Speech Prosody 2024
2-5 July 2024, Leiden, The Netherlands

Acoustic analysis of several laughter types in conversational dialogues
Kexin Wang1,3 , Carlos Ishi2,3 , Ryoko Hayashi3
1 ATR, 2 RIKEN, 3 Kobe University

wkx19970303@hotmail.com, carlos@atr.jp, rhayashi@kobe-u.ac.jp
responds significantly differently when listening to authentic
amusement laughter and controlled voluntary laughter. The
former is characterized by higher activation of bilateral superior
temporal gyri, which indicates that listeners process
information with more emphasis on the sound itself. In contrast,
voluntary laughter was associated with greater activity in theanterior medial prefrontal cortex (amPFC), suggesting thatwhen hearing the posed laughter, listeners try to understand themeaning of it in context or why it happened.
Our recent work reported that spontaneous laughter andintentional laughter tend to have different patterns regarding thenumber of calls, vowel quality, and voice quality characteristics[13]. For example, spontaneous laughter tends to have morepatterns with pressed voice, on the contrary, intentional
laughter includes more patterns with vowel /e/ and nasal sounds.
However, it was limited to the qualitative analyses of laughter
patterns. In the present work, we conducted acoustic analyses
to show the differences between two laughter types
quantitatively. Furthermore, we analyzed the reasons andfunctions of laughter in social interaction and compared theacoustic characteristics of four predominant categories.

Abstract
Previous studies suggest the existence of two distinct forms oflaughter: mirthful/spontaneous laughter and social/intentional
laughter. The current work aims to expand our understandingof the motives behind laughter and its functions in social
conversation. About 1000 laughter events from 4 males and 4
females were extracted from multi-speaker conversation data,
and the four predominant categories were used for acoustic
analysis: mirthful, boosting, smoothing, and softening. Mirthfullaughter and boosting laughter exhibit longer duration, higher
F0 mean, intensity and HNR, as well as lower H1-A1 than othertypes, which suggest that laughter produced with positive
emotion or attitude tends to be longer, higher and tenser voice
quality. On the other hand, smoothing laughter and softening
laughter displayed opposite characteristics, which indicates that
intentional laughter emitted to smooth the interaction or soften
the atmosphere can be acoustically identified to some extent
from those with positive emotions. This work provides
evidence that laughter with different functions has different
acoustic characteristics that help us understand what laughtermeans in dialogue.
Index Terms: laughter types, laughter functions, acoustic
features, voice quality

2. Speech data and annotation of laughter
2.1. Speech data

1. Introduction

Most previous laughter studies used induced laughter, forexample, funny video clips, rather than spontaneousconversational scenes [14]. To consider the social aspect oflaughter, we think it is more appropriate to use a dialogue
speech corpus. Thus, in this work, a three-party dialogue
database containing several sessions of topic-free conversations
with full-channel video and audio was used. The speech dataaround 12 hours, from four males and four females were usedin the analysis. They are all colleagues in the workplace andnative speakers of Japanese.
The data recording was conducted in a sound-proof room at
the ATR labs, and each conversation session lasts for 15-20
minutes. Three speakers are positioned approximately 1.8 to 2
meters apart from each other. The audio signals are captured
using headset microphones (DPA4060). To minimize interchannel leakages, Wiener filtering is applied among the threechannels, utilizing the interfering channels as noise references,
so that high signal-to-interference ratios are achieved before
acoustic analyses. Additionally, we set a power threshold anddo not use acoustic features of frames with low power where
the inter-channel leakages are possibly remaining.

