Download Tuning Fork Testing - Max Stanley Chartrand, Ph.D.

Indiana Jones & the Lost of Art of Tuning Fork Testing
by
Max Stanley Chartrand, Ph.D.
As in an Indiana Jones adventure we search for the lost art of tuning fork testing like that
used before the advent of modern electronic audiometers, impedance audiometry, real ear and
electroacoustic analyzers.
Unearthed, our Adventurer finds deep in the
dusty bins of history a soft leather case containing
six heavy-duty alloy tuning forks that resonate to
the octaves of 128Hz, 256Hz, 512Hz, 1024Hz,
2048Hz, 4096Hz (Figure 1). First proposed in 1550
A.D. by Italian physician Capivacci to determine the
location of hearing disorders, it was not until
Englishman John Shore developed a single tuning
fork for tuning musical instruments at A423.5 cps
that the modern tuning fork took shape. Thereafter,
German physicist Chladni in 1800 developed a set
of forks for testing human hearing.1
This rare artifact is accompanied with a tattered
tutorial2 which speaks of skills and capabilities lost
in the mad rush to modern technology: Weber,
Rinne, Bing, and Schwabach, along with updated
and unique approaches for trouble-shooting and
counseling hearing aid users, such as balancing
binaural hearing aids, ear-training for spatial skills,
and contemporary skills for Transcranial CROS
fittings.
Figure 1. Set of six heavy duty tuning forks.
The forgotten manuscript speaks of a convenient, lightweight, and portable soundfield
system that can be taken anywhere one serves the hearing impaired. It requires no electricity,
set up or maintenance. Illustrations for holding and striking the forks are shown in Figure 2.
In the hands of the skilled clinician, this compact system solves myriad problems that still
exist even with today’s digital technology. Coupled with recent scientific discoveries on the
plasticity of the human brain, revival of an ancient practice promises to offer all hearing
instrument specialists with a modality with which to extend their rehabilitative services.
Journey of Rediscovery
As our intrepid archeologist slogs through the
manuscript in an attempt to decipher precious timeproven test methods, while he pieces together the
following lost tests for the mastery of contemporary
enthusiasts:
Figure 2. Position for striking tuning forks.
 The Weber Test, once upon a time, an important
tuning fork that was once smugly replaced by the
electric bone oscillator, only to fall out of favor in the
face of bruised sinuses, poked out eyes and scraped
foreheads. Its purpose is to detect possible unilateral
conductive involvement in a hearing loss.
With these newly unearthed tuning forks, however, the test is quick and safe: We present a
tone—usually 512Hz and/or 1024Hz—to the frontal sinuses of the forehead, while the recipient
is asked to indicate in which ear they hear the tone the loudest (as shown in Figure 3). If the
tone gravitates to the ear with the worst air-conduction thresholds, a unilateral conductive loss is
indicated and the exam form is marked “Weber Positive”, indicating a conductive involvement in
the loss. If the tone is heard in the ear with the best air-conduction thresholds or heard equally
in the case of symmetrical thresholds, the form is marked “Weber Negative”, meaning that there
is no apparent conductive loss indicated.
As validation for video otoscopy and middle ear assessment, the Weber is a quick qualitative
indication as to whether or not more investigation is needed, or perhaps, whether medical
referral is indicated.

The Rinne Test, a qualitative test for
sensorineural involvement, begins by informing the
patient that a tuning fork will be struck and held about
2” from their ear (Figure 4). When they indicate that
they no longer hear the tone, the tuning fork handle
will be immediately placed over the prominence of the
mastoid bone in back of their ear to see if the tone
returns. If they hear the tone again, there is at least
some conductive component, and the test form is
marked “Rinne Negative”. If the tone does not return,
a sensorineural loss is indicated and the form marked
“Rinne Positive”.

An auxiliary test closely related to the Weber
and Rinne tests is the Bing Test, which is a qualitative
test of bilateral conductive involvement. It is begun by
placing the struck fork handle against the mastoid and
asking the patient to indicate when they no longer
hear the tone. When they indicate the tone has
stopped, the examiner closes their tragus over the
entrance to the external auditory canal (EAC) to see if
the tone comes back. If it does, on either side, there is
no indication of conductive component, marked “Bing
Negative”. Theoretically, the closure (or collapse) of
the EAC should cause an increase of energy
conducted to the cochlea by about 10-14dB (Figure 5).

