We know from observations and experiments that sound - it swings. Sound propagates in a well-solids, slowly - in liquid, even more slowly - in gases. The oscillation frequency is measured in hertz is the reciprocal of the period. So, if the air vibrations occur with a frequency of 16 to 20000 Hz, it is perceived as sound. Only very large "listener" can hear the whole frequency range. Usually heard from 20 to 18000 Hz; 20Hz - this is perhaps the thunder, and 18 000 - the finest mosquito squeak.

Sound propagates in the air at a speed of 332 meters per second

Sound propagates in the air at a speed of 332 meters per second (0 degrees Celsius), and iron - 10,5 times greater. This shows that it runs through the air is much slower than light. The sound in vacuum is not covered.

Sounding the body leads to the fluctuation of the air particles. The vibrations reach our ears body vibrate the eardrum, and thus we hear.

To capture the sound in the military special rangefinder used. Musical instruments, telephone - all this came from the study of the nature of sound.

Volume or amplitude of sound vibrations - one of the main characteristics of the sound. Loudness is measured in decibels, is in honor of the inventor of the telephone physics AG Bell (1847-1922). The weakest sound perceived by our ear - about 10 dB. Creek - 70 dB. Strongest thunder - about 100 dB and more than 130 dB - is perceived as pain in the ears. As it turns out: the ticking of watches at a distance of 1 m - 30 dB?

The fact that the volume is not proportional to dB. As we already know, 10 dB, or 1 B (wonder why it was to enter the decibels when just bels much easier and shorter?) - the weakest sound, still perceived normal hearing. But as the origin, or 0 B, taken a sound is 10 times weaker. Suddenly, so someone would hear! The sound of a 2 B, or 20 dB, -.. Is not a 2, but 100 times stronger than in 0 B, etc. That is, the number of white measuring order to increase the volume. Sound 10 B (or 100 dB) is the volume of the 1010, or 10 billion times louder than the threshold in 0 B!