Biomedical subjects

P E Souza

Publications and source records attributed to P E Souza.

16 recordsLinked to original sources

PubMed2001

Randomized trial of amplification strategies.

BACKGROUND: Little is known about quality of life after the use of specific types of hearing aids, so it is difficult to determine whether technologies such as programmable circuits and directional microphones are worth the added expense. OBJECTIVE: To compare the effectiveness of an assistive listening device, a nonprogrammable nondirectional microphone hearing aid, with that of a programmable directional microphone hearing aid against the absence of amplification. DESIGN: Randomized controlled trial. SETTING: Audiology clinic at the VA Puget Sound Health Care System, Seattle, Wash. PATIENTS: Sixty veterans with bilateral moderate to severe sensorineural hearing loss completed the trial. Half the veterans (n = 30) had hearing loss that the Veterans Affairs clinic determined was rated as "service connected," which meant that they were eligible for Veterans Affairs-issued hearing aids. INTERVENTION: Veterans with non-service-connected hearing loss, who were ineligible for Veterans Affairs-issued hearing aids, were randomly assigned to no amplification (control arm) or to receive an assistive listening device. Veterans with service-connected loss were randomly assigned to receive either the nonprogrammable hearing aid that is routinely issued ("conventional") or a programmable aid with a directional microphone ("programmable"). MAIN OUTCOME MEASURES: Hearing-related quality of life, self-rated communication ability, adherence to use, and willingness to pay for the amplification devices (measured 3 months after fitting). RESULTS: Clear distinctions were observed between all 4 arms. The mean improvement in hearing-related quality of life (Hearing Handicap Inventory for the Elderly) scores was small for control patients (2.2 points) and patients who received an assistive listening device (4.4 points), excellent for patients who received a conventional device (17.4 points), and substantial for patients who received a programmable device (31.1 points) (P<.001 by the analysis of variance test). Qualitative analyses of free-text diary entries, self-reported communication ability (Abbreviated Profile of Hearing Aid Benefit) scores, adherence to hearing aid use, and willingness to pay for replacement devices showed similar trends. CONCLUSIONS: A programmable hearing aid with a directional microphone had the highest level of effectiveness in the veteran population. A nonprogrammable hearing aid with an omnidirectional microphone was also effective compared with an assistive listening device or no amplification.

Aged↗

PubMed2001

The contribution of amplitude envelope cues to sentence identification in young and aged listeners.

OBJECTIVE: The purpose of this study was to examine the importance of amplitude envelope cues to sentence identification for aged listeners. We also examined the effect of increasing alterations (i.e., compression ratio) and amount of available frequency content (i.e., number of channels) for this population. DESIGN: Thirty-six listeners were classified according to their age (35 or younger versus 65 and older) and hearing status (normal hearing versus hearing impaired). Within each hearing status, mean hearing threshold thresholds for the young and aged listeners were matched as closely as possible through 4 kHz to control for sensitivity differences across age, and all listeners passed a cognitive screening battery. Accuracy of synthetic sentence identification was measured using stimuli processed to restrict spectral information. Performance was measured as a function of age, hearing status, amount of spectral information, and degradation of the amplitude envelope (using fast-acting compression with compression ratios ranging from 1:1 to 5:1). RESULTS: Mean identification scores decreased significantly with increasing age, the presence of hear- c ing loss, the removal of spectral information, and with increasing distortion of the amplitude envelope (i.e., higher compression ratios). There was a consistent performance gap between young and aged listeners, regardless of the magnitude of change to the amplitude envelope. This suggests that some cue other than amplitude envelope variations is inaccessible to the aged listeners. CONCLUSIONS: Although aged listeners performed more poorly overall, they did not show greater susceptibility to alterations in amplitude-envelope cues, such as those produced by fast-acting amplitude compression systems. It is therefore unlikely that compression parameters such as attack and release time or compression ratio would need to be a differentially programmed for aged listeners. Instead, the data suggest two possibilities: aged listeners have difficulty accessing the fine-structure temporal cues present in speech, and/or performance is degraded by age-related loss of function at a central processing level.

Adult↗

PubMed2001

Effect of preferred volume setting on speech audibility in different hearing aid circuits.

