Average Hearing Loss Research Articles

Auditory brainstem responses as a function of average hearing sensitivity for 2,000-4,000 Hz.

Average hearing thresholds for 2,000, 3,000 and 4,000 Hz and ABR results were analyzed for 290 patients having some degree of cochlear hearing loss. As average hearing sensitivity in the 2,000- to 4,000-Hz range became poorer, the incidence of abnormal auditory brainstem responses (ABR) increased. When the 2,000-Hz threshold sensitivity was 0-40 dB and the three-frequency average hearing loss was less than 50 dB, nearly 80% of ABR tracings were normal. Steeply sloping audiograms above 2,000 Hz increased the percent of abnormal ABR results.

騒音難聴の臨床的研究 ＩＸ 騒音職場離脱後の聴力変動について

In 20 subjects of noise-induced deafness in whom hearing tests were conducted yearly for 10 years after they left their noisy workshop, changes in hearing were studied and the results were as followes.1) Their hearing after leave from their noisy workshop showed a decline almost equal to changes with aging in terms of both frequency and average hearing loss.2) However, among these 20 cases during the course of study one case had little change in hearing and the other showed further decline in hearing.3) Various frequencies and the average hearing loss were studied in all the subjects. The results of the study showed that there is little difference of hearing in each subject, and that their hearing loss progresses gradually.

Speech reception in noise by hearing‐impaired listeners

The goal of this study was to determine the extent to which the difficulty experienced by impaired listeners in understanding noisy speech may be explained merely on the basis of elevated detection thresholds. Twenty impaired ears of 14 subjects, spanning a variety of audiometric configurations with average hearing losses to 75 dB, were tested for reception of consonants in a speech‐spectrum noise. Speech level, noise level, and frequency‐gain characteristic were varied to generate a range of listening conditions. Results for impaired listeners are compared to those of normal‐hearing listeners tested under the same conditions with extra noise added to approximate the impaired listener's thresholds. Although there are a few exceptions, the conclusion based on this sample of moderate‐to‐severe hearing loss is that, when compared to normals listening under similar conditions of threshold shift (or, more generally, similar values of articulation index), hearing‐impaired listeners exhibit little or no handicap in speech reception. [Work supported by NIH.]

The effect of noise-induced hearing loss on speech intelligibility in quiet and in noise

Following a pilot study (Smoorenburg et al., Scand. Audiol., Suppl. 16, 123–133) based on 44 ears (22 subjects) with noise-induced hearing loss (NIHL) we conducted a study based on 400 ears with different degrees of NIHL. The study included speech reception thresholds for sentences presented in quiet and in noise, tone audiograms measured in quiet and against a low-frequency background noise, and self-rating of the hearing handicap according to the Social Hearing Handicap Index. The results show virtually no correlation between the hearing loss for speech presented in quiet and the loss for speech presented in background noise. Speech thresholds found in quiet show the highest correlation with losses in the tone audiogram at 0.5 and 1 kHz, whereas speech thresholds in noise show the highest correlation with the losses at 2–4 kHz. The speech thresholds will be compared with predictions from the audiogram using the Articulation Index procedure and with the audiograms measured against a low-frequency background noise. Only those questions in the Social Hearing Handicap questionnaire that refer directly to practical situations show a correlation with the speech thresholds. The results for speech perception in noise show that the AAOO fence of 25-dB average hearing loss across 1/2, 1, and 2 kHz implies a severe auditory handicap. The fence should be set at a lower level and it should include audiometric frequencies.

Hearing loss in dogs after lesions of the brachium of the inferior colliculus and medial geniculate.

Seven dogs were tested for their sensitivity to pure tones following lesions of the brachium of the inferior colliculus and medial geniculate body. Bilateral section of the brachium of the inferior colliculus consistently resulted in an average hearing loss of as much as 37 dB in the midrange of the animals' audiograms. Lesions of the medial geniculate appear to produce a similar hearing loss if the ventral division of the medial geniculate is completely destroyed.

Auditory perception of speech contrasts by subjects with sensorineural hearing loss.

