Nasometer estimates nasalance by comparing nasal and oral acoustic energy using two microphones separated by a sound-insulated plate. The device manufacturer claims that this plate provides 25 decibels of acoustic isolation; however, no peer-reviewed studies have validated this claim. We evaluated the actual performance of the nasometer’s separation plate using controlled broadband signals in an anechoic environment, with nasal and oral microphones positioned as in clinical use. Our results show that in the low-frequency range used for clinical nasalance calculations, typically 300–750 Hz, there is little acoustic separation between the microphones. Signal differences are often less than 5 decibels. The claimed 25 dB isolation is only observed above 6000 Hz, but this high-frequency range is excluded from nasalance scores due to bandpass filtering in the device. As a result, the separation plate does not prevent cross-channel acoustic leakage in the frequency range that matters most for clinical assessment. This leakage can significantly inflate nasalance scores and may lead to an inaccurate diagnosis of velopharyngeal dysfunction. These findings raise concerns about the validity of current nasometer designs and support the need for improved calibration procedures and revised frequency weighting in clinical protocols.
Little et al. (Wed,) studied this question.
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