Do men with more masculine voices have better immunocompetence?

The human voice is often considered to be a secondary sexual characteristic that signals underlying information about the immunocompetence of the speaker (i.e. the immunocompetence handicap hypothesis; ICHH). However, no studies have yet shown a relationship between vocal characteristics and biomarkers of immune function or self-reported health. In a sample of 108 men, we examined correlations between masculine vocal characteristics [i.e. relatively low fundamental frequency (F₀), low F₀ variability (F₀-SD), low formant position (P_f), and high vocal tract length (VTL)] in relation to salivary immunoglobulin-A (sIgA; a marker of mucosal immunity), testosterone (T), and well-validated measures of self-reported health status. Results showed that sIgA correlated with masculinized F₀, P_f, and VTL. Self-report health correlated with masculinized P_f and VTL. Anticipated future health correlated negatively with F₀-SD and sick role propensity (less interference of illness in daily life) correlated positively with VTL. Perceived susceptibility to infection correlated with more feminized F₀ and F₀-SD. Our results demonstrated a small relationship between men's vocal characteristics and one putative indicator of mucosal immunity along with self-identified health status. We suggest that more research is warranted to determine whether the masculinity of men's voices may serve as an indicator of their phenotypic quality.     

Spectrographic analysis points to source–filter coupling in rutting roars of Iberian red deer

Source–filter coupling is the rarest acoustic phenomenon not only in Iberian red deer, but in any mammal. In most mammals, sound production can be well described in the framework of source–filter theory. The vocal output is the result of combined work of the larynx (the source) and of the supralaryngeal vocal tract (the filter). The source–filter theory suggests the independence of source and filter. Thus, vocal tract filtering should not affect the fundamental frequency (f0) of the sound created in the larynx. Spectrographically, the source is mostly characterized by the f0 and its harmonics, while the filter by the vocal tract resonances, i.e., formant frequencies. Nevertheless, a non-independent (coupled) source and filter can be proposed when the vocal folds start oscillating at one of the formant frequencies. Coupling between source and filter has been found in human singers and predicted for red deer Cervus elaphus by a computer modeling approach. This study describes different modes of phonation in a natural bout of rutting calls of Iberian red deer Cervus elaphus hispanicus and the transition from a chaotic mode to a probable source–filter coupling mode. This phenomenon might be involved in the production of extremely high-frequency bugles of North American and Asian subspecies of C. elaphus.     

Formant Frequencies are Acoustic Cues to Caller Discrimination and are a Weak Indicator of the Body Size of Corncrake Males

Source–filter theory assumes that calls are generated by a vocal source and are subsequently filtered by the vocal tract. The air in the vocal tract vibrates preferentially at certain resonant frequencies, called formants. Formant frequencies can be a good indicator of the caller's characteristics, such as sex, age, body size or individual identity. Although source–filter theory was originally proposed for mammals, formants are also observed in birds, and some bird species have been shown to perceive formants. In this study, we evaluated the hypotheses that formant frequencies (1) are an indicator of body size and (2) can be used for individual discrimination by a nocturnal bird species, the corncrake (Crex crex). We analysed calls of 104 males from Poland and the Czech Republic. Linear regression models showed that the males with a longer head (including the bill length) had a significantly lower formant dispersion and lower fourth and fifth formant frequencies. However, we found no significant relationships between body weight and any filter‐related acoustic measurement. The formant frequencies had smaller within‐ than between‐individual coefficients of variation. This characteristic of the formant frequencies implies a high potential for individual coding. A discriminant function analysis correctly assigned 94.8% of the calls to the caller based on formants from second to fifth. Our results indicated that the formant frequencies are a weak indicator of the body size of the sender in the corncrake. However, even weak dependence between body size and acoustic properties of signal may be important in natural selection process. Alternatively, such a weak dependence may be observed, because receivers ignore the acoustical, formant‐based cues of body size. Simultaneously, the formants might potentially provide acoustic cues to individual discrimination and could be used to census and monitoring tasks.     

