Protecting health through new ultrasound measurements

Occupational health and safety agencies aim to protect workers from excessive levels of noise at the workplace which can damage hearing. Many industrial processes can generate ultrasound which is generally above the range of human hearing. However, ultrasound can be perceived particularly at high sound pressure levels. As no ratified methodology existed to measure ultrasound its effect on humans was not well known, potentially putting the health of workers at risk.


Around 22.6 million people in the EU live with untreated, disabling
hearing loss. As well as its social effects it also costs the European
economy around €185 billion each year, €25 billion more than the
EU budget for 2018. In Germany four to five million workers are
exposed to harmful occupational noise and the German social
accident insurance institutions for industry and the public sector
pay pensions in excess of €100 million annually due to noiseinduced
hearing loss.
To reduce both the social and economic burden they make
thousands of measurements each year for preventative healthcare.
In this they are supported by the Institute for Occupational Safety
and Health of the German Social Accident Insurance (IFA) that,
as well as producing standardization and legislation, provides
relevant workplace training on how to make measurements.
For some time, the IFA had been concerned about the lack of
standardised measurements for airborne ultrasound, which is
sound above the frequency of human hearing (>16 kHz). Despite
the increased proliferation of devices that generate ultrasound,
such as industrial cleaners, welders and voice alarm systems, little
was known about its effect on human health or upon the routine
measurements for audible sound. As accurate measurements of
noise are essential to protect workers there was an urgent need for
improved metrology in this area.


The EMPIR project Metrology for modern hearing assessment and
protecting public health from emerging noise sources developed new
methodologies for measuring levels of occupational ultrasound.
Based on an existing German guideline and the international standard
ISO 9612 for audible sound measurements two laboratory reference
workplaces were established, one at project partner IFA and another
at Germany’s National Metrology Institute, PTB.
Designed to simulate practical measurements the workplaces
were used to perform systematic, three-dimensional, high spatial
resolution scans of the ultrasound field of an ultrasonic welding
machine. This included effects of environmental factors such as
the influence on the field around a person present. From the
results obtained a new measurement procedure for ultrasound
was drafted. This was then applied in field tests at nineteen
workplaces around Germany routinely using eight different types
of ultrasound generating machines. Exposure patterns of various
types of high frequency sound experienced by workers were
then assessed, ranging from single, short, pulses to continuous
ultrasound emissions.


As a result of the EMPIR project the IFA can make accurate
measurements, as well providing training, on ultrasound in
the workplace. In addition, PTB and IFA have developed an
ultrasound level meter for field use along with a suitable testing
and calibration unit for the new device. This meter not only
allows accurate measurements on the levels of audible sound
and ultrasound in a rapid, 10-minute process, it is capable of
extracting faulty values on audible readings caused by ultrasound
interference giving a more reliable measure of the real effect of
noise in the workplace.
As well as providing calibration services for audible equipment,
including microphones for which the measurement range was
extended to 100 kHz, PTB now offers higher-level measurement services for ultrasound. This includes investigating potential
hazards to hearing from complicated ultrasound fields such as
those generated by advanced haptic displays that deliver text
and graphical information using the sense of touch. For the first
time a practical framework for measuring ultrasound has been
established in Europe. Not only will this help reduce the economic
burden of workplace incidents to insurers but, more importantly,
help protect EU citizens from the danger to health caused by
damaging, excessive workplace noise.

New hearing and noise assessments for public health

The EMPIR project Metrology for modern hearing assessment and protecting public health from emerging noise sources developed three new ear simulators for the calibration of audiometric equipment covering the age ranges 3 months to adult. A new calibration method suitable for the shortduration stimuli typically employed in modern hearing assessment was also developed. Two reference workplaces were built to study the effect of occupational exposure to airborne ultrasound. After testing the methodology in real world settings, it now forms part of regular training on the assessment of ultrasound in workplaces in Germany. The physiological mechanisms of perception of infrasound and ultrasound were studied using audiological and neuroimaging. This included investigating the impact of combined infrasound and audible sound, the effect of binaural hearing on loudness of infrasound. The effect of infrasound and ultrasound on brain activity and personality was examined in a well-defined longitudinal study with more than 70 participants. Combined these results will help improve hearing assessment tests for children and have a positive impact on public safety, especial around the area of airborne ultrasound.

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