Regulation of Voice Communication by Sensory Dynamics

Abstract

People speak more loudly in a noisy room or when momentarily deafened and more softly in a quiet room or when sidetone is artificially increased. The effort to compensate for these changes in the signal-to-noise ratio, or to match directly changes in the intensity of a model, typically falls about halfway short (in decibel units). This is probably because a speaker considers that he has doubled his own vocal level in half as many decibels as it takes to double the loudness of the signal or the noise. More concisely, the Lombard-reflex, sidetone-penalty and cross-morality matching functions have exponents of about one-half because the exponent of the loudness scale is haft that of the autophonic scale of voice level. This amounts to saying that the speaker matches changes in signal or in noise to keep the signal-to-noise ratio nearly constant, but he is misled by the disparity in the sensory operating characteristics of speaking and listening.For a subject to perceive a doubling in loudness, the sound-pressure level mnst be more than tripled if generated by an external source, but less than doubled if generated by the subject himself, vocally. The former relation is well known as the sone scale (Stevens 1); the latter is becoming known as the autophonic scale, a term coined in the pages of this JOURNAL by Lane, Catania, and Stevens," who described the speaker's perception of his own vocal level in some detail.When a speaker judges the dynamic characteristics of his own speech, the possible sources of cues include airborne sound (air sidetone), head sidetone, and proprioception. When the speaker stops talking and listens to someone else instead, he is deprived of most of these cues and, as a listener, he must base his judgments differently. Since the sensoD' characteristics of speaking and listening axe so different structurally (yon B•k•ssa), it is not surprising to learn that they are quite different functionally. After establishing that the exponent (slope, in log-log coordinates) of the antophonic scale is approximately 1.2 whereas that of the sone scale is 0.6, Lane, Catania, and Stevens went on to confirm this disparity by asking subjects to match their vocal levels to changes in the level of a criterion sound. Given In complementary experiments, speakers were instructed to compensate for, rather than match, the changes in the loudness of a criterion sound, so that the loudness would be held constant. The criterion sound was the speaker's own voice, fed back to him at vaxious levels in an interphone system, and his task was to vocalize so as to compensate for changes in amplification introduced into the sidetone channel. Again the

Neural Correlates of the Lombard Effect in Primate Auditory Cortex

“…This dynamic modulation of voice intensity allows an individual to communicate effectively under noisy conditions. The Lombard effect has been demonstrated not only in humans (Hanley and Harvey, 1965;Lane et al, 1970;Lane and Tranel, 1971;Egan, 1972;Siegel and Pick, 1974), but also in every animal species examined, including birds (Potash, 1972;Cynx et al, 1998;Manabe et al, 1998;Brumm and Todt, 2002), cats (Nonaka et al, 1997), and monkeys (Sinnott et al, 1975;Brumm et al, 2004;. The neural mechanisms underlying this important vocal behavior, however, remain largely unknown.…”

Some effects of cochlear implant use on loudness modulation

“…Under that condition, the subject perceives a doubling in loudness when the sound pressure level is less than doubled (Lane et al, 1961 It is evident from the sone scale and the autophonic scale that listeners do not compensate for changes in the way they hear sound (either self-generated or from an external source) with equal-step changes in intensity of vocal output. From this observation, Lane, Tranel, and Sisson (1970) found evidence to support a theory that speaking and listening rely on separate sensory systems for operation.…”

“…Many researchers have noted a relationship between the communication task and its effectiveness in eliciting a Lombard response (Dreher & O'Neill, 1957;Lane & Tranel, 1971;Lane et al, 1970;Webster & Klump, 1962). The present study used a variety of speech tasks.…”

“…This instrumentation is capable of extracting and displaying fundamental frequency and the amplitude envelope of a signal. In the studies reviewed, most researchers have used a graphic level recorder to measure the vocal output of their subjects (Amazi & Garber, 1982;Black, 1951;Charlip & Burk, 1969;Dreher & O'Neill, 1957;Garber et al, 1976;Lane et al, 1970;Ringel & Steer, 1963;Siegel & Kennard, 1984;Siegel et al, 1982;Waldron, 1960;Webster & Klump, 1962). This measuring technique is time-consuming and requires equipment not available in a typical audiology clinic.…”

“…Similarly, Lane et al (1970) used a procedure that placed a premium on intelligible communication; they obtained an enhanced Lombard effect (slope 0.5) and an enhanced sidetone effect. Kalikow and Stevens (1977) reported that a babble of voices produced by several speakers interferes with intelligibility more than random nonspeech noise.…”