Variable asymmetry and resonance in the avian vocal tract: a structural basis for individually distinct vocalizations

The social vocalizations of the oilbird (Steatornis caripensis) frequently have their acoustic energy concentrated into 3 prominent formants which appear to arise from the filter properties of their asymmetrical vocal tract with its bronchial syrinx. The frequency of the second and third formants approximate the predicted fundamental resonances of the unequal left and right cranial portions of each primary bronchus, respectively. Reversibly plugging either bronchus eliminates the corresponding formant. The first formant may arise in the trachea. The degree of vocal tract asymmetry varies between individuals, endowing them with different formant frequencies and providing potential acoustic cues by which individuals of this nocturnal, cave dwelling species may recognize each other in their dark, crowded colonies.     

Estimating the Active Space of Male Koala Bellows: Propagation of Cues to Size and Identity in a Eucalyptus Forest

Examining how increasing distance affects the information content of vocal signals is fundamental for determining the active space of a given species’ vocal communication system. In the current study we played back male koala bellows in a Eucalyptus forest to determine the extent that individual classification of male koala bellows becomes less accurate over distance, and also to quantify how individually distinctive acoustic features of bellows and size-related information degrade over distance. Our results show that the formant frequencies of bellows derived from Linear Predictive Coding can be used to classify calls to male koalas over distances of 1–50 m. Further analysis revealed that the upper formant frequencies and formant frequency spacing were the most stable acoustic features of male bellows as they propagated through the Eucalyptus canopy. Taken together these findings suggest that koalas could recognise known individuals at distances of up to 50 m and indicate that they should attend to variation in the upper formant frequencies and formant frequency spacing when assessing the identity of callers. Furthermore, since the formant frequency spacing is also a cue to male body size in this species and its variation over distance remained very low compared to documented inter-individual variation, we suggest that male koalas would still be reliably classified as small, medium or large by receivers at distances of up to 150 m.     

Dependence of the perception of emotional information of speech on the acoustic parameters of the stimulus in children of various ages

The effect on the perception of the emotional prosody of a vocal signal of the acoustic parameters of the stimulus in children of various ages (7–10, 11–13, and 14–17 years) was studied. Considerable differences in recognition of positive and negative valences of the vocal signal against the background of noise and in its absence were demonstrated. The ontogenetic specific features of the dependence of recognition of the emotional valence on the acoustic parameters of a vocal signal were determined. The most important acoustic characters (the fundamental frequency F0 and the frequency of the first formant F1) that ensure the perception of the emotional prosody of a vocal signal against the background of noise at different age stages were found.     

Retraction of the mobile descended larynx during groaning enables fallow bucks (Dama dama) to lower their formant frequencies

A permanently descended larynx is found in humans and several other species of mammals. In addition to this, the larynx of species such as fallow deer is mobile and in males it can be retracted during vocalization. The most likely explanation for the lowered retractable larynx in mammals is that it serves to exaggerate perceived body size (size exaggeration hypothesis) by decreasing the formant frequencies of calls. In this study, we quantified for the first time the elongation of the vocal tract in fallow bucks during vocalization. We also measured the effect of this vocal tract length (VTL) increase on formant frequencies (vocal tract resonances) and formant dispersion (spacing of formants). Our results show that fallow bucks increase their VTL on average by 52% during vocalization. This elongation resulted in strongly lowered formant frequencies and decreased formant dispersion. There were minimal changes to formants 1 and 2 (−0.91 and +1.9%, respectively) during vocal tract elongation, whereas formants 3, 4 and 5 decreased substantially: 18.9, 10.3 and 13.6%, respectively. Formant dispersion decreased by 12.4%. Formants are prominent in deer vocalizations and are used by males to gain information on the competitive abilities of signallers. It remains to be seen whether females also use the information that formants contain for assessing male quality before mating.     

Visualizing Sound Emission of Elephant Vocalizations: Evidence for Two Rumble Production Types

Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species''.     

