An investigation of the relationship between speaking fundamental frequency and vocal quality improvement

J. COMMUN. DISORD. 17 (1984), 95-100

AN INVESTIGATION OF THE RELATIONSHIP BETWEEN SPEAKING FUNDAMENTAL FREQUENCY AND VOCAL QUALITY IMPROVEMENT JON HUFNAGLE Illinoi.~

State

University

KATY HUFNAGLE Speech

Pathology

The purpose

and Audiology

of the present

and after voice therapy. showed

quality

no significant

AssocirttcJd,

Inc.

study was to measure

Listenerjudgments

speaking

fundamental

frequency

were used to assess vocal improvement.

change in the speaking

fundamental

frequency

before Results

accompanying

vocal

improvement.

INTRODUCTION There is discrepancy in the literature pertaining to the relationship between hoarseness and speaking fundamental frequency (SFF). Some investigators state that hoarseness results in a pitch level that is below “optimal” (Fisher and Logemann. 1970; Luchsinger and Arnold. 1965; Cooper, 1974), while others contend that the consequence of hoarseness is a pitch higher than “optimal” (Van Riper and Irwin, 1958). There also is evidence suggesting that no relationship exists between the SFF and hoarseness (Murry, 1978; Shipp and Huntington, 1965; Hecker and Kreul, 1971). Few studies have been designed to investigate the SFF before and after voice therapy. Laguaite and Waldrop (1964) found no relationship between fundamental frequency and vocal quality before and after therapy. Unfortunately, there was a lack of agreement between the therapist and the judges as to the improvement of the voices following therapy. Cooper (1974) found the fundamental frequency of the voice to be higher following therapy, although he utilized no listener judgments to establish voice improvement following therapy. Address

Audiology,

correspondence

Illinois

State

to Jon Hufnagle.

University,

Normal.

0 1984 by Elsevier Science Publishing CO.. Inc.

52 Vanderbilt Ave.. New York. NY 10017

Ph.D..

Department

of Speech

Pathology

and

IL 61761. 95 002 I-99?4:84/$03 .OO

xl

.I.HUFNAGLExd

K.HUFNAGLFI

In light of this controversy the present study was dcsigncd to ansv,cr the following question: When a dysphonic voice is judged as improved in vocal quality, is there a significant change in the SFF?

METHODS Eight fcmalc

clients demonstrating

dysphonia.

and diagnosed

by an oto-

laryngologist as having vocal nodules participated in the study. The subjects had a mean age of 20 years: 5 months, with a range of I8 years: 3 months to 26 years: I month. All sub.jccts dcmonstratcd no rhythm ot hearing disorders and had undergone no previous voice therapy. Each subject read the first paragraph ofthc Ktrir~ho,l~ P~.ssrl~~c~ (Fairbanks, IY60). Recordings were made prior to and following voice therapy. All rccordings were made in a sound-treated room on one channel of a Revox 77A tape recorder coupled to an Elcctro-Voice microphone. All recordings were made at a transport speed of 7.5 ips. The therapy procedure employed with these subjects was a modification of the program recommended by Wilson and Rice (1977). Specifically. the patient was initially advised of the laryngeal behaviors and structural factors that contribute to ;I voice deviation. A period of soft whisper was recommended to reduce or eliminate vocal abuse and to attain a target voice. Procedures that facilitated vocal productions with proper muscular balance were employed and shaped to conversational levels. Negative practice was used to increase awareness of the difference between the proper and improper voice. Following the termination of therapy. the subject was rerecorded reading the Rrrinho\t~ Pcrssrrgc~. The third sentence of both the pre- and posttherapy passage was edited out and used for the listening task. The scntences were combined in both orders and all pairs were presented in random order to 27 listeners. The listeners consisted of graduate students from the Departments of Speech Pathology and Music. The listening task was of the forced choice type, the listeners being asked to choose the voice that had the best vocal quality. No other responses were allowed and no other questions concerning the perception of the stimuli were asked. The Sign Test (Siegel. 19%) was used to determine if the level of agreement among the judges was significant. Speaking fundamental frequency measurements were obtained by processing the voice samples through a Honeywell Visicorder at a chart speed of 400 mm/set. All samples were low-pass filtered at 400 Hz before the oscillographic record was produced. Measurement of a 250 Hz calibration tone indicated the stability of the entire system to be within acceptable limits. To compute the mean SFF, the paper output was divided into 0. Ixc segments and the periodic waveforms in each segment were tabulated. averaged. and converted into measures of Hz. From these measures. the

SFF AND VOCAL

QUALITY

97

IMPROVEMENT

Table 1. Group Data in Hz for Before

and

After

Therapy Total

Before therapy After therapy

Mean SFF

SD (Hz)

Range

207.25 209.48

25.51 20.09

164.52-243.93 177.90-226.3X

Frequency Shifts 34.75 37.75

mean and standard deviation of the SFF, and the range of the entire vocalic portion were tabulated for each subject. Directional fundamental frequency tfo) shifts, as described by Murry (1978). were obtained from the mean f. of each 0. I-set segment. Two samples were randomly selected for inter- and intrdjudge reliability measures. The results of these measures were 98% and lOO%, respectively. A r-test for related measures (Bruning and Kintz, 1977) was used to test for differences between the pre- and posttherapy groups. On an individual basis, the fundamental frequency was thought to have changed significantly if there was a great enough difference to constitute a semitone.

