Metrology for modern hearing assessment and protecting public health from emerging noise sources

Short Name: Ears II, Project Number: 15HLT03
Image showing a Paediatrician performing an ear exam of a young patient
Paediatrician performing an ear exam of a young patient

Innovative methods, devices and insights protecting the hearing of European citizens

Children with disabling hearing loss represent around 2.5% of the world’s population. The hearing of half of these could be preserved through preventative measures, particularly early detection. However, ‘ear stimulators’, used to calibrate audiometric equipment and provide measurement traceability in hearing tests, had only been designed for the adult ear, failing to consider physiological differences or the developing auditory system of children.
Furthermore, calibration methods for hearing tests were based on steady tones but modern techniques utilised short-duration stimuli such as bursts and clicks. Thus, new methodology was required to ensure calibration procedures were applicable to practice methods.

Another important aspect of hearing conservation is preventing exposure to damaging noise from environmental sources. Although procedures and threshold values were standardised for audible sound no standardised methodology was available for airborne infrasound and ultrasound, below and above human hearing respectively. Ultrasound was of particular concern as devices which produce this, such as industrial cutters or hospital equipment, were becoming increasingly prevalent in the workplace. Thus, there was a pressing requirement to determine the effects of inaudible sound on individuals and establish a measurement infrastructure to assess these sources for potential health risk.


Building upon the work of the EMRP project Ears this project developed three new designs for audiometric calibration termed ‘EARS family occluded-ear simulators ‘. Covering the age ranges three months, two years and ages seven to adult, these were evaluated in an inter-comparison exercise at four laboratories and demonstrated excellent reproducibility in performance. A new calibration method was developed for short-duration stimuli, allowing calibration methods to match existing methodology employed in modern hearing assessment.

To understand the effect of infrasound and ultrasound on human physiology neuro-imaging experiments were performed indicating, for the first time, that infrasound could evoke brain responses at barely perceptible levels. In addition, over 200 adults were assessed for sensitivity to low and high frequency sound and comprehensive lifestyle and sound exposure profiles were evaluated. Results indicated that infrasound and ultrasound are associated with different symptoms, pointing towards a potential role in the emergence of adverse reactions to these types of emissions.

Measurements of noise levels and frequency were made in public places using a novel multi-microphone device and contributed to the first authoritative review on ultrasound exposure in public areas. To study occupational exposure to airborne ultrasound two reference workplaces were built simulating industrial conditions. The information obtained was used to draft a new measurement procedure for ultrasound, trialled at nineteen workplaces around Germany containing ultrasound generating machines. This methodology is now used by the German  Institute for Occupational Safety and Health to assess ultrasound levels at workplaces, leading to a higher level of safety in this field.


The new stimulators and calibration procedures established give more relevant and accurate hearing results for children and adults. In addition, the knowledge about the impact of non-audible sound on hearing, mental health and cognitive abilities will help protect EU citizens from the danger to health caused by damaging, excessive public and workplace noise.


Project website
On the Effectiveness of airborne infrasound in eliciting vestibular-evoked myogenic responses

Journal of Low Frequency Noise, Vibration and Active Control

Public exposure to ultrasound and very high-frequency sound in air

The Journal of the Acoustical Society of America

Amplitude Modulation May Be Confused with Infrasound

Acta Acustica united with Acustica

Other Participants
Carl von Ossietzky Universität Oldenburg (Germany)
Deutsche Gesetzliche Unfallversicherung (Germany)
Universitaetsklinikum Hamburg-Eppendorf (Germany)
University College London (United Kingdom)
University of Southampton (United Kingdom)
Univerza v Ljubljani (Slovenia)