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

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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 Powered By Docstoc
					Hearing Standard Threshold Shift
           You Will Learn

• What is a Standard Threshold Shift?

• How is a Standard Threshold Shift

• What is an employer required to do
  in Washington State?

This presentation will use the
          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

• Over time, with enough
  threshold shift, a person will
  have great deal of trouble
  understanding speech.

• 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

• 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
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
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
         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   3000 Hz   4000 Hz

           2004 Baseline           5         0         10
           Audiogram          dB
           2005 Annual             15        15        30
           Audiogram          dB
           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:
(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   3000 Hz   4000 Hz

          2004 Baseline           20        25        30
          Audiogram          dB
          2005 Annual             25        25        40
          Audiogram          dB
          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.

(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.
  – 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
  – 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
      Follow-up Requirements

• The employer must keep the
  baseline audiogram without revision,
  unless a qualified reviewer
  – The STS is persistent
  – The hearing shown in the annual
    audiogram indicates significant
    improvement over the baseline
      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
  – Background sound levels in the
    audiometric test room.

• 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

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