Transcript Hearing Standard Threshold Shift

Hearing Standard Threshold Shift
You Will Learn
• What is a Standard Threshold Shift?
• How is a Standard Threshold Shift
calculated?
• What is an employer required to do
in Washington State?
Abbreviation
This presentation will use the
abbreviation
“STS”
to mean
“Standard Threshold Shift”
What Is A Standard Threshold Shift?
• A Standard Threshold Shift
(STS) is a significant change
in hearing ability (a hearing
loss).
• Over time, with enough
threshold shift, a person will
have great deal of trouble
understanding speech.
Definition
• The Standard Threshold Shift
definition in the Hearing Loss
Prevention Rule, WAC 296-817 is:
– “A hearing level change, relative to the
baseline audiogram, of an average of 10
dB or more at 2000, 3000, and 4000 Hz
in either ear.”
More Definitions
• dB means “decibel”, a unit of sound
measurement. Often called
“loudness”.
• Hz means “Hertz”, a
measurement of frequency.
Often called “pitch”.
What Is An Audiogram?
• Before being first exposed to
excessive noise, an employer is
required to provide hearing tests or
audiograms to employees, which is
called a “baseline”.
• Subsequent hearing tests are
compared to the original baseline
audiogram.
Note: Employers who use mobile testing units are allowed up to one
year to obtain a valid baseline audiogram for each exposed employee.
The employee must still be given training and hearing protection.
What Is An Audiogram?
• An audiogram is a picture or graph
of a hearing test.
• It measures the quietest sounds you
can hear at different frequencies.
The graph, or audiogram, is laid out like a
piano keyboard, with low to high frequencies
(low to high pitches) going from left to right.
The soft sounds are on the top and
the loud sounds are on the bottom.
When your graph is filled in, it shows your
hearing sensitivity for different frequencies
at different intensities (at different pitches
and different volumes).
This audiogram
shows a person
with relatively
normal hearing.
Normal hearing is
defined as a
hearing threshold
between 10 and 25
decibels. In other
words, the person
can hear the softest
sounds.
This graph only
shows one ear.
The hearing loss shown
in this audiogram is in
the higher frequencies
which is commonly
caused by exposure to
workplace noise.
This person can only
hear loud sounds at the
higher frequencies.
An “X” is for the left
ear, and an “O” is for
the right ear.
Audiograms and STS
Although the
audiogram usually
measures frequencies
between 125 and
8000 Hz, only the
2000, 3000 and 4000
frequencies are used
to calculate a
Standard Threshold
Shift.
Calculation of STS
• When you have an annual re-test, or
subsequent audiogram, the health
care professional will compare the
results of the baseline test with the
new hearing test.
• The annual hearing test can be
conducted during the work shift
while you are experiencing typical
workplace noise exposure.
Calculation of STS
• The health care professional will look
at your test results for the 2000,
3000 and 4000 Hz frequencies.
• A change in these three frequencies
that averages 10 db or more, in
either ear, is called a Standard
Threshold Shift.
Calculation-Example One
2000 Hz
2004 Baseline
Audiogram
dB
2005 Annual
Audiogram
dB
Shift in hearing
dB
3000 Hz
4000 Hz
5
0
10
15
15
30
10
15
20
The table shows an excerpt from a baseline audiogram and an annual
audiogram. It includes results from just one ear and only the
frequencies used to calculate the STS.
The STS is calculated by adding the “Shift in Hearing” results and
averaging. Thus:
(10+10+25)/3 = 45/3 = 15
The average shift is greater than 10 so the follow-up procedures to
prevent further hearing loss must be followed.
Calculation-Example Two
2000 Hz
2004 Baseline
Audiogram
dB
2005 Annual
Audiogram
dB
Shift in hearing
dB
3000 Hz
4000 Hz
20
25
30
25
25
40
5
0
10
The baseline audiogram shows a person with an existing mild hearing
loss. The annual audiogram shows a change in hearing ability, but not
enough to be a Standard Threshold Shift.
(5+0+10)/3 = 15/3 = 5
Although the hearing change is not enough to have a Standard
Threshold Shift, there has been a 10 dB change at 4000 Hz, the most
likely frequency to be damaged by workplace noise. It would be a good
idea for the employer to re-evaluate the noise protection program for
this employee to prevent further hearing loss.
Follow-up Requirements
• If a STS has occurred:
– The employee must be informed of the
decrease or improvement in your
hearing, in writing, within 21 days.
AND
– The audiogram must be reviewed by an
audiologist, otolaryngologist, or other
qualified physician.
Follow-up Requirements
• The health care professional
supervising the audiograms must
give an opinion as to whether any
STS’s indicate a possible
occupational hearing loss and if there
are any recommendations for
changes in the hearing
protection program.
Follow-up Requirements
• A re-test can be ordered, within 30
days of the test that showed a STS.
• The re-test can then be considered
an annual audiogram.
Follow-up Requirements
• The employer must pay for any
clinical audiological evaluation or
otological exam required by the
reviewer if:
– Additional review is necessary to
evaluate the cause of hearing loss
OR
– There is indication of a medical
condition caused or aggravated by the
use of hearing protectors.
Follow-up Requirements
• The audiogram reviewer must
communicate to the employee
any suspected medical conditions
that are found that are unrelated
to the workplace.
• This information is confidential
between the reviewer and the
employee.
Follow-up Requirements
• The employer must keep the baseline
audiogram without revision, unless a
qualified reviewer determines:
– The STS is persistent
OR
– The hearing shown in the annual
audiogram indicates significant
improvement over the baseline
audiogram.
Follow-up Requirements
• The employer must keep records:
– Name and job title of the employee
– Date of audiogram
– Examiner’s name
– Date of last calibration of audiometer
– Employee’s most recent noise exposure
assessment
– Background sound levels in the
audiometric test room.
Resources
• Hearing Loss Prevention Rule
Chapter 296-817 WAC
• Noise Audits Training Kit
• Hearing Protection Training Kit
• On-Line Course for Noise
• Library of safety videos
• Noise Reduction Ideas Bank
Thank you for taking the time to
learn about safety and health and
how to prevent future injuries and
illnesses.