The Visualization of Nasality
The term nasality refers to an auditory impression about speech and is not a precise physical variable. The primary underlying physical variable is the opening and closing of a passageway between the oral vocal tract and the nasal passages. Usually, this opening is controlled primarily by moving the velum or soft palate closer to the walls of the pharynx and sometimes also constricting the walls of the pharynx. However, with persons having a cleft palate, an inability to close the velopharyngeal passageway, or the presence of other passages between the oral and nasal chambers caused by the cleft, may cause an impression of hypernasality (excess nasality) in their speech.
Hypernasality is also often a characteristic of the speech of the hearing impaired, including persons using a cochlear implant. This is because nasality is a subtle characteristic of speech, and not easily perceived by the hearing impaired or with a cochlear implant. Because of these and other applications, noninvasive means are needed for measuring and visualizing the action of the velum, and in the case of the presence of a cleft palate, for measuring the success of attempts to close the cleft.
One popular means for noninvasively visualizing and quantifying the effectiveness of velopharyngeal closure is the measurement and display of the so-called Nasalance of the voice, defined as the ratio of acoustic energy at the nostrils to that at the mouth during vowels, with some form of acoustic separation present between the mouth and nose.
Also important for visualizing nasality are methods for measuring and displaying the airflow through the nose during consonants requiring an oral air pressure, termed Nasal Emission. If the velopharyngeal passageway is not closed during a consonant requiring significant oral pressure, such as p or s in English, the resulting nasal airflow (nasal emission) will have at least two effects on the speech. The escaping airflow will reduce the oral pressure, which will reduce the strength of the consonant. It will also act to deflate the lungs, reducing the amount of speech possible between breaths. A person having this problem may also learn to speak more softly, with less lung pressure, in order to reduce the amount of air lost in the emission. Because of this, overly soft speech can also be associated with hypernasality.
The measurement and display of Nasalance and Nasal Emission are uniquely combined in the Nasality Visualization System from Glottal Enterprises.
History: In 2005, Glottal Enterprises founder and president Martin Rothenberg received a U.S. Patent for a new method of measuring both Nasalance and Nasal Emission, using a dual-chamber form of the CV airflow mask developed by Dr. Rothenberg and marketed by Glottal Enterprises. Glottal Enterprises then set out on a quest for a system for the non-invasive visualization of vowel nasality which was both precise enough for research and clinic use, and sufficiently user-friendly so that the system could be used by technologically unsophisticated persons for home use, including children. The result is NVS system for nasality visualization. The NVS system combines the NAS system for nasalance measurement in vowels and the NEM system for nasal emission measurement in consonants.
Some Actual Speech Training Examples Using the NVS System
Video of the NEM system in use for speech training.
Michael is a 7-year-old using the NEM system to reduce nasal emission.
- The NAS System
In the current version of the NAS system, we have included many features not found in the other nasalance measurement systems on the market, such as the Kay-Pentax version of the Nasometer.
These useful features include:
- USB operation
- Color-differentiated display that clearly separates vowels and vowel-like consonants from pauses, unvoiced consonants and nasal consonants.
- Ability to eliminate nasal consonants from the average-nasalance computation.
- Two options for the oral and nasal separation handle - the OroNasal mask or a separator plate held against the upper lip.
- Easily changeable separator plates for the separator-style handle that can be selected to best fit the face of the user, and are easily cleaned.
- A mask that is also easily removable for cleaning and that comes in two sizes, to fit both children and adult. It yields reliable and reproducible nasalance measurements without the use of head straps or the need for a critical placement that can change during use.
Comfortable mask or convenient separator The NAS system from Glottal Enterprises is unique in that it offers the choice of a hand-held sound separator resting on the upper lip or a soft, comfortable OroNasal mask. Both the separator and the mask separately measure and record nasal and oral voice energy, and both come in different sizes to conform to the face of the user.
Nasal Emission visualization - the NEM system
NEM System for measuring Nasal Emission, shown in its entirety, including an OroNasal dual-chamber mask and a mask handle containing the transducers and all electronics.
The NEM system features:
- A color-differentiated, superimposed display of both nasal emission and speech audio level (SPL).
- Practice and Compare-To-Model modes.
- User–settable target limits for nasal emission or audio in the Practice Mode
- USB operation on any Windows computer – even laptops – XP, Vista, or Windows 7.
- Both average and total airflow values, as well as the average SPL, displayed for any selected NE episode. Peak values are also easy to measure.
- Adult and child size masks are available.
- Periods of nasal inhalation are clearly marked on the Nasal Emission chart and eliminated from the computations. There is no need to control the subject's breathing pattern during testing or training.
- Uses Glottal Enterprises proven aerodynamic measurement technology that is factory calibrated.
- Has the ability to also measure nasal air leakage in standard blowing tasks.
The NEM nasal emission measurement and display system from Glottal Enterprises can be purchased separately or as part of the Nasality Visualization System.
