The Use of Ultrasonic Bone
Conduction to Treat Tinnitus
Josh Vicari
July 23, 2007
What is Tinnitus?
Tinnitus is the perception of sound in the ears when
no external source is present
Typically, it is perceived as a bell-like or ringing tone
however, some people report hearing sounds such as
crickets, music, waves or buzzing
Many people experience this condition at one point in
their lives after events such as concerts however it
usually disappears after 24-48 hours
In severe cases, tinnitus will effect the patient 24
hours a day, seven days a week
Tinnitus Sample
What causes Tinnitus
Tinnitus is usually caused by a head injury, an infection, diseases ranging
from the common cold to diabetes, or exposure to loud sounds such as
gunshots and explosions
It is estimated that in the United States alone, over 36 million people suffer
from tinnitus. Around 10 million of these people have a severe case
It can also be a sign of hearing loss. People who work with loud
equipment, such as power tools, commonly develop the condition
The cochlea contains thousands of tiny hairs which vibrate in response
to sound waves and cells which convert neural signals back into
acoustical vibrations. The sensing cells are connected with the
vibratory cells through a neural feedback loop, which is regulated by
the brain. This loop is normally adjusted just below the onset of selfoscillation, which gives the ear its spectacular sensitivity and
selectivity. If something changes, it's easy for the delicate adjustment
to cross the barrier of oscillation and tinnitus results.
Evidence has been found that the brain reprograms its nerve cells
based on sensory loss. If the brain changes its response as a result of
some hearing loss, then this could be the cause of tinnitus.
Current Tinnitus Treatments
There are many different forms of tinnitus treatments available today for
patients ranging from herbal remedies to cochlear implants
With most methods of treatment, a great deal of time and patience is
required for the therapy to be effective
Bone Conduction
Conduction of sound through the bones of the skull to the inner ear
A transducer is used to convert an electrical signal into mechanical
vibrations
Vibrations are conducted through the skull bones to the cochlea, which
interprets and sends the signal to the brain
Why Use Bone Conduction?
Humans typically cannot hear ultrasound ( > 20 kHz)
through basic air conduction, but can perceive sound
at frequencies up to 108 kHz through bone
conduction
It has been suggested that the reprogramming of the
brain could be reversed with high frequency
stimulation.
Bone conduction has many applications in the
medical and communications industries such as
headphones, hearing aids, cell phones, and
communications systems used in high-noise
environments
The Tests
Used Kyma X and the Capybara 320 to run tests
Kyma X allows us to adjust sound filters and the value of the
ultrasonic frequency
Amplitude Modulation (AM)
Variation of the amplitude
of a carrier wave that is
multiplied (modulated)
with an input signal
When the carrier wave is
modulated with the input
signal, it’s amplitude varies
in the same manner as the
input
AM in Frequency Domain
Frequency components of the input signal
are reproduced at the carrier frequency
The Tests
Live input given to subject in sound booth
Subject wore headphones which gave
clean signal, and a transducer which
delivered processed signal
Objective was to make speech sound as
intelligible and pleasant as possible so that
patients will stay with treatment
The longer a patient undergoes therapy,
the better
What We Tried
Searched for proper filtering algorithms and
appropriate value for carrier
Multiple Carriers at different values – decreased
intelligibility
Placement of Ultrasonic Transducer – depends
on individual
Number of Transducers (one vs. two) – one was
easier to understand; the two transducers
seemed to produce an echo or delay within the
head
Sine Wave vs. Square Wave
“jar”
Carrier Suppression
“twins”
Our Device
The Not-So-Secret Part
References
M. Lenhardt et. al. High Frequency Sound Treatment of Tinnitus.
2001. VCU. 22 July 2007.
<http://www.tinnitus.vcu.edu/Pages/ASA01lay.PDF>.
M. Lenhardt et. al. Human Ultrasonic Speech Perception.
Science. 253, 82-85 (1991).
About Tinnitus. 2007. American Tinnitus Association. 22 July 2007.
<http://www.ata.org/about_tinnitus/>.
M. Lenhardt et. al. Tinnitus Improvement with Ultra-High-Frequency
Vibration Therapy. International Tinnitus Journal. 11, 1, 14-22
(2005).
Acknowledgements
Dr. Martin Lenhardt, mentor
Alan Madsen
Josh Slane
Dr. Allison Johnson and the Howard
Hughes Medical Institute