RESULTS Table 1 summarizes the acoustic data for the before and after therapy voice samples. The results of the t-test for related measures show that the SFF before and after therapy did not differ significantly (t = 0.37, df = 7, p > 0.01). No significant differences between the before and after fundamental frequency shifts were found (t = 1.79, d’ = 7, p > 0.01). Individual acoustic changes and listener agreement on vocal quality improvement are summarized in Table 2. Examination of the fundamental frequency standard deviation for each individual clearly demonstrates that the variations in frequency around the mean fundamental frequency did

Table 2. Comparison

of Changes in SFF and Listener Agreement

for Vocal

Quality Improvement Subject 1 2 3 4 5 6 7 8

Mean SFF Before Therapy

SD

Mean SFF After Therapy

SD

Change in Semitones

Listener Agreement (5%)

243.9 188.9 186.5 219.0 164.5 227.0 213.1 215.0

12.3 17.1 14.0 22.5 16.0 18.9 19.0 14.2

232.2 185.0 177.9 226.4 205.9 227.1 217.8 203.6

20.3 15.4 15.6 27.5 18.1 17.9 20.4 16.5

-0.85 PO.37 - 0.82 +0.57 +3.90 +0.01 +0.38 -0.95

57 9 1l’ 74” 54 54 81” 89“ 89“

y Significant at the p < 0.001.

Y8

J. HUFNAGLE

and

K. HUFNAGL.E

not differ noticeably between the pretherapy and posttherapy recordings. Individual changes in semitones show that one subject changed more than one semitone. Of the remaining seven subjects, three went up in speaking fundamental frequency and four went down. The judges preferred the vocal quality following therapy, but three subjects did not reach a level of significance. Of these three subjects. number five was the subject that changed noticeably upward in speaking fundamental frequency.

DISCUSSION Comparing the mean speaking fundamental frequency for the two conditions of the present study with normative data shown in Table 3. it can be seen that of the five studies (using approximately the same aged subjects) three demonstrate slightly higher fundamental frequency. The small differences (within two semitones) between Stoicheff (l%I), de Pinto and Hollien (1982). Fitch and Holbrook (1970). and the present study may be attributable to procedures used in deriving the fundamental frequency. The present study used a procedure described by Murry (1978). Lechner (1979). and Murry and Doherty (l980), while Stoicheff and de Pinto and Hollien used the Fundamental Frequency Indicator (FFI). and Fitch and Holbrook used a device called FLORIDA. Both procedures and devices are described elsewhere (Hollien and Paul, 1969; Holbrook and Meador. 1969). The procedure used in the present study is a manual one. with greater potential for error in calculating the fundamental frequency relative to the more automatic procedures. Differences not withstanding, the present data seem to be consonant with the existing normative data of fundamental frequency, supporting de Pinto and Hollien’s statement (p. 369). “It appears that modern women can be expected to exhibit SFF level at, or slightly above. 200 Hz when fairly young . .‘* The results of our study support previous investigations by Shipp and Huntington (1965). Hecker and Kreul (1971), and Murry (1978). All of whom suggest that there is no difference between SFF in normal speakers and those with vocal cord pathologies. The number of frequency shifts found in the before therapy sample of the present study is in agreement with Murry’s data using normal subjects. Table 3. Previous Research on the SFF of Normal Adult Females Keference

Michel, Hollien. and Moore Michel, Hollien. and Moore Linke (1973) Fitch and Holbrook (1970) Linville and Fisher ( 198 I)

(1966) (1966)

Hz

AS

207 207 200 217 209.50

I6 17 Adult 17-2s 25-35

SFF AND VOCAL QUALITY

IMPROVEMENT

99

The lack of change in the number of frequency shifts before and after therapy in this study is supportive of Murry’s finding that the number of frequency shifts did not vary significantly between his normal group and his three groups with laryngeal pathologies. The findings of the present study are consistent with Laguaite and Waldrop (1964), in that change in the voice following therapy is not related to changes in the SFF. As to what variable or variables contribute to perceived quality changes, Laguaite and Waldrop conclude that the positive change in vocal quality is more related to changes in the harmonic structure than to changes in the SFF. Supportive of Laguaite and Waldrop, Emanuel and Whitehead (1979) and Yanagihara (1967) suggest that the relative amount of harmonic and noise (inharmonic) energy at varying frequency levels may be a variable. Klich (1982) suggests that vowel duration, among other variables, may be an important factor. The present study did not investigate all possible variables that may have contributed to the judged vocal improvement. It may be that a multifactorial model must be developed to explain vocal quality improvement following therapy. More research is necessary to answer this question.

Within the limits and scope of the present study, the findings suggest that therapy for dysphonias associated with nodules is best managed by procedures other than those manipulating pitch and, thus, changing the SFF. Furthermore, the entire concept of optimum pitch becomes highly suspect when dealing with dysphonias in conjunction with vocal fold nodules. This study was supported in part by a Summer Research Appointment awarded by the Graduate School of Illinois State University. Portions of this paper were presented at the 1982 Convention of the American Speech-Language-Hearing Association in Toronto. Ontario, Canada.

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