Discrimination In Quiet Research Articles

Improved information transfer of phoneme features with a multiple-electrode cochlear implant.

The spectral maxima sound processor (SMSP), recently developed at the University of Melbourne, has been shown to provide improved speech discrimination in quiet and in noise for subjects using the Mini System 22 cochlear implant when compared with commercially available speech processors, including the Mini Speech Processor (MSP) [C. M. McKay and H. J. McDermott, J. Acoust. Soc. Am. 89, 1959 (1991)]. The ability of five subjects to perceive phoneme features using the SMSP has been compared with their ability using the MSP. Information transfer analysis has been applied to the results of open-set CNC word tests and closed-set vowel and consonant recognition tests. Phoneme features studied were consonant manner and place of articulation and voicing, vowel duration, formant frequencies, and formant transitions. The results show an overall improvement in the perception of all phoneme features, with large improvements seen in perception of consonant place of articulation. This consonant feature has been perceived poorly relative to other consonant features with all previous speech processors used with this implant. Further development of the SMSP is being guided by the results of this analysis.

Effects of noise and hearing loss upon frequency discrimination.

Frequency discrimination in quiet and in the presence of several levels of low-frequency masking noise was measured at 500, 1,000 and 2,000 Hz in both normal-hearing and hearing-impaired subjects. The test signals were presented at 80 dB SPL; all test signals were at least 10 dB above each subject's masked threshold. As a group, the hearing impaired subjects had larger frequency difference limens than the normal subjects, especially in frequency regions of greatest sensitivity loss. The masking noise produced a similar increase in frequency difference limens in both groups. Although several previous speech recognition studies have demonstrated an interactive effect between the presence of hearing loss and masking noise, the results of the present study demonstrate that frequency discrimination performance for normal-hearing and hearing-impaired subjects is not differentially affected by the addition of masking noise.

Clinical evaluation of a new nonelectronic all-in-the-ear hearing device for mild hearing loss.

A new, nonelectronic hearing aid was studied in 112 patients with mild sloping sensorineural hearing loss. The device, worn all in the ear and made of clear plastic, produced a mean functional gain of 9.6 dB at 1500 Hz, 12.4 dB at 1750 Hz, and 9.1 dB at 2000 Hz, with lesser gains at adjacent frequencies between 1000 and 2500 Hz. Speech discrimination in quiet and in noise was improved. Patient acceptance of the device (in a group of 884 patients) was 76%. The device appears to be useful in the treatment of mild hearing loss.

Frequency discrimination in quiet and in noise for signals with triangular spectral envelopes.

The just-noticeable-difference in frequency (jndf) for complex signals with triangular spectral envelopes is found to depend on the envelope slope. For shallow slopes (less than 140 dB/oct), jndf increases with decreasing slope. Addition of noise also impairs frequency discrimination within a region of about 20 dB above masked threshold. This is found for both maskers used: a wideband noise and a narrow-band masker which is below the signal in frequency. When wideband noise is used, frequency discrimination of complex signals with shallow slopes deteriorates more rapidly with decreasing signal-to-noise ratio than it does when the signals have steep spectral slopes.

Loudness scaling and masking in rats.

Two groups of rats were trained on operant discriminations in which the discriminanda were two different sound pressure levels of a 4-kHz tone. The discriminanda were chosen so that the loudness difference between stimuli was equivalent for each group when calculated from a power function with an exponent of .35. Half of each group learned the discrimination in quiet, and the other half learned it in a background of white noise. Within the quiet and the noise conditions, the asymptotic discriminability of stimuli separated by equal loudness differences was equivalent, and discriminability was lower in noise. This is consistent with both the human literature on masked loudness and a model of psychophysical scaling (Pierrel-Sorrentino & Raslear, 1980) in which animals judge perceived differences between stimuli.

Effect of tinnitus masker noise on speech discrimination in quiet and two noise backgrounds.

