Measuring Hearing (1960s)

Procedures employed in measuring the capacity of the auditory system of the hearing impaired child vary according to the age of the child, the stimulus presented and the response antic. ipated. Determination of hearing loss as early as possible is critical to the development of the infant's audio vocal system. Newborn infants are screened in a hospital nursery. One of the first techniques developed in the United States uses trained volunteers who introduce a warbled pure tone between 2500 and 3500 hertz at an intensity level of 90 dB SPL. [Music] The observers record the neonates reaction as to intensity and type independently and then compare their results. Judgments of reactions must be unanimous to be considered a pass. Okay. 24th test at 100. Failing three trials at 90 dB SPL, the intensity is increased to 100 dB. Lack of response to the stimulus may be for reasons other than irreversible hearing loss, such as an allergy, mental retardation, or neurological damage. In a recent California study testing over 5,000 neonates, nurses using a flat 100 to 6,000 hertz broadband stimulus found 23 failures, a higher incidence than has been previously reported. Identification in the hospital nursery may be followed at a later date by electrphysiological measurements such as electroinsphilography using evoked auditory responses to acoustic stimuli. Electrodes are attached to the infant's head and the acoustic signal introduced. Changes in the patterns of the electron and sephlogram are recorded and computer averaged. At the control panel adjacent to the test booth, the aiologist manipulates the intensity and frequency of the stimuli, marks and checks the readout. Comparisons are made to tactile threshold measurements. I'll drop back to 250 moderate level. Sound field testing of the same infant. Note the location where the electrode was placed correlates with the EEG results. Change in the intensity, frequency, and type of signal facilitates the infant's responding. He may become immobile, localize, or attend. At this age, usually only a single response to the stimulus is given. The twoman team judges the reliability of the response. [Music] The infant responds to selected acoustic signals to warbled pure tones to environmental sounds. Yes. Good. And to speech while visual attention is held. Oh, yes. I think so. That one too. Good. Before conditioned play aometric techniques can be used, the young child must learn to discriminate the sound stimulus and to make the appropriate motor response. I don't hear anything. You listen. Hey. Discrimination of gross sounds following visual association of objects and pictures is preliminary to the next stage of behavioral audiometry. Note the learning sequence, the use of biensory stimulation and the auditory skills emergent, established and yet to be [Music] developed. Okay, just a minute. Let's try to learn to put it on. Okay, let's get another one now. Listen carefully. Watch. For the older child at initial testing, the same behaviors must be learned. Try something else to learn the game. Failing to respond to condition play audiometry, Courtney learns the task tactilally, holding the oscillator in his hand. We'll leave that on. That's okay. Hold it. Okay. Put it on. Put it on. And you feel it. Whoops. Okay. Feel it, Courtney. Yes. You could feel that. Feel it. Good boy. All right. Transferred to the mastoid process. The association is made. To obtain reliable results, the aiologist must be assured that the child understands the task required of him. Finally, the earphones. And testing continues until threshold measurements are obtained. Okay, put it on. You heard it. Combat. Choose boot. Job. For hearing impaired school-aged children, standard audiometry is used and special techniques of speech audiometry are employed for the older deaf child and adolescent. I'm going to make it louder now. Okay. Tape recorded lists of acoustically analyzed words are presented at specific intensity levels. Spine head. What? Hush. Boom. Boom. Goose. Gift. Not. Yes. Shed. Jeff, Dr. Booth comments on his test of auditory discrimination. The subject is asked to repeat what he hears and to guess if he isn't sure. Each list consists of only 10 words and the subject's response is scored as the number of sounds correctly repeated. There are three reasons for scoring on the basis of sounds rather than words. Firstly, the the resulting score is less dependent on the subject's vocabulary. Secondly, it is statistically more reliable. And thirdly, it makes possible the use of these very short lists with a corresponding saving of time. Each list takes one minute of testing time. And it becomes possible to plot a complete curve showing the relation of discrimination score to intensity. From this curve, one can see the maximum score, the levels at which this maximum score is obtained and also find out where the score drops to half of its maximum value which gives a measure of the hearing loss for speech. This should correlate very closely with the pure tone aiogram uh measured at 1,000 cycles per second. The usual test evaluation of the auditory system in the deaf from infancy to late adolescence is essential for establishing thresholds of sensitivity for providing appropriate amplifying aids for assessing the functioning of the auditory residual in the developing audio vocal system and for determining the effectiveness of the educational program in improving auditory skills. [Music]