The goal of these studies was to find out how much of the acoustical information in amplified speech is accessible to children with varying degrees of sensorineural hearing loss. Context-varying, forced-choice tests of speech perception were presented, without feedback on performance, to orally trained subjects with better ear, three-frequency average hearing losses in the range 55-123 dB HL. As expected, average performance fell with increasing hearing loss. The values of hearing loss at which scores fell to 50% (after correction for chance) were 75 dB HL for consonant place; 85 dB HL for initial consonant voicing; 90 dB HL for initial consonant continuance; 100 dB HL for vowel place (front-back); 105 dB HL for talker sex; 115 dB HL for syllable pattern; and in excess of 115 dB HL for vowel height. Performance on the speech contrast tests was significantly correlated with the intelligibility of the subjects' own speech and with the open-set recognition of phonemes in monosyllabic words, even when pure-tone threshold was held constant.

Total Energy and Critical Intensity Concepts in Noise Damage

Groups of chinchillas were given a series of noise exposures of approximately equal energy ranging from 22 minutes at 120 dB SPL to 150 days at 82 dB. For all exposures involving levels of 112 dB or less, the same average permanent hearing losses (15-20 dB) and degree of outer hair cell destruction (8-10%) resulted, thus confirming the validity of the total energy principle for assessing the hazard associated with single continuous exposures at moderate levels. The 22-minute, 120-dB exposure, however, produced a 60-dB hearing loss and massive hair cell destruction (70-80%), indicating that some critical level had been exceeded, thus producing acoustic trauma. Further histological study suggests that the massive destruction is a result of breaks in the organ of Corti, produced by severe mechanical stress, that permit the mixture of endolymph with perilymph, thus creating a hostile environment for the hair cells.

Hearing loss and habits of the audiophiles among shipyard workers (author's transl)

It is well known that the occupational hearing loss has very often occurred in the shipyard. Although factors contributing to the occupational hearing loss show a tendency to decrease according to the recent progress of tenchnology, it is reported that young workers in the shipyard having a seght hearing loss show a tendency to increase. It is presumed that this is related to the damage due especially to listening to stereophonic phonograph records in their daily life. Acoustic instruments such as stereophonic phonograph records, radio-cassette recorders, video recorders, and headphones for such acoustic instruments are easily available for daily convenience. They are playing important parts as factors of the daily sound environment. Measured sound levels to which young age groups were exposed in listening to the stereophonic phonograph records were 61 to 78 dB (A) in the case of Japanese songs and 63 to 98 dB (A) in the case of rock and roll music. Hearing losses were measured and the habits of such audiophiles were investigated among 382 workers in a shipyard from March to September in 1977. The results were as follows: 1) The percentage of the audiophiles is 48.6% of the sample subjects. And the younger the age group, the higher this percentage. 2) Difference of the average hearing loss by age group is significant at 1% level. This means that the natural loss of hearing exists as a result of aging. 3) Most of the audiophiles belong to the young age groups, and the average hearing loss of the audiophiles is less than of the non-audiophiles. 4) The average hearing loss of the audiophiles in twenties is less than that of the non-audiophiles in the same age group. 5) Average hearing losses classified both by listening durations and by kinds of chief listening music are not different at 5% level of significance. 6) The relation between the average hearing loss of the audiophiles and the duration of listening to stereophonic phonograph records is not significant. However, the relation between the average hearing loss and the listening frequencies is significant at 1% level. 7) 14.5% of the audiophiles are using headphones. The relation between the average hearing loss and the use of headphones is not significant. From the above facts, the authors consider that hearing loss of the younger age group has not been influenced by the sounds from sterephonic phonograph records under the present state. However, we have to pay attention to acoustic instruments generating sounds in the daily environment. Note: The average hearing loss is expressed in (a+2b+2c+d)/6, where a stands for threshold at 500Hz, b at 1, 000 Hz, c at 2, 000 Hz and d at 4, 000 Hz.

Narrow-band AP latencies in normal and recruiting human ears.

