## 2 Ultrasound Generation  
Devices for generating ultrasonic waves consist of three basic elements:  
- An electrical power generator;  
- A transducer(s);  
- An emitter. The electric generator is the source of energy for the ultrasonic system, which must supply the transducer. In general, the electric generator produces an electric current of a certain rated power. Its task is to convert alternating current with a frequency of 50 Hz or 60 Hz into alternating current with the desired frequency, usually from 20 kHz to 40 kHz. Most generators allow the power to be set indirectly by setting the voltage (V) and current (I). The transducer is the central element of each ultrasonic device, and its role is to generate ultrasonic waves. The transducer converts electrical energy into mechanical vibrations at ultrasonic frequencies. The transducer converts, for example, 20 kHz electrical energy from the generator into 20 kHz mechanical vibrations. The aim of the emitter, called a reactor by some and an ultrasonic cell by others, is to radiate an ultrasonic wave from the transducer to the medium. Emitters can also act as an amplification of ultrasonic vibrations during their emission. The two primary types of lab apparatus in the food industry are:  
- An ultrasonic cleaning bath;  
- A probe system. **Ultrasonic cleaning bath**  
The ultrasonic cleaner, also known as an ultrasonic bath, is a special device used for cleaning and sanitation in beverage processing operations. It consists of the following elements (Figure 1):  
Tank: This is the main part of the ultrasonic cleaner, and is usually made of stainless steel or another chemical-resistant material. The tank has the shape of a bathtub and serves as a working chamber in which the sonication process is carried out. It is available in various sizes to accommodate different object sizes. Power source with an electric generator: This converts an electric current of typical frequency into an electric current of ultrasonic frequency and delivers it to the transducer. Transducer: This is the heart of the system. This element converts electrical energy into ultrasonic waves. This is the piezoelectric element attached to the bottom or sides of the tank. The transducer generates high-frequency ultrasonic waves, which create alternating high-pressure and low-pressure zones in the liquid. Heater: Some ultrasonic baths include a heating element to warm the liquid. This maintains the cleaning solution at an elevated temperature, which can enhance the effectivity of process for certain applications. Timer: most ultrasonic baths come equipped with a timer that allows the duration of the cleaning cycle to be set. Drain valve: a drain valve is positioned at the bottom of the tank for easy removal of used liquid once the treatment cycle is complete. Lid: many models come with a removable or hinged lid to prevent solution evaporation and to reduce noise generated by the ultrasonic waves. Fan: A cooling fan may be installed on some models to prevent overheating during extended work cycles. Control panel: on the control panel, the user can adjust the settings of the washer, such as time, treatment temperature and other options. **Advances in ultrasonic bath technology**  
In the construction and operation of ultrasonic cleaners, several new trends and innovations can be noticed, which are aimed at improving efficiency, precision and comfort of use. Additional features include, among others:  
1. The ability to choose the frequency of ultrasonic vibrations of two 25/45 or 35/130 kHz, or even three 45-80-100 [8];
2. Work at two different ultrasound frequencies simultaneously. The ultrasonic cleaner comprises two types of ultrasonic transducers operating at two equal resonance frequencies, for example, 25 and 40 kHz, which are attached on the bottom and the side, respectively. The result is uniform ultrasonic power distribution [9];
3. Power regulation: the ultrasonic power ranges from 10 to 100% of the total power;
4.