Use of masking devices is achieving recognition as a means of providing tinnitus relief. While palliative results have been described, possible disruptive consequences have not yet received attention. The present study examined the effects of tinnitus masker noise on speech intelligibility. Twenty young normals listened to NU-6 word lists presented in sound field in quiet white noise, and cocktail party noise backgrounds (S/N = O dB) with and without a tinnitus masker. Although there was little impairment while wearing the masker in quiet, substantial discrimination loss was observed in the two noise backgrounds. The potential disruption in communication function while wearing a masking device is discussed.

Effects of acetylsalicylic acid on speech discrimination.

Speech discrimination scores were obtained in quiet and against a background of competing noise for 5 persons both before and after they had ingested large doses of acetyl-salicylic acid (aspirin). The results indicate that for some persons, aspirin produces a substantial decrease in speech understanding in noise, even though there may not be a decrease in pure-tone sensitivity or speech discrimination in quiet.

Children's speech discrimination in quiet and noise

Normal children 5–8 years old, were tested on a new speech discrimination procedure. Stimuli were monosyllabic nouns within the receptive vocabularies of three‐year‐old inner‐city children. An up—down procedure tracked the 71% correct level of response. Open‐ and closed‐set conditions were tested. Closed‐set conditions used four‐alternative picture responses. Subjects were tested in quiet with an open response set (no pictures) and then on three closed‐set conditions: quiet, with a 12‐talker‐babble masker at 70 dB SPL, and with a filtered‐noise masker (filtered to have the same spectrum as the babble) at 70 dB SPL. Thresholds in babble were about 10 dB higher than thresholds in noise, and open‐set quiet thresholds were about 10 dB higher than closed‐set quiet thresholds. No age differences were observed. The absence of an age effect with the monosyllable stimulus items contrasts with an earlier report [L. L. Elliott, J. Acoust. Soc. Am. 60, S28 A (1976)] where there was an age effect for older children tested in noise on a linguistically more complex task. [Supported by BEH.]

Speech discrimination in quiet and in white noise by patients with peripheral and central lesions.

Speech-discrimination scores in quiet and in white noise (O dB S/N ratio) were obtained from six groups of subjects. Differences of 40% or more between scores in quiet and in white noise were observed for less than 1% of the normal ears tested but were found for 8.0% of ears with noise trauma, 48% of ears with Meniere's disease, 62% of ears with subsequently surgically confirmed 8th-nerve tumors, 14% of ears of patients with multiple sclerosis, and 42% of ears contralateral to the lesion in patients with temporal-lobe damage.

A Factor Analysis of Competing Message Testing in Hearing Aid Evaluations

Retrospective data compiled from routine clinical hearing aid evaluations were examined to identify the primary factors influencing test performance of hearing-impaired listeners. Results were analyzed from representative and similarly conducted evaluations with 68 patients. Unaided test measurements were obtained bilaterally, and included pure-tone thresholds, slope of the audiometric contour, speech reception thresholds (SRT), and speech discrimination scores. Aided tests included speech reception threshold, speech discrimination in quiet, and speech discrimination against a competing message. When intercorrelations among 27 test variables were subjected to factor analysis, five factors emerged: speech discrimination, nontest ear thresholds, unaided sensitivity-test ear, interear high frequency thresholds, and aided SRT. The 68 sets of data were subdivided into two groups on the basis of severity of hearing impairment, and new factor analysis were run. Here the same array of factors emerged with the addition of (1) a nontest ear high-frequency factor for the milder loss subgroup and (2) two factors designated as SRT—poorest aided performance, and discrimination—poorest aided performance for the greater loss subgroup.

Examination of the CROS type hearing aid.