Derived narrow-band action potential latencies increase monotonically with decreasing central frequency, and can be interpreted as reflecting the traveling wave delay in the cochlea. It was found that, for recruiting human ears with average flat hearing losses around 40 dB, this accumulating latency increase was smaller than for normal ears. A comparison of 15 normal ears and 37 recruiting ears showed, however, that in only half of the recruiting ears this difference was significant. These recruiting ears were therefore divided in two groups based on the waveform of the narrow-band action potential AP, which correlated well with the subdivision according to latency. The findings have been explained on the basis that latency of the narrow-band APs is not determined solely by the mechanical traveling-wave delay, but also by the response time of the (second?) cochlear filter. When this filter broadens, one expects a decrease in its impulse response time. Since this impulse response time. Since this impulse response depends on the sum of the high- and low-frequency slope values of the cochlear filter, one expects only a latency decrease when the steep high-frequency slope also becomes more shallow. A support for the influence of the response times of the cochlear filter is found in the narrow-band AP latencies for restricted cochlear losses (e.g., in a 4-kHz noise dip). It appears that the latency in that area actually is shorter than for the higher central frequencies, a fact which cannot be explained solely on the basis of a traveling wave phenomenon.

Audiologic Findings after Stereotactic Radiosurgery in Nine Cases of Acoustic Neurinomas

Nine cases of acoustic neurinoma were treated by stereotactic radiosurgery between 1969 and 1974. The follow-up period can now be regarded as sufficiently long for a preliminary evaluation of the results. An arrest of growth or shrinkage of the tumour was observed in 8 of the 9 cases. In one case open surgery was performed 2 years after irradiation and histological examination showed regressive changes of the type expected after irradiation. Audiological examination revealed that in the majority of cases radiosurgery could be performed without causing serious damage to the hearing function. The average hearing loss present before treatment increased on average only 20.0 dB in the most successful 7 cases. None of the patients suffered facial nerve involvement. In small and medium-sized acoustic tumours this method offers a satisfactory therapeutic alternative worthy of consideration.

Auditory handicap of hearing impairment and the limited benefit of hearing aids.

The aim of this article is to promote a better understanding of hearing impairment as a communicative handicap, primarily in noisy environments, and to explain by means of a quantitative model the essentially limited applicability of hearing aids. After data on the prevalence of hearing impairment and of auditory handicap have been reviewed, it is explained that every hearing loss for speech can be interpreted as the sum of a loss class A (attenuation), characterized by a reduction of the levels of both speech signal and noise, and a loss D (distortion), comparable with a decrease in speech-to-noise ratio. On the average, the hearing loss of class D (hearing loss in noise) appears to be about one-third (in decibels) of the total hearing loss (A + D, hearing loss in quiet). A hearing aid can compensate for class-A-hearing losses, giving difficulties primarily in quiet, but not for class-D hearing losses, giving difficulties primarily in noise. The latter class represents the first stage of auditory handicap, beginning at an average hearing loss of about 24 dB.

Auditory handicap of hearing impairment and the limited benefit of hearing aids

The aim of this paper is to promote a better understanding of hearing impairment as a communicative handicap, primarily in noisy enviornments, and to explain the essentially limited applicability of the hearing aid. From available data we can conclude that about 7.5% of the population is auditory handicapped, with a hearing loss for speech ⩾ 24 dB. Every hearing loss can be interpreted as the sum of a loss class A (Attenuation), characterized by a reduction of the levels of both speech signal and noise, and a loss class D (Distortion), comparable with a decrease in speech-to-noise ratio. On the average, the hearing loss of class D (= hearing loss in noise) appears to be about one-third (in dB) of the total hearing loss (A + D = hearing loss in quiet). A hearing aid can compensate class-A hearing losses, giving difficulties primarily in quiet, but not class-D hearing losses, giving difficulties primarily in noise. The latter class represents the first stage of auditory handicap, beginning at an average hearing loss of about 24 dB. An algorithm for computing speech level relative to speech-reception threshold as a function of hearing losses of classes A and D, as well as acoustic gain, internal noise, and quality of the hearing aid, has been developed and examples will be given.