Soprano singing in gibbons

Diversifications in primate vocalization, including human speech, are believed to reflect evolutionary modifications in vocal anatomy and physiology. Gibbon song is acoustically unique, comprising loud, melodious, penetrating pure tone‐like calls. In a white‐handed gibbon, Hylobates lar, the fundamental frequency (f₀) of song sounds is amplified distinctively from the higher harmonics in normal air. In a helium‐enriched atmosphere, f₀ does not shift, but it is significantly suppressed and 2f₀ is emphasized. This implies that the source is independent of the resonance filter of the supralaryngeal vocal tract (SVT) in gibbons, in contrast to musical wind instruments, in which the filter primarily determines f₀. Acoustic simulation further supported that gibbons' singing is produced analogously to professional human soprano singing, in which a precise tuning of the first formant (F₁) of the SVT to f₀ amplifies exclusively the f₀ component of the source. Thus, in gibbons, as in humans, dynamic control over the vocal tract configuration, rather than anatomical modifications, has been a dominant factor in determining call structure. The varied dynamic movements were adopted in response to unique social and ecological pressures in gibbons, allowing monogamous gibbons to produce pure‐tonal melodious songs in the dense tropical forests with poor visibility. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Bee Threat Elicits Alarm Call in African Elephants

Unlike the smaller and more vulnerable mammals, African elephants have relatively few predators that threaten their survival. The sound of disturbed African honeybees Apis meliffera scutellata causes African elephants Loxodonta africana to retreat and produce warning vocalizations that lead other elephants to join the flight. In our first experiment, audio playbacks of bee sounds induced elephants to retreat and elicited more head-shaking and dusting, reactive behaviors that may prevent bee stings, compared to white noise control playbacks. Most importantly, elephants produced distinctive “rumble” vocalizations in response to bee sounds. These rumbles exhibited an upward shift in the second formant location, which implies active vocal tract modulation, compared to rumbles made in response to white noise playbacks. In a second experiment, audio playbacks of these rumbles produced in response to bees elicited increased headshaking, and further and faster retreat behavior in other elephants, compared to control rumble playbacks with lower second formant frequencies. These responses to the bee rumble stimuli occurred in the absence of any bees or bee sounds. This suggests that these elephant rumbles may function as referential signals, in which a formant frequency shift alerts nearby elephants about an external threat, in this case, the threat of bees.     

The structure of genetically modified iron-sulfur cluster Fx in photosystem I as determined by X-ray absorption spectroscopy

Photosystem I (PS I) mediates light-induced electron transfer from P700 through a chlorophyll a, a quinone and a [4Fe-4S] iron-sulfur cluster F_X, located on the core subunits PsaA/B to iron-sulfur clusters F_A/B on subunit PsaC. Structure function relations in the native and in the mutant (psaB-C565S/D566E) of the cysteine ligand of F_X cluster were studied by X-ray absorption spectroscopy (EXAFS) and transient spectroscopy. The structure of F_X was determined in PS I lacking clusters F_A/B by interruption of the psaC2 gene of PS I in the cyanobacterium Synechocystis sp PCC 6803. PsaC-deficient mutant cells assembled the core subunits of PS I which mediated electron transfer mostly to the phylloquinone. EXAFS analysis of the iron resolved a [4Fe-4S] cluster in the native PsaC-deficient PS I. Each iron had 4 sulfur and 3 iron atoms in the first and second shells with average Fe-S and Fe-Fe distances of 2.27 Å and 2.69 Å, respectively. In the C565S/D566E serine mutant, one of the irons of the cluster was ligated to three oxygen atoms with Fe-O distance of 1.81 Å. The possibility that the structural changes induced an increase in the reorganization energy that consequently decreased the rate of electron transfer from the phylloquinone to F_X is discussed.     

Vocal Tract Morphology Determines Species-Specific Features in Vocal Signals of Lemurs (Eulemur)