This study compared preferred volume setting for linear peak clipping, compression limiting, and wide dynamic range compression (WDRC) amplification and quantified speech audibility at the preferred volume setting for each amplification type. Ten listeners with mild-to-moderate hearing loss were fitted monaurally with a behind-the-ear hearing aid programmed sequentially with WDRC, compression limiting, and linear peak clipping amplification. Speech was presented in quiet and in noise at a range of input levels. In each condition, the listener adjusted the volume for maximum clarity. Signal levels were measured using a probe microphone system. There was no significant difference in speech audibility between amplification strategies for any speech level regardless of the presence or absence of background noise. These results imply that the improved audibility advantage of WDRC over linear amplification demonstrated in controlled environments may not be maintained in situations where the hearing aid wearer controls the volume.

Adult↗

PubMed2000

Effect of compression ratio on speech recognition and speech-quality ratings with wide dynamic range compression amplification.

This project examined the effect of varying compression ratio on speech recognition and quality. Both listeners with mild-to-moderate sensorineural hearing loss and a control group of listeners with normal hearing participated. Test materials were sentences from the Connected Speech Test (R. M. Cox, G. C. Alexander, & C. Gilmore, 1987) which were digitally processed with linear amplification and wide dynamic range compression amplification with 3 compression ratios. Speech-recognition scores were obtained with sentences in quiet and in noise at a 10-dB signal-to-noise ratio for each amplification condition. Additionally, the participants rated each amplification condition in terms of clarity, pleasantness, ease of understanding, and overall impression. Results indicated that, for speech in quiet, compression ratio had no effect on speech-recognition scores; however, speech-quality ratings decreased as compression ratio increased. For speech in noise, both speech-recognition scores and ratings decreased with increasing compression ratio for the listeners with hearing loss. These results suggest that selection of compression ratio on the basis of speech-quality judgments does not compromise speech recognition.

Adult↗

PubMed2000

Older listeners' use of temporal cues altered by compression amplification.

This study compared the ability of younger and older listeners to use temporal information in speech when that information was altered by compression amplification. Recognition of vowel-consonant-vowel syllables was measured for four groups of adult listeners (younger normal hearing, older normal hearing, younger hearing impaired, older hearing impaired). There were four conditions. Syllables were processed with wide-dynamic range compression (WDRC) amplification and with linear amplification. In each of those conditions, recognition was measured for syllables containing only temporal information and for syllables containing spectral and temporal information. Recognition of WDRC-amplified speech provided an estimate of the ability to use altered amplitude envelope cues. Syllables were presented with a high-frequency masker to minimize confounding differences in high-frequency sensitivity between the younger and older groups. Scores were lower for WDRC-amplified speech than for linearly amplified speech, and older listeners performed more poorly than younger listeners. When spectral information was unrestricted, the age-related decrement was similar for both amplification types. When spectral information was restricted for listeners with normal hearing, the age-related decrement was greater for WDRC-amplified speech than for linearly amplified speech. When spectral information was restricted for listeners with hearing loss, the age-related decrement was similar for both amplification types. Clinically, these results imply that when spectral cues are available (i.e., when the listener has adequate spectral resolution) older listeners can use WDRC hearing aids to the same extent as younger listeners. For older listeners without hearing loss, poorer scores for compression-amplified speech suggest an age-related deficit in temporal resolution.

Adult↗

PubMed2000

Evaluation of p53, PCNA, Ki-67, MDM2 and AgNOR in oral peripheral and central giant cell lesions.

OBJECTIVES: Peripheral giant cell lesion (PGCL) and central giant cell lesion (CGCL) of the jaws have a distinct clinical behaviour. Whether such biological differences are supported by a distinct pattern of proliferation markers or cell cycle associated proteins expression is not known. Therefore the purpose of the present study was to compare the immunohistochemical expression of p53, MDM2, Ki-67, PCNA and the histochemical expression of argyrophilic nuclear organiser region (AgNOR) on PGCL and CGCL of the jaws. MATERIALS AND METHODS: Paraffin wax blocks of 14 cases of PGCL and 12 cases of CGCL were retrieved. A biotin-streptavidin amplified system was used for identification of the antigens. The AgNOR number was also evaluated. RESULTS: Ki-67 immunoreactivity was greater in the mononuclear cells of PGCL compared to CGCL. PCNA and AgNOR staining were similar in PGCL and CGCL. Prominent MDM2 immunoreactivity was observed in all tissues investigated. By contrast, there was no p53 immunoreactivity. CONCLUSIONS: Although CGCL present a more aggressive clinical behaviour, it has a decreased proliferative activity compared to PGCL. Finally, p53, MDM2, PCNA, Ki-67 immunohistochemical expression and AgNOR histochemical expression do not reflect their distinct biological behaviour.

