Voice and Speech Systems

Products > Computerized Nasalence Measurement and Therapy

Vagmi Nasalence Therapy
a comprehensive system for nasalence measurement and therapy

Vagmi Nasalence Therapy is easy to operate and user friendly software package. It requires no programming skills. It requires customezed hardware developed by VSS. It consists of 2 microphone setup with 2 channel balanced amplfier.

Contents of this Page: (A) Free Download (B) Introduction (c) VSS customized hardware setup (D) Nasalence Menus

A. Free Download
Power Point Presentation of Demo:
Instructions:Right click on the link and 'Save Target As:

Vagmi_Therapy_Nasalence_Demo.pps

B. Introduction

Hyper and Hypo Nasal

If sound comes out through nostrils for sounds other than m, n, ng voice is said to be hyper nasal.
Some persons are unable to produce nasals such as m and n. Such voices are called hypo-nasal. Vagmi Nasalence Therapy is useful to

Monitoring nasalence in pre and post-operative cleft palate cases

Normal persons with mis-articulation problems

Hard of hearing childern to identify and teach nasals etc

What is Nasaelence?

The energy in sound output radiated out of nostrils is called 'nasal output', denoted by 'N'.
The energy in sound output radiated out of lips is called 'oral output', denoted by 'O'.
Nasalence is defined as the ratio N/(O+N). Note that (O+N) is the total energy.
TONAR denotes the 'The Oral to Na>sal Ratio and is eqaual to O/N. In case N=0, TONAR is not defined.

C. VSS Customized Hardware Setup

The customzied hardware as two components: (a) 2 channel amplifier (shown on left side of the figure) and (b) Oral_Nasal setup (shown on the right side of the figure).
Oral-Nasal setup has 2 microphone capsules separated by a wodden baffle. The wodden baffle is held against the bridge just below the nostrils above the upper lip. The upper microphone capsule picks up mostly the nasal output. The lower microphone capsule picks up mostly the oral output.
The amplfied output is fed into the Line-In of the sound card. (Blue coloured socket in the backpanel of the PC.)
On some computers, the built-in gain is high so that the oral-nasal output can be given directly to 'Line-In' without the amplifier. In such a case the 2-channel amplifier need not be purchased.

Cross-talk and Setting Threshold

Two microphone capsules are separated by a wooden baffle. Wood is a good absorber of sound. Howeverm even for a non-nasal sound, the upper microphone capsule may pick some of the lip output. This is called cross-talk.
In order to make a reasonably accurate measurement of 'Nasalence', the 'Threshold' must be set appropriately. 'Threshold' has to be set just before making a measurement.

Procedure: Let a person with normal voice, i.e., without nasality utter a steady vowel using oral-nasal setup. Select 'Oral-Nasal Indicator' menu. Click on 'Start'. There are two tubes; the tube on the left shows the oral output in cyan colour. The tube on the right shows the nasal output in pink colour. Strictly there must not be any output seen in Nasal channel since the input is a non-nasal vowel. In the Figure on the left, the oral output reads 111 dB whereas the nasal output reads 85 dB. Click on 'Lower Threshold' and enter a value a couple of dB above (ex. 88 dB) the reading seen in the nasal channel for a non-nasal vowel input. Now when a pure non-nasal vowel is uttered there will not be any output seen in the nasal channel. All measurements are made when the signal in either channel is above the lower threshold.
Although the levels are shown in dB to compute nasalence the energy in respective channel is used.

Nasal Therapy

Two Microphone setup is used to measure the relative oral and nasal levels and are shown by Blue and Pink bars as dscribed above.
There are three programs for Nasalence therapy.

(a) Oral-Nasal indicator shows the relative levels of oral and nasal channel outputs in cyan and pink colurs respectively along with the dB levels.
(b) In Nasalence menu, nasalence is measured during the the user selected interval. Nasalence measurement begins when the user clicks on 'Start'. Nasalence measurement ends when the user clicks on 'Stop'. No measurement is made when the level in either of the channels is below the lower threshold. Passages without nasals may be used, like 'Betty bought butter, buter was bitter, Betty bought better butter to make bitter butter better'. In such a case the nasalence must be low. Passages like 'moon shine', 'sun shines in noon', 'One nine' etc may be used in which case nasalence must be high. Sustained sounds like vowels or nasals may also be used.
(c) In Clock menu a pendulum swings while the subject phonates, the extent of swing is proportional to percent nasalence. Using the visual feedback, the user can voluntarily control the velum thus reduce or increase nasality as desired.

PC Requirement, Support Hardware and Accessories (Click to open the link)

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