This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.
|European Metrology Programme for Innovation and Research (EMPIR)
|Metrology for modern hearing assessment and protecting public health from emerging noise sources
This project concerns two aspects of hearing assessment and conservation; the further development of the next generation of ear simulators that will provide measurement traceability for hearing tests on adults, children and neonates, and improvement in our understanding of human response to infrasound and ultrasound, including novel assessment methods for potential health risks.
Virtually everyone will have their hearing tested at stages throughout their life. It is essential for effective diagnosis that these tests are accurate and quality assured. Ear simulators provide the basis for measurement traceability, but in the past have been designed for adults only. The EMRP HLT01 EARS project made the first significant steps at specifying ear simulators for other age groups, and produced a prototype neonatal ear simulator. However the concept of a universal ear simulator needs further refinement and extending to cover all forms of audiological testing, before it can be adopted into clinical practice. One specific aspect is that new methods for transient calibration are needed, to replace the current, technically flawed methods. The move to the next generation of ear simulators is the ideal time to introduce new improved calibration methods for transient stimuli.
Another aspect of hearing conservation concerns environmental and industrial exposure to noise which represents a major public and occupational health issue. With urbanisation and industrial innovation often come undesirable consequences such as new types of noise hazard from infrasound and airborne ultrasound. Greater understanding of the human perception mechanisms is needed in order to tackle the risks posed by this emerging noise. Due to the inaudible nature of some of these noise sources, a multi-disciplinary approach is needed combining neuro-imaging and advanced audiological investigations. Alongside the development of this understanding, new methods and instrumentation are needed to measure and assess noise sources in both public and workplace environments.
The overall objective of this project is the improvement and further development of strategies and methods of metrology and calibration for hearing assessment, hearing diagnosis and safety. The specific objectives of the project are:
- To finalise the universal ear simulator concept to fulfil the whole range of audiological requirements for traceability to sound pressure, including the development of an alternative approach to transient calibration based on impulse response and adaptors for the most common devices. A demonstrator will be realised for the novel ear simulator.
- To generate robust normative reference threshold data (transfer and input impedance), calibrate devices across partners, quantify the degree of equivalence with currently established practices and provide a user guide summarising features, calibration and handling for application of the novel ear simulator in practice.
- To exploit neuro-imaging and audiology to further develop understanding of perception as well as response and loudness thresholds for ultrasound (16 kHz – 80 kHz), infrasound (4 Hz – 16 Hz), and the influence of infrasound on sound within the normal hearing range; together with the development of instrumentation and measurement methods for the determination of noise and its hazards in those frequency ranges in both public and workplace environments.
- To determine experimentally the impact of infrasound and ultrasound on hearing, mental health, cognitive abilities and general wellbeing, and their contribution to annoyance and loudness, including the study of individuals with particular sensitivity to noise.
- To engage and work closely with stakeholders to establish the clinical protocols and international standards proposals for the use of the universal ear simulators in the calibration of audiometric equipment used for hearing assessment and hearing aid fitting for both children and adults; and to create the knowledge for future guidelines and policy framework to enhance the wellbeing of European citizens and protect them from health hazards associated with infrasound and ultrasound.
Progress beyond the state of the art
Having produced and tested a prototype of an ear simulator for neonates in the EMRP EARS project, this project will develop the concept further to become practically viable for all age ranges. This includes a reduction in the number of different designs, in conjunction with alternative criteria for matching the ear simulator to the patient, and an extension to allow the coupling of circumaural and supra-aural headphones.
Separately, the project will develop an innovative approach to the calibration of audiological transducers for transient stimuli, based on the impulse response of the ear simulator. Starting from the selection and characterisation of short-duration stimuli based on properties of the auditory system, novel methods for determining the impulse response of the ear simulator will be investigated and form the basis for a new calibration strategy for the transducer under test. Together these elements represent a significant departure from established practice and mark the first attempt to improve on the flawed method currently specified in international standards.
The EARS project developed the first primary measurement standard for airborne ultrasound measurements and made first attempts to develop exposure measurement techniques for use in laboratories. This project will design, assemble and validate practical ultrasound measurement devices and components.
Results of the EARS project showed that infrasound leads to a hearing sensation and indications exist that an emotional response is activated in brain. This project will pursue these findings further with new more comprehensive study designs including other indicator modalities as frequency-following techniques in magnetoencephalography (MEG).