How screeching affects the body?

How screeching affects the body?

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Most times when I hear a screech (such as moving a sharp object on a chalkboard thereby causing such unpleasant noise), my body twitches. There are also other unpleasant sounds that causes the twitching, but whenever it sounds only my dad, my brother and I that feels it, but my two sisters and my mum says they don't feel anything. My question is:

Is there any scientific term for this feeling?

Is it hereditary?

What happens in the body or brain when the sound is produced?

Dinosaur thermoregulation

Beyond eating, digestion, assimilation, reproduction, and nesting, many other processes and activities went into making the dinosaur a successful biological machine. Breathing, fluid balance, temperature regulation, and other such capabilities are also required. Dinosaurian body temperature regulation, or lack thereof, has been a…

Distribution of organisms

…mechanisms to maintain a constant body temperature, and two categories are commonly distinguished: the term cold-blooded is understood to refer to reptiles and invertebrates, and warm-blooded is generally applied to mammals and birds. These terms, however, are imprecise the more accurate terms, ectotherm for cold-blooded and endotherm for warm-blooded, are…

Fahrenheit temperature scale

…point of water and normal body temperature, respectively these later were revised to 32° and 96°, but the final scale required an adjustment to 98.6° for the latter value.


…extreme and uncontrolled elevation of body temperature (106 to 110 °F [41 to 43 °C], or even higher), which can harm the central nervous system.


The control of body temperature in humans is a good example of homeostasis in a biological system. In humans, normal body temperature fluctuates around the value of 37 °C (98.6 °F), but various factors can affect this value, including exposure, hormones, metabolic rate, and disease, leading to excessively…

Pregnancy indication

Persons who note their body temperature upon awakening, as many women do who wish to know when they are ovulating, may observe continued elevation of the temperature curve well beyond the time of the missed period this is strongly suggestive of pregnancy. During the early months of pregnancy, women…


… and maintenance of an elevated body temperature they are dependent upon heat from their surroundings that is, they are ectothermic. As ectotherms, many reptiles have body temperatures which fluctuate with that of the environment. This condition is called poikilothermy. Mammals and birds, often described as warm-blooded animals, produce heat by…

Temperature stress

…induced by excessive heat or cold that can impair functioning and cause injury or death. Exposure to intense heat increases body temperature and pulse rate. If body temperature is sufficiently high, sweating may cease, the skin may become dry, and deeper and faster breathing may follow. Headaches, nausea, disorientation, fainting,…


body temperature and metabolic activity assumed by many animals in response to adverse environmental conditions, especially cold and heat. The torpid state may last overnight, as in temperate-zone hummingbirds and some insects and reptiles or it may last for months, in the case of true…


An individual’s body temperature, for example, rarely varies (when taken at the same anatomical site) by more than a degree (from time of rising until bedtime) without being indicative of infection or other illness.

The science and biology of PTSD

In the study and science of Post Traumatic Stress Disorder it’s important to understand that PTSD is considered to be a psychological injury rather than a mental illness. This is because neuroanatomical studies have identified changes in major brain structures of those with PTSD — the amygdala and hippocampus – showing that there are significant physical changes within the brain as a result of trauma.

These brain changes from PTSD, particularly if not diagnosed yet, can make life seem very confusing, and understanding your own mind can become almost impossible.

  • A PTSD sufferer may struggle to find the right words to express what they are thinking and feeling. This is due to the prefontal lobe (responsible for language) being adversely affected by trauma and so disrupts its linguistic function.
  • People with PTSD can find it hard to control their emotions as the amygdala (responsible for emotional regulation) is in overdrive, due to its increase in physical size.
  • Short term memory loss can also affect those with PTSD as the hippocampus (responsible for memory and experience assimilation) actually shrinks.
  • PTSD can make you feel frightened no matter what you’re doing – your medial prefontal cortex is responsible for this (its role is to regulate emotion and fear responses) as it can’t regulate itself or function properly after trauma.

Effect of trauma specifically on the hippocampus

Under normal conditions, when a memory is built or retrieved, the hippocampus blends together all the elements of a memory from all the sensory areas. Initially, short-term memories are stored in the hippocampus, but when they are no longer required as ‘conscious memories’, the hippocampus processes these into other parts of the brain (to create longer term memories).

As mentioned above however, the hippocampus tends to reduce in volume in those with PTSD and so the recording of new memories and retrieval of older memories in response to specific and relevant environmental stimuli can become distorted.

