Audiometric Testing

Audiometric testing meaures how well a worker can hear and documents any hearing loss.

Description:

Audiometric testing measures and documents hearing and hearing loss.  The person being tested sits in a quiet environment, usually a soundproof booth, and uses a pair of headphones to listen to a series of tones of alternating volume and pitch.  The person being tested presses a button or signals as soon as they are able to hear a tone, no matter how faintly. After the person has responded to a variety of tones, the information is compiled and presented in an audiogram, a table that shows a person’s degree of hearing loss across several pitches, or frequencies.  Because the human ear is better at hearing lower frequencies (a deep rumble is easier to hear than an extremely high-pitched whistle), the degree of hearing loss usually increases as the frequency (measured in Hertz, or Hz) of the sound gets higher. A person with excellent hearing can usually hear sounds between 20 and 20,000 Hz, although human speech normally stays between 500 and 5000 Hz. A standard audiogram will show the degree of hearing loss from 250 Hz to 8000 Hz, measured as the increase in volume needed for the person to hear the sound compared to a person with normal hearing.

Figure 1 below shows a sample audiogram for a person with normal hearing at the lowest frequency, and severe hearing loss at the highest frequency.  This is a common pattern in people with age-related hearing loss.
 
Figure 1. Source: www.terracehearing.com
 
The x-axis along the bottom of the audiogram shows the frequency, or pitch, in Hz.  The y-axis along the left-hand side shows a range of volumes, measured in decibels (dB), and ranges from very soft (-10) to extremely loud (120).  The red circles show results for the right ear, and the blue x’s show results for the left.  
 
The audiogram in Figure 1 tells us that in their right ear, the person who was tested can hear sounds as low as about 15 decibels when they are played at 250 Hz. At this frequency, their hearing is in the normal range.  However, as the frequency increases, the audiogram shows increasing hearing loss.  At 2000 Hz, the person’s right ear cannot hear sounds lower than about 40 decibels, representing mild to moderate hearing loss.  At 8000 Hz, the person’s right ear cannot hear sounds lower than about 75 decibels, representing severe hearing loss.
 
Figure 2 below shows a different audiogram with a "notch" around 4000 Hz, a typical pattern for people with noise-induced hearing loss. 
 
 
Figure 2. Source: Thais C. Morata via researchgate.net
 
In this case, in their right ear, the person being tested cannot hear sounds softer than about 63 dB at 4000 Hz.  The lowest sound a person can hear at a given frequency is considered their auditory threshold. A healthy person with no hearing loss usually has a threshold of about 0 decibels across all frequencies.  In Figure 2, at 4000 Hz, the person’s threshold has shifted to about 60 decibels.  Threshold shift is usually measured against the most recent audiogram.  So, if the previous audiogram taken by the person tested in Figure 2 showed that their auditory threshold at 4000 Hz was 30 decibels, the new audiogram above would represent a threshold shift of 30 decibels (60-30=30) at that frequency. The first audiogram that a person gets, usually upon starting a new job, is called a baseline. All future threshold shifts should be measured against this baseline.
 
In contrast, Figure 3 below shows a normal audiogram for a person with negligible hearing loss.  In this case, the person being tested can hear sounds as low as 0-15 decibels across all frequencies.
 
Figure 3. Source: https://www.intechopen.com/books/update-on-hearing-loss/classification-of-hearing-loss
 

Risks Addressed:

Repeated overexposure to noise causes permanent hearing loss and ringing in the ears (tinnitus).  It has also been associated with hypertension and other cardiovascular diseases (Girard et al, 2015).
 
The Occupational Safety and Health Administration (OSHA) requires that workers’ 8-hour exposure (also known as LAeq) remain under 90 decibels (dB), while NIOSH has recommended that it remain under 85 dB. NIOSH’s recommendations are more protective, even though they do not completely eliminate the risk of sustaining hearing loss. Table 1 shows how long a worker can be exposed to different levels of noise (measured in A-weighted decibels, or dBA) according to both OSHA and NIOSH criteria.
 

dBA

OSHA

NIOSH

80

32 hours

>24 hours

85

16 hours

8 hours

90

8 hours

2.5 hours

95

4 hours

47.6 minutes

100

2 hours

15 minutes

105

1 hour

4.7 minutes

110

30 minutes

1.5 minutes

115

15 minutes

28 seconds

120

7.5 minutes

9 seconds

125

3.8 minutes

3 seconds

Table 1.

