 rau.

Age-related changes in monosyllabic word recognition performance when audibility is held constant.

Monosyllabic word recognition was studied in 140 subjects between the ages of 20 and 90 years. The subjects were tested under a condition of fixed audibility that was achieved by presenting bandpass-filtered Northwestern University Auditory Test No. 6 (NU-6) word lists at a constant signal-to-noise ratio and limiting threshold losses at the speech frequencies to 25 dB HL. The results indicated the following: (1) Performance did not vary appreciably with age, except among subjects over 70 years. Subjects from 70 to 80 years produced modestly reduced scores (significantly below only the 30-year-old group). Those over 80 years produced significantly lower scores (than all other groups). (2) There were no significant differences in learning or test-retest reliability associated with age. (3) The performance of the oldest subjects could not be explained by differences in speech audibility. Based on these results, a strategy is proposed for correcting predicted word recognition scores for the effects of age.

Directivity of the human vocal source in the horizontal plane.

The directional characteristics of a male and a female voice in the horizontal plane were measured in an anechoic room. Results were compared with the only two other studies known to have been done using human subjects. The results of the three studies agree very well. The directional characteristics of two loudspeakers were also measured. One loudspeaker, about the size of the human head, did a fairly good job of emulating the directional characteristics of the human vocal source. Another large loudspeaker did a very poor job. The directional characteristics of a manikin designed and evaluated by Olson (1972. J. Audio. Eng. Soc. 20, 446-451) agreed well with the averaged results from the three studies of human talkers.

A "rationalized" arcsine transform.

Arcsine or angular transformations have been used for many years to transform proportions to make them more suitable for statistical analysis. A problem with such transformations is that the arcsines do not bear any obvious relationship to the original proportions. For this reason, results expressed in arcsine units are difficult to interpret. In this paper a simple linear transformation of the arcsine transform is suggested. This transformation produces values that are numerically close to the original percentage values over most of the percentage range while retaining all of the desirable statistical properties of the arcsine transform.

Importance weighted audibility and the recognition of hearing aid-processed speech.

The purpose of this study was to determine the extent of the agreement between the speech-recognition performance of normally hearing subjects with each of six linear hearing aids and the performance predicted for those aids by a carefully derived articulation index. Also investigated was how much of the remaining variability in average subject performance across hearing aids could be attributed to harmonic distortion. It was found that predicted performance and average observed performance never differed by more than 8.4 rau (mean = 2.3 rau) and that the articulation index procedure used alone accounted for 90 to 94% of the variance in averaged subject performance.

Side branch and parallel vent effects in real ears and in acoustical and electrical models.

The purpose of the project was to demonstrate and explain the acoustic effects of side branch and parallel vents in individual real ears. It was shown that parallel and side branch vents produce similar low frequency filtering effects and vent-associated reactance resonances. However, when the input system incorporates a side branch vent the sound pressure produced in the ear canal at frequencies above the vent-associated resonance is less than that produced when the input system is unvented. This effect is not seen when the input system is associated with a parallel vent. Data obtained in the real ear canals were compared to analogous measurements made using an acoustical model (the Zwislocki coupler) and an electrical model designed to simulate the hearing aid receiver, input tubing, earmold, ear canal, and eardrum. Both models yielded data very similar to the real ear results. The advantages of each model in predicting the effects of individual earmold vents are discussed.

Frequency-importance and transfer functions for recorded CID W-22 word lists.

Frequency-importance and transfer functions for the Technisonic Studios' recordings of the CID W-22 word test are reported. These functions may be used to calculate Articulation Index (AI) values or to predict scores on the W-22 test. The functions were derived from the word recognition scores of 8 normal-hearing listeners who were tested under 308 conditions of filtering and masking. The importance function for the W-22 test has a broader frequency range and a different shape than the importance function used in the current ANSI standard on the Articulation Index (ANSI, 1969). The transfer function is similar in slope to the ANSI transfer function for 256 PB-words, but is shifted to the right of that function by 0.05 AI.

An evaluation of some assumptions underlying the articulation index.

The purposes of this investigation were to derive measurement and calculation procedures for the articulation index (AI) that were as precise and accurate as possible, and to evaluate the significance of the differences in assumptions made by early investigators. A nonsense syllable test specifically designed for this application was recorded. The implications of various assumptions utilized in different approaches to predicting speech sound identification were tested using 13 different conditions which differed with respect to filtering, level of interfering noise, or level of the speech signal. The listeners were three normal hearing individuals. A set of preferred assumptions was chosen based on a post hoc evaluation of the data. Predictions of speech sound identification were good, both for the average listener and for individual listeners.

Effects of intensity on speech recognition in high- and low-frequency bands.