The hippocampus is also responsible for distinguishing between past and present memories, and so those with PTSD can lose the ability to discriminate between past and present experiences (resulting in flashbacks).

Effect of trauma specifically on the ventromedial prefrontal cortex

The ventromedial prefrontal cortex region of the brain regulates negative emotions (such as fear).

Due to this region shrinking in those with PTSD, the ability to regulate these emotions is reduced – causing fear, anxiety, and extreme stress responses even when faced with things not connected – or only remotely connected – to their original trauma.

Effect of trauma specifically on the amygdala

Trauma has been shown to increase activity in the amygdala region.

This region of the brain helps us process emotions, and is also linked to fear responses. It uses the hippocampus to query situations from the past to ascertain answers to questions such as ‘Is this safe’, ‘Do I like this’ and most significantly in PTSD ‘Do I need to start up the stress responses and trigger hormones’. As you may imagine, if this region of the brain is hyperactive, and is connecting with an already ‘broken’ hippocampus, the effects it will have on our emotional regulation will be a distorted view of a situation.

Studies have shown that PTSD sufferers exhibit hyperactivity in the amygdala in response to stimuli that are connected to their trauma – however, the amygdala is so hyperactive in some patients that they exhibit fear and stress responses even when they are ‘simply shown photographs of people exhibiting fear’.

Effect of trauma specifically on Cortisol Levels

The biologic alterations observed in PTSD do not uniformly resemble those associated with other types of stress. For example, cortisol levels have been lower than normal in some studies of patients with PTSD, however corticotropin-releasing factor in cerebrospinal fluid appear to be increased.

This pattern differs from the patterns associated with brief and sustained periods of stress and with major depression, which are typically associated with increased levels of both cortisol and corticotropin-releasing factor.

These psychological and biologic data supports the hypothesis that the development of PTSD is facilitated by a failure to contain the biologic stress response at the time of the trauma, resulting in a cascade of alterations that lead to PTSD.

Furthermore, it has been shown that patients with chronic PTSD have even more increased circulating levels of norepinephrine and reactivity of adrenergic receptors. These alterations, in addition with the findings that thyroid hormone levels are generally increased in patients with PTSD, also explain some of the somatic or physical symptoms of the PTSD.

Understanding how PTSD alters brain chemistry is critical to understanding the symptoms of PTSD, devising treatment methods, and to providing the answers as to why some people develop PTSD from trauma, and others do not.

There is evidence that successful treatment of PTSD with therapies such as EMDR and CBT do produce measurable structural changes in brain regions associated with fear conditioning. Several studies have also reported significantly larger hippocampal volumes following treatment of PTSD psychotherapy. These studies show why it’s possible to heal from PTSD.

If the full science details seem to complex, we’ve written a simpler science based blog post here: Understanding PTSD if you’ve seen Pixars’ Inside Out


Although Hylidae species can turn their heads relative to their bodies to some extent (Caldwell and Bee, 2014), music frogs only rotated the body or moved around in response to external stimuli in our experiment. Changing the position of the ears relative to a sound source enables animals to optimally localize sound sources by utilizing the resulting variations in either the amplitude or phase of tympanum vibrations between the two ears (Christensen-Dalsgaard, 2005). Thus, turning of the body in situ in music frogs was assumed to be the functional homolog to head turning in mammals and birds, and was taken as an indication of lateralization for fine auditory stimulus processing. However, the generalizability of the orienting-asymmetry paradigm and the relationship between orienting asymmetries and brain lateralization for acoustic processing is still being evaluated (Teufel et al., 2010). A goal of the present study was to contribute to the evaluation of this paradigm. Explication of anuran vocal/auditory lateralization should entail behavioral tests for side preferences in conjunction with study of the physiological processes directly reflecting ongoing brain activities, such as EEG and/or positron emission tomography (PET). Pertinent to this, we previously conducted an electrophysiological study demonstrating a right ear/left brain advantage in auditory processing in this species (Fang et al., 2014b), supporting the present behavioral results.

