Dynamics of high-frequency hearing loss of operators of industrial ultrasonic devices

Abstract

This investigation was aimed at elucidating the dynamics of hearing loss in the range of 500 Hz to 20 kHz of 26 Ultrasonic (Uls)-operators exposed to high-frequency noise exceeding known hygienic limits. Results of audiometric tests performed twice, before and after a period of three years, were compared. The determined hearing-threshold-shift in the range of 500 Hz to 13 kHz could be explained as the effect of aging, whereas in the range of 13 to 17 kHz the stated mean threshold elevation of 2-5 dB, beyond the hearing loss connected with aging within three years, is the consequence of high-frequency noise exposure. On this basis the dynamics of high-frequency hearing loss of 1 dB/year in the case of continued exposure to high-frequency noise could be calculated. Apart from the observed threshold elevation, the fraction of ears responding to acoustic stimuli at the highest frequencies decreases by about 10% with frequency increase of 1 kHz in the range of 13 to 19 kHz. This indicates that the hearing organ is more susceptible to high-frequency noise at the highest hearing frequencies.

Are some people suffering as a result of increasing mass exposure of the public to ultrasound in air?

“…All ultrasound emissions were accompanied by subharmonics produced in the audible high-frequency range as by-products of industrial ultrasonic processes'. Maccà et al [110] found correlations that indicated adverse effects on hearing from those who had worked with ultrasonic devices, in agreement with earlier studies [111][112][113], but hoped to separate out the effect of the audio frequency noise that accompanies most occupational exposures to industrial ultrasound of the type described above. Their findings are plotted in figure 7.…”

“…These conclusions were drawn by looking at averages of the cohort [114], whereas in a companion paper [115] Grezsik & Pluta returned to the factory they examined in 1983 [111] and tested again the 26 workers out of the original 55 who were still employed by the factory, using the same methods they employed in 1983. This enabled them to compare the effect of 3 years of additional industrial exposure on individuals, and they detected an additional hearing loss (over and above ageing) of 1 dB per year in the range 14-17 kHz for workers with prolonged exposure.…”

Effects of Ultrasonic Noise on the Human Body—A Bibliographic Review

“…Furthermore, the age of study participants and the potential presence of chemical factors in the working environment are also important. Nevertheless, some reports indicated that components with ultrasonic frequencies may cause sound sensations associated with hearing defects within the high frequency range, which audiometric tests do not always taken into account [15,20]. Subjective symptoms like headache and dizziness, tinnitus, balance disturbances and nausea are typical for workers exposed to ultrasounds of low frequencies.…”

“…According to Parrack, TTS of 8-18 kHz resulted from a short-term exposure to signals of 17-37 kHz and intensity of 148-154 dB [14]. In their environmental studies, Grzesik and Pluta observed NIHL at 13-17 kHz in workers exposed to ultrasonic noise over several years of work with washers and welding machines at level exceeding 80 dB [15]. They also reported that high-frequency hearing loss would aggravate at a rate of 1 dB per year of work in workers exposed to noise emitted by those machines.…”

“…Most countries assess ultrasonic noise by measuring equivalent sound pressure level in one-third-octave bands referred to 8-h noise exposure at workstations [2]. France determines admissible values of ultrasonic noise and recommends limiting noise exposure in the high audible frequency range (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) and the low-frequency ultrasonic range (20-50 kHz). In Poland, ultrasonic noise is assumed, for practical reasons, as noise whose spectrum includes high audible and low ultrasonic frequencies (i.e., 10-40 kHz) [3].…”