1) Highly directional : The higher the frequency is, the better the straightness of the sound wave.
2) Reflection and transmission : The larger the acoustic impedance (Z) difference between the media is, the larger the ultrasonic wave reflection is at the interface; on the contrary, less difference means larger transmittance.
By this feature, after ultrasonic sonar sensor emit the sound wave, wait for it to be reflected back for calculating distance based on the time required.
| Materials |
ρ (kg/m3) |
c (m/s) |
Z (106kg/m2s) |
| air |
1.3 |
330 |
0.00043 |
| water |
1000 |
1500 |
1.5 |
| copper |
7700 |
5850 |
45 |
| rubber |
950 |
1500 |
1.5 |
3) Acoustic matching layer :
It is inserted between the media with different acoustic impedances to increase the transmittance of the ultrasonic wave.
- To increase the transmittance by inserting the junction layer M between media 1 and 2
a). Set the matching material with acoustic impedance ZM to make the identical albedo (r) for the media M-1 and M-2.
b). Set the matching material with acoustic impedance ZM to make the identical albedo (r) for the media M-1 and M-2.
4) Cavitation :
- Refers to the phenomenon in which ultrasonic wave accelerates the liquid, forming bubbles in parts with low pressure.
- Bubbles repeatedly contract and expand through continuous compression and decompression of the ultrasonic wave, grow to the threshold, and explode.
| Bubble Size |
Failure Time |
Generated Temperature |
Generated Pressure |
| Single-digit ㎛ – double-digit ㎛ |
Single-digit ㎲ |
5000 K |
1000 MPa |
Ultrasonic Applications
The ultrasonic wave is used in various areas, including medium transmission, reflection, and energy concentration. Its applications are divided into industrial, medical, and military.
Ultrasonic sonar sensor and Ultrasonic sensor are representative products.
