@article{PincasJackson_JASA06,
        AUTHOR  =       "Pincas, J. and Jackson, P. J. B. ",
        TITLE   =       "Amplitude modulation of turbulence noise by voicing in fricatives",
	JOURNAL	=	"J.~Acoust.\ Soc.\ Am.",
	VOLUME	=	"120",
	NUMBER	=	"6",
        PAGES   =       "3966-3977",
	MONTH   =       "Dec.",
        YEAR    =       "2006",
	ABSTRACT =	
"The two principal sources of sound in speech, voicing and frication, occur 
simultaneously in voiced fricatives as well as at the vowel-fricative boundary in 
phonologically voiceless fricatives. Instead of simply overlapping, the two sources 
interact. This paper is an acoustic study of one such interaction effect: the 
amplitude modulation of the frication component when voicing is present. Corpora of 
sustained and fluent-speech English fricatives were recorded and analyzed using a 
signal-processing technique designed to extract estimates of modulation depth. 
Results reveal a pattern, consistent across speaking style, speakers and places of 
articulation, for modulation at f0 to rise at low voicing strengths and subsequently 
saturate. Voicing strength needed to produce saturation varied 60-66 dB across 
subjects and experimental conditions. Modulation depths at saturation varied little 
across speakers but significantly for place of articulation (with [z] showing 
particularly strong modulation) clustering at approximately 0.4-0.5 (a 40-50% 
fluctuation above and below unmodulated amplitude); spectral analysis of modulating 
signals revealed weak but detectable modulation at the second and third harmonics 
(i.e., 2f0 and 3f0)." 
}