Sound Recording and Reproduction


Sound recording and reproduction are two separate processes used to record, store, and play back sounds. Sound recordings use microphones to pick up sound waves in the air. The pressure changes associated with the waves are converted into electrical signals, which can be coded and stored for future access. Sound reproduction, or playback, uses additional devices to retrieve the stored information and convert it back into electrical signals. The signals are then sent to a loudspeaker, which converts them back into sound.

To record sound, a microphone changes the acoustic energy of sound waves in the air into electrical signals. Inside a microphone is thin, flat, metallic surface, called a diaphragm that is suspended in a magnetic field. When a sound wave reaches the microphone, the air pressure changes around the diaphragm causing the diaphragm to move. This movement within a magnetic field creates an electrical signal. The signal is then transferred to a storage medium, such as a cassette tape, compact disc (CD), or phonograph record.

To reproduce sound, a playing device-such as a CD player, cassette deck, or phonograph accesses the stored data. The playing device reads the data and converts the information back into electric energy. The electrical signal is sent to a loudspeaker, which has a diaphragm housed in a magnetic field in much the same way as a microphone’s diaphragm is housed. The electrical signal creates a disturbance in the magnetic field. These resultant variations in the magnetic field cause the diaphragm to move. As the diaphragm moves, it pushes out and pulls in, creating changes in air pressure to recreate the sound that was originally recorded.

Sound recordings and reproduction form the foundation of many industries, including entertainment, communications, and multimedia businesses. Recording and reproduction of sound allow people to play their favourite music, whether it was recorded yesterday or many years ago. Radio networks rely on sound recording and reproduction for storing news and other types of programming. Television and motion pictures combine images with music, speech, and sound effects to provide the viewer with an enriched experience. Computer programs, multimedia software, and video games also use sound to make programs more engaging.


Making Paper from Woodchips

Do you have any paper in your bag? It may seem like a silly question but do you know how to make paper? What is paper made of? Right! And how is about ‘wood chipping’? Have you ever heard about it? Well, wood chipping is a process used to obtain pulp and paper products from forest trees.

First of all, the tops and branches of the trees are cut out and then the logs are taken to the mill. At the mill the bark of the logs is removed and the logs are taken to a chipper which cuts them into small pieces called woodchips. The woodchips are then screened to remove dirt and other impurities. Hmm … at this stage they are either exported in this form or changed into the pulp by chemicals and heat. Oh, I almost forgot, the pulp is then bleached and the water content is removed. Finally, the pulp is rolled out to make paper.

Considering the complexity of making paper, let’s appreciate any paper on our hands. Use it more effectively. Thank you for listening. Bye.




Life Cycle of the Malaria Parasite


Malaria is an infectious disease caused by a one celled parasite known as Plasmodium. The parasite is transmitted to humans by the bite of the female Anopheles mosquito. The plasmodium parasite spends its life cycle partly in humans and partly in mosquitoes.

Mosquito infected with the malaria parasite bites human, passing cells called sporozoites into the human’s bloodstream.

Sporozoites travel to the liver. Each sporozoite undergoes sexual reproduction, in which its nucleus splits to form two new cells, called merozoites.

Merozoites enter the bloodstream and infect red blood cells.

In red blood cells, merozoites grow and divide to produce more merozoites, eventually causing the red blood cells to rupture. Some of the newly released merozoites go on to infect other red blood cells.

Some merozoites develop into sex cells known as male and female gametocytes.

Another mosquito bites the infected human, ingesting the gametocytes.

In the mosquito’s stomach, the gametocytes mature. Male and female gametocytes undergo sexual reproduction, uniting to form a zygote. The zygote multiplies to form sporozoites, which travel to the mosquito’s salivary glands.

If this mosquito bites another human, the cycle begins again.