Acoustic energy of airborne ultrasounds can penetrate into the human body via the hearing organ and through the whole body. In rare cases low-frequency ultrasounds can penetrate into human body  even if they are not airborne, for example through direct contact with source of ultrasound.

 

By reaching the body ultrasonic noise may adverse impact on the state and functioning of not only hearing organ but also other organs and systems of the human body (including vestibular organ, cardiovascular system, nervous system).

 

Determining influence of ultrasonic noise on hearing is hard because of accompanying him most often in industrial conditions audible noise. This makes it difficult to distinguish between the effects of these two types of noise. The results of the research conducted so far presented in the literature on the subject, including those analyzed and discussed in [Pawlaczyk-Łuszczyńska M., Koton J., Śliwińska-Kowalska M., Augustyńska D., Kameduła M., Hałas ultradźwiękowy. Dokumentacja proponowanych wartości dopuszczalnych poziomów narażenia zawodowego (Ultrasonic noise. Documentation of the proposed occupational exposure limit values), Podstawy i Metody Oceny Środowiska Pracy, 2001, 2(28), pp. 55-88.] shows the presence of auditory effects of ultrasonic noise on humans. This phenomenon occurs despite the fact that the components of ultrasonic noise with frequencies above 16-20 kHz do not cause auditory sensations in humans. This is believed to be due to nonlinear phenomena in the ear structures and the resulting subharmonic ultrasonic components (that is, sounds with frequencies that are a fraction of the ultrasonic component frequency).

 

There are also reports evidencing negative effects of ultrasounds on the vestibule organ in the inner ear  that can manifest themselves in,: headache and dizziness, pressure in the temples, disorders of the sense of balance, nausea, tiredness. In the publications on the research on the effects of the extra-auditory impact of ultrasonic noise on the human body, functional changes of a vegetative-vascular nature are also discussed. (effect on nervous and cardiovascular system).