PSYCH 3A03 Lecture Notes - Acoustic Impedance, Inverse-Square Law, Instantaneous Phase
5 Nov 2013
School
Department
Course
Professor
Document Summary
Free field: boundary of near field far field and where you start to get reverberation. Usually extends about 1-2 wavelengths from source. Pressure displacement travels as a wave away from source. Cross in the graph indicates where near field because far field. Pressure more dominant in far field; distance more dominant in near field. Causes sound energy to dorp more quickly then otherwise expected from geometric spreading. Stepper curve then spherical spreading is excess attenuation, gerater than. Larger absorption coefficient with increases in humidity. Sound attenuates then would be expected from geometric spreading. Inverse square law holds true when sound waves propagate through a free, unbounded medium. A free, unbounded medium is a theoretical construct. In reality, transmission media have obstacles and other conditions that interfere with sound transmission. Reflected sounds encounter an obstacle and bounce back toward the source (echos) Diffracted sounds scatter about the obstacle.