STUDIES OF AUDITORY ABILITY OF HARD-OF-HEARING PATIENTS

Studies were made on the relationship between the results of speech discrimination test at the level of daily conversation and of pure tone audiometry and the results of self-ratings of the hearing impaired. The subjects employed were 596 patients with the age ranged between 16 and 69 complaining of hearing troubles in daily conversation. The speech discrimination test was also conducted on 112 out of the above subjects under the conditions of employing the body-worn type hearing aids.1. The scores obtained in the speech discrimination test were lowered as the threshold for pure tone increased. At the average hearing loss of 50 dB, the scores were sharply lowered.2. The rate of the cases with poor vowel articulation was high among the patients with scores of syllable articulation less than 60 %. A large deviation was observed in the scores of sound articulation on the patients with the syllable articulation less than 50 %.3. The degree of hearing handicaps in the cases with the average hearing loss of 50 dB was considered close to that with 60 dB loss rather than that with 40 dB loss.4. In the speech discrimination test conducted on the patients with body-worn type hearing aids whose average hearing loss was more than 50 dB, delivering test words with 60 phons almost the same results were obtained between the patients with 50 dB of average hearing loss and with 60 dB.

STUDIES OF AUDITORY ABILITY OF HARD-OF-HEARING PATIENTS

Studies were made on the relationship between the results of speech discrimination test at the level of everyday speech and/or of pure tone audiometry and the results of self-ratings of the impaired hearing, the subjects employed were 596 patients with the age ranged between 16 and 69 complaining of hearing troubles in everyday speech. The speech discrimination test was also conducted on 112 out of the above subjects under the conditions of employing the bodyworn type hearing aids.1. The studies on ‘hearing of the radio and T.V. with usual volume’ and ‘hearing of everyday speech with usual loudness’ revealed that the number of answers with ‘capable of hearing’was large and that of answers with ‘incapable of hearing’ was small in the latter rather than the former, at the average hearing loss of the same level.2. A significant difference was observed in the self-evaluation of the above two items between those with average hearing loss of less than 40 dB and those with more than 60 dB.A similar tendency was observed between those with more than 80 % and those with less than 60 % in syllable articulation.3. The evaluation of self-ratings was more strict in the cases with mild hearing loss, than in those with severe hearing loss. In order to assume the auditory ability of hard-of-hearing patients by their case histories, the hearing condition of ‘hearing of the radio and T.V.’ was found to be preferable rather than that of ‘hearing of everyday speech’.

The Hazardous Noise Exposure to Which Airline Passengers are Subjected

Babies and children, in particular, and adults should not be exposed to the noise levels inside commercial aircraft. The passenger cabin noise levels during flight equal or exceed even the inappropriately high legal limits which have been shown not to protect hearing and health. Studies have shown that airline pilots have above normal hearing loss. Thus, each day (in the U. S.) about 400,000 airline passengers are exposed to long periods of excessive and hazardous noise radiation. This unfunded study shows that cruise flight noise levels inside Boeing 737 and 727, Lockheed L-1011, and McDonnell-Douglas DC-10 aircraft are in the 85 to 100+ dBC (or 80 to 90+ dBA) range. A few data released by the EPA indicate there are similar noise levels in all commercial aircraft. Despite the seriousness of the problem, the Cumulative Indices for JASA and contemporary literature on acoustics for the years 1948 to 1972 show no published reports on jet aircraft cabin noise. Consequently, airline passangers have not been informed about the noise levels and effects, and have been deprived of information necessary for making rational judgments about the acceptability of air travel noise environments.

聴力障害児の発音様式に関する研究

The purpose of this study was to investigate the abnormalities of articulation and the effectiveness of speech training in the hearing-impaired children. Twenty-one hard-of-hearing children were selected as subjects, who were ten or eleven years old and had impaired hearing by congenital causes or postnatal diseases before two years of age. The subjects were divided into two groups ; the group A, consisting of ten hard-of-hearing children with average hearing losses between 51dB and 85dB in the better ear and, the group B, eleven children with average losses greater than 86dB in the better ear. They were tested by three methods, namely articulation test, sound spectrogram and air-dynamic measurements during phonation, before and after speech training of two years duration. The articulation test was carried out by three speech therapists on the spoken sound phonated by the subject reading one of the three test card-decks, each consisting of sixty-seven Japanese monosyllabic sounds arranged at random. Nasal and oral air flow rates and oral air pressure during phonation were examined by means of electro-transducer and recorded by paper oscillogram. Results were as follows : 1. The most probable cause of mistakes in spoken sounds was discooperation of vocal sound and orally composed sound (s-factor), the second was the lack of stability of oral resonance for vowel production (v-factor), and the least one was the inaccuracy of orally composed sound (o-factor). 2. The lack of stability of aspiration before and during phonation was pointed out as one of the causes of inaccurate vowels, and the poor control of intraoral air pressure was revealed on phonation of pressure consonants. 3. The effectiveness of speech training was shown largely in improvement of o-factor, somewhat in v-factor, and a little in s-factor of some consonants. 4. So far as o-factor was concerned, speech training was more effective in group A than in group B, but concerning s-factor and v-factor, no difference was shown in effectiveness between the groups.

EARLY INTERVENTION OF PARS TENSA RETRACTION POCKETS IN CHILDREN BY CARTILAGE REINFORCED TYMPANOPLASTY

Posterosuperior retraction pockets involving pars tensa of a tympanic membrane is not an uncommonproblem particularly in pediatric population. This occurs as a sequelae of chronic otitis media with effusion.The management options include “wait and watch,” medical treatment and surgery. But in patients inwhom retraction is severe and seems to be irreversible the treatment should be surgery at the earliest. Weperformed cartilage reinforced tympanoplasty in 29 ears of 28 children who had grade III and IVposterosuperior retraction pockets of the pars tensa. Their average pre-operative hearing loss was 16.6 and19.4dB for grade III and IV retraction pockets respectively with 10 and 12.4dB post operative gain. Norecurrences were noted except few minor complications. We suggest that such procedures are safe andshould be performed at the earliest rather than to keep under surveillance and medical treatment only.Key Words: Pars tensa retraction pockets, Tympanic membrane atelectasis, atelectatic ear, Tympanoplasty.

Noise Hazard Meter

A small electronic instrument has been developed to appraise noise exposures in terms of the hazard to human hearing. An analog computer integrates the A-weighted sound level of the noise over the exposure period according to the laws describing growth and recovery of temporary threshold shift [see J. H. Botsford, “Theory of TTS,” J. Acoust. Soc. Amer. 44, 352 (A) (1968)]. The result is a meter reading that indicates the average temporary loss of hearing that the exposure would produce in a group of normal ears. Since this average temporary hearing loss is roughly proportional to the permanent hearing loss that would result from many repetitions of the same exposure, the meter is valuable for appraising noise hazard. All noise exposures that indicate little or no temporary loss are probably safe. The new instrument can be worn by a roving workman and permits evaluation of many exposures to irregular noise that are unassessable by present methods.

Deterioration of the residual hearing of children with sensorineural deafness.

Deterioration in the residual hearing of the aided and unaided ears of children with sensorineural deafness was investigated by comparing the mean Average Hearing Losses of their initial audiograms with the mean Average Hearing Losses of recent audiograms, and relating the changes to various variables. The results of the investigation confirm previous findings that the use of high-powered hearing aids tends to cause deterioration of the hearing of the aided ear, that this effect of aid use is about the same in degree in endogenous and exogenous deafnesses and that small amounts of deterioration of unknown origin tend to occur in the unaided ears of children with sensorineural deafness, and tend to be greater in ears with less initial hearing loss. It was also found that the general deterioration of hearing tends to be bilateral and greater in exogenous than in endogenous deafnesses.

Hearing in Menière's disease. A study of pure-tone audiograms in 334 patients.

This work was supported by the Swedish Medical Research Council (Project No. 17X-617–02).In 334 patients with Meniere's disease the pure-tone audiograms were analysed, and the age at onset, onset symptoms and bilaterality were studied. The flat curve was most common (60%), followed next by the rising curve (17%) and then the falling curve (12%). The average hearing loss for the whole material was 52 dB. Patients with flat, rising and falling curves had hearing loss of approximately the same order of magnitude. Patients with rising and trough curves had, on the average, the shortest duration of disease. The hearing loss progressed most rapidly during the first year of the disease, after which only minor deterioration took place. The mean age for patients with falling curves was on the whole the same as for the whole material.Fluctuation of the auditory threshold was recorded with all types of curves, but was somewhat more common with rising and trough curves. Fluctuations were recorded in approximately hal...