Nasal emission practice screen showing /apa/ pronounced with three degrees of nasal emission
Using the NVS system
The NVS system offers the next generation of tools needed to measure and display the pattern of NASALANCE and NASAL EMISSION in speech and singing as an aid in learning to control nasality, both in the clinic and at home, and as a computer based aid for monitoring progress. Based on 30 years of research and application in the aerodynamics of speech, the NVS system provides clinic-level power and accuracy in a home therapy system.
Who can use the NVS system? The NVS system works as a professional therapy supplement and as a standalone system. It is appropriate as a speech traning aid for speech disorders in children and adults related to neurological conditions, cleft palate and hearing impairments, as well as for speech training after a cochlear implant. The system is also valuable in learning to speak a new language and in singing instruction.
Affordable, effective therapy booster. Developed as a supplement to professional therapy, the line of Glottal Enterprises systems for visualizing the pattern of nasality in speech make professional sessions more effective. Therapists can assign activities, pre-record models and review practice recordings. With practice, learners stay on track, and progress is easier.
Convenient system needs only a desktop or laptop computer. The NVS system can be used anywhere there's a desktop or laptop multimedia computer (Windows XP or newer). Just install the software, plug in the separator or mask into the computer's USB jack and begin.
Getting started is quick and easy. With a mouse click, the student selects the type of variable to be displayed, Nasalance or Nasal Emission, and if Nasalance, select the speech input mode to be used – separator handle or mask handle. The student then chooses between the Practice screen or the Compare-to-Model screen.
Real-time feedback, rapid progress. Beginning with the Practice activity, the student can produce sounds, words or complete phrases, and view the pattern of nasalance or nasal emission in real time. In the Practice mode, students can see instantly how the nasalance or nasal emission associated with their velar posture compares to an on-screen target level. This clear feedback lets students find out immediately if they are practicing correctly.
In the Compare to Model activity, two nasalance or nasal emission graphs are displayed. The upper graph, labeled Model, can be of a pre-recorded model utterance, or it can be of a student-created model that the student can attempt to match or improve on.
SW-1 Student-Teacher Switch
Glottal Enterprises now offers a USB switch that makes it easy to change from a student's mask or separator handle to that of a teacher in nasality testing or speech training using the Nasality Visualization System. The switch can also be used by a student doing home training to change from a nasalance handle to a nasal emission handle. Just a flip of a finger and you are there. No switching USB connectors.
The OroNasal Mask
The unique OroNasal mask is a two-chamber version of the Glottal Enterprises circumferentially vented (CV) mask that has long been the choice of clinics, hospitals and research centers worldwide for measuring voice airflow with high fidelity and with minimal speech distortion. Use of the mask option for the Nasality Visualization System allows the user to measure both Nasalance and Nasal Emission (nasal airflow during consonants that require an oral pressure buildup) using the same mask.
What's special about the OroNasal mask?
The OroNasal mask is...
Soft and flexible, fitting comfortably over nose and mouth. The OroNasal mask is well suited for long periods of use and easy for children to accept.
Innovative and accurate, based on the clinically proven Glottal Enterprises voice-transparent circumferentially vented (CV) mask design. For Nasalance or Nasal Emission recording, the OroNasal mask has transducers and electronics built into an easily changeable handle.
Non-invasive, so there's no hard plate pressing on the student's mouth (as in some other systems for recording nasalance) and nothing goes in the mouth or nose. The OroNasal mask fits over both nose and mouth and separates airflows with proprietary pneumotach technology to reduce cross-sound-leakage between nose and mouth.
User-controlled, the mask works without the uncomfortable, awkward head straps or harnesses used in competing systems. Whether for nasalance or nasal emission measurements, The student simply holds the mask in place when ready to use it - it does not require accurate placement for consistent results. Interruptions that occur during testing or practice are easily accommodated.
For the measurement of Nasalance, Glottal Enterprises offers a choice between the OroNasal mask and a separator-style measurement handle that is interchangeable with the mask. The separator handle is especially recommended for speech training exercises, whether at home or in the clinic.
The separator handle comes in a clinic-version that has interchangeable partition plates or a more economical single-user style that may be adequate for home training use. Both the clinic and single user models contain all transducers and electronics, and are ready to be plugged in to your computer’s USB jack.
Owners of older Glottal Enterprises systems
for measuring nasalance can upgrade their software free of charge
when purchasing a separator-style handle. Contact
us if you would like more information about this option.
Following the examples of WaveviewStudent and AeroviewStudent
for providing students, clients and potential purchasers with low
cost interactive software for studying the functioning of new voice
analysis techniques available from Glottal Enterprises, we are
The NasalityStudent CD contains a highly functional
version of the Nasality Visualization System, a detailed interactive
manual for taking the user through the operation of the NVS and
the interpretation of the results, and a number of prerecorded
voice segments that go along with the exercises in the manual.