PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Expression of the feelings to noise using cepstral parameters
Masanori AKITA1; Wataru SAITO1; Satoshi ITO1, Yoichi MIDORIKAWA1

Oita University, Japan

ABSTRACTThe influence that noise environment gives in human feelings becomes one important topics of theenvironmental problem. This paper shows the unpleasant feelings of human when hearing different type ofnoises. Previous our research showed that the unpleasant feelings are changed even if the sound pressurelevel hearing noise is same. In this paper, we define the feature parameters using spectral envelopes of noisy
signal using cepstral coefficients. Relation between the feeling test of examinees and the feature parameters
are compared. The results show that the spectral level on high frequency domain affect the feelings. Next,
examination between the feelings and the Lombard effect are tested. The amount of the Lombard effect are
defined using the center of the gravity of the pentagon by the first and the second formant frequency ofJapanese 5 vowels or the average of the moving distance of the selected vowels. Examination shows somerelationship between amount of the effect and feelings. The other experiments show that relationshipbetween the kind of noise and feelings are tested and results are also shown.
Keywords: Feeling to sounds, Colored noise, Lombard effect, Cepstrum, Formant

1. INTRODUCTION
The influence of the environmental noise to the person is very important problem for social life.
The feelings of noises affect to the safety life and it is considered that the detection of the quality ofnoises is important for this problem.
We measured the sound inside of the body using NAM microphones (1) and piezoelectric sensors
to obtain the sleep in sleep-wake state (2). This paper showed that the noise from inside the body ischanged when the examinees feel the sleepiness or comfortable. In sleeping state, the noise from thebody made like the white noise. We measured the comfortableness of the human in this method andshowed the effectiveness (3).
Lombard effect is known to happen when human pronounce a sound under the inferior noiseenvironment. This effect is explained that improvement of intelligibility using the change of thepronunciation (4). Lombard effect is remarkable in poor noisy environment. The loudness of theutterance is increasing at the same time, and the uttering person feels unpleasantness.
We examined the Lombard effect under the noisy environment and showed the relationshipbetween utterance of the vowels and the sound level of the noise (5). In this paper the Lombard
effect is remarkable when examinees hear the white noise. And the Lombard effect is decreasing incase when examinees hear the pink noise even if the hearing sound pressure level is equal. Thesefacts show that the Lombard effect is affected with the frequency features of the noises. Thesefeatures are also concerned with the feelings of examinees. However, the relationship between thespectral feature of the noise and the Lombard effect is not clearly found.
In this paper, the Lombard sound using three kinds of the band noises are obtained. The shift of
the formant frequencies and the difference of speech sound level is measured in case that theexaminee is hearing several types of noises. We define the spectral feature parameter of the noiseusing cepstral coefficients obtained from noisy waveforms. We compare the feature parameters andthe amount of the Lombard effect with the feeling test by examinees. The experimental results areshown in case the quality of the noise is changed. We also performed other set of the feeling test
using these band the noises. Comparison between the feeling test and feature parameter in thisexperiments are also shown.

15836

makita@oita-u.ac.jp

2. THE EXPERIMENT OF RECORING LOMBARD SOUND
We recorded the Lombard voice using Japanese 5 vowels. Four Japanese male speakers speak thevowels while hearing the noise from headphone as shown in Figure 1. The source of the noise isobtained by audio check compact discs shown in Table 1. The spectral envelopes of noises are shownin Figure 2.
The level of the noise from headphone are determined as 60dB(A),73dB(A) and 85dB(A). Four
examinees uttered 5 Japanese vowels while hearing these noises. In the experiment, examinees
uttered voice as their pronunciation is able to be recognized.
Uttered speech sounds are sampled by sampling frequency 10 kHz and quantized by 12bit. The
speech data analyzed into 25 cepstral coefficients using improved cepstral method (6). In analysis,
frame period is 10ms and the frame length is 25.6ms. Spectral envelopes of vowels are obtained
from these 25 cepstral coefficients and formant frequencies are calculated by detecting local peaks ofthe spectral envelopes of the center part of vowels.

Listen the noise by headphone
Microphone

Sound level meter
Speaker

30 cm

Figure 1 – Example illustration of the recording the Lombard sounds

Table 1 – Source of the noise waveforms used in this experiment
Noise or Equipment
SourceHeadphone
SONY MDR-480AV
White noise
DENON CD COCQ-84695 Track 10
Pink noise
DENON CD COCQ-84695 Track 11
Band noise 125Hz/1kHz/8kHz DENON SACD COGQ-28 Track 9-11
(1/1 oct.)