Probably the most important of skills to be
mastered in tuning fork testing is the Schwabach
Test, which is actually a test of air conduction
thresholds that can be closely correlated onto a
standard audiogram. It is given much like a pure-tone
test is normally given, except that instructions and
procedure is slightly different. Since the calibrator is
an ear with normal hearing it is imperative to have one
whose thresholds are normal (i.e., close to
audiometric zero) standing beside the patient so that
when the patient no longer hears the tone at 2” from
the EAC, the fork is moved to a similar position to the
calibrator ear and the number of seconds counted
while the tone is still heard (Figure 6).
Depending upon the fork’s decay rate (shown in
Figure 7), the number of seconds heard by the
calibrator is multiplied by the rate of decay (i.e., 2.5dB
per second for the 1024 Hz fork) to determine the
Figure 3. Position for Weber test.
Figure 4. Positions for Rinne Test.
Figure 5. The Bing test begins with struck
fork held against mastoid. When the tone is
no longer heard, the examiner closes the
canal entrance to see if tone is heard again.
estimated threshold. So that if the calibrator ear heard
the tone, in our hypothetical example, for 15 seconds,
the approximate air-conduction threshold would be
32.5dBHL.
The test is begun by instructing the patient to listen
to a struck fork at the distance of 3’ from their ear and
to indicate when they no longer hear the tone. Then,
the fork is moved to within 2” of the EAC to see how
long they hear it at that distance. When they no longer
hear the tone, the fork is shifted over to the calibrator’s
ear and the seconds counted until they no longer hear
the tone. The results are recorded and the procedure
is repeated for the desired frequencies (generally
done only with 512Hz, 1024Hz, 2048Hz and 4096Hz.
If presented properly and ambient noise is
sufficiently low enough (<70dBC), the results should
be within +/- 5dB of the audiometer readings. In
today’s examination regiment, the most practical uses
for the Schwabach are 1) a quick and easy way to
take unaided-aided soundfield relative comparisons,
2) a demonstration for third parties who otherwise
might not realize the extent of the patient’s loss, and
3) in a pinch, can be used as a threshold screening
method until a more accurate audiometric reading can
be taken. Note: In case of soundfield testing, be sure
to test unaided before measuring aided thresholds.
Special Tuning Fork Tests
Next, we find tuning fork tests that are important to
auditory rehabilitation and trouble-shooting of hearing
aids. One test involves simply striking a fork at 3’ to
balance binaural hearing aid fittings, while others
involve clicking tuning fork handles as methodology in
training of spatial functions and integration. More
relevant to today’s rehabilitative needs, these tests
prove invaluable in the delivery of new hearing aids,
regardless of how advanced they are. They are:
 Balancing Binaural Fittings: There is no
better way to balance the VCs (user-adjusted or
computer programmed) than by using the discrete
signal of a I024 Hz tuning fork tone.3,4 First set the
VC of one side of a binaural fitting to a comfortable
level with user’s voice at normal levels (not yours).
Then, turn up the other side until it sounds about
the same. Let the user know that you will be
striking a 1024 Hz tuning fork and holding it about
3’ feet azimuth (directly in front of them). They are
to note in which ear they hear the tone the loudest,
turning down that side slightly until the tone is
heard the same in both ears (without any
movement of their head). The reason for turning
down the side that is loudest is because of
binaural summation of approximately 6-8dB when
Figure 6. Positions for Schwabach
threshold testing, also used for unaidedaided soundfield frequency-specific testing.
Time/Decibel Chart
(In ambient environment <70dBC)
Fork (Hz)
Decay Rate
(dBHL per second)
512
1024
2048
4096
1.25dB
2.5dB
5.0dB
10.0dB
Figure 7. Relative decay rate chart for tuning
forks that is used in Schwabach and soundfield
testing.
Figure 8. Use the 1024Hz or 2048Hz tuning forks at
3’ azimuth for balancing VCs in binaural fittings.
the signal is heard binaurally.5 In high frequency
(open ear) cases, the 2048 Hz fork may be a
better choice. See Figure 8.
