Free Field voice testing:
This test can be used for
1. Screening purposes - To detect whether a hearing impairment is persent in one or both ears. Only a whispered voice is used for this purpose.
2. Determining the severity of hearing impairment that has been identified. This can easily be achieved by assessing the hearing threshold for speech by varying the vocal effort and the distance from the test ear.
This test just takes a couple of minutes to complete. It may not be as reliable as a tuning fork test by still is of value in the following scenario:
Audiometry may not be required:
There are two circumstances where audiomety may be dispensed with as a result of free field voice testing. The 1st is where a pervious audiogram is available and there has been no change in symptoms and the 2nd is where hearing screening is required. There may be patients without otologial symptoms such as elderly, or those who need to be reassured that they have normal hearing.
To check audiometry:
Following otoscopy and free field voice testing it should be possible to predict the type and severity of impairment in each ear using free field voice testing. Audiometric findings can be grossly cross checked in these patients.
The procedure:
1. The patient should be explained that he / she is expected to repeat back what he / she hears being uttered by the examiner as accurately as possible.
2. The examiner stands behind the patient to prevent the patient from resorting to lip reading tactics.
3. A combination of numbers and alphabets are used for testing eg. 6E9. This permits a large variety of combinations.
4. In children bisyllabic words (cowboy, football) are often used. It is easier to read from a list of prepared words.
5. The better hearing ear is tested if possible
6. The non test ear is masked using tragal rubbing
7. Masking can be omitted in children and elderly.
When free field voice testing is used for screening purposes then the examiner uses a whispered voice 2 feet away and then gradually increases the loudness of the voice. The patient's free field threshold is acutally the voice and distance level at which he / she gets more than 50% correct. The test can be terminated when the patient repeats 50% of the words correctly at any one voice / distance level.
Monaural free field speech when done by experienced audiologist then patients can be reliably screened for hearing impairment with an accuracy of 25 dB.
