The Influence of Acoustic Factors on the Communicationof ‘Importance’ in Speech
Maria Raluca Draguna*, Toshie Nakamura*,Chika Nagaoka*, Satoshi Kawase*, Makiko Yuki*,
Tomotsugu Kataoka* and Masashi Komori**
Abstract – The present study investigated how the manipulation of pauses, as well as the manipulation of the intensity
level across sentences influence the listeners’ understanding of the intended message in their native language. Longerpauses (especially preceding pauses) result in a change in the perception of emphasized speech, and are thus animportant cue for detecting ‘importance’. Further, louder speech is perceived as more important.

These results

indicate that the manipulation of acoustical cues has a significant role in the communication of importance.
Keywords: pause duration, intensity level, communication of ‘importance’

1. Introduction
It is often assumed that the main predictor for focus inspeech is the change in the pitch accents. However,perception experiments with manipulated speech(Streefkerk et al., 1997) that investigated the effect ofthe acoustic correlates on the perception of emphasis,
report that even when the pitch was manipulated andkept monotone across the sentences, listeners were still
able to mark consistently some of the emphasized words.
In light of this, it is of high interest to investigate which
acoustic cues are responsible for the detection ofimportance. We assumed that pauses (especially inJapanese, where pauses (Ma) have a special culturalvalue) and also the intensity level have a considerable
influence on the perception of emphasis, and therefore
we proposed a perception experiment that manipulated
only the duration of the pauses, or the intensity level, inorder to investigate how the manipulation of vocal cues
influences the listener’s understanding of the intended
message.
2. Method
2.1 Stimuli
The material used as stimuli consisted of a text
structured into an introductory sentence and five
Table 1. Text
Introductory
Text
Sentence 1
Sentence 2
Sentence 3
Sentence 4
Sentence 5

sentences presented in varied order. The material waspresented in Japanese (Table 1). The speeches weredelivered by one speaker selected for the clarity of her
pronunciation (the speaker was relatively trained inspeech delivery. Each stimulus was about 15-20 seconds
long.
2.2 Subjects
95 undergraduate students (16 females, 79 males) of
Osaka University participated in the experiment to fulfil
a requirement in an introductory course in Psychology.
The participants were all Japanese native speakers witha mean age of 19 years.
2.3 Procedure
The experiment consisted of 14 conditions,corresponding to the various manipulations of theduration of pauses between sentences and of theintensity level across sentences. Initially, all the pauses
between sentences were made equal in duration(1.1sec.), and the intensity level across each sentence
constant (76dB(A)) – ‘equal pauses, equal level’.
Further, the preceding pause of one sentence in the text
was lengthened by 0.44sec. while the other acoustic
factors were kept constant (the amount of increase wasbased on previous speech delivery experiments whichshowed that the pauses before and after the most

面接を受ける時に、重要な事柄がいくつかあります。思いつくままにいいますと次のような項目をあげることができます。
適切な服装をすること。
丁寧な話し方をすること。
質問の意味を十分に理解すること。
よく考えて答えること。
身振りやリアクションに注意すること。

*1: Graduate School of Human Sciences, Osaka University*2: Faculty of Information Science and Technology, Osaka Electro-Communication University

Order

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important sentence are 1.4 times longer than the pauses
preceding and following unimportant sentences) –‘pre-pause+’.
Similarly, the pause following asentence was lengthened by 0.44sec, while the otherfactors were kept constant - ‘post-pause+’, then thepauses preceding and following one sentence wereincreased in duration by 0.44sec. – ‘pre-pause+,
post-pause+’; further, the intensity level (LAeq) across
one sentence was increased with 3.8dB(A) while theduration of the pauses was kept constant – ‘level+’. The
14 experimental conditions consisted of 2 ‘equal pauses,equal level’ speeches, 3 ‘pre-pause +’ speeches, 3‘post-pause +’ speeches, 3 ‘pre-pause +, post-pause +’speeches, and 3 ‘level +’ speeches. The material wascreated using a Professional Digital Audio Editor(Sound Forge 5.0), and played back using a Toshiba
Dynabook E7/518CME computer and loudspeakers.
The level of the stimuli was set so that the peak level inthe center of the room (measured with a RION Sound
Level Meter NA-20) would reach 70dB(A). The
subjects were instructed to listen to the speeches andjudge which was the sentence that the speakeremphasized as the most important, and to assess on a7-point scale how natural the speech sounded.
3. Results and Discussion
The results indicated that the manipulation of pause
durations and intensity level within speech have asignificant effect on the subjects’ perception ofemphasis. This effect was assessed comparing thepercentage of the subjects that chose the manipulated
sentence as the most important with that of the subjects
that chose the respective sentence as emphasized whenthese acoustic factors were kept constant (Table2).
Table 2 Choices for the ‘Important’ Sentence (%)

represents a salient cue for the detection of importantmessages (Fig.4).
(%)

Equal pause
Pre-pause+

30
28
26
2422Fig. 1 Changes in the subjects’ choices for the ‘important’sentence when the preceding pauses were manipulated.
(%)
30

Equal pause
Post-pause+

28
26
2422Fig.2 Changes in the subjects’ choices for the ‘important’sentence when the following pauses were manipulated.
(%)

Equal pauses

3028

Pre-pause+,
post-pause+

262422Fig. 3 Changes in the subjects’ choices for the ‘important’sentence when the preceding and following pauses weremanipulated.
Equal level
Level+

(%)
80
60
40
200

1

Equal pause

PausesDifference(%)

Pre-pause+

27.36829.9122.543

sentence when the intensity level was manipulated.

Post-pause+

24.38526.5782.192

Pre-pause+,post-pause+

25.61427.3681.754

Level+

25.61

71.57

45.96

These results indicate that the manipulation of thepreceding and/or following pauses, as well as themanipulation of the intensity level, plays a significant
role in the communication and perception of importancein speech.

As predicted, the manipulation of pauses represent a cue
for the listener that the respective sentence is important,the preceding pauses being particularly considered(Fig.1, Fig.2, Fig.3). However, other factors such as thesubjects’ personal opinion regarding the importance ofthe contents of the sentences, as well as how natural thespeeches sounded, may also influence the perception of‘importance’. Further, the significant increase in thesubjects’ choice for the louder sentence as the mostimportant shows that the intensity level of a sentence

Fig. 4 Changes in the subjects’ choices for the ‘important’References[1]

Streefkerk, B.M., Prominence in Read Aloud Sentences,
as Marked by Listeners and Classified Automatically,
Proceedings 21 (1997), 101-116, Amsterdam University.

[2]

Draguna, R.M., Vocal Strategies in Communicating‘Importance’ – Cross-Language Study, Masters Thesis,
Osaka University, 2003.