Hearing Standard Threshold Shift

1
Hearing Standard Threshold Shift
2
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?

3
Abbreviation

• This presentation will use the abbreviation
• STS
• to mean
• Standard Threshold Shift

4
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.

5
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.

6
More Definitions

• dB means decibel, a unit of sound measurement.
  Often called loudness.
• Hz means Hertz, a
• measurement of frequency.
• Often called pitch.

7
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.
8
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.

9
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.
10
The soft sounds are on the top and the loud
sounds are on the bottom.
11
When your graph is filled in, it shows your
hearing sensitivity for different frequencies at
different intensities (at different pitches and
different volumes).
12

• 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.

13
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.
14
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.

15
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.

16
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.

17
Calculation-Example One
2000 Hz 3000 Hz 4000 Hz
2004 Baseline Audiogram dB 5 0 10
2005 Annual Audiogram dB 15 15 30
Shift in hearing dB 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 (101025)/3 45/3
15 The average shift is greater than 10 so the
follow-up procedures to prevent further hearing
loss must be followed.
18
Calculation-Example Two
2000 Hz 3000 Hz 4000 Hz
2004 Baseline Audiogram dB 20 25 30
2005 Annual Audiogram dB 25 25 40
Shift in hearing dB 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. (5010)/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.
19
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.

20
Follow-up Requirements

• The health care professional supervising the
  audiograms must give an opinion as to whether any
  STSs indicate a possible occupational hearing
  loss and if there are any recommendations for
  changes in the hearing
• protection program.

21
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.

22
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.

23
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.

24
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.

25
Follow-up Requirements

• The employer must keep records
• Name and job title of the employee
• Date of audiogram
• Examiners name
• Date of last calibration of audiometer
• Employees most recent noise exposure assessment
• Background sound levels in the audiometric test
  room.

26
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

27

• Thank you for taking the time to learn about
  safety and health and how to prevent future
  injuries and illnesses.