Monaural/binaural preferences: effect of hearing aid circuit on speech intelligibility and sound quality.

This investigation compared monaural and binaural hearing aid preferences of 15 adults with mild-to-moderately-severe bilaterally symmetrical sensorineural hearing losses. Subjects listened to connected discourse in quiet and background noise at 70 and 80 dB SPL with K-Amp, linear Class D, linear output limiting compression (OLC), Manhattan II, and linear asymmetrical peak clipping circuits (APC). In Experiment 1, subjects made judgments of sound quality and speech intelligibility in a modified paired-comparison paradigm during which they compared the monaural and binaural fittings of each circuit. In Experiment 2, subjects engaged in subjective ratings on a scale of 0 to 10. Subjects benefitted from improved sound quality and speech intelligibility in high-noise conditions when fit with binaural K-Amp, linear Class D, linear OLC, and Manhattan II circuits. Monaural listening was preferred with the APC circuit. Results indicate that improved sound quality and speech intelligibility may be obtained with binaural fittings of circuits that include high fidelity, low distortion, or increased head-room.

Probe-microphone measurements with body-worn instruments: loudspeaker and reference microphone effects.

Probe-microphone measurements are typically made with behind-the-ear (BTE) and in-the-ear (ITE) hearing aids with the loudspeaker located at 0-degrees or 45-degrees azimuth at head level and the reference microphone positioned on the head near the hearing aid microphone. With body-worn instruments, these conditions may not accurately reflect in situ hearing aid performance. This study compared the real-ear aided response (REAR) and real-ear insertion response (REIR) for a body-worn hearing aid using the substitution method and an off-line equalization modified pressure method with three different loudspeaker locations (0 degrees and 45 degrees at head level and 0 degrees at body hearing aid level) and two reference microphone positions (over-the-ear [OTE] and next to the body hearing aid microphone). Results indicated that each of the responses was affected by changes in loudspeaker and reference microphone location. If the substitution method measured from 0-degrees azimuth at head level is considered to be the most realistic representation of hearing aid performance, the closest agreement with body-worn hearing aids was obtained with the modified pressure method when the loudspeaker was located at 0-degrees azimuth at head level and the reference microphone was located over the ear. If the clinician uses the modified pressure method and desires to approximate results with the substitution method, correction values are needed for REAR measurements but not for REIR measurements.

Mycobacterial cervical adenitis in children: medical and surgical management.

This is a review of the treatment results of cervicofacial mycobacterial adenitis in 85 children and adolescents. Twenty-three patients were treated with only anti-tuberculous medications (Group A). Thirteen underwent surgical procedures at the time of presentation for drainage of abscess or diagnostic biopsy, followed by treatment with anti-tuberculous medications (Group B). Forty-nine were initially treated with anti-tuberculous medications, with or without needle aspirations, and subsequently required surgery for one of the following reasons: 1) drainage and/or excision of abscess (Group C); 2) diagnostic biopsy (Group D); and 3) excision of persistent, enlarging, or recurrent nodes, or of draining fistulas (Group E). Four patients who were initially treated with surgery required a second procedure for persistent or recurrent disease. The cure rate for patients treated only with medications (Group A) was 95%. The cure rate for patients in the surgical groups after the initial procedures were 50% for Group B, and 100% for Groups C, D, and E. The overall cure rate was 92% for surgical treatment groups B-E and 93% for all 5 treatment groups. The clinical features of the disease, treatment outcome, and guidelines for management are discussed.

Tonsil and adenoid surgery for airway obstruction: perioperative respiratory morbidity.

A series of 160 consecutive patients undergoing tonsil and adenoid surgery for upper airway obstruction is reported. The ages ranged from 8 months to 13 years. Sixty-seven percent were 2, 3, or 4 years of age. All were routinely admitted overnight postoperatively. Forty-five (28%) remained in the hospital longer than one night (2 to 20 days). Postoperative respiratory problems were the reason for prolonged hospital stay in 30 of these 45 patients. Preoperative "danger-signals" of potential postoperative respiratory problems were: a history of severe obstructive symptoms with apnea and moderate or strongly positive sleep study, daytime somnolence, need for urgent T&A, and cardiomegaly. Risk factors present in a smaller number of patients were obesity, congenital stenosis of airways, and bronchopulmonary dysplasia. We suggest that children with these danger signals not be considered as candidates for outpatient T&A surgery.

Comparison of sound quality and clarity with asymmetrical peak clipping and output limiting compression.

