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Sound is more effectively transmitted into a stethoscope
Chapter 17, Problem 28(choose chapter or problem)
Problem 28PE
Sound is more effectively transmitted into a stethoscope by direct contact than through the air, and it is further intensified by being concentrated on the smaller area of the eardrum. It is reasonable to assume that sound is transmitted into a stethoscope 100 times as effectively compared with transmission though the air. What, then, is the gain in decibels produced by a stethoscope that has a sound gathering area of 15.0 cm2 , and concentrates the sound onto two eardrums with a total area of 0.900 cm2 with an efficiency of 40.0%?
Questions & Answers
QUESTION:
Problem 28PE
Sound is more effectively transmitted into a stethoscope by direct contact than through the air, and it is further intensified by being concentrated on the smaller area of the eardrum. It is reasonable to assume that sound is transmitted into a stethoscope 100 times as effectively compared with transmission though the air. What, then, is the gain in decibels produced by a stethoscope that has a sound gathering area of 15.0 cm2 , and concentrates the sound onto two eardrums with a total area of 0.900 cm2 with an efficiency of 40.0%?
ANSWER:Solution 28PE
Sound intensity level in units of decibels (dB) is
(dB) =
Here is the threshold intensity of hearing.
The intensity in terms of power and area is,
Here, stands for power and
stands for cross section area.
Powers of both the intensities are same with different cross section area thus the ratio is,