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This entry was posted on 8th July 2013 by Gary.
Not only is medical audiometry concerned with the audibility of pure tones, but it also includes the perception of speech, fatigue, differential sensitivity, and even psychological magnitudes like pitch and loudness.
The majority of procedures in pure tone and speech-in-noise audiometry demand that the patients respond, verbally or nonverbally, as they follow the tester’s verbal instructions. While nonverbal procedures have been sought after for a long period, a rapid growth in such methods can be seen since 1948 when the threshold technique was discovered.
History around why Pure tone audiometry is used
As long as there was only scientific interest in the absolute auditory threshold, no concern was shown about specifying a normal threshold. Nevertheless, the introduction of pure tone audiometry and its extensive use in clinics has led to a request for expressing such threshold measurements to a standard norm. The history of the current standard began when the earphone was developed and the sound pressure in the ear canal was adopted.
The pressure was obtained by balancing the sound volume generated by a standard phone and the sound produced when certain fixed voltages were applied to the earphone. This technique was necessary because earphones respond differently when placed on different ears. The sensation of equal loudness corresponds directly to equal sound pressure at the entrance to the ear canal. This was a fundamental assumption upon which the threshold transfer by loudness balance was based.
As a rule, it is worth knowing whether or not a person or a group can respond to certain stimuli. Thereby, many procedures for screening industrial, school and military groups have become available. One of these appeared to be most effective when validation is measured in terms of individual pure tone audiograms.
Pure tone audiometry is performed in specialist audiology clinics. Patients are placed in a soundproof room wearing earphones, where the loudness threshold for hearing tones of different pitch can be determined. This enables detection of auditory requirements, quantification of conductive hearing loss and identification of whether hearing aids will be helpful.
Recent trends towards speech understanding
Although one of the purposes of pure tone audiometry has been to replace the old-fashioned spoken and whispered speech tests, more recently speech has returned to audiometry this time as a moderately well-controlled incentive. Many of the concepts that were developed in connection with evaluating communications equipment have been taken over and at least two kinds of clinical measurement have become almost classical. When the level at which speech is presented to listeners is varied until the listeners report that they hear something or can recognize 50 per cent of the words, the thresholds of detectability are measured.
The most important recent contributions towards speech understanding are associated with distinguishing between pathologic conditions of the cochlea and those of the auditory nervous system. Therefore, speech-in-noise measures are an accurate way of predicting overall benefit to patients before implantation of cochlear implants.
This entry was posted in Hearing Information on 8th July 2013 by Gary.
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