Laughter occurs commonly in human interaction and forms anessential part of nonverbal communication. It is not only related
to joking and humour, but also plays an important role in social
communication such as acting as a sign of politeness orrelieving embarrassment [1-4]. Previous studies suggest thatlaughter can be roughly divided into two different types:
mirthful/spontaneous laughter and social/intentional laughter.
The former is likely to be elicited by positive moods andexpressed toward the dialogue itself, whereas the latter tends to
be used to “fill” the conversation and maintain communication
with the other [5, 6].
In [7, 8], various types of laughter were categorized intoeither genuinely mirthful laughter or polite formal laughter.
Analysis revealed that, compared to polite laughter, mirthfullaughter tends to have longer duration and more calls per bout,as well as shorter bursts, ingressive laugh and chuckle sounds.
The perceptual experiment in [6] demonstrated that humans candiscriminate social laughter from spontaneous laughter basedon auditory or audiovisual presented without any context.
Acoustic analysis indicated that spontaneous laughter has not
only a longer total duration but also a voiced duration thansocial ones. However, there was no significant difference in F0means.
In addition, the neuro-physiological distinctions between
these two types of laughter were also proved in brain imaging
studies of laughter [9-12]. [9] revealed that the human brain

2.2. Annotation of laughter
Depending on the positional relationship between speech andlaughter, laughter is classified as “stand-alone laughter” (i.e.,“ha ha ha”) and “speech laughter” (speaking while laughing)[15]. We focus our target on stand-alone laughter. Speech

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10.21437/SpeechProsody.2024-135

laughter is also common in the speech data but is not addressedin this work.

involuntary manner (sp), or in a controlled manner (in), or
ambiguous (sp/in). As a result, out of a total of 857 laughter
events, 129 spontaneous laughter, 507 intentional laughter, 152
sp/in laughter, and 69 laughter with disagree judgement (i.e.,complete disagreement among all annotators) were extracted.
Intentional laughter was approximately four times more
frequent than spontaneous laughter. Sp/in laughter was also alittle bit more frequent than spontaneous one.

According to [14, 16-18], the structure of laughter ishierarchical and usually analyzed at bout, call and segmentlevels. Segment level is the lowest level which consists ofvowels and consonants, or any other changes in production
mode usually reflected by the spectrogram components. Calllevel is syllables consisting of the combination of consonants
and vowels or a single vowel. The next higher level is the boutlevel, which involves at least one call during one exhalation. In
many cases, laughter ends with inhalations, but they are notincluded in the bout level, except for the sounds that are deemed
to be critical to the laughter itself, such as ingressive laughter.

3.2. Laughter functions
Laughter is expressed in various emotional and intentional
states, having different functions in social interaction. Referring
to several existing studies devoted to classifying laughter
functions [19-22], we used the following labels for annotationand summarized them into 9 categories (Table 1).

We also found “silent segments” which often appear after
the regular laughter and before the inhalation, without soundbut with the smiling face maintained. Some were also
accompanied by head nodding, upper body down, or handclapping, especially when the speaker is in high tension or
struggles to hide laughter. Although the silent segment is notacoustically perceptible, we included them within the bout. An
example of annotation of laughter with a 0.85s silent segment
is shown in Figure 1.

Table 1: Labels for annotation of laughter functions.
Categories
Mirthful
Boosting
Smoothing
Softening
Bitter
Self-conscious
Dumbfounded
Afterglow
Other

Labelsfunny/joyful/happy
boosting/joke/self-mockery/invitingsmoothing/backchannel/contagious/
considerate/conflict/relax
Softening
bitter/deceptive
self-conscious
dumbfounded/derision
Afterglow
awkward/surprised/sympathetic/
anticipatory/etc.

Figure 2 illustrates the result of distributions of laughter
functions.

18%

13%
6%

Figure 1: Example of annotation of laughter withsilent segment. (Speech waveform, annotation layers,
F0 contour, intensity contour and spectrogram areshown from the top panel.)
6%

In the present work, the annotation of laughter functions
was conducted at the bout level, by segmenting the laughter
events based on clear inhalation.