 Ear-Training for Spatial Mapping: For many
new hearing aid users development of spatial
ability is an automatic occurrence. The auditory
cortex, through the central auditory apparatus,
develops a unified spatial map utilizing two
hemispheres of the brain. To train both depth
perception and localization (only two dimensions of
spatial mapping), you instruct the patient that you
Figure 9. Using tuning fork handle clicks, spatial
will be clicking the handles of two tuning forks and
mapping (localization and depth perception) may
sweeping from side to side at about 3’ from their
be developed by sweeping from side to side until
head. They are to close their eyes and using only
midline is transparent. A similar procedure is
one hand, point toward the clicking. They are to
used also for adjusting and training for
Transcranial fitting cases.
stay right with the “clicks”, regardless how lost they
may become at first (see Figure 9).
In new users, especially where there are disparities between hearing thresholds, they will
typically have difficulty finding “midline” or that point where one cortical hemisphere “let’s go”
of a signal and “hands it off” to the other hemisphere. In such cases they will hesitate at
midline and when the clicking has moved well toward the other ear they will “run to catch
up”. By sweeping steady clicks back and forth, they will eventually achieve binaural
integration in which case they will be able to stay with the clicking even at midline. This
function is vitally important for users to enjoy the wider bandwidth responses in today’s
digital instruments, and to become more secure with their sound environment. Most cases
will require ten or more sweeps before they develop a solid spatial map.
 Ear-Training for Transcranial (Internal CROS) fittings: An effective alternative to
traditional CROS fitting configuration is the Transcranial Method developed by this author
and others over many years.5 It involves the fitting of an essentially “dead” ear so that the
tactile perception of that ear will coincide with the auditory perception of the normal ear.
Also, using an interaural attenuation chart, we can predict about how much sound from the
amplified ear will reach the other (unamplified) cochlea via a common temporal bone. An
important benefit of such fittings is the elimination of the “head shadow effect” that typically
plagues one-eared individuals, and also activation to some extent of their bilateral central
auditory functions. A more complete protocol for this type of fitting may be found in
Chartrand (1991).5 In short, tuning fork handle clicks are used much in the same way as the
spatial mapping exercise described above (see Figure 9).
In Summary
Admittedly, tuning forks are an everyday part of the otolaryngological regimen. But these
same skills plus some newer, more valuable ones, have been lost in everyday hearing
instrument dispensing.
Unearthing and acquiring skills of the lost art of tuning fork testing can serve a valuable
purpose as a screening protocol. Such skills can inspire confidence in patients seeking answers
to difficult-to-describe complaints. They can provide additional tools of measurement and
verification, and lay a foundation for more effective hearing instrument counseling.
This lost art can bring back into the armamentarium of the professional dispenser a measure
of creativity, imagination and resourcefulness into the art and science of hearing instrument
dispensing. These skills, coupled with recent advancements in digital hearing aid technology,
can go far in achieving greater fitting and post-fitting success for the recipient of our resurrected
skills, the hearing impaired hearing aid users we serve.
Max Stanley Chartrand, Ph.D. (Behavioral Medicine) serves as
Managing Director at DigiCare Hearing Research & Rehabilitation
and as Adjunct faculty for Northcentral University. He has been
involved in training hearing health professionals for many years and
publishes and lectures widely on topics of hearing healthcare. He
may be contacted at: www.digicare.org or by calling (719)676-3277.
References
1. Feldmann, H. (1997). History of the Tuning Fork. Laryngorehinootologie, 76(2): 116-122.
2. Chartrand, M.S. (2003). The Lost Art of Tuning Fork Testing. Colorado City, CO: DigiCare Hearing Research &
Rehabilitation.
3. Chartrand, M.S. (2001). In Vigorous Defense of Volume Control. The Hearing Professional, May-June, pp. 9-11.
4. Chartrand, M.S. (2003). Another Elephant in the Living Room: To VC or Not to VC. The Hearing Review, March.
5. Chartrand, M.S. (1999). Hearing Instrument Counseling: Practical Applications for Counseling the Hearing
Impaired, 2nd Edition. Livonia, MI: international Institute for Hearing Instruments Studies, pp. 61-66, 144-145.
6. Chartrand, M.S. (1991). Transcranial or Internal CROS Fittings: Evaluation and Validation Protocol. Hearing
Journal, 44(9): 24-28.