Stethoscope paramete
The stethoscope is an acoustic medical device for auscultationof thesound changes  of human heart, lungs, veins and other organs ,when the diaphragm is placed on the patient, body sounds vibrate the diaphragm, creating acoustic pressure waves which travel up the tubing to the listener's ear
Main material: copper, rubber tube, spring
Frequency response curve: using 100-500HZ to test the sound source as a benchmark, the attenuation is not greater than 12dB,  with 500-1000HZ ,the attenuation is not greater than 20 
Spring hardness：HR15N82.90-88.40
Earplugselastic:Two earplugs opened 140mm,  the range of elasticityis 1.372 ~ 1.960N
Elasticity of Earplugs : pull the Two earplugs to 300 mm,recuperate after 1 minute , the deformation should not be more than 10mm.