48%

3. Laughter types and laughter functions
Figure 2: Distribution of 9 categories of laughter
function.

The judgement of laughter types (spontaneous or intentional)
and laughter functions was conducted by three
annotators(research assistants), based on audio and video of thelaughter events with 5-second pre- and 6-second post-context.
The three annotators have reviewed all conversation data ofeight speakers. All three annotators have some degree offamiliarity with the speakers, so they have prior knowledge
about the personality of the speakers. When the results of thethree annotators disagreed, the majority vote was adopted.

Excluding the disagreement samples, smoothing laughter
occupies the most, approximately half (48%), followed bymirthful laughter (13%), boosting laughter (6%) and softening
laughter (6%). The other 5 categories were all less than 3%,
therefore they were not used for acoustic analysis. As for thefour predominant categories, mirthful laughter is spontaneous,while boosting, smoothing, and softening laughter are
intentional. The definitions are shown as follows:•
Mirthful laughter: authentic amusement laughter, forexample, funny incidents or in a pleasant mood.

3.1. Laughter types
Following previous studies, we categorized laughter into threegroups: spontaneous (sp), intentional (in), and both of them(hereby sp/in). Definitions of the type of laughter provided toannotators were: if it seems to you that the speaker laughs in an•

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Boosting laughter: laughter to liven up the atmosphere ofconversation, for example, making it a joke.

•Smoothing laughter: laughter to facilitate and smoothconversation, for example, showing comprehension,
expressing interest or acting as a backchannel.

•

Softening laughter: laughter to soften tense, awkward
atmosphere or to soften one's statements or arguments.

The mean duration for spontaneous laughter is longer thanintentional laughter about 0.96s for females (t = 0.96, p < .01),
and 0.25s for males (t = 0.96, n.s.). Between spontaneous orintentional laughter, females exhibit longer durations thanmales. Considering the prevalence of outliers is likely to be dueto the varied lengths of silent segment, we compared theduration of silent segment between females and males. Results
revealed that the mean duration of silent segment generated byfemale speakers was 1.09s, which is 0.41s longer than malespeakers (t = 8.26, p < .01).
Significant differences are also found between spontaneousand intentional laughter in F0 mean and intensity max for both
female and male speakers. Compared to intentional laughter,the F0 mean of spontaneous laughter is about 4.29 semitones
higher for females (t = 4.29, p < .01) and 4.51 semitones higher
for males (t = 4.52, p < .01). The intensity max of spontaneouslaughter is about 3.47dB higher for females (t = 3.47, p < .01)
and 5.44dB higher for males (t = 5.44, p < .01).

4. Acoustic Analysis
Acoustic analysis was conducted at the bout level, focused on
the difference between spontaneous and intentional laughter, as
well as the difference among four predominant categories oflaughter functions (mirthful, boosting, smoothing, andsoftening). Acoustic features including duration, fundamental
frequency (F0), intensity, and spectral features H1-A1 and HNR
computed at frame level, in intervals of 10ms. F0 values areconverted to semitone units and normalized by subtracting themean value of each speaker.
4.1. Spontaneous and intentional laughter

H1-A1 (the difference between the amplitudes of the firstharmonic and the harmonic closest to the first formant) is aclassical measure to discriminate “tense voice” from “laxvoice”, and to characterize pressed voice segments [23, 24].
Lower values of H1-A1 indicate high vocal fold tension.
Compared to intentional laughter, the H1-A1 of spontaneouslaughter is lower for male speakers (t = 3.81, p < .01), whichindicates that spontaneous laughter has a tenser voice quality
than intentional one.
HNR (harmonics-to-noise ratio) is a measure of periodicity
degree and reflects the effects of the aspiration noise
components of breathiness [25, 26]. The HNR of intentional
laughter is lower than spontaneous one for female speakers (t =2.96, p < .01), indicating intentional laughter tends to include
more elements with high breathiness.

Figure. 3 illustrates the differences in acoustic features between
the two laughter types based on gender.

