Imbalance of the Vocal Cords as a Factor for Dysphonia

The effect of various imbalance of the vocal cords was investigated in dog through the use of a high speed camera. Within the limit of our experimental procedure, the two vocal cords asymmetrical in mass or tension vibrated at the same frequency. Experimental evidence and clinical experiences indicated that imbalance between the glottal condition and expiratory air flow could be an important factor in the etiology of functional dysphonia or aphonia

Factor Analysis of Hoarseness

1. Analyses of 16 various hoarse voice samples by semantic differential method revealed that hoarseness consits of 4 factors, which may be represented by R (rough), B (breathy), A (Asthenic), and N (semi-normal). Factor N can reciprocally replaced by factor D (degree of hoarseness.) 2. Two simple methods of assessing hoarseness as regard to the 4 factors mentioned above were devised. The results of single entry method, the method to represent hoarseness by one of the 4 factors demonstrated high consistency among different judges and with those of the semantic differential method. The quaternary rating method in which the voice is rated on the 4 factors has an advantage to disclose more detailed content of the 4 factors. Conversion of the results by the quaternary rating into single entry form confirmed high consistency between the two methods

Rheological Characteristics of the Vocal Cord : Measurement of the Damping Ratio

The damping ratio of the vocal cord was measured in human larynges extirpated at autopsy or at surgery. The damped oscillation was produced by releasing the vocal cord from a displaced position. The damping ratio of the vocal cord in the autopsy case was 0.237 and in the surgical cases 0.320 and 0.344. Damped oscillation with a given damping ratio was simulated by use of computer

Laryngeal Movement during Cough

An analysis of ultra high speed motion pictures of the larynx indicates that each cough burst consists of three stages : 1) a wide opening of the glottis for deep inspiration, 2) an extraordinary tight closure of the glottis, and 3) dynamic vibrations of the laryngeal structures, including the vocal folds, the mucous membrane of the posterior laryngeal wall, the ary-epiglottic folds, and the epiglottis. The vibratory movements are apparently not active, but caused by the strong air current, in accordance with Bernoulli's law. The vibrations are characterized by constant and rapid changes. The entire episode is extremely short and all laryngeal activities are transient. Additional experiments have been initiated to correlate these findings with aerodynamic studies, electromyographic investigations, and acoustic measurements of a cough

Application of Reflectionless Acoustic Tube for Extraction of the Glottal Waveform

A reflectionless acoustic tube described by Sondhi is utilized to obtain the glottal waveform. The rationale of this method is that the effect of vocal tract resonances on glottal waveform is considerably reduced by a reflectionless uniform tube connected with the mouth during phonation. Measurement of the transmission characteristic (frequency response) of the tube proved minimal attenuation caused by the tube. The obtained glottal waveform for four normal subjects and for nine patients with laryngeal pathologies are reported herein and methods presently available for estimating the glottal waveform are also discussed. The method to obtain the glottal waveform with the reflectionless acoustic tube proved to be simpler and more practical for clinical use than the other ones

Use of a Hot-Wire Flow Meter in the Study of Laryngeal Function

Hot-wire flow meter was used to obtain the glottal waveform. The output of the flow meter showed a good approximation to the glotal wave form. When the efficiency of voice was defined as the ratio of rms (root mean square) of AC component in the output wave to DC component (mean volume velocity) in it, 0.5 was the critical efficiency value which is separating the normal and pathologic aryngles. Normal subjects always showed the values higher than 0.5

Pitch Perturbation in Normal and Pathologic Voice.

(1) Pitch perturbation was analyzed both in sustained phonation and in phrase-reading (2) In sustained phonation, the values over 0.23 s.t. for male and 0.25 s.t. for female was defined as pathologic.(3) In the phrase-reading over 0.19 s.t. was abnormal (4) To fascililate and simplify the procedure, laboratory computer was used