Many common construction tasks produce high levels of noise. A concrete saw typically produces around 98 dB, and a jackhammer usually gives off around 102 dB.  Hearing loss is a function of noise intensity and duration. According to the NIOSH criteria in Table 1 above, a worker could operate a bulldozer (about 100 dB) for around 15 minutes before they started to sustain permanent hearing loss (https://www.osha.gov/Publications/3498noise-in-construction-pocket-guide.pdf).  

How Risks are Reduced:

Audiometric testing measures and documents hearing loss.  Because hearing loss is progressive and irreversible, prevention is extremely important. Since many construction workers are regularly exposed to noise above 85 dB, your employer should take steps to ensure that your hearing is protected.  This can include buying quieter tools, isolating noisy work, or providing effective hearing protection.  Annual audiometric testing will show if these controls are working.  

The Occupational Safety and Health Administration (OSHA) requires employers in the construction industry to institute a “continuing, effective hearing conservation program” when any employees are exposed to noise levels of at least 90 decibels averaged over 8 hours, or the equivalent (see the OSHA column in Table 1 above).  Although the construction standard does not specify the components of an effective hearing conservation program, regular audiometric testing should be a key component.  A letter of interpretation from OSHA lists the following recommended items as part of an effective hearing conservation program in the construction industry:
 
  • Monitoring of employee noise exposures.
  • The institution of engineering, work practice, and administrative controls for excessive noise.
  • The provision of each overexposed employee with an individually fitted hearing protector with an adequate noise reduction rating.
  • Employee training and education regarding noise hazards and protection measures.
  • Baseline and annual audiometric testing.
  • Procedures for preventing further occupational hearing loss by an employee whenever such an event has been identified.
  • Recordkeeping.
These recommendations are very similar to the requirements for hearing conservation programs under General Industry.  After getting a baseline, audiograms are recommended once a year or whenever there is a change in tasks or procedures that affects noise exposure.

Additional Considerations:

If you suspect you may be overexposed to noise at work, there are several steps you can take in addition to getting audiometric testing.  Many different apps that can measure the level of noise in your workplace are available for free.  The NIOSH Sound Level Meter is available for iPhone, and SPL Meter by AudioControl is available for Android.  If you don’t have a sound level meter, try standing at arm’s length from your coworker.  If you have trouble being heard at a normal speaking volume, it is safe to assume that the environment is noisier than 85 dB.  
 
If you work in a noisy environment, suspect you may have work-related hearing loss, or have trouble hearing or understanding people, ask your employer for audiometric testing as part of a hearing conservation program.  If audiometric testing shows that you have hearing loss, there are ways to keep it from getting worse.  A standard threshold shift is considered to be a threshold shift in either ear of at least 10 dB at 2,000, 3,000, and 4000 Hz.  If you have incurred a standard threshold shift (or if you are exposed to 85 dB over 8 hours, or the equivalent in Table 1 above), your employer must provide hearing protection.  Other recommendations include substituting quieter tools and isolating workers from noise sources. Keep in mind that impulse noise (such as jackhammers, nail guns, or an explosion) can be especially damaging to hearing, and that the limits in Table 1 above may not be sufficient to prevent hearing loss from impulse noise.
 
Many solvents and other chemicals can damage hearing and worsen the effects of noise exposure. These include toluene, trichloroethylene, lead, and mercury. 

Contributors:

Sara Brooks, MPH: CPWR - The Center for Construction Research and Training

Rosemary K. Sokas, MD, MOH: Georgetown University School of Nursing and Health Studies

Bruce Lippy, Ph.D., CIH, CSP, FAIHA: CPWR - The Center for Construction Research and Training