REA behaviors correspond to known neural lateralization patterns

Twenty-five frogs turned in situ when HSA calls were presented from a speaker immediately behind them, 76% of which turned rightwards. This rightward bias is comparable to results of head orientation studies in other vertebrates (Böye et al., 2005 Basile et al., 2009 Hauser and Andersson, 1994 Reinholz-Trojan et al., 2012 Siniscalchi et al., 2008) and supports the idea that among land vertebrates, most individuals orient the right side of the head towards sound sources when listening to conspecific calls. Recent work on sound localization behavior in gray treefrogs, which differ from music frogs in both habitat and phylogenetic position (Alexander Pyron and Wiens, 2011), showed no consistent tendency to turn rightwards for females in response to male advertisement calls, in either 0 or 180 deg sound presentations (Caldwell and Bee, 2014). This may be attributed to the fact that music frogs live on the ground and prefer responding to sounds varying in azimuth in contrast to arboreal frogs, which must process sounds varying both azimuthally and vertically.

Previous electrophysiological studies in the Emei music frog have supported the idea that lateralization of processing of conspecific vocal signals occurs in this species (Fang et al., 2011,, 2014b,, 2012). These studies report that power in the EEG bands of the left hemisphere, especially of the left mesencephalon, tends to be greater or to change significantly compared with that of the right in response to conspecific call stimulation. As auditory pathways in anurans tend to project information most strongly to the contralateral midbrain (Wilczynski and Endepols, 2006), the behavioral results of the present study indicating an REA for all stimuli except the screech are consistent with these electrophysiological studies.

Cerebral lateralization of auditory processing has been demonstrated in anuran (Bauer, 1993), avian (Cynx et al., 1992) and mammalian (Heffner and Heffner, 1995) species using the lesion method. Lesions of the left hemisphere reduce the ability to discriminate and/or produce conspecific sounds to a greater degree than lesions of the right hemisphere. Neurophysiological studies in bats have shown that the left hemisphere neurons are more responsive to social calls while those of the right are more responsive to navigational signals (Kanwal, 2012). Theoretically, neural lateralization would improve information processing efficiency by providing specialized analysis within each hemisphere, thereby enhancing the ability of land vertebrates to make critical decisions related to mating or feeding in dangerous environments (Rogers et al., 2004). Our behavioral and electrophysiological studies of the lateralization of auditory perception in anurans provides experimental evidence in support of the idea that hemispheric asymmetry in processing cues related to complex perception originated at an early stage in vertebrate evolution (Ocklenburg et al., 2013 Vallortigara, 2000 Vallortigara et al., 1999).

Mating strategy influences the response to advertisement calls

Both HSA and LSA advertisement calls elicited more body turning to the right than to the left however, only HSA calls elicited a statistically significant bias in the rightward direction in this study. Nevertheless, LSA calls evoked behavioral response patterns that differed from those of the non-biological thunder and WN stimuli (see Fig. 1). These results are consistent with those of previous phonotaxis experiments, which showed that when HSA and LSA calls were played back antiphonally from both sides of a test chamber to female music frogs, more than 70% of the subjects approached the speaker broadcasting HSA calls (Cui et al., 2012). The results of the present study are also consistent with previous behavioral tests of male vocal competition. Fang et al. (2014a) showed that when male frogs listen to an HSA and an LSA call presented alternately, the male subjects preferred competing vocally with the HSA calls rather than the LSA calls. Therefore, the sexual attractiveness of the stimuli, which plays an important role in female mate selection and male vocal competition, also affects rightward turning for both males and females, consistent with the idea that the neural resources involved in processing signals with high biological significance differ between the hemispheres.

As animals are able to assess the costs and benefits of competing for resources (Arnott and Elwood, 2008), it is reasonable to hypothesize that music frogs would pay less attention to males producing the LSA call because such individuals lack a nest and would therefore be less valued targets for mating or competition (Kirkpatrick et al., 2006). Such a strategy would thus enable males to allocate energy and attention resources toward more valued targets (Greenfield and Rand, 2000) as well as enable males to reduce the predation risk that usually accompanies reproductive activities (Magnhagen, 1991 Reznick, 1992), which would thereby increase fitness.

Fear as a motivator of the frogs’ behavior

The screech stimulus evoked a tendency to turn leftwards and was associated with longer response latencies than for the HSA or LSA calls despite the fact that the screech is also a conspecific call. Similar response patterns have been shown in dogs, which turn their heads left in response to playbacks of barking stimuli (Reinholz-Trojan et al., 2012) and displays of a picture of a snake (Siniscalchi et al., 2010). These authors pointed out that this behavioral pattern appears to reflect activation of the left ear/right hemisphere system consistent with the fact that the right hemisphere is specialized to process stimuli evoking negative affect (Vallortigara and Rogers, 2005).

