Measurement of nasalance scores without touching the philtrum for better comfort during speech assessment and therapy

Abstract Background: The Kay Pentax Nasometer uses a separator plate that touches the philtrum of a patient to separate the nasal and oral sound energies for nasalance measurement. However, the separator plate could restrict the natural movement of the patient’s upper lip and generate an unpleasant pressure to the patient’s philtrum. The present study was intended to measure nasalance scores without touching the philtrum for better comfort during speech assessment and therapy.Methods: Nasalance scores of 10 males and 10 females having no speech disorders were measured under four levels (0, 5, 10, and 15 mm) of the gap between the plate and the philtrum (denoted as plate-to-philtrum gap) using Nasometer II 6450 for nasal (Nasal Sentences) and oral (Zoo Passage) stimuli. Regression formulas were established to examine the relationships between nasalance score and plate-to-philtrum gap for the Nasal Sentences and the Zoo Passge, respectively. To provide equivalent nasalance scores measured under the 5-mm plate-to-philtrum gap to those measured under the conventional contact measurement condition (i.e., the 0-mm plate-to-philtrum gap in the present study), compensation factors were identified as the ratio of the mean nasalance measured under the 0-mm gap to that measured under the 5-mm gap for the Nasal Sentences and the Zoo Passge, respectively. The validation of the identified compensation factors was examined.Results: The nasalance scores were significantly different between the four different plate-to-philtrum gaps for the stimuli. Nonlinear and linear regression formulas were established for the relationships between nasalance score and plate-to-philtrum gap for the Nasal Sentences and the Zoo Passage, respectively. Compensation factors for the Nasal Sentences and the Zoo Passage were identified as 1.17 and 0.71, respectively. Validation results showed that the adjusted nasalance scores after mutiplying the identified compensation factors were similar to those measured under the conventional contact measurement condition for both the oral and nasal stimuli.Conclusions: The 5-mm plate-to-philtrum gap condition after multiplying the compensation factors can provide equivalent nasalance scores to the conventional contact measurement condition and better comfort in speech assessment and therapy.