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What was the txalaparta, and where was it used?

The txalaparta was an instrument of communication that was used by the Basque people of Spain. Just as the Africans had their talking drums, these people have the txalaparta.The txalaparta was made of wooden planks leaning over logs. When hit with a special stick, it would produce a sound. The tone would vary according to where the instrument was hit. The Basque were thus able to send messages by producing different sounds on the txalaparta. Today, the txalaparta is no longer needed for communication. However, it is still widely used as a musical instrument.

What is cave art?

The earliest form of art that has been found is cave art. It is found on the walls of caves around the world from Europe and Asia to Africa and Australia.Cave art consists of pictures, mostly of the animals hunted by early man. The first pictures were probably drawn with charcoal. Later, clay, lime and charcoal were ground into a powder, and mixed with water or animal fats. So, the pictures became more colourful and life-like. Early artists made brushes with animal fur, feathers, twings, and moss. Sometimes they used just their hands to draw the pictures.Cave art represents one of the first attempts of man to communicate by means other than speech, and is therefore, an important milestone in human development

What is drum communication and who used it?

BOOM! BOOM! BOOM! Tha-ki-da… the –ki-da…tha! Rat-a-tat-tat… don’t you just love the sound of different types of drums?Did you know that early man used drums as a means of communication? In Africa, New Guinea and tropical America, people used drums to send messages to other tribes who were far away. Such drums were of-ten called ‘talking drums’. They could warn a tribe that a stranger was approaching, or could convey a message from one person to another. Of course, you had to understand the meaning of different beats to understand what the drums were trying to tell you!Drums played an important role, not just in communication, but also in cultural and religious rituals as well.                                

                                                                                                                                                                                              

Why do we not hear sound while sleeping or meditating?

Sleep does not reflect an inactive brain and so we do hear sound while sleeping.  It is a recurrent healthy state of inertia and reduced responsiveness found among higher vertebrates. It is controlled by the brain and is associated with characteristic electrical rhythms in the brain. Sleep is induced when the central core of the brainstem situated below the cerebral hemisphere is stimulated. Stimulation of the reticular formation (portion of the central nervous system which consists of small islands of gray matter separated by fine bundles of nerve fibres running in every direction) by natural sensory input, by messages from the cerebral cortex can awaken sleeping persons.

 Neurons (nerve cells) in REM sleep are as active as they are in wakefulness. Mental capacity also does not decrease. Incoming sounds are subjected to ceaseless scrutiny. Unimportant sounds are ignored but important ones even if feeble cause arousal. Arousal thresholds are variable and they are a function of the meaningfulness of the stimulus.

 With a stimulus having no significance, to the sleeper, thresholds can be rather high. So irrelevant stimuli are actively shut out during REM. Behaviourally, it has been established that motor responses can be evolved in all stages of sleep, but it is difficult to demonstrate that new responses can be acquired during sleep. But, in meditation man achieves a state of rest deeper than sleep indicated by slower heartbeat and breathing and so we do not hear sound. 

 

Why does the flow of ink increases when pens are about to run out of ink?

When the pen is full of ink, there is very little space for air inside the pen. So while writing the ink gradually oozes out through the cut in the nib. This leads to a very weak vacuum inside the pen. So the outside air tries to enter the pen and holds the ink from flowing out freely. This ensures a smooth flow of ink.

As the ink runs out and when there are only a few drops of ink the air column inside the pen is no longer isolated from outside the air. Hence the outside air can enter the pen freely and there is no difference in air pressure. Thus the force acting on the ink will be only the gravitational pull and so the ink begins to drain out. 

What does Dolby printed on sound systems signify?

Dolby mentioned in tape recorders and other sound system actually refers to a noise reduction circuit used in them. Over the past 30 years, sound recording has been revolutionized by technical developments by Dolby labs founded by Ray. M. Dolby, a sound engineer. His first invention was a circuit that eliminates the noise, usually heard as a hiss, inherent in most tape recordings. Unlike the earlier antihiss technologies which distorted the quality of sound, Dolby’s method involved separating the acoustic components of a given sound into different electronic channels based on their frequency and amplitude, eliminating those signals that contributed most to noise and then recombining the other components. 

How does audible sound pass through hard material such as a wall and be audible on the other side?

Sound is nothing but a form of energy. It travels in the form of waves. When these waves strike the wall the molecules or the atoms vibrate due to the sound energy.

The vibration passes from one atom onto its adjacent atom thus travelling vibration travels through the whole wall and when the wall ends the vibration in turn takes place in the air molecules.

Thus the sound travels through the wall and further into the air. Due to these sound created on one side of the wall can be heard on the other side. This phenomena proves that sound needs medium to travel. In vacuum the sound cannot travel because there are no atoms or molecules present to vibrate. In solids the atoms are packed together tightly than those of liquids and gases.

The vibrations need much less gap between the atoms in order to travel faster. Sound travels more intensely in solids. That is why audible sound passes through hard materials and be audible on the other side.

Is there any significance in using gravel on railway tracks?

            Yes, Gravel used on railway tracks is known as ballast. It is used to dissipate the vibration produced by trains travelling at high speeds. In effect, the gravel layer acts as a cushion and damps the vibrations so that they do not travel long distances. If the rails are laid on a solid base, these vibrations can travel long distances and lead to cracks on the base as well as on nearby buildings.

            The ballast provides a foundation for the sleepers distributes the pressure on to the formation and helps in diverting the rain water. In typical ballast, voids constitute 20 to 30 percent of the volume.

 

Why do radios receive signals well only when kept in certain directions?

  In radio sets, the problem of not receiving signals in certain directions is felt in the medium wave band (530-1620 kHz). This is because for this band they use a coil wound on a ferrite rod as the antenna.

  Ferrite rod is directional in its sensitivity. It picks up all signals that come in a direction perpendicular to its axis and rejects them if they come parallel to its axis. Therefore the reception is entirely based on the direction in which they reach the radio set. 

 Radio receivers use an inbuilt loop antenna for receiving radio frequency (RF) signals, which are nothing but electromagnetic signals, broadcast by transmitting stations. Some sets use telescopic antenna to receive frequency modulated (FM) signals.

Normally the dimensions of the loop are chosen to be comparable to the wavelength of the signals that will be received by the set. The dimensions of the loop are such that the current generated by the signal in the loop are of same magnitude and phase throughout the loop. If the phase of the loop is set at right angles (perpendicular) to the direction from which the vertically polarized waves are coming, then currents are induced in each of the vertical side antennas.

But these two antennas send currents around the loop in the opposite directions; hence, they cancel out each other as both the currents are equal in magnitude and opposite in phase. It is because during normal position of the loop antenna plane with respect to the incoming waves, both the sides are equidistant from the transmitter signal and there is no induced EMF. If the loop is rotated by 90 degrees, the plane of the loop will be along the direction of incoming radio waves, and so the voltages induced in the vertical side of the loop are not cancelled.

Because the distance involved between the vertical sides is equal to the width of the loop the voltage is maximum when the plane of the loop is along the direction of the incoming radio waves. External antennae help reduce this directional effect to a certain extent.