Bo Håkansson shows a bone conduction vibrator
​Bo Håkansson shows the small, specially developed vibrator that the Chalmers researchers designed for medical examinations of the balance organ in patients suffering from dizziness.​​​​​​​​

Bone conduction improves diagnosis of dizziness

​Researchers at Chalmers University of Technology have developed a test method that can be used to diagnose symptoms of dizziness more accurately, also giving the patient less discomfort. The results are very promising and several patient studies are now underway, using a specially designed vibrator to test the function of the balance system via bone conduction of vibrations through the skull.
Dizziness is one of the most common reasons why, not least, older people urgently seek medical attention. More than half of all over the age of 65 suffer from health problems related to dizziness at some point.

“This is a new research field that is emerging”, says Bo Håkansson, Professor in Biomedical Engineering at the Department of Electrical Engineering at Chalmers. “The Promobilia foundation has recently granted us SEK 400 000 in a two-year funding period, which enables us to pursue further studies on different kinds of patients. Healthcare as well as academia show a great interest in our results. We are collaborating mainly with the ear clinics at Sahlgrenska University Hospital in Gothenburg and the Karolinska Institute in Stockholm, and also with the University Hospital in Halle, Germany.”

Boneconduction testHearing and balance are related 
Since hearing and balance are closely connected, sound can be used to diagnose diseases in the balance system of the body. The method is called VEMP, Vestibular Evoked Myogenic Potential. The mechanical vibrators used for VEMP tests in healthcare today, are either too weak or too large and cumbersome.

“We realised that there simply was no equipment available, directly adapted for this type of tests of the balance organ”, says Bo Håkansson. “The vibrator we have designed is small and compact in size. The sound vibrator is attached with a headset behind the patient's ear. It is optimised to provide a high sound level at frequencies as low as 250 Hz, a frequency we found to be favourable for bone conduction VEMP testing. Therefore, we call it B250.”

Improved results using bone conduction
The Chalmers researchers have shown that better results from VEMP tests can be obtained by using bone conduction technology rather than air conducted sounds – the most common method until now.

“Our method also works on children, and it allows patients with a mechanically impaired hearing function to perform the test successfully”, says Bo Håkansson.

A first pilot study was conducted in 2018, and a second patient study in collaboration with Sahlgrenska University Hospital has recently been completed, which included 30 healthy participants with normal hearing.

“The results collected from the healthy and normal-hearing patient group fully support our previous results. This confirms that the method we propose can provide safer test results, and also avoid that patients need to undergo tests that risk damaging their hearing.”

The researchers aim at introducing the B250 as a standardised diagnostic method for VEMP testing of patients suffering from dizziness. The conditions are good for this to become a reality in a not too distant future.

“We are collaborating with the Danish company Ortofon, that manufactures the vibrator prototypes used in our patient studies. Ortofon is planning to make the device commercially available as soon as the necessary specifications have been settled – hopefully within the coming year”, says Bo Håkansson.

More about the research – this is how it works
In patients with dizziness, sound is used to diagnose diseases that originates from the balance system. The sound triggers a reflex that gives a muscle signal (Vestibular Evoked Myogenic Potential, VEMP) from the neck muscle (electrode shown in the picture) and the oblique eye muscle respectively, which gives different responses depending on the patient's underlying problem. The test can be performed either by emitting a loud air-conducted sound in the ear canal, or by using a mechanical sound conducted through the bones of the skull. The disadvantage of using air-conducted sound is that the volume must be so loud that the patient's hearing is at risk of damage. It can be compared to having a machine gun going off next to the ear, since the test procedure is repeated many times to obtain stable results by averaging.​
test for dizzinesss










The method introduced by the Chalmers researchers, which is based on bone conduction hearing via a specially designed vibrator placed against the skull, has several advantages. The noise levels to which patients are exposed can be kept much lower, which makes the test procedure more pleasant and harmless. The new vibrating device provides a maximum sound level of 75 decibels, and the test can be performed at up to a 40 decibels lower level than today's method using air-conducted sounds. There is thus no risk that the test itself could cause hearing damage.

The benefits also include safer testing for children, and that patients with mechanically impaired hearing function, due to chronic ear infections or congenital malformations in the ear canal and middle ear, can be diagnosed for the origin of their dizziness in a VEMP test.


Text: Yvonne Jonsson
Photo: Johan Bodell (photo on top) and Henrik Sandsjö (other photos)


Read more
New innovation improves the diagnosis of dizziness, news article in connection with the researchers’ publication of a scientific article in the journal Medical Devices: Evidence and Research, autumn 2018.

The research is funded by the Promobilia foundation
The aim of Promobilia is to promote the development of technical aids so that disabled persons could benefit of a more active life. The foundation supports research and development of technical aids as well as ensures they get into production and reach those in need.

For more information, contact
Bo Håkansson, Professor in Biomedical Engineering at the Department of Electrical Engineering at Chalmers, boh@chalmers.se
Karl-Johan Fredén Jansson, Researcher at the Department of Electrical Engineering at Chalmers, karljohf@chalmers.se
Sabine Reinfeldt, Associate Professor and Head of the unit Biomedical Signals and Systems, Department of Electrical Engineering at Chalmers, sabine.reinfeldt@chalmers.se
Måns Eeg-Olofsson, Associate Professor, medically responsible at the ENT clinic, Sahlgrenska University Hospital, 

Published: Thu 27 Aug 2020.