Hearing Screening E-Learning Course
Hearing Screening Equipment
Screening is a method of checking hearing that is not dependent upon risk assessment/ history interpretation, but instead utilizes standardized equipment to obtain reliable results.
Pure Tone Audiometer: A pure tone audiometer is a device that produces sounds at set frequencies and decibels through headphones worn by the child or adolescent being screened. The pure tone audiometer is the standard instrument used in school and clinic hearing screening programs for children 3 years and older.
In order to provide pure tone audiometry screening according to recommended procedures, the audiometer must test sounds ranging from 250 to 8000 Hz and volumes of 0-80/100 decibels. This allows the screener to perform both pure tone audiometry screening and threshold screening.
Note: MDH does not recommend speech stimuli screening equipment such as Verbal Auditory Screening for Children (VASC), where a word is presented to the child, and the child has to identify a related picture. Evidence indicates that the VASC is less effective than pure tone audiometry in identifying hearing loss. Some VASC equipment does have the option to do pure tone audiometry, which is acceptable to use.
Specifications vary somewhat between brands but most audiometers have the following dials:
- Power or On/Off Switch: Needs to be on when screening.
- Frequency Dial: The frequency dial rotates from 250 to 8000 Hz. This dial controls the test frequency or the pitch of the tone.
- Decibel (dB) or Hearing Level Dial: This dial controls the test intensity or loudness of the tone. This is typically a rotary dial, which allows the screener to vary the sounds presented in 5dB steps from approximately 0 to 80/100dB.
- Tone Presentation Bar or Stimulus Switch: Pressing this bar presents the tone.
Otoacoustic Emissions (OAE)*: This test evaluates hearing in infants and young children who cannot be screened using standard screening methods. The test measures cochlear emissions produced by a healthy functioning cochlea in response to sound. OAE equipment provides a practical and effective hearing screening method for children from the post-newborn period to 3 years of age and for older children who have developmental delays.
Tympanometry* (acoustic Immittance): Tympanometry provides an objective measurement of tympanic mobility (compliance) and middle ear pressure through the use of sound (probe tone) and air pressure. Performing tympanometry along with pure tone audiometry or OAE screening may reduce the need for multistage screening and improve loss to follow-up.
*More detail on this equipment is provided in the Hearing and Vision Screening for Nurses Training.
Audiometer General Care
Handle the audiometer gently and avoid dropping it. When transporting the audiometer in a car, secure it so it will not fall during a sudden stop. Avoid extreme temperatures (below freezing and above 90°F). Keep cords free of tangles and twists. Check all electrical connections, dials and switches for signs of problems. The headphone jacks should be removed from their plugs occasionally and wiped with an alcohol pad to improve the connection (Note: Do not use alcohol pads on the headphone ear pieces.) Take care to prevent moisture from getting inside the audiometer.
Keep the case closed to prevent dust build-up. If the case or exposed surfaces become dirty, mild soap and water are usually sufficient to clean them.
Perform a mechanical function check each day, on each audiometer, before use.
Headphones are calibrated to a specific audiometer and are not interchangeable with other machines.
Environmental Noise Level Check
Most clinics do not have the equipment to take ambient noise level measurements in the areas used for screening. However, an environmental noise level check may be substituted. This is the process of establishing that the screening room is quiet enough for a person with hearing in the normal range (15 dB or lower) to detect sounds of 1000, 2000, and 4000 Hz presented at 10 dB and the 500 Hz sound at 15 dB. If this level cannot be established, the area must not be used for screening. If 500 Hz is not detectable, that level may be deleted from the screening protocol. You may download the Environmental Noise Level Check Procedure (PDF).
Characteristics of an effective hearing screening facility
An effective hearing screening room is quiet and free from distractions.
Avoid areas near:
- Equipment that makes noise (fans, air conditioners, refrigerators, vending machines, copy machines, etc.)
- Hall traffic (reroute if possible)
- Playground or street traffic
- Group activity areas such as break rooms
Avoid excess noise within screening area, such as:
- Paper shuffling
- Open windows
- Ticking clock
- Movement of desks or other furniture
Room should be uncluttered and free of visual distraction:
- Avoid mirror or reflecting surfaces
- Avoid facing child towards a window
- Avoid child facing others who may give clues to correct response
- Avoid people coming in and out of the room
Pause screening momentarily if any distracting noise occurs.
As screening is usually conducted in a clinic, try using the last room at the end of a hall or one that is away from other rooms. More information on Environmental Noise Level Check Procedure (PDF).
Cerumen (ear wax) is not infectious, but it can contain substances that can be infective such as dried blood or mucous.
The American Academy of Audiology recommends cleaning headphones before each re-use. Antimicrobial or hospital grade disinfectants in towel or spray are the most effective disinfectants. Do not use alcohol because it may dry out the rubber cushions on headphones. When the headphones cushions need cleaning, remove them from the headset, clean and dry thoroughly before replacing. Keep all moisture away from the diaphragm (the hole in the center of the headphones).
The American Academy of Audiology (2011) recommends to modify screening schedules in the event of a current lice outbreak.
Audiometers should be calibrated yearly. A more extensive calibration is typically recommended at a repair facility or factory about every five years.
The audiometer needs repair if:
- Tone does not sound normal, static is heard, or sound is not produced when tone lever/button is pressed.
- Headphones do not remain in proper position over ears.
- A dial or switch does not function or indicator lights do not glow.
For more information, refer to audiometer supplies and repair.
Biologic Calibration Check
(Optional unless performing threshold audiometry)
To ensure that the audiometer is ready for accurate screening, the person with primary responsibility for the hearing screening program should do biologic calibration checks. Perform this check prior to threshold screening or when there is reason to suspect the audiometer may not be working properly. Use procedure described below. For more information you may download the Biologic Calibration Check Form (PDF).
Same Ear Hearing Level Procedure
- Obtain a threshold screening on the better ear with the right (red) headphone and record the results.
- Obtain a threshold on the same ear with the left (blue) headphone and record the results.
- Check thresholds at each frequency to see that they differ by no more than ±5dB. If they vary more than this, do not use the audiometer and have it checked by a technician.
Ensuring Proper Functioning
Mechanical and biological function checks must be done regularly on each audiometer before being used (copies of instructions and documentation forms are enclosed with each audiometer). For more information refer to the Audiometer Mechanical Function Check.
Note: Please answer the following questions to continue with the course.