The source-filter theory describes vocal production as a two-stage process involving the generation of a sound source, with its own spectral structure, which is then filtered by the resonant properties of the vocal tract. This theory has been successfully applied to the study of animal vocal signals since the 1990s. As an extension, models reproducing vocal tract resonance can be used to reproduce formant patterns and to understand the role of vocal tract filtering in nonhuman vocalizations. We studied three congeneric lemur species —Eulemur fulvus, E. macaco, E. rubriventer— using morphological measurements to build computational models of the vocal tract to estimate formants, and acoustic analysis to measure formants from natural calls. We focused on call types emitted through the nose, without apparent articulation. On the basis of anatomical measurements, we modeled the vocal tract of each species as a series of concatenated tubes, with a cross-sectional area that changed along the tract to approximate the morphology of the larynx, the nasopharyngeal cavity, the nasal chambers, and the nostrils. For each species, we calculated the resonance frequencies in 2500 randomly generated vocal tracts, in which we simulated intraspecific length and size variation. Formant location and spacing showed significant species-specific differences determined by the length of the vocal tract. We then measured formants of a set of nasal vocalizations (“grunts”) recorded from captive lemurs of the same species. We found species-specific differences in the natural calls. This is the first evidence that morphology of the vocal tract is relevant in generating filter-related acoustic cues that potentially provide receivers with information about the species of the emitter.     

CO2 assimilation,photosystem II photochemistry,carbohydrate metabolism and antioxidant system of citrus leaves in response to boron stress

Seedlings of Citrus grandis were fertilized every other days for 15 weeks with nutrient solution containing 0 (deficiency), 10 μM (control) or 500 μM (excess) H₃BO₃. CO₂ assimilation and chlorophyll (Chl) content decreased to a greater degree in B-deficient than in B-excess leaves, but photosynthetic enzyme activities were similarly decreased. Starch accumulated in B-deficient leaves, but not in B-excess ones. Chlorophyll a fluorescence transient showed that the positive L- and K-steps were more pronounced in B-excess than in B-deficient leaves. Maximum quantum yield of primary photochemistry (F_v/F_m), maximum variable fluorescence (F_v), oxygen-evolving complex (OEC) were less decreased in B-deficient than in B-excess leaves, whereas minimum fluorescence (F₀) was less increased in B-deficient leaves. Boron-deficient leaves displayed higher or similar antioxidant enzyme activities and higher ascorbate (AsA) and reduced glutathione (GSH) contents compared to B-excess leaves. Content of thiobarbituric acid (TBA) reactive compounds was less increased by B-deficiency than by B-excess. We conclude that B-deficient leaves are less damaged by oxidative stress than B-excess leaves due to their higher ability to scavenge reactive oxygen species. Both the donor (i.e. the OEC) and the acceptor sides of photosystem II were less photoinhibited by B-deficiency than by B-excess. The greater decrease in CO₂ assimilation and Chl content in B-deficient leaves may be caused by the excessive accumulation of starch. The reduction of CO₂ assimilation by B-excess is probably caused by a combination of factors such as oxidative damage, reduced photosynthetic enzyme activities and impaired electron transport capacity.     

Combined Effects of Lead and Acid Rain on Photosynthesis in Soybean Seedlings

To explore how lead (Pb) and acid rain simultaneously affect plants, the combined effects of Pb and acid rain on the chlorophyll content, chlorophyll fluorescence reaction, Hill reaction rate, and Mg²⁺-ATPase activity in soybean seedlings were investigated. The results indicated that, when soybean seedlings were treated with Pb or acid rain alone, the chlorophyll content, Hill reaction rate, Mg²⁺-ATPase activity, and maximal photochemical efficiency (F _v/F _m) were decreased, while the initial fluorescence (F ₀) and maximum quantum yield (Y) were increased, compared with those of the control. The combined treatment with Pb and acid rain decreased the chlorophyll content, Hill reaction rate, Mg²⁺-ATPase activity, F _v/F _m, and Y and increased F ₀ in soybean seedlings. Under the combined treatment with Pb and acid rain, the two factors showed additive effects on the chlorophyll content in soybean seedlings and exhibited antagonistic effects on the Hill reaction rate. Under the combined treatment with high-concentration Pb and acid rain, the two factors exhibited synergistic effects on the Mg²⁺-ATPase activity, F ₀, F _v/F _m, as well as Y. In summary, the inhibition of the photosynthetic process is an important physiological basis for the simultaneous actions of Pb and acid rain in soybean seedlings.     

Impact of elevated temperatures on greenhouse gas emissions in rice systems: interaction with straw incorporation studied in a growth chamber experiment

Aims

Two pot experiments in a “walk-in” growth chamber with controlled day and night temperatures were conducted to investigate the influence of elevated temperatures along with rice straw incorporation on methane (CH₄) and nitrous oxide (N₂O) emissions as well as rice yield.

