Dept. for Speech, Music and Hearing

Quarterly Progress andStatus Report

Formant frequencies of basssingers

Sundberg, J.

journal: STL-QPSRvolume: 9number: 1year: 1968pages: 001-006

http://www.speech.kth.se/qpsr

STL-QPSR 1/1968

SPEECH PRODUCTION AND SINGING

A. FORMANT FREQUENCIES OF BASS SINGERS*

J. Sundberg

It is a common observation that the vowel articulation of trained

s ingers a r e different i n speech and singing (I) . Two questions ar ise:

what changes i n formant frequencies accompany these quality differen-

c e s and what a r e the corresponding changes i n the vocal t r ac t a r e a

function? This a r t ic le will deal with these questions.

The subjects I

As measurements of formant frequencies a r e most easily made i n

spec t ra where the fundamental frequency F O i s low, bass s ingers were

chosen a s subjects. They will he re be re fer red to a s B1, BZ, B3, and

B4. I B 1 and B4 a r e frequently engaged a s soloists i n church music per -

formances and sometimes a l so at the Royal Opera i n Stockholm. B2 is

an experienced soloist of this Opera. B3 is to be considered a s an ama-

teur , but has twelve years of vocal training.

The s ingers represent different types of voices: B1 has an extreme-

ly d a r k voice quality and a range f r o m C 2 t o F4, BZ a ra ther d a r k voice

ranging f rom F2 to G4, B3 a ra ther light voice ranging f r s m D2 to F4,

and B4 a light voice ranging f rom F to G4. 2

The total length of the vocal t r ac t has a considerable influence on

the formant frequencies. Therefore, th ree frontal and three la te ra l

X-ray pictures were taken of each subject: one at res t , one during (2) speech, and one during singing a note i n the subjec t ' s lower reg is te r .

In o rde r to obtain comparable measures the vocal t r ac t lengths were

defined a s the distance f rom the upper incisors to the back pharynx wall

added to the distance f rom the sagittal midpoint of the r ima glottis t o

the straight line prolongation of the palatum durum. These lengths

were determined f rom the la te ra l pictures of the vocal t r ac t s a t rest .

The different positions of the larynx in speech and singing were meas-

ured on the frontal pictures with the spinal column contour as a reference,

s ee Fig. I-A-1. The lengths, thus defined, a r e reported i n Table I-A-1.

* t o be presented a t the NAS-68 meeting i n Trondheim, 14-16 M a y 1968,

Fig. I -A -1 . Trac ings of frontal X - r a y pictures of four s ingers ' neck and chin. Solid l ines: spoken vowel; dashed lines: sung vowels.

kHz 3 - - - -

---+ ---- *----*--------+--- - 4

-,-*---

FN kHz

3

. Fig. I-A-2. Formant freqasncies of four eingers' leag Swedish vowels. Solid lines: mpoken vowels; dashed liner: sung vowels.

STL-QPSR 1/1968 3.

The lighter voices tend to show more formants on the sonagrams

than the darker, i. e. to have higher levels on the higher formants:

The darkest voice B1 produced only four visible formants on the sona-

grams, the rather dark voice B2 produced four in speech and five in

singing whereas the lighter voices produced five formants i n speech and

in singing.

Some differences were found in the formant frequencies. The dark-

est voice generally shows the lowest and the lightest voice the highest

formant frequencies. In most cases, thus, the voices can be ordered

B1, B2, B3, B4 using the formant frequency values a s a ranking prin-

ciple. Probably these differences in the formant frequencies of the in-

dividual singers a r e mainly due to the different lengths of the vocal

tracts. The four diagrams in Fig. I-A-2 all show grossly the same dif-

ferences between the spoken and the sung vowels. Therefore the mean

value was calculated for each vowel's formant frequencies in speech

and in singing for all four subjects. These mean values a r e shown in

Fig. I-A-3. Fant has given mean values of the formant frequencies of

the same vowels for seven male Swedish speakers (5). These values

a r e also plotted in Fig. I-A-3 for comparison.