(a)

(b)

(c)

(d)

(e)

Figure 2 – Spectral envelope of the noise used in this experiment(a) white noise (b) pink noise (c) band noise 125Hz(d) band noise 1kHz (e) band noise 8kHz5837

3. THE SHIFT OF THE FORMANT FREQUENCIES BY LOMBARD EFFECT
The results of the difference of the Lombard effect when examinees hea r different types of noises.
Table 2 shows that the sound level of the vowels when examinees pronounced with hearing noises.
The results show that the sound levels of the pronounce vowels are affected to the noise in territory
below the frequency 1 kHz.
The Lombard effect of the vowels is measured using the distribution of the first and the second
formant frequencies of the uttered vowels. Figure 3 shows the first and the second formant
frequencies when examinees hear the white noise and the pink noise. In Japanese, the distribution of
the first and the second formant is known to become the pentagon when the turn of the vowel is /i/,/e/, /a/, /o/, /u/ like Figure 3. This figure also shows that the movement of the formant frequency isincreasing when examinees hear the louder noise.
The movement of the formant frequencies is caused by the change of the shape of vocal tract
when the examinees utter the loud voice. We measure the shift of the formant frequencies byLombard effect using the movement of the center of gravity of the pentagon (5). The movement of
the pentagon is expressed in Figure 4. We define the variation of the center of gra vity as equation 1,
where the coordinates of the first and the second formants before movement and after movement arerepresented as ሺ‫ܨ‬஺ଵ ǡ ‫ܨ‬஺ଶ ሻ andሺ‫ܨ‬஻ଵǡ ‫ܨ‬஻ଶ ሻ.
(1)‫ܨ‬஺஻ ൌ  ඥሺ‫ܨ‬஻ଵ െ ‫ܨ‬஺ଵ ሻଶ െ ሺ‫ܨ‬஻ଶ െ ‫ܨ‬஺ଶ ሻଶ

The moving distances of the coordinate of the center of the gravity of pentagons are shown in
Table 3. This results show that the movement is concerned with the power of the spectral envelopesof noises on low frequency domain and the movement becomes large when the hearing noise level
beyond 73dB(A).
Table 2 – Relationship between the hearing noise level and the sound level of voice (dB(A))
noise level
vowel
white noisepink noiseband noise (125Hz)
band noise (1kHz)band noise (8kHz)(a)61dB(A)/a//i/91
82
93
84
90
80
89
80
90
7873dB(A)/a//i/93
88
97
92
97
87
93
82
90
7985dB(A)/a//i/101
92
102
95
100
92
98
90
93
84(b)

Figure 3 – Example illustration of the first and the second formant frequencies ofJapanese 5 vowels in case that examinee is hearing the noise (Speaker A)(a) white noise (b) pink noise5838

Figure 4 – Movement of the centroid of pentagon by the first and the second formant ofJapanese 5 vowels caused by Lombard effect (Speaker A)
Table 3 – Moving distances of the center of the gravity of the pentagon by formant frequency
Quiet to 61dB(A)

61dB(A) to 73dB(A)

73dB(A) to 85dB(A)white noise

0.114

0.158

0.115

pink noise

0.069

0.058

0.080

band 125Hz

0.107

0.004

0.061

band 1kHz

0.044

0.014

0.064

band 8kHz

0.032

0.034

0.067

5839

We define the spectral feature parameter of the noise using cepstral coefficients of the noisy
signals. The summation of the first cepstral coefficients to the nth cepstral coefficients are defined as
equation 2, which express the broad inclination of spectrum. In this equation, ܿ௜ఔ indicates the ith
cepstral coefficient at ɋ frame.
ఔܲఔ ൌ σெ௜ୀே ܿ௜(2)This parameter expresses the value of spectral envelopes at zero frequency expressed by M
cepstral coefficients. In this paper, N=1 and M=15 is used. The value of the parameter becomes
small in case that the noise level is decreasing on high frequency domain. The Figure 5 shows thevalue of parameters when noisy waveform change. It is found that and the amount of the parameter isconcerned with Lombard effect.

Figure 5– The spectral feature parameters of noises by cepstral coefficients(Cepstral order 1 to 15)

We have another test for detecting of the preference of the noisy tone using 11 examinees. Eachexaminee heard the 5 kinds of the noise of the same pressure level. The examinee put number one on
the noise felt most unpleasantly and put 5 on the noise felt least unpleasantness. The result is shownin Table 4 and this result shows that the unpleasantness is related with the amount of the Lombard
effect. However, in the test the standard deviation in case of the band noise 8kHz is large and there
are different taste patterns are seen. Further preference test may be required to investigate therelation with the amount of Lombard effect.

Table 4 – Results of the preference score using five types of noises (60dB (A))

2.45Band noise
125Hz
2.55

Band noise
1kHz
4.27

Band noise
8kHz
3.64

0.79

2.79

0.56

1.50

White noise

Pink noise

Average ranking

2.09

Standard deviation

0.99

4. CONCLUSIONSIn this paper, the Lombard sounds obtained from five types of noise are measured to detect theinfluences of the frequency features of the noises. The previous our report suggested Lombard effect5840

is concerned with the noise on high frequency domain. The experiments in this paper showed that theband noise which has large level on lower frequency domain affect the Lombard effect. And thefeature parameters by cepstral coefficients of noises are defined and we found out that a definedparameter is correlated with the Lombard effect. The hearing test of noisy waveforms showed thatthe some relationship between the Lombard effect and the feelings to noise . However, there are large
deviations at the test using 8 kHz band noise and further hearing test will be required.

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