Non-verbal Vocalisations - the Case of Laughter

Jürgen Trouvain

Institute of Phonetics, Saarland University, Saarbrücken, Germany

trouvain@coli.uni-sb.de

The most frequently used form of communication between humans is
conversation consisting of both speech as verbal vocalisation and
non-verbal vocalisations.  The question addressed here is how non-verbal
vocalisation such as laughter differs from speech articulation.  Data
inspections to be presented here give an idea how laughter is integrated
in every-day speech as a unique signalling system in non-verbal as well
as verbal vocalisations. 

In dialogues, many features are transmitted by paralinguistic vocal
parameters such as pitch range, intensity and speech tempo.  In addition
to these prosodic properties, which modify the articulation of verbal
material, there are the less well-studied non-verbal vocalisations. 
These include e.g.  backchannel-utterances (indispensible for
dialogues), filled pauses (frequent in spontaneous speech), and
affective interjective calls which are produced by speakers and hearers
for attitudinal and emotional signalling. 

The observation of laughter-like calls in apes and monkeys (e.g. 
Preuschoft, 1992) led to a debate whether only humans laugh.  In
contrast to non-human primates, the situations in which humans laugh
during speech show a great range: mirth and joy, humour, malice,
embarrassment, and even despair.  Likewise, human laughter does not show
just one form but a great repertoire of different kinds of laughter. 
Bachorowski et al.  (2001), e.g., divide laughter in song-like,
snort-like and grunt-like types.  Further forms are speech-laughs
(Nwokah et al., 1999) which are produced simultaneously to speech. 
Trouvain (2001) found in a German dialogue database that most laughing
events occur during articulation of lexical items, not as vocalisations
of their own. 

However, the production of laughter is clearly distinct from speech
production.  Although the consonant-vowel pattern in laughter (cf. 
lexicalised "haha", "ahah", "xaxa") superficially resembles speech, the
control for respiration, phonation and articulation is much simpler.  A
typical voiced laugh combines a simple exhalation muscle command with a
"program" for voiced-unvoiced alternations.  This pattern is highly
rhythmic but with a timing pattern completely different to
phonologically comparable ones in speech.  In contrast, speech-laughs
are nested in the articulatory processes of segments: the stronger
aspiration typically occurs in aspirated parts just as the voice vibrato
appears in voiced segment portions. 

References:

Bachorowski, J.-A., Smoski, M.J.  & Owren, M.J.  (2001).  The acoustic
features of human laughter.  Journal of theAcoustical Society America
111 (3), pp.  1582-1597. 

Nwokah, E.E., Hsu, H.-C., Davies, P.  & Fogel, A.  (1999).  The
integration of laughter and speech in vocal communication: a dynamic
systems perspective.  Journal of Speech, Language & Hearing Research 42,
pp.  880-894. 

Preuschoft, S.  (1992).  "Laughter" and "smile" in Barbary macaques
(Macaca sylvanus).  Ethology 91, pp.  220-239. 

Trouvain, J.  (2001).  Phonetic aspects of "speech-laughs".  Proc. 
Conf.  Orality & Gestuality (Orage), June 2001, Aix-en-Provence, pp. 
634-639.