OBJECTIVE: This study investigated the intensive effects of a low-frequency (200 to 400 Hz) and a high-frequency (1000 to 5000 Hz) band of speech presented jointly and in isolation. DESIGN: Each band was presented at a reference intensity level equivalent to the average normal conversational level. To investigate intensive effects, the low-frequency band was presented at 20 dB and 36 dB, and the high-frequency band at 20 dB above the reference level. Each band was presented at a fixed signal-to-noise ratio. Subjects were four normal-hearing adult females. The AI was used to predict performances and to determine audibility of each band. RESULTS: The best performance occurred for a joint band presentation with each band at the reference level. Increasing intensity of one band by 20 dB, for joint band conditions, did not significantly affect performance. However, increasing the low-frequency band by 36 dB or both bands by 20 dB resulted in a significant decrease in performance. CONCLUSIONS: Reduced performance with the low-frequency band at 36 dB and the high-frequency band at the reference level is attributed primarily to upward spread of masking by speech. Performance decrements for other joint band conditions are attributed to combined effects of high intensity.

Magnitude estimations of the intelligibility and quality of speech in noise.

Inexperienced normal hearing listeners judged the intelligibility and quality of hearing aid processed speech using magnitude estimation. Four trials were conducted for each judgment type at two S/N ratios, 0 and 7 dB. There were no significant effects due to judgment type, S/N ratio or trial; however, noticeable differences in the variability of these factors were apparent. Inter- and intrasubject standard deviations for quality estimations were lower than for intelligibility estimations while intersubject standard deviations were greater at 0 dB than at 7 dB S/N ratio and decreased over trial. Overall intrasubject variability was greater than would probably be acceptable for clinical applications. Across hearing aid conditions, magnitude estimations were positively correlated with word recognition scores but were less affected by changes in S/N ratio.

Spectral changes produced by earphone-cushion reproduction of hearing aid-processed signals.

This investigation was conducted to assess the extent to which hearing aid-processed signals present an acoustic signal to the subject which has a frequency response equivalent to that which the hearing aid itself would have provided. The frequency response of a hearing aid receiver which was coupled directly to the ear canal ("aided" condition) was compared with the frequency response of the same receiver when its output was recorded on magnetic tape and then presented to the subject via a TDH-49 earphone ("pseudoaided" condition). Results indicated that when the earphone was mounted in an MX-41/AR cushion or either of two circumaural cushions, the spectrum of the sound arriving at the subject's eardrum in the pseudoaided condition was substantially different from the spectrum delivered in the aided condition.

Hearing-aid-processed signals: a new approach.

A new protocol for obtaining and utilizing hearing-aid-processed signals in hearing aid research or hearing aid selection is described. Data are presented which illustrate the extent to which this procedure may be expected to result in a signal spectrum at the subject's eardrum which is the same as the spectrum the subject would have received if the hearing aid itself had been placed on his ear (a directly-aided situation). An earlier investigation by the authors indicated that the traditional protocol for the production and utilization of hearing-aid-processed signals results in substantial discrepancies between these two spectra. The data presented were obtained using the KEMAR as the subject with a Zwislocki coupler as the KEMAR's ear canal/eardrum. The discrepancy between directly-aided and hearing-aid-processed spectra was typically +/- 2 dB for ear-level hearing aids fitted using standard, vented, or open earmolds (in open earmold fittings only the amplified component of the directly-aided spectrum is reproduced).

The effect of noise spectrum on speech recognition performance-intensity functions.

Articulation theory predicts that a subject's absolute or masked threshold configuration will affect the slope of the speech recognition performance-intensity (P-I) function. This study was carried out to test that prediction. Performance-intensity functions for the Technisonic Studios W-22 recordings were obtained from 12 subjects with normal hearing. Four continuous thermal noise maskers, high-pass (HP) noise, white noise, ANSI noise, and talker-spectrum-matched (TSM) noise, were used to shape threshold. P-I function slopes for the averaged data ranged from about 1.6%/dB in HP noise to about 6.7%/dB in TSM noise. At low to moderate speech intensity levels, the positions and slopes of the P-I functions were accurately estimated by an articulation index-type model that included corrections for subject proficiency and for high- and low-frequency spread of masking. At higher intensity levels, performance was overestimated by the model.

Sound levels in a 2-cc cavity, a Zwislocki coupler, and occluded ear canals.

Probe-tube measurements of the differences in sound levels at three locations in ear canals were compared to the differences in levels measured at analogous positions in a Zwislocki coupler and a 2-cc cavity. The results support the recommendation of Sachs and Burkhard that probe tube measurements should not be made with the probe tube flush with the earmold tip and close to the sound inlet bore. In real ear canals the transfer functions to the eardrum presented by Bruel, Frederikson, and Rasmussen and by Studebaker agree well with each other but differ somewhat from the one used by Sachs and Burkhard. In agreement with Bruel et al., the data of this study reveal a plateau in the relationship between real ear and 2-cc cavity responses between about 1.6 and 4.0 kHz, the relative intensity level of which may depend upon residual ear canal volume.