Sensor is a device that responds to a physical, chemical, biological or electrical stimulus as an electrical output signal which is a function of input stimulus.
The device responds to the input stimulus by monitoring the change in oscillation frequency for acoustic waves.
The input stimulus could be physical such as changing pressure, temperature or stress. It also may be chemical such as particular gas concentration or the chemical agent. It also include biological input stimulus which include bacterial concentration, antibodies concentration. It also may be electrical which consists of strength of electrical or magnetic field or the change in conductivity of the materials.
The acoustic wave devices respond by changing its resonant frequency when transduction is given to the devices by the input stimulus. Due to change in environmental factors such as change in temperature, pressure and stress the manufacturing of acoustic based products were very sensitive.
QUATRZ BULK ACOUSTIC WAVE
In BAW (Quartz Bulk Acoustic Wave), the resonant frequency get dramatically shifted due to the amount of metallization on its surface. This property is utilised for tuning the resonant frequency in a fine manner within the tolerance range. This process of tuning is called mass loading.
SURFACE ACOUSTIC WAVE
In this acoustic wave there is a delay line. If the deposition of the metal occurs in the delay path of this device, there will be increase in delay. When this device is combined with feedback amplifier to form an oscillator then surely there will be decrease in oscillation frequency.
It is a branch of physics which deals with generation, propagation, reception and analysis of sound waves. The following are the important application of acoustics:
• Architectural acoustics
• Biomedical acoustics and also
• Musical acoustics.
Acoustic inheritance determines the similarities between acoustic and electrical systems in an acoustic system which is given as follows:
m= effective mass of the element
This can be applied to Helmholtz resonator and the above equation is modified. There is an analogy between electrical inductance and acoustic inheritance.
Acoustic compliance of acoustic system is defined as the volume displacement produced by applying unit pressure. And there is an analogy between electrical capacitance. Electrical capacitance is also defined as charge produced on a capacitor per unit of applied voltage.
When loudspeaker is radiating sound energy there will be a phase difference of 180. This energy is radiated from the back of vibrating cone. There will be increase in mechanical impedance due to the radiation effect when the loudspeaker is mounted in an infinite baffle. Example: speaker get mounted in the room wall in such a manner that only one face of the room should radiate. If the baffle dimensions are made small...