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.

Efficacy of 3 commonly used hearing aid circuits: A crossover trial. NIDCD/VA Hearing Aid Clinical Trial Group.

CONTEXT: Numerous studies have demonstrated that hearing aids provide significant benefit for a wide range of sensorineural hearing loss, but no carefully controlled, multicenter clinical trials comparing hearing aid efficacy have been conducted. OBJECTIVE: To compare the benefits provided to patients with sensorineural hearing loss by 3 commonly used hearing aid circuits. DESIGN: Double-blind, 3-period, 3-treatment crossover trial conducted from May 1996 to February 1998. SETTING: Eight audiology laboratories at Department of Veterans Affairs medical centers across the United States. PATIENTS: A sample of 360 patients with bilateral sensorineural hearing loss (mean age, 67.2 years; 57% male; 78.6% white). INTERVENTION: Patients were randomly assigned to 1 of 6 sequences of linear peak clipper (PC), compression limiter (CL), and wide dynamic range compressor (WDRC) hearing aid circuits. All patients wore each of the 3 hearing aids, which were installed in identical casements, for 3 months. MAIN OUTCOME MEASURES: Results of tests of speech recognition, sound quality, and subjective hearing aid benefit, administered at baseline and after each 3-month intervention with and without a hearing aid. At the end of the experiment, patients ranked the 3 hearing aid circuits. RESULTS: Each circuit markedly improved speech recognition, with greater improvement observed for soft and conversationally loud speech (all 52-dB and 62-dB conditions, P

Monosyllabic word recognition at higher-than-normal speech and noise levels.

The effects of intensity on monosyllabic word recognition were studied in adults with normal hearing and mild-to-moderate sensorineural hearing loss. The stimuli were bandlimited NU#6 word lists presented in quiet and talker-spectrum-matched noise. Speech levels ranged from 64 to 99 dB SPL and S/N ratios from 28 to -4 dB. In quiet, the performance of normal-hearing subjects remained essentially constant in noise, at a fixed S/N ratio, it decreased as a linear function of speech level. Hearing-impaired subjects performed like normal-hearing subjects tested in noise when the data were corrected for the effects of audibility loss. From these and other results, it was concluded that: (1) speech intelligibility in noise decreases when speech levels exceed 69 dB SPL and the S/N ratio remains constant; (2) the effects of speech and noise level are synergistic; (3) the deterioration in intelligibility can be modeled as a relative increase in the effective masking level; (4) normal-hearing and hearing-impaired subjects are affected similarly by increased signal level when differences in speech audibility are considered; (5) the negative effects of increasing speech and noise levels on speech recognition are similar for all adult subjects, at least up to 80 years; and (6) the effective dynamic range of speech may be larger than the commonly assumed value of 30 dB.

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.

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.

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.

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.

Frequency-importance and transfer functions for the Auditec of St. Louis recordings of the NU-6 word test.

Frequency-importance and transfer functions for the Auditec of St. Louis recordings of the NU-6 word test are reported. The functions were derived from the word recognition scores of 24 subjects with normal hearing who were tested under 128 conditions of filtering and talker-spectrum-matched noise. The importance function was broader and had a lower midpoint than the NU-6 importance function reported by Schum, Matthews, and Lee (1991), but still displayed a bimodal shape. The transfer function was steeper than the transfer function reported by Schum et al., but comparable in slope to the transfer function for low-context CNC words reported by Bell, Dirks, and Trine (1992). Results from a limited set of conditions presented in quiet suggest that the use of masking noise was partly responsible for the dissimilar importance and transfer functions obtained by Schum et al. and this study. Differences in the equipment used in each experiment and in the methods used to analyze the data appear to have contributed as well.

Performance-intensity functions at absolute and masked thresholds.

In most applications of audibility and articulation theories, it is assumed that absolute thresholds and thermal noise maskers affect speech recognition performance-intensity (P-I) functions similarly. The purpose of this study was to evaluate that assumption. Performance-intensity functions for NU-6 monosyllabic words were obtained from eight normal-hearing subjects in quiet and in the presence of two levels of a noise that produced masked pure-tone thresholds parallel to, but higher than, those of each individual in quiet. The results support the practice of treating absolute threshold as a noise-masked threshold in predictions of speech recognition performance.

Speech spectra for six recorded monosyllabic word tests.

Speech spectra (long-term RMS levels and 1% speech peaks) in third-octave bands were determined for six monosyllabic word test materials: digital recordings of the Central Institute for the Deaf W-22 word test and the Northwestern University NU-6 word test obtained from Qualitone; audiotape recordings of the Central Institute for the Deaf W-22 word test, the Northwestern University NU-6 word test, and the Harvard Psycho-Acoustic Laboratory PB-50 word test obtained from Auditec of St. Louis; and an audio-tape recording of the Maryland CNC word test obtained from Olsen Distributors. The spectra were generally within 2 SD of previous results for continuous speech spoken by an average male talker (Cox, Matesich, & Moore, 1988; Cox & Moore, 1988), but differed sufficiently from those data and from one another to affect the accuracy of Articulation Index calculations. The relationship between the level of the calibration tone and the speech in the third-octave band centered at 1000 Hz was different for each recording.

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.

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.

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.

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.

Frequency importance functions for a feature recognition test material.

The relative importance of different parts of the auditory spectrum to recognition of the Diagnostic Rhyme Test (DRT) and its six speech feature subtests was determined. Three normal hearing subjects were tested twice in each of 70 experimental conditions. The analytical procedures of French and Steinberg [J. Acoust. Soc. Am. 19, 90-119 (1947)] were applied to the data to derive frequency importance functions for each of the DRT subtests and the test as a whole over the frequency range 178-8912 Hz. For the DRT as a whole, the low frequencies were found to be more important than is the case for nonsense syllables. Importance functions for the feature subtests also differed from those for nonsense syllables and from each other as well. These results suggest that test materials loaded with different proportions of particular phonemes have different frequency importance functions. Comparison of the results with those from other studies suggests that importance functions depend to a degree on the available response options as well.

Earphones in audiometry. Committee on Hearing, Bioacoustics, and Biomechanics. Commission on Behavioral and Social Sciences and Education. National Research Council Working Group.

The advantages and disadvantages of three types of earphones for audiometric testing are discussed. Supraaural earphones continue to be recommended for this purpose, in preference to circumaural and insert types.

A frequency importance function for continuous discourse.

Normal hearing subjects estimated the intelligibility of continuous discourse (CD) passages spoken by three talkers (two male and one female) under 135 conditions of filtering and signal-to-noise ratio. The relationship between the intelligibility of CD and the articulation index (the transfer function) was different from any found in ANSI S3.5-1969. Also, the lower frequencies were found to be relatively more important for the intelligibility of CD than for identification of nonsense syllables and other types of speech for which data are available except for synthetic sentences [Speaks, J. Speech Hear. Res. 10, 289-298 (1967)]. The frequency which divides the auditory spectrum into two equally important halves (the crossover frequency) was found to be about 0.5 oct lower for the CD used in this study than the crossover frequency for male talkers of nonsense syllables found in ANSI S3.5-1969 and about 0.7 oct lower than the one for combined male and female talkers of nonsense syllables reported by French and Steinberg [J. Acoust. Soc. Am. 19, 90-119 (1947)].