Abstract
This study was carried out to investigate oral and nasal airflow of cleft palate patients during sound production. A Flow Nasality Graph (FNG, Rion Co. ) which measures and displays oral and nasal airflow simultaneously was utilized for data sampling, coupled with a Sound Spectrograph (SG, Rion Co. ) to determine the timing of sound production of each syllable. Preliminary experimentation indicated that the most efficient way to appreciate oral and nasal airflow during syllable production is to express it in terms of Nasal Air Flow Ratio (NFR: the ratio of the amount of air expired from the nose to the amount of air expired from the nose and mouth combined). Our subjects consisted of twenty normal controls (ten males and ten females,24 to 26 years) and ten patients with repaired cleft palate (four males and six females,6 to 31 years). Target syllables were /a/, /i/, /pa/, /pi/, /sa/, /asa/, /if i/, /ma/ and /mi/.
Results obtained were as follows.
1. The FNG could provide reliable and valuable data about NFR.
2. Normal subjects exhibited a difference between the NFR of non-nasal syllables and that of nasal syllables. We were able to statistically plot the normal ranges of their data.
3. Cleft palate patients without speech aid appliances exhibited a larger NFR in non-nasal syllables than normal subjects. However with speech aid appliances NFRs of non-nasal syllables were similar to th ose of normal subjects.
4. NFRs of nasal syllables of cleft palate patients were similar to those of normal controls.
5. NFRs of vowels showed little relationship with the listeners' judgement of hypernasality, but NFRs of plosives and fricatives related closely with listeners' judgement of nasal distortions.