This study was designed to examine the CROS type hearing aid under a number of listening conditions, both advantageous and disadvantageous, in order to determine whether the relative merits of the instrument could be demonstrated in the laboratory. CNC word lists were presented against a background of cafeteria noise to evaluate the performance of 20 unilaterally impaired subjects under five unaided and five aided listening conditions. Speech intelligibility scores obtained under the experimental conditions were converted to deterioration scores relative to better ear discrimination in quiet. Deterioration of unaided speech scores ranged from 14% under the most favorable listening condition to 58% under the least favorable condition. Deterioration of aided scores ranged from a low of 20% to a high of 39%. The results suggest that while the CROS hearing aid enhances intelligibility under favorable use conditions, it degrades speech intelligibility in some demanding situations.

Auditory training and speech discrimination.

Thirty-two adults with sensorineural hearing loss participated in a short-term auditory training program. The listeners were assigned to one of four matched groups which were equivalent in pure-tone sensitivity, speech-reception threshold, PB discrimination in quiet and in noise, intelligence, age, education, duration of loss, sex, and hearing-aid use. Each group responded during training to a different combination of listening condition (S/N varied or S/N-constant) and speech material (closed-set or open-set response formats). Statistically significant increase in auditory discrimination was shown on the W-22 and Rhyme tests, while the increase revealed by the Semi-Diagnostic test was not significant. Results indicated that the two listening conditions were equally effective. Similarly, the two types of training material brought about equivalent increases in overall speech discrimination. Trends suggested that open-set and closed-set training each had most effect on the respective type of speech discrimination. In addition, improvement in auditory discrimination was associated with those individuals who were oldest, with those who had highest intelligence, and with those who responded to training material at the most intense presentation level. Finally, listeners who reported the most hearing handicap also tended to show the greatest loss in speech reception and in speech discrimination in noise.

Interaction of competing speech signals with hearing losses.

Four groups of subjects were tested monaurally in a sound field with Northwestern University Test 2, which measures discrimination for monosyllables against competing sentences. Presentation was both direct and indirect. Four primary-to-secondary ratios were used. Discrimination in quiet was also determined. The interference functions plotted from these data revealed that the conductive loss cases functioned as did the normal hearing subjects. By contrast, the two groups of persons with sensorineural loss were excessively disturbed by the competing sentences. The disruption was equivalent to having the masking efficiency of the sentences enhanced from 12 to 15 db. The implication of these findings, which have confirmation in other research, is that a third dimension of handicap may be imposed by sensorineural pathology: namely, such a pathology not only changes threshold and often impairs intelligibility in quiet but can also disturb the ability to resist masking when in complex environments containing background sounds, particularly speech.

Clinical evaluation of a "master hearing aid".

IN RECENT years it has been questioned whether a hospital clinic should engage in hearing aid selection. Carhart¹(1950) states that the clinic probably should not seek to find the "best hearing aid fitting" but that rather it should assess the person's need for amplification and his difficulties with wearable instruments. The method suggested by Carhart²in 1946 has been the basic means for selection of hearing aids since World War II. By this method an audiologist, after reviewing the patient's hearing test results, selects two or three aids that, based on his experience, will most likely meet the needs of that particular patient. He then determines which is the most suitable aid after testing for sensitivity (gain), for discrimination in quiet and in noise, and for tolerance. The usual method of hearing aid selection necessitates the scheduling of two hours of the audiologist's time. In 1946 Davis

Speech Perception through Different Hearing Aids

In a previous statistical study, Shore, Bilger, and Hirsh found, for 15 clinical patients, that four different hearing aids, each with two different tone settings, did not yield significant differences in speech discrimination in quiet or in noise when test results were based upon four different testing days. In order to explore further whether the lack of significant difference came from a lack of acoustical difference among these hearing aids, response-frequency characteristics were obtained for the four different makes of hearing aids, each with the necessary number of combinations of tone setting, earphone, cord, and insert, to provide both good and bad “fittings” for each of the 15 patients. There are some substantial differences in the frequency response of the various hearing-aid combinations used but only rarely do these differences correspond to differences in test results based upon speech perception with patients. [This study was supported by Grant (B-1854) from the National Institutes of Health (NINDB).]