Fig. I-A-3 shows that there a r e only small differences in the values

of the F1 between speech, singing, and Fant' s data. Fo r the F2 only

small differences appear between Fant' s data and the singers' spoken

vowels except for (u) and (b ) , whereas F2 i s much lower in the sung

vowels, the back vowels excluded. F3 also shows clear differences:

Fant' s data a r e higher than in the singers' speech, and considerably

higher than in the sung vowels. This i s not t rue for the back vowels,

where the relations a r e approximately inversed. The values of F4 show --- -- - the most evident differences. Here again Fant' s data a r e highest, and

the values of the sung vowels a r e lowest, and this statement applies to

all vowels.

Thus we find that the f i rs t two formants a r e close to the normal I

values in the singers' speech, which seems natural, since those for-

mants a r e important to the intelligibility of the speech. In the singers'

spoken vowels the third and fourth formants a r e - with few exceptions - lower in frequency than those reported by Fant and these formants a r e

still lower in the sung vowels. A possible interpretation of this i s that

the articulation habits acquired during the voice training have some

bearings on the speech articulation of the singers.

FN kHz 1

0 L I I I I I I I I

U: o : a : a: e : I : Y: u: Id:

Fig. I -A-3. Mean values of formant frequencies af long Swedish vowels. Dashed lines: Fant' s data; solid lines: singers' spoken vowels; chain-dashed lines: singers' sung vowels.

STL-QPSR 1/1968

It i s interesting to observe the relations between the third and fourth

formants i n spoken and sung vowels shown in Table I-A-2. The mean

value of F4-F3 i s fo r the spoken vowels 0.63 kHz and for the sung 0.50

kHz. The corresponding mean value for Fant ' s data i s 0.90 kHz. Thus,

F 3 and F 4 a r e c lose r i n singing than i n speaking and appear to be c lose r

i n trained voices than in untrained speaking voices..

Table I-A-2

Frequency distance i n kHz between F3 and F4.

Vowel

( 4

(0:)

(a:)

(=:I ( 4

( i :)

(Y:)

(4 (#:I

Mean value

Fant ' s mean values

1.07

0.69

0.81

0.95

0.89

0.44

0.88

1.17

1-19

0.90

Singers ' spoken vowels

0.55

0.46

0.79

0.71

0.66

0.35

0.68

0.69

0.74

0.63

Singers ' sung vowels

0.38

0.39

0.38

0.67

0.57

0.39

0.51

0.64

0.56

0.50

Such a reduction of the frequency distance between two formants

leads to high formant levels (6). Consequently, these two formants

will tend t o appear a s one single peak in the spec t ra l envelope obtained

in a broad band spec t ra l analysis. This effect will be eepecially pro-

nounced for vowels a s (u:), (a:), and (i:) where these formants l ie very

close. As a mat te r of fact , severa l investigations of the singing voice

have been res t r ic ted to these th ree vowels constituting the co rne r s i n

a n F1-F2 vowel diagram. It i s therefore understandable that the peak in

the spec t r a l envelope found between 2 and 3 kHz of these very vowels

commonly i s re fer red to a s the "singing formant" (7 ,8 , 9, 10' 11, 12)

Above, cer ta in changes in formant frequency have been found be-

tween spoken and sung vowels. The X-ray pictures showed differences

in the vocal t r a c t between speech and singing. The question then a r i s e s

if the changes i n formant frequencies may be explained by the obse rved

changes in vocal t r ac t shape. F o r this purpose a number of experi- (13) ments with the electr ic line analogue LEA were made .

LEA synthesis

The mean values of the formant frequencies of the s ingers ' spoken

vowels were matched on LEA. Fant has given a r e a functions fo r some (14)

of the vowels he re concerned, and these were used a s a starting point . The agreement between the measured and matched formant frequencies

is shown in Fig. I-A-4. The a r e a functions obtained in this manner were

perturbed i n two different respects, the reason fo r this being the follow-

ing. ]

I

The lowering of the larynx and widening of the sinus Morgagni i n

singing can be expected to be almost constant fo r a l l vowels, but this is

probably not t rue f o r the lowering of the jaw ( I 5 ) . Consequently, only

the two f i r s t mentioned perturbations were made on the a r e a functions

of a l l vowels on the analogue.