Biomarkers↗

PubMed2000

Improving audibility with nonlinear amplification for listeners with high-frequency loss.

In contrast to fitting strategies for linear amplification that have been frequently refined for listeners with different degrees of hearing loss, we know relatively little about the effects of nonlinear amplification for differing audiometric configurations. The purpose of the current study was to determine whether increases in audibility with nonlinear amplification improved speech recognition to a comparable degree for listeners with sloping sensorineural loss as for a comparison group of listeners with flat sensorineural loss. Consonant recognition was examined as a function of audibility with wide dynamic range compression amplification and with linear amplification. For linearly amplified speech, listeners with flat and sloping loss showed similar improvements in recognition given the same increases in audibility. Results for nonlinearly amplified speech indicated that the listeners with flat loss showed a greater rate of improvement as audibility increases than the listeners with sloping loss. This difference is largely due to superior performance by the listeners with sloping loss for low-audibility speech in comparison to equivalent group performance for high-audibility speech.

Adult↗

PubMed1999

Quantifying the contribution of audibility to recognition of compression-amplified speech.

OBJECTIVE: The speech-recognition advantages of wide-dynamic range compression (WDRC) hearing aids are believed to be a direct result of improved audibility. The main objective of this study was to compare the relationship between increasing audibility and recognition for compression-amplified versus linearly amplified speech, using a quantitative measure of audibility. A second objective was to explore the adequacy of the Aided Articulation Index (Stelmachowicz, Lewis, Kalberer, & Creutz, 1994) in describing performance with WDRC-amplified speech. DESIGN: Sixteen listeners with mild to severe sensorineural hearing loss were tested on recognition of nonsense syllables that had been digitally processed with linear or WDRC amplification. Speech recognition scores were obtained for three input levels that differed in audibility relative to the listeners' hearing thresholds. An Aided Audibility Index (AAI), ranging from 0.0 (inaudible) to 1.0 (fully audible), was calculated for each listener and condition. This importance-weighted index represents the portion of the speech signal that is available to the listener. The relationship between audibility and recognition was then examined for each type of amplification. RESULTS: At low and moderate input levels, AAI values and corresponding recognition scores were higher for the compression-amplified than for the linearly amplified speech. At high input levels, AAIs and recognition scores were essentially the same for both types of amplification. Recognition scores increased monotonically as a function of the AAI for both linear and WDRC amplifiers. There was no significant difference between the functions for linearly amplified versus compression-amplified speech. In other words, a given increase in audibility resulted in the same increase in recognition for both types of amplification. CONCLUSIONS: Increasing the amount of audible speech information plays the same role in recognition for compression-amplified as for linearly amplified speech. This suggests that, at least for the conditions tested here, compression does not introduce detrimental changes to the speech signal that offset the benefits of improved audibility. Accuracy of the compression-amplified AAI can be improved by substituting measured speech ranges for the estimated speech ranges used in the standard AAI calculation. In the absence of measured speech ranges, the standard AAI provides a close approximation.

Aged↗

PubMed1999

Improving speech audibility with wide dynamic range compression in listeners with severe sensorineural loss.

OBJECTIVE: In contrast to fitting strategies for linear amplification, which have been refined frequently for listeners with different degrees of hearing loss, we know relatively little about the effects of wide dynamic range compression (WDRC) amplification for listeners with severe auditory thresholds. The primary objective of this study was to determine if increases in audibility with WDRC amplification improved speech recognition to a comparable degree for listeners with different degrees of hearing loss. DESIGN: Listeners with mild to moderate or severe sensorineural loss were tested on recognition of vowel-consonant-vowel (VCV) syllables and sentences digitally processed with linear and WDRC amplification. The speech materials were presented under conditions of controlled audibility, in which WDRC amplification improved speech audibility over linear amplification. Presentation levels were chosen to provide equivalent increases in audibility with WDRC amplification for both listener groups. A control condition in which audibility was equated for the two amplification conditions was also included. RESULTS: Recognition results for VCV stimuli indicated that both listener groups received the same benefit from the improved audibility provided by WDRC amplification. Results for sentence recognition showed a greater benefit of WDRC amplification for listeners with mild to moderate than for listeners with severe loss. CONCLUSIONS: Increasing the amount of audible speech information with WDRC has similar effects on consonant recognition for listeners with different degrees of hearing loss. Differences in sentence recognition for listeners with different degrees of loss may be due to processing effects or to differences in available acoustic information for longer segments of WDRC-amplified speech.