Emotion can motivate behavior (Zhu and Thagard, 2002) and fear is a common emotion linked to behaviors elicited by potential danger (Faure et al., 1983 Galac and Knol, 1997 Prather et al., 2001). The amygdaloid complex and right hemisphere pallial structures are believed to be involved in processing affective stimuli in mammalian and avian species (Andrew, 1983 Crowne et al., 1987 Davidson and Tomarken, 1989 Denenberg, 1981 Fernández-Carriba et al., 2002 Slotnick, 1973 Wallez and Vauclair, 2011). Although the frog's telencephalon is not as well differentiated compared with that of mammals and birds (Butler and Hodos, 2005), limbic system structures that appear homologous to the amygdala and hippocampal formation of mammals have been described in frogs (Bruce and Neary, 1995), which possess ascending and descending connections comparable to the corresponding structures of mammals (Laberge et al., 2006).

Yao et al. (2004) studied the distribution of corticotrophin releasing hormone (CRH)-like peptides in the clawed frog (Xenopus laevis) brain, which conform to the distribution of CRH-positive neurons in mammals and are hypothesized to serve similar functions. It is notable that when clawed frogs are stressed by shaking, the concentration of CRH-like peptides in the medial amygdala significantly increases, similar to the effect of stressors in the mammalian amygdala. In addition, functional studies indicate that the modulation of CRH within the hypothalamic-pituitary–adrenal axis is similar in diverse vertebrate species (Denver, 2009).

Comparative neuroanatomical and immunohistochemical studies support the idea that frogs can process affective stimuli, especially those associated with fear evoked by predator avoidance (Dill, 1977 Lippolis et al., 2002). Nevertheless, affective behavior is more limited in frogs than in birds and mammals, as indicated by studies reporting the lack of an emotional fever response in amphibians (Cabanac and Cabanac, 2004 Cabanac, 1999). As the screech call used in our study was recorded during a snake attack, it is reasonable to categorize this screech call as a defensive call that would help frogs avoid predation (Toledo et al., 2014). Therefore, the screech call serves as a warning of potential predators and also transmits a negative emotion (e.g. fear and distress).

Fear activates the amygdala complex and results in freezing responses in many prey animals (Ryan, 1985). Consistent with this idea, a longer response latency was associated with the screech call stimulus. Moreover, frogs either moved directly away or turned to the left side in response to the screech. These behaviors are consistent with the idea that the screech signals danger, further processing of which is best served by the left ear/right hemisphere system, which, in mammals, is functionally important for mediating withdrawal behavior, behavioral inhibition and negative emotion (Davidson, 1984a,,b Davidson et al., 1990 Quaranta et al., 2007 Siniscalchi et al., 2013 Sutton and Davidson, 1997). In this way, the subjects are able to rapidly make an escape action decision based on trade-offs between the costs and benefits (Broom and Ruxton, 2005 Cooper and Frederick, 2007).

In summary, the REA and corresponding behaviors exist in Emei music frogs and appear comparable to those described in other vertebrates. The existence of a right ear preference for advertisement calls and a left ear preference for calls signaling danger supports the idea that the frogs' REA behavior is modulated by mating strategies as well as negative emotions such as fear.

Respiratory Disorders top

People with obesity have reduced breath capacity. They are not able to breathe in as much air in and out. These people are at higher risk for respiratory (lung) infections, asthma, and other respiratory disorders. Asthma has been shown to be three to four times more common among people with obesity (8).

More than half of those affected by obesity (around 50 to 60 percent) have obstructive sleep apnea (OSA). In cases of severe obesity, this figure is around 90 percent (7). OSA is a very serious breathing disorder. It occurs when extra fat in the neck, throat, and tongue block air passageways during sleep. This blockage causes apnea, which means a person stops breathing for a time. A person with OSA may have hundreds of apnea episodes each night. Apnea episodes reduce the amount of oxygen in a person’s blood.

OSA may lead to high blood pressure, pulmonary hypertension, and heart failure. OSA can cause sudden cardiac death and stroke. Because apnea episodes interrupt the normal sleep cycle, you may not reach restful sleep. This can lead to fatigue (tiredness) and drowsiness. If untreated, this drowsiness may raise your risk of motor vehicle accidents.

Bone density and frame size in adult women: Effects of body size, habitual use, and life history

Katharine M. N. Lee, Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, IL.