Methods

Three temperature regimes–29/25, 32/25, and 35/30 °C (Exp. I) and 29/22, 32/25, and 35/28 °C (Exp. II), representing daily maxima/minima were used in the study. Two amounts of rice straw (0 and 6 t ha^?1) were applied with four replications in each temperature regime. CH₄ and N₂O emissions as well as soil redox potential (Eh) were monitored weekly throughout the rice-growing period.

Results

Elevated temperatures increased CH₄ emission rates, with a more pronounced effect from flowering to maturity. The increase in emissions was further enhanced by incorporation of rice straw. A decrease in soil Eh to <?100 mV and CH₄ emissions was observed early in rice straw–incorporated pots while the soil without straw did not reach negative Eh levels (Exp. I) or showed a delayed decrease (Exp. II). Moreover, soil with high organic C (Exp. II) had higher CH₄ emissions. In contrast to CH₄ emissions, N₂O emissions were negligible during the rice-growing season. The global warming potential (GWP) was highest at high temperature with rice straw incorporation compared with low temperature without rice straw. On the other hand, the high temperature significantly increased spikelet sterility and reduced grain yield (p?<?0.05).

Conclusions

Elevated temperature increased GWP while decreased rice yield. This suggests that global warming may result in a double negative effect: higher emissions and lower yields.     

Noise improves transfer of near-threshold, phase-locked activity of the cochlear nerve: evidence for stochastic resonance?

 Stochastic resonance can be described as improved detection of weak periodic stimuli by a dynamic nonlinear system, resulting from the simultaneous presentation of a restricted dynamic range of low-intensity noise. This property has been reported in simple physical and biological activities. The present study describes data consistent with the interpretation that stochastic resonance can be observed in the response of cochlear neurons. These experiments utilized low levels (−5 to 25 dB SPL) of stimuli and noise (5 to 30 dB SPL). Stimuli consisted of simultaneously presented 8 kHz (F ₁) and 8.8 kHz (F ₂) tone bursts, which generated an 800 Hz F ₂–F ₁ cochlear nerve envelope ensemble response in the gerbil. The mean response threshold was approximately −3 dB SPL. Simultaneous presentation of a low-intensity wideband noise increased the amplitude of this response. This was observed with tonal stimuli having intensities of 0–5 dB SPL; responses to stimulus levels >10 dB were attenuated by noise. Response amplitude was increased by noise levels of 10–15 dB; the amplitude was unaffected by lower levels of noise, and decreased in the presence of higher noise levels. These properties are compatible with those of stochastic resonance. Accepted: 11 March 1999     

Can listeners assess men's self-reported health from their voice?

Men's voices may provide cues to overall condition; however, little research has assessed whether health status is reliably associated with perceivable voice parameters. In Study 1, we investigated whether listeners could classify voices belonging to men with either relatively lower or higher self-reported health. Participants rated voices for speaker health, disease likelihood, illness frequency, and symptom severity, as well as attractiveness (women only) and dominance (men only). Listeners' were mostly unable to judge the health of male speakers from their voices; however, men rated the voices of men with better self-reported health as sounding more dominant. In Study 2, we tested whether men's vocal parameters (fundamental frequency mean and variation, apparent vocal tract length, and harmonics-to-noise ratio) and aspects of their self-reported health predicted listeners' health and disease resistance ratings of those voices. Speakers' fundamental frequency (f_o) negatively predicted ratings of health. However, speakers' self-reported health did not predict ratings of health made by listeners. In Study 3, we investigated whether separately manipulating two sexually dimorphic vocal parameters—f_o and apparent vocal tract length (VTL)—affected listeners' health ratings. Listeners rated men's voices with lower f_o (but not VTL) as healthier, supporting findings from Study 2. Women rated voices with lower f_o and VTL as more attractive, and men rated them as more dominant. Thus, while both VTL and f_o affect dominance and attractiveness judgments, only f_o appears to affect health judgments. Results of the above studies suggest that, although listeners assign higher health ratings to speakers with more masculine f_o, these ratings may not be accurate at tracking speakers' self-rated health.