Adult↗

PubMed1999

Retrospective analysis of 15 cases of nasolabial cyst.

The nasolabial cyst is classified as a nonodontogenic cyst and is the only nonodontogenic cyst to occur in soft tissue. The aim of this retrospective analysis was to gather demographic, clinical, radiographic, and histopathologic data on the nasolabial cysts described in the files of the Oral Pathology Laboratory of Minas Gerais University School of Dentistry. Fifteen cases were included in the analysis. The mean age of the patients at the time of diagnosis was 42 years, and there was a female predilection. All the cysts were asymptomatic. Pseudostratified columnar (respiratory) epithelium, alone or in combination with other types of epithelium, was present in all cysts. Recurrence was not observed after surgical excision.

Adult↗

PubMed1998

Multichannel compression, temporal cues, and audibility.

Although multichannel compression systems are quickly becoming integral components of programmable hearing aids, research results have not consistently demonstrated their benefit over conventional amplification. The present study examined two confounding factors that may have contributed to this inconsistency in results: alteration of temporal information and audibility of speech cues. Recognition of linearly amplified and multichannel-compressed speech was measured for listeners with mild-to-severe sensorineural hearing loss and for a control group of listeners with normal hearing. In addition to the standard speech signal, which provided both temporal and spectral information, the listener's ability to use temporal information in a multichannel compressed signal was directly tested using a signal-correlated noise (SCN) stimulus. This stimulus consisted of a time-varying speech envelope modulating a two-channel noise carrier. It preserved temporal cues but provided minimal spectral information. For each stimulus condition, short-term level measurements were used to determine the range of audible speech. Multichannel compression improved speech recognition under conditions where superior audibility was provided by the two-channel compression system over linear amplification. When audibility of both linearly amplified and multichannel-compressed speech was maximized, the multichannel compression had no significant effect on speech recognition score for speech containing both temporal and spectral cues. However, results for the SCN stimuli show that more extreme amounts of multichannel compression can reduce use of temporal information.

Adult↗

PubMed1996

Effect of single-channel compression on temporal speech information.

Although syllabic compression systems are available in many currently marketed hearing aids, the benefit of such systems continues to be debated. The goal of this study was to determine the effect of single-channel amplitude compression on use of speech information were considered, with particular focus on temporal cues. Speech recognition scores were assessed under four conditions, using two types of speech materials. Both temporal and spectral information were provided in the FullSpeech or natural speech stimuli. Unlike previous studies in which use of temporal information may have been confounded by spectral changes, in this study the listener's ability to use temporal information was tested directly using signal-correlated noise (SCN) stimuli, which consisted of a time-varying speech envelope modulating a broad-band noise carrier. Two conditions (FullSpeech and SCN) retained their natural amplitude characteristics. In two corresponding conditions the same stimuli were compressed digitally, using compression parameters appropriate for syllabic compression. This compression reduced the range of time-intensity variations. Recognition scores were obtained from listeners with mild-to-severe sensorineural loss and from a control group of listeners with normal hearing. All stimuli were presented at high levels to reduce potential effects of reduced audibility. Additionally, short-term speech level measurements were compared to individual listener's hearing thresholds to determine the range of speech levels in each frequency region that was audible for each stimulus condition. Results demonstrated no effect of compression on recognition scores for either the FullSpeech or SCN signals for listeners with normal hearing or listeners with hearing loss. This suggests that single-channel syllabic compression processing, of the type used in this study, does not alter the temporal (or spectral) signal sufficiently to cause decreased recognition for VCV syllables when speech audibility is maintained.

Adult↗

PubMed1995

Use of temporal envelope cues in speech recognition by normal and hearing-impaired listeners.

The temporal acuity of listeners with sensorineural hearing loss is currently a matter of some controversy. In this study, the ability of normal-hearing and hearing-impaired listeners to utilize temporal cues of speech was measured directly. In addition to natural (unprocessed) nonsense syllables, several processed-speech conditions were employed. Nonsense syllables were digitally processed to remove the original spectral information, resulting in a time-varying speech envelope amplitude modulating a noise carrier. The processed-speech conditions were the envelope of a broadband speech signal modulating a broadband noise, a low-pass speech signal modulating a low-pass noise, a high-pass speech signal modulating a high-pass noise, and a two-channel signal comprised of the low- and high-pass modulated signals combined. Recognition of the envelope stimuli in quiet and also in modulated and steady noise backgrounds was tested. Listeners were tested at presentation levels yielding their maximum performance on a syllable recognition task. The hearing-impaired listeners performed more poorly on a recognition task than the normal-hearing listeners for unprocessed speech signals. However, for listeners with hearing losses of either flat or sloping configuration, there was no significant deficit in their ability to use temporal cues in speech, even in frequency regions of hearing loss up to 70 dB HL. These results demonstrate that moderate to severe sensorineural hearing loss does not impair the temporal (nonspectral) acuity of listeners in terms of speech recognition, when audibility of the stimuli is compensated for.

