Low volume change detection
First Claim
1. Volume change detection apparatus comprising means defining a cavity, said cavity having means for communicating with a variable volume to be measured, a D.C. microphone connected with said cavity for response to fluid pressure changes therein due to variations in the variable volume, an adjustable diaphragm operably connected with said cavity, a servo-control means operably connected between said microphone and said diaphragm to adjust the latter in response to the output from the former to maintain the pressure in said cavity constant, and output means connected to said servo-control to present a signal representing the diaphragm adjustment.
3 Assignments
0 Petitions
Accused Products
Abstract
Low volume flow measurement apparatus developed for hearing dysfunction diagnosis but also suited to other applications comprises means (10) defining a cavity operably communicable with the variable volume, a D.C. microphone (15) responsive to ambient pressure changes in the cavity due to variations in said volume, and a reference diaphragm (17) operably connected with the cavity and moveable under servo-control responsive to the microphone to maintain the cavity pressure constant. The cavity will normally have a vent valve (18) and in non-hearing application may be coupled with the subject volume by a plunger seal. For hearing diagnosis the apparatus is suitably carried by a helmet (21) or harness with a headphone on the opposite side for sound stimulus application, the helmet itself being at one end of a boom (22) with a counterweight (23).
12 Citations
8 Claims
- 1. Volume change detection apparatus comprising means defining a cavity, said cavity having means for communicating with a variable volume to be measured, a D.C. microphone connected with said cavity for response to fluid pressure changes therein due to variations in the variable volume, an adjustable diaphragm operably connected with said cavity, a servo-control means operably connected between said microphone and said diaphragm to adjust the latter in response to the output from the former to maintain the pressure in said cavity constant, and output means connected to said servo-control to present a signal representing the diaphragm adjustment.
Specification