Contribution: Conceptualization, Data curation, Formal analysis, Funding acquisition, ​Investigation, Methodology, Resources, Visualization, Writing - original draft, Writing - review & editing

Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Contribution: Data curation, Funding acquisition, ​Investigation, Methodology, Resources, Writing - review & editing

Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland

Contribution: Resources, Supervision, Writing - review & editing

Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland

Contribution: Formal analysis, Funding acquisition, Resources, Supervision, Writing - review & editing

Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Beckman Institute of Advanced Science & Technology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Contribution: Conceptualization, Funding acquisition, Methodology, Resources, Supervision, Writing - review & editing

Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Katharine M. N. Lee, Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, IL.

Contribution: Conceptualization, Data curation, Formal analysis, Funding acquisition, ​Investigation, Methodology, Resources, Visualization, Writing - original draft, Writing - review & editing

Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Contribution: Data curation, Funding acquisition, ​Investigation, Methodology, Resources, Writing - review & editing

Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland

Contribution: Resources, Supervision, Writing - review & editing

Department of Environmental Health, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland

Contribution: Formal analysis, Funding acquisition, Resources, Supervision, Writing - review & editing

Department of Anthropology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Beckman Institute of Advanced Science & Technology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Contribution: Conceptualization, Funding acquisition, Methodology, Resources, Supervision, Writing - review & editing

Funding information: American Philosophical Society Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign Department of Anthropology, University of Illinois at Urbana-Champaign Directorate for Social, Behavioral and Economic Sciences, Grant/Award Numbers: 131740, BCS-1650839, BCS-1732117 Division of Graduate Education, Grant/Award Number: DGE-1144245 Graduate College, University of Illinois at Urbana-Champaign Narodowe Centrum Nauki, Grant/Award Number: UMO-2017/25/B/NZ7/01509 Sigma Xi Wenner-Gren Foundation, Grant/Award Numbers: 084918, 089912 National Science Foundation



Bone mineral density (BMD) and frame size are important predictors of future bone health, with smaller frame size and lower BMD associated with higher risk of later fragility fractures. We test the effects of body size, habitual use, and life history on frame size and cortical BMD of the radius and tibia in sample of healthy adult premenopausal women.


We used anthropometry and life history data from 123 women (age 18-46) from rural Poland. Standard techniques were used to measure height, weight, and body fat. Life history factors were recorded using surveys. Grip strength was measured as a proxy for habitual activity, wrist breadth for skeletal frame size. Cortical BMD was measured at the one-third distal point of the radius and mid-point of the tibia using quantitative ultrasound (reported as speed of sound, SoS).


Radial SoS was high (mean t-score 3.2 ± 1.6), but tibia SoS was average (mean t-score 0.35 ± 1.17). SoS was not associated with age, although wrist breadth was positively associated with age after adjusting for height. Radius SoS was not associated with measures of body size, habitual use, or life history factors. Wrist breadth was associated with body size (p < .05 for all), lean mass, and grip strength. Tibia SoS was associated with height. Life history factors were not associated with frame size or cortical SoS.


Habitual use and overall body size are more strongly associated with frame size and cortical SoS than life history factors in this sample of healthy adult women.

Appendix S1: Supporting information.

Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.


3 Bhaskaran K, Douglas I, Forbes H, dos-Santos-Silva I, Leon DA, Smeeth L. Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5&bull24 million UK adults. Lancet. 2014 Aug 30384(9945):755-65. doi: 10.1016/S0140-6736(14)60892-8. Epub 2014 Aug 13.

4 Kasen, Stephanie, et al. &ldquoObesity and psychopathology in women: a three decade prospective study.&rdquo International Journal of Obesity 32.3 (2008): 558-566.

5 Luppino, Floriana S., et al. &ldquoOverweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies.&rdquoArchives of general psychiatry 67.3 (2010): 220-229.

6 Roberts, Robert E., et al. &ldquoProspective association between obesity and depression: evidence from the Alameda County Study.&rdquo International journal of obesity 27.4 (2003): 514-521.

Dance's Effects on the Human Body & Mind

We all know that exercise has a major affect on the body. However, what we do not know is how specific art forms affect different aspects of our lives. More specifically, the art form of dance can not only stretch your flexibility, but increase your strength & health among many other things. In addition, dancing not only has a measurable affect on one's physical health, but also on one's mental health.