Hearing↗

PubMed1994

Masking of speech in young and elderly listeners with hearing loss.

This study examined the contributions of various properties of background noise to the speech recognition difficulties experienced by young and elderly listeners with hearing loss. Three groups of subjects participated: young listeners with normal hearing, young listeners with sensorineural hearing loss, and elderly listeners with sensorineural hearing loss. Sensitivity thresholds up to 4000 Hz of the young and elderly groups of listeners with hearing loss were closely matched, and a high-pass masking noise was added to minimize the contributions of high-frequency (above 4000 Hz) thresholds, which were not closely matched. Speech recognition scores for monosyllables were obtained in the high-pass noise alone and in three noise backgrounds. The latter consisted of high-pass noise plus one of three maskers: speech-spectrum noise, speech-spectrum noise temporally modulated by the envelope of multi-talker babble, and multi-talker babble. For all conditions, the groups with hearing impairment consistently scored lower than the group with normal hearing. Although there was a trend toward poorer speech-recognition scores as the masker condition more closely resembled the speech babble, the effect of masker condition was not statistically significant. There was no interaction between group and condition, implying that listeners with normal hearing and listeners with hearing loss are affected similarly by the type of background noise when the long-term spectrum of the masker is held constant. A significant effect of age was not observed. In addition, masked thresholds for pure tones in the presence of the speech-spectrum masker were not different for the young and elderly listeners with hearing loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Forward- and backward-masked intensity discrimination measured using forced-choice and adjustment procedures.

A "midlevel" hump in the intensity jnd has been reported for pure tones preceded [e.g., Zeng et al., Hear. Res. 55, 223-230 (1991)] or followed [Plack and Viemeister, J. Acoust. Soc. Am. 92, 3097-3101 (1992)] by an intense masker where the signal-masker interval was 100 ms. These previous studies used forced-choice procedures, in which subjects were required to indicate the more intense tone. Plack and Viemeister [J. Acoust. Soc. Am. 92, 3097-3101 (1992)] have proposed that the task of judging the intensity of the short probe tone, when it is presented along with an intense masker, may lead to cognitive or central factors influencing the results. The present experiments attempted to reduce these possible effects by measuring intensity jnd's using two additional paradigms. First, a "multiple-look" forced-choice method, in which subjects listened to the stimulus pairs several times before responding, was used to obtain only forward-masked intensity jnd's. Second, the method of adjustment was used to obtain both forward- and backward-masked intensity jnd's. Both the standard forced-choice method and the multiple-look forced-choice method yielded jnd data with a midlevel hump, when compared to jnd's measured without a masker. In contrast, jnd's obtained with the method of adjustment yielded jnd data with no midlevel hump. The present results suggest that the traditional method of adjustment for intensity discrimination, where subjects adjust the signal level to a point of subjective equality, may measure a fundamentally different quantity than that measured by forced-choice procedures.

Humans↗

PubMedDate not supplied

Fitting hearing aids with the Articulation Index: impact on hearing aid effectiveness.

Although most clinical tests focus on how much a particular hearing aid improves speech audibility under controlled conditions, it is unclear how these measures relate to hearing aid effectiveness, or the benefit perceived by the patient under everyday conditions. In this study, the relationship between audibility and hearing aid effectiveness was examined in a cohort of patients who obtained hearing aids through the Veteran's Administration. The measure of audibility was the Articulation Index, a common index of speech audibility. Measures of effectiveness included two hearing-specific surveys and self-reported ratings of global satisfaction and hearing aid use adherence. Results indicated that there were no systematic relationships between measurements of improved audibility and patient ratings of communication ability. Additionally, improved audibility was not related to overall satisfaction with the amplification characteristics of the hearing aid (fitting). However, improved audibility is related to hearing aid use adherence, with patients who achieve better audibility reporting that they use their hearing aids more frequently.

Adult↗