This study compared the preferences of 12 subjects with mild-to-moderate hearing losses for a linear circuit when the type of output limitation could be changed between asymmetrical peak clipping and output limiting compression. Through a paired-comparison paradigm, subjects rated the sound quality and clarity of speech in quiet, speech in noise, and music when the output levels were well below saturation and when slight saturation and high saturation occurred. A significant preference was found for the output limiting compression for each of the three stimuli for both sound quality and clarity. The preference became stronger with increases in saturation. The results suggest that if linear hearing aids are being used, the output should be limited with compression rather than peak clipping.

Aided masked thresholds: case of deception.

A case of contaminated functional gain measures from internal hearing aid noise is presented and clinical implications addressed. The contaminated functional gain measures underestimated real ear insertion gain. Recognition of this source of functional gain measurement error is essential for accurate hearing aid fitting.

A comparison of sound quality judgments for monaural and binaural hearing aid processed stimuli.

Fifteen adults with bilaterally symmetrical mild and/or moderate sensorineural hearing loss completed a paired-comparison task designed to elicit sound quality preference judgments for monaural/binaural hearing aid processed signals. Three stimuli (speech-in-quiet, speech-in-noise, and music) were recorded separately in three listening environments (audiometric test booth, living room, and a music/lecture hall) through hearing aids placed on a Knowles Electronics Manikin for Acoustics Research. Judgments were made on eight separate sound quality dimensions (brightness, clarity, fullness, loudness, nearness, overall impression, smoothness, and spaciousness) for each of the three stimuli in three listening environments. Results revealed a distinct binaural preference for all eight sound quality dimensions independent of listening environment. Binaural preferences were strongest for overall impression, fullness, and spaciousness. Stimulus type effect was significant only for fullness and spaciousness, where binaural preferences were strongest for speech-in-quiet. After binaural preference data were obtained, subjects ranked each sound quality dimension with respect to its importance for binaural listening relative to monaural. Clarity was ranked highest in importance and brightness was ranked least important. The key to demonstration of improved binaural hearing aid sound quality may be the use of a paired-comparison format.

Comparison of SSPL90 selection procedures.

Recommended SSPL90 values were determined at 500, 1000, and 2000 Hz for 16 subjects with mild-to-moderate sensorineural hearing losses using six different selection procedures, including an Upper Limit of Comfortable Listening (ULCL) and threshold-based procedure by Cox (1988), a threshold-based procedure by Seewald and Ross (1988), and loudness discomfort procedures by Berger (1988), McCandless and Lyregaard (1983), and Hawkins et al (1987) and Libby (1985). Statistically significant differences were found among the procedures at 500 and 2000 Hz. Analysis of individual data showed that while some subjects obtained similar recommended SSPL90s across the procedures, others showed dramatically different values.

Effect of reference microphone location and loudspeaker azimuth on probe tube microphone measurements.

The effects of loudspeaker azimuth and reference microphone location on probe tube microphone measures were assessed. The real ear unaided response (REUR), real ear aided response (REAR), and real ear insertion response (REIR) were obtained on a KEMAR. Aided measures were obtained with both a behind-the-ear and an in-the-ear hearing aid. All three measurements were affected by changes in the loudspeaker azimuth and reference microphone location. Responses obtained with a 90 degree loudspeaker azimuth or with the reference microphone located at-the-ear revealed greater disparity than those obtained under other conditions. Most of the differences occurred at frequencies above 2000 Hz, with measurements utilizing the behind-the-ear hearing aid showing greater dispersion. These results suggest that the location of the loudspeaker and the reference microphone are important variables when utilizing probe tube microphone measurements.

Abscesses of the neck in infants and young children. A review of 112 cases.

A review of 112 patients 5 years of age and younger with cervical abscesses is reported. Staphylococcus aureus and group A beta-hemolytic Streptococcus were cultured most often: in 39% and 17% of patients, respectively. Sixteen patients (14%) had unusual abscesses such as infected congenital cysts, cat-scratch disease, or myocobacterial abscesses. One patient had a necrotizing infection with group A streptococci and anaerobic streptococci. Intravenous antibiotic therapy was used in 104 patients, with 94% of these patients receiving a penicillin derivative, usually an antistaphylococcal penicillin. Ninety-six percent of the patients had incision and drainage of their abscesses; 8 patients required more than one incision and drainage. Two patients required airway intervention, 1 by intubation and 1 by trachetomy. Most pediatric cervical abscesses respond well to appropriate intravenous antibiotic therapy and incision and drainage.

Avoiding a wrapped endotracheal tube in laser laryngeal surgery: experiences with apneic anesthesia and metal laser-flex endotracheal tubes.

