Device of rectangular piezoelectric bimorph bone conduction
Currently, bone conduction hearing device from the formal distinction can be anchored into the bone with an external wearable. Bone anchored in the skull is the anchor for the hearing-impaired patients are more, but this means the application up, not only cause human suffering, and the configuration is very inconvenient to use; wide range of external wearable, normal people can also use the , painless and easy, but its use is in the preliminary stage, the performance and the sound needs to be improved.
Distinction from the structure material, the application of more electromagnetic, piezoelectric type two, and most commercial applications of electromagnetic bone conduction device. With the structure of technological developments, electromagnetic bone conduction hearing device performance continues to improve and is getting more stable, but it still exists bulky, energy consumption, susceptible to electromagnetic interference, radiation of electromagnetic signals and other shortcomings. The piezoelectric bone conduction with fast response, the output signal strength per unit mass, low power, low mass, immune to electromagnetic interference, electromagnetic radiation, low temperatures and other characteristics can be used normally, concern.
Sound pathway is divided into two air conduction and bone conduction, and gas conduction is divided into two types. The first path is "Sonic - tympanic membrane - ossicles - oval window - inner ear lymph - auger - auditory nerve - central auditory cortex"; second path is "Sonic - tympanic membrane - - tympanic air - oval window - inner ear lymph - auger - auditory nerve - central auditory cortex ", under normal circumstances, is the first of a path at work.
Bone conduction path: external acoustic vibrations directly through the skull bone wall of afferent and cochlear inner ear to stimulate the auditory nerve, causing hearing. Bone conduction is divided into compression bone conduction (direct bone conduction) and mobile bone conduction (indirect bone conduction) two kinds, both of which can stimulate collaboration auger cause hearing, the specific pathways: "Sonic - the skull - bone lost - inner ear lymph - auger - auditory nerve - central auditory cortex. "
Piezoelectric bone conduction hearing device and principle: the use of sound vibration structure element is a rectangular piezoelectric wafer laminated plate (referred piezoelectric vibrator), piezoelectric wafer electrode parallel rectangular bimorph were pasted on both sides of the substrate. Piezoelectric equation is first class piezoelectric equations:
Where S1 is integrated in the E3 strain bimorph and T1 together to produce, including a piezoelectric strain and elastic strain two parts. Piezoelectric oscillator fixed at both ends using the intermediate substrate clamping methods, shown below:
Both ends of the substrate through the fixed platen and the housing, the piezoelectric transducer mounted on the housing of the hearing device as a vibration element. Pasting side of the piezoelectric vibrator vibrating in a plane conductive post, the other side of the membrane in contact with the conductive contact or close to the column, the column at the time of conduction of the piezoelectric vibrator, by contacting the membrane to vibrate the human skull, having a small size and simple structure installation and flexible.
When the piezoelectric vibrator as a sound generating element, if the vibration displacement is small, that is, the amplitude is small, can cause hearing loudness enough, and people feel the sound will be small, how to use a piezoelectric bone conduction hearing device, so that the loudness produced to meet the requirements of human bone conduction hearing , is also a factor to be addressed. If the displacement of the piezoelectric transducer to increase the deformation of the structure, will be a corresponding increase in loudness.
