Sound produced above the range of human hearing is called ultrasound. The Ultrasonic transducer is an acoustic sensor. Although ultrasound is usually started at 20 kHz, most Ultrasonic transducer start at 200 kHz depending on their application. Ultrasound is naturally like an audible sound, with a much lower wavelength, better suited to identify glitches. These shorter wavelengths are special because they make ultrasound and Ultrasonic transducer very useful in measuring materials and nondestructive testing. These transducers are the primary components of flow, level and distance sensors and in biomedical, electrical and other ultrasonic applications.

                                                                                   

What's a Ultrasonic transducer?
The Ultrasonic transducer is a very significant and important part of any ultrasound test. Choosing the right sensor for a particular application is a very important thing. Factors including instrument conditions and settings, material characteristics, and coupling conditions also affect test results. The Ultrasonic transducer can be selected by resolution or sensitivity.
Resolution is the ability of a sensor to disconnect two reflectors when they are close together. Sensitivity is introduced as the ability of ultrasonic sensors to detect small defects in materials. Highly damped transducers help to reduce the reflected signal, allowing the transducer to correct faults at close intervals. Manufacturers of transducer systems can provide focused transducers for increased sensitivity and resolution, as well as a variety of polarized ceramic materials and single crystals to change the transducer process. For more information about the Ultrasonic transducer structure, visit here.
The Ultrasonic transducer sends an electrical signal to the target, and when the signal hits an object, it returns to the transducer. In this process, the sensor measures the distance of the target, not the quality of the sound. These transducers use ultrasound to evaluate some variables. It is widely used in many fields. The frequency range of ultrasonic wave is above 20khz. These are usually used to measure distance ge.
A Ultrasonic transducer is a system that generates and receives ultrasonic vibrations. The sensor consists of a wear-resistant plate, an active component and a backing. Active components are piezoelectric or monocrystalline materials that convert electrical energy into ultrasonic energy. It then recycles the ultrasonic energy and converts it into electricity. The electric energy pulse is produced by fault detector and other equipments.
In ultrasonic NDT (non-destructive testing) , the transducer converts electrical energy pulses from the test equipment into mechanical energy of the type of sound waves that move within the test piece. The sound wave from the test piece is converted by the transducer into an electrical energy pulse, which can be executed and described by the test system. In effect, the transducer is used as an ultrasonic speaker and microphone to generate and recover acoustic pulses at frequencies far above human hearing levels.
Type of Ultrasonic transducer
Different types of Ultrasonic transducer can be used depending on key factors such as the arrangement of the piezoelectric crystals, their area and frequency. The most effective types are as follows:
Linear Transducer-in this transducer, the piezoelectric crystal array is linear.
Phased array Ultrasonic transducer -- these are small in area and low in frequency. (the main frequency is 2 Mhz-7 MHz)
Standard transducer-this model is also introduced as a convex transducer. In this type, piezoelectric crystals take a curved shape. These are all great for deep applications.
There are many types of ultrasonic transducers for nondestructive testing, including angular beam transducers, delay line transducers, immersion transducers, contact transducers, and Bicrystal transducers.
The Ultrasonic transducer
A Ultrasonic transducer is a device that produces and receives ultrasonic waves. It consists of three basic components. The performance of each section is described below.
Piezoelectric crystals
The center of the transducer is introduced as the"Active component" of the system. It tolerates sparsity and compression in order to convert electrical energy into ultrasonic energy or vice versa. A fault detector is another device used to generate electrical pulses that are then transmitted to a transducer.
Back Up
It's a very dense substance, and that's pretty basic. The only goal is to monitor vibrations by absorbing energy from the back of the crystal. A highly accurate sensor can be constructed by controlling the acoustic impedance of the crystal backing material. This difference in acoustic impedance can be changed if the backing material changes. This will certainly affect the sensor, as the resolution may change to a higher resolution.
Wear-resistant plate
A wear-resistant plate is arranged in the transducer to support the piezoelectric crystals in different applications. It protects the Ultrasonic transducer from environmental problems, usually wear and corrosion. Wear plates are usually used as acoustic converters between crystals and water, wedges, or delay lines.
How the Ultrasonic transducer works
When an electrical signal is applied to a Ultrasonic transducer, it vibrates in the characteristic frequency range and produces sound waves. These sound waves move, and whenever any obstacle occurs, the sound waves are sent back to the sensor data. Finally, the data is converted to an electrical signal.
Here, the transducer evaluates the time interval between the sending of the sound wave and the acquisition of the echo signal. The ultrasonic sensor emits an ultrasonic pulse at a frequency of 40 kHz that moves through the air. These transducers are more popular than infrared sensors because the Ultrasonic transducer are not affected by black materials, dust, smoke, etc. 
In recent years, the use of micromachined parts instead of the usual solid ceramic plate or composite device has increased. They are tiny piezoelectric ceramic cylinders that are fixed in a epoxy matrix.
Composite components can provide higher bandwidth and sensitivity in many fault detection applications. When it is stimulated by an electrical pulse, this piezoelectric part produces a sound wave, which generates a voltage when it is vibrated by a return signal. This particular element prevents damage to the worn plate or acoustic lens and is supported by a damping material that silences the transducer after the sound pulse is generated. The ultrasonic subassembly is mounted in a housing having an appropriate electrical coupling. All corner beams, delay lines, common contacts and immersion transducers adopt this main model.
The phased probe used in the imaging system can easily integrate multiple individual transducer components into a single design. BIMORPH sensors, commonly used in corrosion inspection systems, differ in that they have different emission and receiving parts, separated by a sound barrier and an integrated delay line, to guide and combine sound energy, not worn plate or lens.