4.2. Mirthful, boosting, smoothing, and softening
We also compared the acoustic features among the four
predominant categories of laughter function: mirthful, boosting,smoothing, and softening. Results (Figure 4) revealed that themean duration and F0 mean of mirthful laughter are longer andhigher than smoothing and softening laughter for female
speakers. The intensity max of mirthful laughter is higher thansmoothing laughter for male speakers, and of boosting laughter
higher for female speakers. H1-A1 of boosting laughter is lower
than smoothing laughter and softening laughter for female
speakers. HNR of smoothing and softening laughter is lower
than mirthful and boosting laughter for female speakers.
Based on the above results, a general contrast between
mirthful, boosting laughter and smoothing, softening laughter
was observed. Regarding duration and F0, the contrast was
between mirthful laughter and smoothing, softening laughter.
While, as for H1-A1, the contrast was between boostinglaughter and smoothing, softening laughter. Moreover, thetendency of intensity and HNR in mirthful and boostinglaughter was similar in contrast to smoothing and softening
laughter. Although boosting laughter is intentional, as well assmoothing and softening laughter, there are notable differences
between them. Analysis results indicate that boosting laughter
is more similar to mirthful laughter acoustically.
Figure 3: Mean duration, F0 mean, intensity max, H1A1, and HNR for spontaneous and intentional
laughter at the bout level based on gender.

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5. Discussion
The results of the annotation of laughter type and laughter
function indicated that most laughter in social interaction is notabout pleasantness, but more in an intentional manner,
especially to smooth and facilitate conversation, which provesthat laughter serves as an important form of nonverbal
communication to establish and maintain social bonds withothers.
Acoustic analysis revealed that spontaneous laughter tends
to be longer, higher and tenser voice quality. This is because
when laughing spontaneously, especially in high tension, the air
will be squeezed from the lungs with remarkably higher
pressure than when produced intentionally. The various
differences observed in acoustic features are presumed to berelated to physiological distinctions between spontaneous andintentional vocalizations.
Acoustic analysis of four predominant categories oflaughter function suggested a contrast between the laughter
produced with positive emotion or attitude (mirthful andboosting) and the laughter emitted to facilitate communicationor ease tension (smoothing and softening). Intentional boostinglaughter has some common features with spontaneous mirthfullaughter, such as higher intensity and HNR, and is characterized
by a lower H1-A1, indicating that boosting laughter is produced
in tenser voice quality due to the effort put into voice. [27] statesthat voice quality is an important aspect of prosodic information
which varies consistently according to the speaker’s affect andattitude. This work supported this argument by showing thatlaughter with different functions was generated in different
voice qualities.

6. Conclusions
In this present work, we analyzed the acoustic features of
spontaneous and intentional laughter and four predominantcategories of laughter function extracted from multi-speaker
conversation data. Results revealed that spontaneous laughter
has a longer duration, higher F0, intensity and HNR, as well asa lower H1-A1 than intentional one. As for the laughter function,
mirthful and boosting laughter produced with positive emotion
or attitude tends to be longer, higher, tenser voice quality, andmore elements with breathiness. On the other hand, smoothinglaughter and softening laughter that emitted to smooth theinteraction or soften the atmosphere displayed opposite
characteristics.
Regarding gender differences, more significant differencesin the laughing styles were observed in females compared tomales, which suggests that in laughter production, laughter
functions can be distinguished to some extent in females basedon acoustic information, while in males conversation contexts
or visual modality, such as facial expressions and body
movements, might be taken into account. The analysis of othermodalities and the aspect of perception will be topics for future
investigation. For the acoustic analysis, we also intend to
conduct a more detailed analysis of the dynamics features at thecall level.

7. Acknowledgements
This work is supported by JSPS KAKENHI Grants (No.
JP22H04875, and 21H04348). We also thank Yuka Nakayama,
Naomi Uratani and Yumiko Kondo who contributed to theannotations and data analyses.

Figure 4: Mean duration, F0 mean, intensity max, H1A1, and HNR for mirthful, boosting, smoothing, andsoftening laughter at the bout level based on gender.

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