One major affect of dance on the human body is weight control. Depending on the specific type of dance, a dancer can lose a tremendous amount of weight. For example, the highest calorie burning form of dance is ballet. It is said that a ballerina can burn up to 432 calories per hour while engaging in this activity.

Dancing can also improve one's balance and coordination. Because dancing is a series of quickly paced melodic moves, a dancer must learn to center their core. Without the balance that is required to become a dancer, one would not have the necessary tools to successfully carry out all the twists & turns that are required of them. Coordination is also a predominant effect on the human body. Especially, in group & partnering dances, a dancer must be & will become equipped with the necessary tools to not only coordinate their body to do several different things at once, but will also learn how to control their partner's body at the same time.

Dancing improves posture due to the contracted muscle tissues surrounding the spine and also develops exceptionally good muscle tone surrounding the legs and glutes.

However, one thing that most people don't know is that dancing also has a psychological effect on the human body. Dancing is a type of exercise and every type of exercise releases endorphins in the brain. This will cause the dancer to experience happiness. Over a longer period time, dancing will condition the brain to be able to learn & pick up information more easily. In addition, a Dancer's skill of repeating will be sufficiently higher than a non-dancer, since they have been taught to do so their whole life.

Dance has also been proven to be a therapeutic outlet for many. It is seen as a way to express yourself and let your emotions be free rather than have them harvest inside. Dance has also been found to help improve problem-solving skills. In addition, it has also been noted that improvisational dance can help with divergent & creative thinking.

What I personally have found most interesting is that dance has a significant effect on those with Parkinson's disease. Once the disease has developed it can affect the victim's thinking patterns. Peter Lovatt recently conducted an PD group experiment to see if dancing could beneficially improve their divergent thinking skills. The results were exactly that. He & the rest of his followers believe that a possible cause for this is that once they get the person affected with Parkinson's dancing, neural-passages become "unblocked" and therefore there is space for a more steady flow of thinking.

If you would like to learn more about dance's impact on the human body and mind click on the links below:
Link 1
Link 2
Link 3

How Can You Avoid Audio Feedback?

The most important thing you must do to avoid feedback is to distance the mic from the speaker as far as practically possible, and position these devices in a way so that the mic doesn&rsquot catch the sound coming out of the speaker too directly. This is why in public addresses or musical shows, the microphone is usually not set facing the speakers. Instead, the mic is brought out in the front, usually in the middle of the left and right speakers, which are kept at the two forward corners of the stage.

Many times during formal addresses, there is a particularly loud and sharp howl that makes everyone squint their eyes or put their hands around their ears. This is because the speaker in question either speaks too softly or is standing too far away from the mic. Consequently, the sound operator has to increase the &lsquovolume gain&rsquo (thereby increasing the sensitivity of the mic) of the system to make the orator audible to the audience.

Therefore, it is recommended to hold the mic no more than an inch or two away from one&rsquos mouth, so that the mic doesn&rsquot have to work extra hard to capture the sound of one&rsquos voice.

How screeching affects the body? - Biology

Scientific name: Poecile atricapillus
Common name:
Black Capped Chickadee

(Information for this species page was collected in part by Timothy Burg (Spring 2002) and Dean Ladifian (Spring 2004) for Biology 220W at Penn State New Kensington)

Black capped chickadees (Poecile atricapillus) are small birds (4.75 to 5.75 inches long with a wing span of 8.5 inches) with short, rather rounded bodies. Individual birds only weigh between 11 and 12 grams and are marked with a solid black forehead, crown, neck ("bib") and white cheeks. The rest of the body is whitish to olive gray with darker grays on the wings and tail. The black bibs of the males are larger than those of the females and can be used by those with good vision to distinguish gender during field observations. The bills, legs, and feet of both sexes are dark (usually black).

Chickadees are most typically found in mature forests of the northeastern and north-central United States up through southern Canada. They migrate seasonally within this broad, northern range spending most of the winter in the more southern regions and most of the summer in the northern. Specific habitat selection by P. atricapillus is governed by food supply, the presence of suitable nesting sites, and by the need of this very small bird to avoid the wind. Deep, dense woods, well sheltered from wind, is an ideal habitat for these remarkably fragile birds.

