Air conditioning fundamentals

Air conditioning is a process of producing air controlling simultaneously its temperature, humidity, cleanliness and distribution for the fulfillment of required condition of the confined space. An absorbent is a material which removes one or more substances from vapour or liquid due to difference in pressure. Calcium chloride is a solid absorbent and ethylene glycol is a liquid absorbent. The part of air which is not processed through the air conditioning system is called recirculated air. Circulation of chilled air with high velocity is called air blast. To remove impurities from air, air cleaners are used. Commonly used air cleaners are mechanical cleaners and electrostatic cleaners. Air diffuser is a device which converts a fraction of kinetic energy into pressure energy by circulating air against flow resistances. For measuring the velocity of air, anemometers are used. Antifreeze is a chemical which can cross freezing point of water. Typical examples are alcohol, glycol, ethylene glycol and ethyl ether. Antifreeze materials are generally less corrosive and have superlative thermal properties.

Fundamentals of digital audio communication

Audio information communication is an important task in multimedia. Sound is a form of longitudinal wave motion and its amplitude changes with time. The first step in digitization of audio signal is sampling where measurements are taken at evenly spaced intervals. The rate at which sampling is performed is called sampling frequency. For audio digitization, sampling rates ranges from 8KHz to 48 KHz. For better results, we follow Nyquist rate. Here sampling rate is maintained at a level which is equal to twice the maximum frequency content in the signal. Other important terms in this category are signal to noise ratio, signal to quantization noise ratio, linear and non linear quantization, audio quality versus data rate, audio filtering, synthetic sounds, coding of audio, pulse code modulation, differential coding, lossless predictive coding etc.