The perturbations observed in the lower par t of the pharynx will , I

tend to lower a l l formant frequencies, whereas a n enlarged mouth open- (16) ing would affect the formant frequencies i n the opposite direction .

If the changes i n formant frequency between the spoken and sung vowels

a r e compared with the changes i n formant frequency obtained by the per -

turbation of the a r e a function of the analogue, the remaining difference

should be related to the influence of the enlarged mouth opening and

other possible articulatory modes i n singing affecting the formants i n

the opposite direction.

In one experiment we therefore increased the equivalent a r e a i n

the f i r s t section by about 50 O/o simulating the observed mean widening of

the sinus Morgagni. The changes i n formant frequencies obtained i n this

way a r e shown i n Fig. I-A-5. The second perturbation was to connect

two more sections to the line corresponding to the lowering of the larym

by 1 cm. The formant changes thus obtained a r e a l so shown in Fig.

I-A-5.

The smal l changes obtained on LEA on F 1 agree well with the small

changes on this formant found between the spoken and sung vowels.

Similarly, the changes on F2 match the changes between the spoken and

sung vowels well. This i s a l so t rue fo r F 3 and F 4 if the back vowels

a r e excepted.

Thus we may conclude that the lowering of the larynx and the widen-

ing of the sinus Morgagni probably a r e responsible for the main changes

kHz N

3.5 -

2.0 -

0 I I I I I I I I

u: o : a: ae : e: i : Y: u: 6:

Fig. I-A-4. Formant frequencies of long Swedish vowels. Solid l ines: mean values of s ingers ' spoken vowels; dashed lines: LEA synthesis.

STL-QPSR 1/1968 6.

in formant frequencies between the spoken and sung vowels, but a lso that

other perturbations a r e made in singing that tend t o increase some for-

mant frequencies to a cer ta in extent. Rather detailed physiological and

acoustical studies will be needed to gain fur ther insight i n these problems..

One possible factor could be differences i n nasalization,

Acknowledgments

This work was made possible by support f r o m the Tri-Centennial

Fund of the Bank of Sweden and by most val11.able suggestions of and co-

operation with Prof. G. Fant and his staff a t the Dept. of Speech Com-

munication, KTH, Stockholm. The author a l so wishes to thank the

s ingers f o r the i r kind assistance.

References

(1) See, fo r instance, Cornut & Lafon, Fol ia Phoniatrica 12 (1 960), - pp. 188-196.

(2) By kind assis tance f rom Docent Curt Lagergren, Karolinska Sjuk- hus et, Stockholm.

(3) Similar observations were made by Vennard, Folia Phoniatrica 16 - (1964), p. 150.

(4) Frommhold & Hoppe, Folia Phoniatrica 17 (1965), pp. 83-91. - (5) Fant: lrAcoustic Analysis and Synthesis of Speech with Applications

to Swedish", Er icsson Technics 15 (1959), No, 1, p. 64 et sqq. \ - (6) Fant , op. cit. , p. 56 et sqq.

(7) Bartholomew, J. Acoust. Soc. Am. 6 (1 934), pp. 25-33. - (8) Wolf, Stanley & Sette, J. A c o ~ ~ s t . Soc. Am. 6 (1 935), pp. 255-266. 1 - (9) Rzhevkin, Soviet Physics Acoustics (1 9561, pp. 21 5-220.

(1 0) McGinnis, Zlnick & Kraichman, 2. A c ~ u e t , Soc, Am. 2 3 (1951), - pp. 440-446.

(1 1) F r y & Mankn, J. Acoust. Soc. Am. 29 (1 957), pp. 690-692. -- (12) Vennard, op.cit., pp. 146-153.

(1 3) Fant , Acoustic Theory of Speech Production (Mouton (3r Co, , ' s-Gravenhage 19601, p. 99 et sqq.

(14) Fant , op-ci t . , p. 115,

(15) Vennard, op. cit., p. 150.

(16) Fant, STL-QPSR No. 4/1966, p. 25.