Ninety-one laser laryngeal procedures using the apneic technique of anesthesia were performed in 28 patients between 2 months and 64 years of age. Seventy-two procedures (79%) were performed on children and 19 on adults. There were no complications. Eight laser laryngoscopies were performed using a new metal Laser-Flex endotracheal tube. Obstruction of the endotracheal tube with a mucous plug occurred in one case. The apneic technique described in this paper provides a laser operative field free of an endotracheal tube, virtually eliminating the danger of a laser fire. It is a relatively safe and effective means of performing laser laryngeal surgery. In addition, the Laser-Flex endotracheal tube appears to be an acceptable alternative to a metallic tape-wrapped endotracheal tube.

Removal of blunt foreign bodies from the esophagus.

Historically, removal of blunt foreign bodies from the esophagus by esophagoscopy under general anesthesia has been considered to be relatively safe and effective. In recent years, alternative techniques of blind removal with balloon catheters or bougies have been advocated. This paper reports 246 esophagoscopies performed over a 19-year period to remove blunt esophageal foreign bodies. Eighty-one percent of the foreign bodies were coins and 74% were in children under 3 years of age. There were no deaths, no perforations, and no instances of mediastinitis. The only complications encountered were those due to esophageal erosion and/or respiratory problems secondary to long-standing foreign bodies. In the author's opinion, esophagoscopy is the best method for removal of all esophageal foreign bodies. There simply does not seem to be a need for alternative methods involving blind removal.

Familial vocal cord dysfunction associated with digital anomalies.

Familial vocal cord dysfunction is a rare condition that has been reported in only a few instances. This is a report of identical male twins, both of whom had congenital bilateral abductor vocal cord paresis associated with finger deformities. The vocal cord paresis progressed to paralysis that required tracheotomy, then returned to a slowly resolving paresis during which the vocal cords had uncoordinated motion generally known as synkinesis. Another male sibling and the mother had a history of stridor during infancy and finger deformities. Several other relatives had digital abnormalities, and an infant first cousin with finger abnormalities required a tracheotomy for vocal cord paralysis.

Comparisons among SPLs in real ears, 2 cm3 and 6 cm3 couplers.

Sound pressure levels (SPLs) were measured in the ear canals of 30 adult subjects with standard audiometric earphones (TDH-39) and insert earphones (Etymotic ER-3A) and compared to those generated in 2 cm3 and 6 cm3 couplers. Transfer functions are shown for real ear to 2 cm3 coupler, real ear to 6 cm3 coupler, 6 cm3 to 2 cm3 coupler, and dB HL under standard earphones to 2 cm3 coupler SPL. In general, the data agreed rather well with published transfer functions that in most cases were derived by adding together a series of partial transfer functions from various studies. The conversion values from dB HL to 2 cm3 coupler SPL could be useful in selection of certain hearing aid parameters, but the intersubject variability may limit their usefulness somewhat.

Complex and pure-tone signals in the evaluation of hearing-aid characteristics.

In recent years, a number of commercially available systems have been developed to analyze the electroacoustic characteristics of hearing aids. In addition to pure-tone signals, these systems often use a wide variety of complex signals such as broadband noise, clicks, and multitonal complexes. In this paper, a number of practical and theoretical issues concerning the use of pure-tone and complex signals in the evaluation of hearing-aid characteristics are described. The circumstances under which discrepancies in estimated gain and maximum output might occur using these two types of signals are described and the clinical implications of these differences are discussed.

Visual biasing of normal and impaired auditory speech perception.

Intersensory biasing occurs when cues in one sensory modality influence the perception of discrepant cues in another modality. Visual biasing of auditory stop consonant perception was examined in two related experiments in an attempt to clarify the role of hearing impairment on susceptibility to visual biasing of auditory speech perception. Fourteen computer-generated acoustic approximations of consonant-vowel syllables forming a /ba-da-ga/ continuum were presented for labeling as one of the three exemplars, via audition alone and in synchrony with natural visual articulations of /ba/ and of /ga/. Labeling functions were generated for each test condition showing the percentage of /ba/, /da/, and /ga/ responses to each of the 14 synthetic syllables. The subjects of the first experiment were 15 normal-hearing and 15 hearing-impaired observers. The hearing-impaired subjects demonstrated a greater susceptibility to biasing from visual cues than did the normal-hearing subjects. In the second experiment, the auditory stimuli were presented in a low-level background noise to 15 normal-hearing observers. A comparison of their labeling responses with those from the first experiment suggested that hearing-impaired persons may develop a propensity to rely on visual cues as a result of long-term hearing impairment. The results are discussed in terms of theories of intersensory bias.