1. What are the relationships between the NAS system, the NEM system and the NVS system?
There are a number of ways that our systems for visualizing nasality can be purchased. The full Nasality Visualization System (NVS) includes the capability for measuring Nasal Emission (NEM-1, formerly NE-1) and the system for measuring nasalance (NAS-1 system). As part of the NVS system, the NAS-1 system has both the mask and partition options. (Nasal Emission measurement requires the mask.) There is a price advantage when purchasing the complete NVS system over purchasing the NAS-1 and NEM-1 separately.
2. How does the NEM system for recording nasal emission work? Is it accurate enough for research applications?
The NEM-1 system uses the standard Glottal Enterprises dual-chamber (OroNasal) mask to isolate nasal airflow. The flow rate is measured by a transducer mounted in the mask handle, as is the acoustic signal. The software records and displays both signals simultaneously and they are superimposed on the screen in a chart display. (See the dual-chamber mask and a typical screen at http://www.glottal.com/Products/NVS.htm#NE1.) Average values of NE and SPL can be obtained for a chosen speech segment. You definitely can do research measuring nasal emission with the NEM-1. It is also useful in speech training tasks.
3. Can the so-called SNAP test (Simplified Nasometric Assessment Procedure, as described by Ann W. Kummer in Cleft Palate and Craniofacial Anomalies, Singular Press, 2001) be used with the NAS-1 system?
The SNAP test or its equivalent can be used on any device for displaying nasalance, including ours.
4. Can systems for measuring nasalance be used for measuring nasal emission in pressure consonants?
No. If a manufacturer claims that its nasalance system does measure nasal emission, it is a misstatement
5. Can a system for measuring nasal emission in pressure consonants also measure nasal airflow in vowels?
Yes, though perhaps not as conveniently as with a system measuring naslance.