On our Nature Trail, chickadees are most commonly observed in their winter flocks (see "Winter Birds"). These mixed species flocks (which include titmice, downy and hairy woodpeckers, and other species) represent a significant behavioral adaptation which increases the winter survival rates of these small, foraging bird species. In the spring and summer, especially during the breeding season, these flocks disperse and individual chickadees establish territories. Observations around local bird feeding sites have confirmed the year-round presence of chickadees in our area. They are much less obvious during the spring and summer, however, because of their disperse distributions. Territories for chickadees range from six to over thirteen acres. It would be easy to miss this tiny bird in such a large habitat volume.

Chickadees eat insect eggs and larvae and are especially fond of ants. They also consume mites, many species of small arthropods (especially spiders), seeds, and even, in the winter, fat from animal carcasses. At bird feeders, chickadees readily eat sunflower seeds (especially the black, oil varieties) and suet. These tiny birds are under a considerable metabolic demand to maintain their 107 degree F body temperatures even on the coldest days and nights of winter. Individuals must consume their body weights in high caloric food stuffs each day in order to satisfy their considerable energy needs. Much of their daylight hours, then, are spent in the search for food. In good weather conditions, chickadees cache food typically away from the edges of their forest habitats. That way they can with relative ease recover their caches within the shelter of deeper forest during periods of stressful weather.

Nesting and Reproduction
Chickadees nest in cavities found or excavated in both living and downed wood. Favored tree species include birches and alders but willows, aspens, cottonwoods, apple, and cherry are also commonly used. The chickadees may excavate their hole themselves (usually in soft, already rotting tissue) or quite frequently will simply move into an abandoned woodpecker cavity. Chickadees also readily utilize nest boxes. Nests are typically found four to eight feet above the ground but may be located as high as forty feet above the forest floor. Complexity and age of the forest habitat is essential to generate a sufficient quantity and quality of nesting sites. Nests are cup shaped and are constructed from gathered mosses, grasses, bark, feathers, animal hair, and a variety of human-made materials. Clutches of 4 to 12 eggs are laid throughout the months of early spring to mid-summer. Eggs are incubated by the females for eleven to thirteen days. During this time period, the male feeds the female. After hatching, first the male and then both the male and the female feed the rapidly growing nestlings. The young fledge in fourteen to eighteen days and will remain with the parental pair for another three to four weeks. Flocks of juvenile birds form through the breeding season and may become incorporated into the multi-aged mixed flocks with the onset of winter.

Life Expectancy and Effect of Memory on Survival
The average life expectancy for a black capped chickadee is 1.5 years for a female and 1.8 years for a male. Mortality from predation is especially high for very young individuals but weather and accidents seem to be the primary causes of death of all age groups. Aldo Leopold in his book "Sand County Almanac" described one banded, black capped chickadee (# 65290) returning to his winter feeders for five consecutive winters. He commented, though, upon the uniqueness of this bird's long life span relative to his birth cohort and speculated on the luck and accumulated wisdom from experience that could have allowed this bird to live so long.

An interesting set of studies by V. Pravosudov (published in Behavioral Neurosciences in 2002) examined the importance of memory in chickadees. Caching, as mentioned above, is a very important behavior especially in chickadees living in more northern (and, therefore, more weather stressed) environments. Its is obviously important for an individual chickadee to be able to remember where its caches are. Memory, then, would be expected to play a greater role in the survival of chickadees in more stressful habitats than for chickadees in less stressful habitats. Pravosudov compared the size of the hippocampus of the brain (a part of the brain involved in memory) in chickadees collected in Alaska (where caching and efficiency of cache recovery is expected to be a critical factor in a bird's survival) with those of chickadees collected in Colorado (where caching and cache recovery is expected to be of less importance in survival). Pravosudov found that the hippocampi in Alaskan chickadees were significantly larger than those of Colorado birds in spite of the fact that the overall sizes of the birds were larger in the Colorado populations.

Chickadees are preyed upon by small hawks (especially sharp shinned hawks), owls (especially eastern screech owls), and shrikes. They also have a high human-induced mortality due to automobiles, window strikes, chemical poisoning (especially pesticides and herbicides), and domesticated cats.

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  1. Maichail

    Huge human salvation!

  2. Tygosar

    It is a pity, that now I can not express - I hurry up on job. But I will be released - I will necessarily write that I think on this question.

  3. Gojind

    Sorry for not being able to take part in the discussion right now - I'm very busy. I will be released - I will definitely express my opinion on this issue.

  4. Maelisa

    the same urbanesi something

  5. Meztigami

    Let me help you?

  6. Mathews

    It is nonsense!

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