Sound waves

Introduction

Sounds are waves generated through compression and expansion of any medium that is solid, liquid or gas into certain frequencies. To human ear sound is defined as 20 to 20000Hz. Waves above 20000Hz are called ultrasound and below 20Hz are called infra-sound.

Sound waves are called longitudinal mechanical waves since the medium contents oscillate in the direction of wave propagation.

Figure 1. Longitudinal wave (http://www.acs.psu.edu/drussell/demos/waves/wavemotion.html)

Sound wave has its own intensity which is defined by common word sound level. Sound intensity is gotten by following pattern:

Sound level is gotten by following pattern:

Sound pressure level table:

Speed of sound table: